linux-stable/arch/x86/kernel/uprobes.c

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// SPDX-License-Identifier: GPL-2.0-or-later
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/*
* User-space Probes (UProbes) for x86
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
*
* Copyright (C) IBM Corporation, 2008-2011
* Authors:
* Srikar Dronamraju
* Jim Keniston
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/uprobes.h>
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
#include <linux/uaccess.h>
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
#include <linux/kdebug.h>
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
#include <asm/processor.h>
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
#include <asm/insn.h>
#include <asm/mmu_context.h>
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/* Post-execution fixups. */
/* Adjust IP back to vicinity of actual insn */
#define UPROBE_FIX_IP 0x01
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/* Adjust the return address of a call insn */
#define UPROBE_FIX_CALL 0x02
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/* Instruction will modify TF, don't change it */
#define UPROBE_FIX_SETF 0x04
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
#define UPROBE_FIX_RIP_SI 0x08
#define UPROBE_FIX_RIP_DI 0x10
#define UPROBE_FIX_RIP_BX 0x20
#define UPROBE_FIX_RIP_MASK \
(UPROBE_FIX_RIP_SI | UPROBE_FIX_RIP_DI | UPROBE_FIX_RIP_BX)
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
#define UPROBE_TRAP_NR UINT_MAX
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/* Adaptations for mhiramat x86 decoder v14. */
#define OPCODE1(insn) ((insn)->opcode.bytes[0])
#define OPCODE2(insn) ((insn)->opcode.bytes[1])
#define OPCODE3(insn) ((insn)->opcode.bytes[2])
#define MODRM_REG(insn) X86_MODRM_REG((insn)->modrm.value)
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
(b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
(b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
(bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
<< (row % 32))
/*
* Good-instruction tables for 32-bit apps. This is non-const and volatile
* to keep gcc from statically optimizing it out, as variable_test_bit makes
* some versions of gcc to think only *(unsigned long*) is used.
*
* Opcodes we'll probably never support:
* 6c-6f - ins,outs. SEGVs if used in userspace
* e4-e7 - in,out imm. SEGVs if used in userspace
* ec-ef - in,out acc. SEGVs if used in userspace
* cc - int3. SIGTRAP if used in userspace
* ce - into. Not used in userspace - no kernel support to make it useful. SEGVs
* (why we support bound (62) then? it's similar, and similarly unused...)
* f1 - int1. SIGTRAP if used in userspace
* f4 - hlt. SEGVs if used in userspace
* fa - cli. SEGVs if used in userspace
* fb - sti. SEGVs if used in userspace
*
* Opcodes which need some work to be supported:
* 07,17,1f - pop es/ss/ds
* Normally not used in userspace, but would execute if used.
* Can cause GP or stack exception if tries to load wrong segment descriptor.
* We hesitate to run them under single step since kernel's handling
* of userspace single-stepping (TF flag) is fragile.
* We can easily refuse to support push es/cs/ss/ds (06/0e/16/1e)
* on the same grounds that they are never used.
* cd - int N.
* Used by userspace for "int 80" syscall entry. (Other "int N"
* cause GP -> SEGV since their IDT gates don't allow calls from CPL 3).
* Not supported since kernel's handling of userspace single-stepping
* (TF flag) is fragile.
* cf - iret. Normally not used in userspace. Doesn't SEGV unless arguments are bad
*/
#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
static volatile u32 good_insns_32[256 / 32] = {
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* 00 */
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
W(0x10, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 10 */
W(0x20, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */
W(0x30, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 30 */
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */
W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */
W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* e0 */
W(0xf0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/* ---------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
#else
#define good_insns_32 NULL
#endif
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/* Good-instruction tables for 64-bit apps.
*
* Genuinely invalid opcodes:
* 06,07 - formerly push/pop es
* 0e - formerly push cs
* 16,17 - formerly push/pop ss
* 1e,1f - formerly push/pop ds
* 27,2f,37,3f - formerly daa/das/aaa/aas
* 60,61 - formerly pusha/popa
* 62 - formerly bound. EVEX prefix for AVX512 (not yet supported)
* 82 - formerly redundant encoding of Group1
* 9a - formerly call seg:ofs
* ce - formerly into
* d4,d5 - formerly aam/aad
* d6 - formerly undocumented salc
* ea - formerly jmp seg:ofs
*
* Opcodes we'll probably never support:
* 6c-6f - ins,outs. SEGVs if used in userspace
* e4-e7 - in,out imm. SEGVs if used in userspace
* ec-ef - in,out acc. SEGVs if used in userspace
* cc - int3. SIGTRAP if used in userspace
* f1 - int1. SIGTRAP if used in userspace
* f4 - hlt. SEGVs if used in userspace
* fa - cli. SEGVs if used in userspace
* fb - sti. SEGVs if used in userspace
*
* Opcodes which need some work to be supported:
* cd - int N.
* Used by userspace for "int 80" syscall entry. (Other "int N"
* cause GP -> SEGV since their IDT gates don't allow calls from CPL 3).
* Not supported since kernel's handling of userspace single-stepping
* (TF flag) is fragile.
* cf - iret. Normally not used in userspace. Doesn't SEGV unless arguments are bad
*/
#if defined(CONFIG_X86_64)
static volatile u32 good_insns_64[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1) | /* 00 */
W(0x10, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) , /* 10 */
W(0x20, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) | /* 20 */
W(0x30, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
W(0x60, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */
W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */
W(0x80, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1) , /* 90 */
W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */
W(0xd0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0) | /* e0 */
W(0xf0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */
/* ---------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
#else
#define good_insns_64 NULL
#endif
/* Using this for both 64-bit and 32-bit apps.
* Opcodes we don't support:
* 0f 00 - SLDT/STR/LLDT/LTR/VERR/VERW/-/- group. System insns
* 0f 01 - SGDT/SIDT/LGDT/LIDT/SMSW/-/LMSW/INVLPG group.
* Also encodes tons of other system insns if mod=11.
* Some are in fact non-system: xend, xtest, rdtscp, maybe more
* 0f 05 - syscall
* 0f 06 - clts (CPL0 insn)
* 0f 07 - sysret
* 0f 08 - invd (CPL0 insn)
* 0f 09 - wbinvd (CPL0 insn)
* 0f 0b - ud2
* 0f 30 - wrmsr (CPL0 insn) (then why rdmsr is allowed, it's also CPL0 insn?)
* 0f 34 - sysenter
* 0f 35 - sysexit
* 0f 37 - getsec
* 0f 78 - vmread (Intel VMX. CPL0 insn)
* 0f 79 - vmwrite (Intel VMX. CPL0 insn)
* Note: with prefixes, these two opcodes are
* extrq/insertq/AVX512 convert vector ops.
* 0f ae - group15: [f]xsave,[f]xrstor,[v]{ld,st}mxcsr,clflush[opt],
* {rd,wr}{fs,gs}base,{s,l,m}fence.
* Why? They are all user-executable.
*/
static volatile u32 good_2byte_insns[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1) | /* 00 */
W(0x10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 10 */
W(0x20, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */
W(0x30, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 60 */
W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1) , /* 70 */
W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1) | /* a0 */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
W(0xe0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* e0 */
W(0xf0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) /* f0 */
/* ---------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
#undef W
/*
* opcodes we may need to refine support for:
*
* 0f - 2-byte instructions: For many of these instructions, the validity
* depends on the prefix and/or the reg field. On such instructions, we
* just consider the opcode combination valid if it corresponds to any
* valid instruction.
*
* 8f - Group 1 - only reg = 0 is OK
* c6-c7 - Group 11 - only reg = 0 is OK
* d9-df - fpu insns with some illegal encodings
* f2, f3 - repnz, repz prefixes. These are also the first byte for
* certain floating-point instructions, such as addsd.
*
* fe - Group 4 - only reg = 0 or 1 is OK
* ff - Group 5 - only reg = 0-6 is OK
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
*
* others -- Do we need to support these?
*
* 0f - (floating-point?) prefetch instructions
* 07, 17, 1f - pop es, pop ss, pop ds
* 26, 2e, 36, 3e - es:, cs:, ss:, ds: segment prefixes --
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
* but 64 and 65 (fs: and gs:) seem to be used, so we support them
* 67 - addr16 prefix
* ce - into
* f0 - lock prefix
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
*/
/*
* TODO:
* - Where necessary, examine the modrm byte and allow only valid instructions
* in the different Groups and fpu instructions.
*/
static bool is_prefix_bad(struct insn *insn)
{
int i;
for (i = 0; i < insn->prefixes.nbytes; i++) {
insn_attr_t attr;
attr = inat_get_opcode_attribute(insn->prefixes.bytes[i]);
switch (attr) {
case INAT_MAKE_PREFIX(INAT_PFX_ES):
case INAT_MAKE_PREFIX(INAT_PFX_CS):
case INAT_MAKE_PREFIX(INAT_PFX_DS):
case INAT_MAKE_PREFIX(INAT_PFX_SS):
case INAT_MAKE_PREFIX(INAT_PFX_LOCK):
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
return true;
}
}
return false;
}
static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool x86_64)
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
{
u32 volatile *good_insns;
x86: Remove arbitrary instruction size limit in instruction decoder The current x86 instruction decoder steps along through the instruction stream but always ensures that it never steps farther than the largest possible instruction size (MAX_INSN_SIZE). The MPX code is now going to be doing some decoding of userspace instructions. We copy those from userspace in to the kernel and they're obviously completely untrusted coming from userspace. In addition to the constraint that instructions can only be so long, we also have to be aware of how long the buffer is that came in from userspace. This _looks_ to be similar to what the perf and kprobes is doing, but it's unclear to me whether they are affected. The whole reason we need this is that it is perfectly valid to be executing an instruction within MAX_INSN_SIZE bytes of an unreadable page. We should be able to gracefully handle short reads in those cases. This adds support to the decoder to record how long the buffer being decoded is and to refuse to "validate" the instruction if we would have gone over the end of the buffer to decode it. The kprobes code probably needs to be looked at here a bit more carefully. This patch still respects the MAX_INSN_SIZE limit there but the kprobes code does look like it might be able to be a bit more strict than it currently is. Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Jim Keniston <jkenisto@us.ibm.com> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: x86@kernel.org Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: "David S. Miller" <davem@davemloft.net> Link: http://lkml.kernel.org/r/20141114153957.E6B01535@viggo.jf.intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-11-14 15:39:57 +00:00
insn_init(insn, auprobe->insn, sizeof(auprobe->insn), x86_64);
/* has the side-effect of processing the entire instruction */
insn_get_length(insn);
if (!insn_complete(insn))
return -ENOEXEC;
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
if (is_prefix_bad(insn))
return -ENOTSUPP;
/* We should not singlestep on the exception masking instructions */
if (insn_masking_exception(insn))
return -ENOTSUPP;
if (x86_64)
good_insns = good_insns_64;
else
good_insns = good_insns_32;
if (test_bit(OPCODE1(insn), (unsigned long *)good_insns))
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
return 0;
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
if (insn->opcode.nbytes == 2) {
if (test_bit(OPCODE2(insn), (unsigned long *)good_2byte_insns))
return 0;
}
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
return -ENOTSUPP;
}
#ifdef CONFIG_X86_64
/*
* If arch_uprobe->insn doesn't use rip-relative addressing, return
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
* immediately. Otherwise, rewrite the instruction so that it accesses
* its memory operand indirectly through a scratch register. Set
* defparam->fixups accordingly. (The contents of the scratch register
* will be saved before we single-step the modified instruction,
* and restored afterward).
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
*
* We do this because a rip-relative instruction can access only a
* relatively small area (+/- 2 GB from the instruction), and the XOL
* area typically lies beyond that area. At least for instructions
* that store to memory, we can't execute the original instruction
* and "fix things up" later, because the misdirected store could be
* disastrous.
*
* Some useful facts about rip-relative instructions:
*
* - There's always a modrm byte with bit layout "00 reg 101".
* - There's never a SIB byte.
* - The displacement is always 4 bytes.
* - REX.B=1 bit in REX prefix, which normally extends r/m field,
* has no effect on rip-relative mode. It doesn't make modrm byte
* with r/m=101 refer to register 1101 = R13.
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
*/
static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
{
u8 *cursor;
u8 reg;
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
u8 reg2;
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
if (!insn_rip_relative(insn))
return;
/*
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
* insn_rip_relative() would have decoded rex_prefix, vex_prefix, modrm.
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
* Clear REX.b bit (extension of MODRM.rm field):
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
* we want to encode low numbered reg, not r8+.
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
*/
if (insn->rex_prefix.nbytes) {
cursor = auprobe->insn + insn_offset_rex_prefix(insn);
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
/* REX byte has 0100wrxb layout, clearing REX.b bit */
*cursor &= 0xfe;
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
}
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
/*
uprobes/x86: Fix RIP-relative handling of EVEX-encoded instructions Since instruction decoder now supports EVEX-encoded instructions, two fixes are needed to correctly handle them in uprobes. Extended bits for MODRM.rm field need to be sanitized just like we do it for VEX3, to avoid encoding wrong register for register-relative access. EVEX has _two_ extended bits: b and x. Theoretically, EVEX.x should be ignored by the CPU (since GPRs go only up to 15, not 31), but let's be paranoid here: proper encoding for register-relative access should have EVEX.x = 1. Secondly, we should fetch vex.vvvv for EVEX too. This is now super easy because instruction decoder populates vex_prefix.bytes[2] for all flavors of (e)vex encodings, even for VEX2. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-kernel@vger.kernel.org Cc: <stable@vger.kernel.org> # v4.1+ Fixes: 8a764a875fe3 ("x86/asm/decoder: Create artificial 3rd byte for 2-byte VEX") Link: http://lkml.kernel.org/r/20160811154521.20469-1-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-11 15:45:21 +00:00
* Similar treatment for VEX3/EVEX prefix.
* TODO: add XOP treatment when insn decoder supports them
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
*/
uprobes/x86: Fix RIP-relative handling of EVEX-encoded instructions Since instruction decoder now supports EVEX-encoded instructions, two fixes are needed to correctly handle them in uprobes. Extended bits for MODRM.rm field need to be sanitized just like we do it for VEX3, to avoid encoding wrong register for register-relative access. EVEX has _two_ extended bits: b and x. Theoretically, EVEX.x should be ignored by the CPU (since GPRs go only up to 15, not 31), but let's be paranoid here: proper encoding for register-relative access should have EVEX.x = 1. Secondly, we should fetch vex.vvvv for EVEX too. This is now super easy because instruction decoder populates vex_prefix.bytes[2] for all flavors of (e)vex encodings, even for VEX2. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-kernel@vger.kernel.org Cc: <stable@vger.kernel.org> # v4.1+ Fixes: 8a764a875fe3 ("x86/asm/decoder: Create artificial 3rd byte for 2-byte VEX") Link: http://lkml.kernel.org/r/20160811154521.20469-1-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-11 15:45:21 +00:00
if (insn->vex_prefix.nbytes >= 3) {
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
/*
* vex2: c5 rvvvvLpp (has no b bit)
* vex3/xop: c4/8f rxbmmmmm wvvvvLpp
* evex: 62 rxbR00mm wvvvv1pp zllBVaaa
uprobes/x86: Fix RIP-relative handling of EVEX-encoded instructions Since instruction decoder now supports EVEX-encoded instructions, two fixes are needed to correctly handle them in uprobes. Extended bits for MODRM.rm field need to be sanitized just like we do it for VEX3, to avoid encoding wrong register for register-relative access. EVEX has _two_ extended bits: b and x. Theoretically, EVEX.x should be ignored by the CPU (since GPRs go only up to 15, not 31), but let's be paranoid here: proper encoding for register-relative access should have EVEX.x = 1. Secondly, we should fetch vex.vvvv for EVEX too. This is now super easy because instruction decoder populates vex_prefix.bytes[2] for all flavors of (e)vex encodings, even for VEX2. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-kernel@vger.kernel.org Cc: <stable@vger.kernel.org> # v4.1+ Fixes: 8a764a875fe3 ("x86/asm/decoder: Create artificial 3rd byte for 2-byte VEX") Link: http://lkml.kernel.org/r/20160811154521.20469-1-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-11 15:45:21 +00:00
* Setting VEX3.b (setting because it has inverted meaning).
* Setting EVEX.x since (in non-SIB encoding) EVEX.x
* is the 4th bit of MODRM.rm, and needs the same treatment.
* For VEX3-encoded insns, VEX3.x value has no effect in
* non-SIB encoding, the change is superfluous but harmless.
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
*/
cursor = auprobe->insn + insn_offset_vex_prefix(insn) + 1;
uprobes/x86: Fix RIP-relative handling of EVEX-encoded instructions Since instruction decoder now supports EVEX-encoded instructions, two fixes are needed to correctly handle them in uprobes. Extended bits for MODRM.rm field need to be sanitized just like we do it for VEX3, to avoid encoding wrong register for register-relative access. EVEX has _two_ extended bits: b and x. Theoretically, EVEX.x should be ignored by the CPU (since GPRs go only up to 15, not 31), but let's be paranoid here: proper encoding for register-relative access should have EVEX.x = 1. Secondly, we should fetch vex.vvvv for EVEX too. This is now super easy because instruction decoder populates vex_prefix.bytes[2] for all flavors of (e)vex encodings, even for VEX2. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-kernel@vger.kernel.org Cc: <stable@vger.kernel.org> # v4.1+ Fixes: 8a764a875fe3 ("x86/asm/decoder: Create artificial 3rd byte for 2-byte VEX") Link: http://lkml.kernel.org/r/20160811154521.20469-1-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-11 15:45:21 +00:00
*cursor |= 0x60;
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
}
/*
* Convert from rip-relative addressing to register-relative addressing
* via a scratch register.
*
* This is tricky since there are insns with modrm byte
* which also use registers not encoded in modrm byte:
* [i]div/[i]mul: implicitly use dx:ax
* shift ops: implicitly use cx
* cmpxchg: implicitly uses ax
* cmpxchg8/16b: implicitly uses dx:ax and bx:cx
* Encoding: 0f c7/1 modrm
* The code below thinks that reg=1 (cx), chooses si as scratch.
* mulx: implicitly uses dx: mulx r/m,r1,r2 does r1:r2 = dx * r/m.
* First appeared in Haswell (BMI2 insn). It is vex-encoded.
* Example where none of bx,cx,dx can be used as scratch reg:
* c4 e2 63 f6 0d disp32 mulx disp32(%rip),%ebx,%ecx
* [v]pcmpistri: implicitly uses cx, xmm0
* [v]pcmpistrm: implicitly uses xmm0
* [v]pcmpestri: implicitly uses ax, dx, cx, xmm0
* [v]pcmpestrm: implicitly uses ax, dx, xmm0
* Evil SSE4.2 string comparison ops from hell.
* maskmovq/[v]maskmovdqu: implicitly uses (ds:rdi) as destination.
* Encoding: 0f f7 modrm, 66 0f f7 modrm, vex-encoded: c5 f9 f7 modrm.
* Store op1, byte-masked by op2 msb's in each byte, to (ds:rdi).
* AMD says it has no 3-operand form (vex.vvvv must be 1111)
* and that it can have only register operands, not mem
* (its modrm byte must have mode=11).
* If these restrictions will ever be lifted,
* we'll need code to prevent selection of di as scratch reg!
*
* Summary: I don't know any insns with modrm byte which
* use SI register implicitly. DI register is used only
* by one insn (maskmovq) and BX register is used
* only by one too (cmpxchg8b).
* BP is stack-segment based (may be a problem?).
* AX, DX, CX are off-limits (many implicit users).
* SP is unusable (it's stack pointer - think about "pop mem";
* also, rsp+disp32 needs sib encoding -> insn length change).
*/
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
reg = MODRM_REG(insn); /* Fetch modrm.reg */
reg2 = 0xff; /* Fetch vex.vvvv */
uprobes/x86: Fix RIP-relative handling of EVEX-encoded instructions Since instruction decoder now supports EVEX-encoded instructions, two fixes are needed to correctly handle them in uprobes. Extended bits for MODRM.rm field need to be sanitized just like we do it for VEX3, to avoid encoding wrong register for register-relative access. EVEX has _two_ extended bits: b and x. Theoretically, EVEX.x should be ignored by the CPU (since GPRs go only up to 15, not 31), but let's be paranoid here: proper encoding for register-relative access should have EVEX.x = 1. Secondly, we should fetch vex.vvvv for EVEX too. This is now super easy because instruction decoder populates vex_prefix.bytes[2] for all flavors of (e)vex encodings, even for VEX2. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-kernel@vger.kernel.org Cc: <stable@vger.kernel.org> # v4.1+ Fixes: 8a764a875fe3 ("x86/asm/decoder: Create artificial 3rd byte for 2-byte VEX") Link: http://lkml.kernel.org/r/20160811154521.20469-1-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-11 15:45:21 +00:00
if (insn->vex_prefix.nbytes)
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
reg2 = insn->vex_prefix.bytes[2];
/*
uprobes/x86: Fix RIP-relative handling of EVEX-encoded instructions Since instruction decoder now supports EVEX-encoded instructions, two fixes are needed to correctly handle them in uprobes. Extended bits for MODRM.rm field need to be sanitized just like we do it for VEX3, to avoid encoding wrong register for register-relative access. EVEX has _two_ extended bits: b and x. Theoretically, EVEX.x should be ignored by the CPU (since GPRs go only up to 15, not 31), but let's be paranoid here: proper encoding for register-relative access should have EVEX.x = 1. Secondly, we should fetch vex.vvvv for EVEX too. This is now super easy because instruction decoder populates vex_prefix.bytes[2] for all flavors of (e)vex encodings, even for VEX2. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-kernel@vger.kernel.org Cc: <stable@vger.kernel.org> # v4.1+ Fixes: 8a764a875fe3 ("x86/asm/decoder: Create artificial 3rd byte for 2-byte VEX") Link: http://lkml.kernel.org/r/20160811154521.20469-1-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-11 15:45:21 +00:00
* TODO: add XOP vvvv reading.
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
*
* vex.vvvv field is in bits 6-3, bits are inverted.
* But in 32-bit mode, high-order bit may be ignored.
* Therefore, let's consider only 3 low-order bits.
*/
reg2 = ((reg2 >> 3) & 0x7) ^ 0x7;
/*
* Register numbering is ax,cx,dx,bx, sp,bp,si,di, r8..r15.
*
* Choose scratch reg. Order is important: must not select bx
* if we can use si (cmpxchg8b case!)
*/
if (reg != 6 && reg2 != 6) {
reg2 = 6;
auprobe->defparam.fixups |= UPROBE_FIX_RIP_SI;
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
} else if (reg != 7 && reg2 != 7) {
reg2 = 7;
auprobe->defparam.fixups |= UPROBE_FIX_RIP_DI;
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
/* TODO (paranoia): force maskmovq to not use di */
} else {
reg2 = 3;
auprobe->defparam.fixups |= UPROBE_FIX_RIP_BX;
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
}
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/*
* Point cursor at the modrm byte. The next 4 bytes are the
* displacement. Beyond the displacement, for some instructions,
* is the immediate operand.
*/
cursor = auprobe->insn + insn_offset_modrm(insn);
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/*
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
* Change modrm from "00 reg 101" to "10 reg reg2". Example:
* 89 05 disp32 mov %eax,disp32(%rip) becomes
* 89 86 disp32 mov %eax,disp32(%rsi)
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
*/
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
*cursor = 0x80 | (reg << 3) | reg2;
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
}
static inline unsigned long *
scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
if (auprobe->defparam.fixups & UPROBE_FIX_RIP_SI)
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
return &regs->si;
if (auprobe->defparam.fixups & UPROBE_FIX_RIP_DI)
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
return &regs->di;
return &regs->bx;
}
/*
* If we're emulating a rip-relative instruction, save the contents
* of the scratch register and store the target address in that register.
*/
static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
if (auprobe->defparam.fixups & UPROBE_FIX_RIP_MASK) {
struct uprobe_task *utask = current->utask;
unsigned long *sr = scratch_reg(auprobe, regs);
utask->autask.saved_scratch_register = *sr;
*sr = utask->vaddr + auprobe->defparam.ilen;
}
}
static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
if (auprobe->defparam.fixups & UPROBE_FIX_RIP_MASK) {
struct uprobe_task *utask = current->utask;
unsigned long *sr = scratch_reg(auprobe, regs);
*sr = utask->autask.saved_scratch_register;
}
}
#else /* 32-bit: */
/*
* No RIP-relative addressing on 32-bit
*/
static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
{
}
static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
}
static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
}
#endif /* CONFIG_X86_64 */
struct uprobe_xol_ops {
bool (*emulate)(struct arch_uprobe *, struct pt_regs *);
int (*pre_xol)(struct arch_uprobe *, struct pt_regs *);
int (*post_xol)(struct arch_uprobe *, struct pt_regs *);
void (*abort)(struct arch_uprobe *, struct pt_regs *);
};
uprobes/x86: Fix detection of 32-bit user mode 32-bit processes running on a 64-bit kernel are not always detected correctly, causing the process to crash when uretprobes are installed. The reason for the crash is that in_ia32_syscall() is used to determine the process's mode, which only works correctly when called from a syscall. In the case of uretprobes, however, the function is called from a exception and always returns 'false' on a 64-bit kernel. In consequence this leads to corruption of the process's return address. Fix this by using user_64bit_mode() instead of in_ia32_syscall(), which is correct in any situation. [ tglx: Add a comment and the following historical info ] This should have been detected by the rename which happened in commit abfb9498ee13 ("x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()") which states in the changelog: The is_ia32_task()/is_x32_task() function names are a big misnomer: they suggests that the compat-ness of a system call is a task property, which is not true, the compatness of a system call purely depends on how it was invoked through the system call layer. ..... and then it went and blindly renamed every call site. Sadly enough this was already mentioned here: 8faaed1b9f50 ("uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and arch_uretprobe_hijack_return_addr()") where the changelog says: TODO: is_ia32_task() is not what we actually want, TS_COMPAT does not necessarily mean 32bit. Fortunately syscall-like insns can't be probed so it actually works, but it would be better to rename and use is_ia32_frame(). and goes all the way back to: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Oh well. 7+ years until someone actually tried a uretprobe on a 32bit process on a 64bit kernel.... Fixes: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Signed-off-by: Sebastian Mayr <me@sam.st> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Dmitry Safonov <dsafonov@virtuozzo.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190728152617.7308-1-me@sam.st
2019-07-28 15:26:17 +00:00
static inline int sizeof_long(struct pt_regs *regs)
{
uprobes/x86: Fix detection of 32-bit user mode 32-bit processes running on a 64-bit kernel are not always detected correctly, causing the process to crash when uretprobes are installed. The reason for the crash is that in_ia32_syscall() is used to determine the process's mode, which only works correctly when called from a syscall. In the case of uretprobes, however, the function is called from a exception and always returns 'false' on a 64-bit kernel. In consequence this leads to corruption of the process's return address. Fix this by using user_64bit_mode() instead of in_ia32_syscall(), which is correct in any situation. [ tglx: Add a comment and the following historical info ] This should have been detected by the rename which happened in commit abfb9498ee13 ("x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()") which states in the changelog: The is_ia32_task()/is_x32_task() function names are a big misnomer: they suggests that the compat-ness of a system call is a task property, which is not true, the compatness of a system call purely depends on how it was invoked through the system call layer. ..... and then it went and blindly renamed every call site. Sadly enough this was already mentioned here: 8faaed1b9f50 ("uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and arch_uretprobe_hijack_return_addr()") where the changelog says: TODO: is_ia32_task() is not what we actually want, TS_COMPAT does not necessarily mean 32bit. Fortunately syscall-like insns can't be probed so it actually works, but it would be better to rename and use is_ia32_frame(). and goes all the way back to: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Oh well. 7+ years until someone actually tried a uretprobe on a 32bit process on a 64bit kernel.... Fixes: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Signed-off-by: Sebastian Mayr <me@sam.st> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Dmitry Safonov <dsafonov@virtuozzo.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190728152617.7308-1-me@sam.st
2019-07-28 15:26:17 +00:00
/*
* Check registers for mode as in_xxx_syscall() does not apply here.
*/
return user_64bit_mode(regs) ? 8 : 4;
}
static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
riprel_pre_xol(auprobe, regs);
return 0;
}
uprobes/x86: Emulate push insns for uprobe on x86 Uprobe is a tracing mechanism for userspace programs. Typical uprobe will incur overhead of two traps. First trap is caused by replaced trap insn, and the second trap is to execute the original displaced insn in user space. To reduce the overhead, kernel provides hooks for architectures to emulate the original insn and skip the second trap. In x86, emulation is done for certain branch insns. This patch extends the emulation to "push <reg>" insns. These insns are typical in the beginning of the function. For example, bcc in https://github.com/iovisor/bcc repo provides tools to measure funclantency, detect memleak, etc. The tools will place uprobes in the beginning of function and possibly uretprobes at the end of function. This patch is able to reduce the trap overhead for uprobe from 2 to 1. Without this patch, uretprobe will typically incur three traps. With this patch, if the function starts with "push" insn, the number of traps can be reduced from 3 to 2. An experiment was conducted on two local VMs, fedora 26 64-bit VM and 32-bit VM, both 4 processors and 4GB memory, booted with latest tip repo (and this patch). The host is MacBook with intel i7 processor. The test program looks like: #include <stdio.h> #include <stdlib.h> #include <time.h> #include <sys/time.h> static void test() __attribute__((noinline)); void test() {} int main() { struct timeval start, end; gettimeofday(&start, NULL); for (int i = 0; i < 1000000; i++) { test(); } gettimeofday(&end, NULL); printf("%ld\n", ((end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec * 1000000 + start.tv_usec))); return 0; } The program is compiled without optimization, and the first insn for function "test" is "push %rbp". The host is relatively idle. Before the test run, the uprobe is inserted as below for uprobe: echo 'p <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable and for uretprobe: echo 'r <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable Unit: microsecond(usec) per loop iteration x86_64 W/ this patch W/O this patch uprobe 1.55 3.1 uretprobe 2.0 3.6 x86_32 W/ this patch W/O this patch uprobe 1.41 3.5 uretprobe 1.75 4.0 You can see that this patch significantly reduced the overhead, 50% for uprobe and 44% for uretprobe on x86_64, and even more on x86_32. Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-team@fb.com Link: http://lkml.kernel.org/r/20171201001202.3706564-1-yhs@fb.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-01 00:12:02 +00:00
static int emulate_push_stack(struct pt_regs *regs, unsigned long val)
{
uprobes/x86: Fix detection of 32-bit user mode 32-bit processes running on a 64-bit kernel are not always detected correctly, causing the process to crash when uretprobes are installed. The reason for the crash is that in_ia32_syscall() is used to determine the process's mode, which only works correctly when called from a syscall. In the case of uretprobes, however, the function is called from a exception and always returns 'false' on a 64-bit kernel. In consequence this leads to corruption of the process's return address. Fix this by using user_64bit_mode() instead of in_ia32_syscall(), which is correct in any situation. [ tglx: Add a comment and the following historical info ] This should have been detected by the rename which happened in commit abfb9498ee13 ("x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()") which states in the changelog: The is_ia32_task()/is_x32_task() function names are a big misnomer: they suggests that the compat-ness of a system call is a task property, which is not true, the compatness of a system call purely depends on how it was invoked through the system call layer. ..... and then it went and blindly renamed every call site. Sadly enough this was already mentioned here: 8faaed1b9f50 ("uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and arch_uretprobe_hijack_return_addr()") where the changelog says: TODO: is_ia32_task() is not what we actually want, TS_COMPAT does not necessarily mean 32bit. Fortunately syscall-like insns can't be probed so it actually works, but it would be better to rename and use is_ia32_frame(). and goes all the way back to: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Oh well. 7+ years until someone actually tried a uretprobe on a 32bit process on a 64bit kernel.... Fixes: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Signed-off-by: Sebastian Mayr <me@sam.st> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Dmitry Safonov <dsafonov@virtuozzo.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190728152617.7308-1-me@sam.st
2019-07-28 15:26:17 +00:00
unsigned long new_sp = regs->sp - sizeof_long(regs);
uprobes/x86: Fix detection of 32-bit user mode 32-bit processes running on a 64-bit kernel are not always detected correctly, causing the process to crash when uretprobes are installed. The reason for the crash is that in_ia32_syscall() is used to determine the process's mode, which only works correctly when called from a syscall. In the case of uretprobes, however, the function is called from a exception and always returns 'false' on a 64-bit kernel. In consequence this leads to corruption of the process's return address. Fix this by using user_64bit_mode() instead of in_ia32_syscall(), which is correct in any situation. [ tglx: Add a comment and the following historical info ] This should have been detected by the rename which happened in commit abfb9498ee13 ("x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()") which states in the changelog: The is_ia32_task()/is_x32_task() function names are a big misnomer: they suggests that the compat-ness of a system call is a task property, which is not true, the compatness of a system call purely depends on how it was invoked through the system call layer. ..... and then it went and blindly renamed every call site. Sadly enough this was already mentioned here: 8faaed1b9f50 ("uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and arch_uretprobe_hijack_return_addr()") where the changelog says: TODO: is_ia32_task() is not what we actually want, TS_COMPAT does not necessarily mean 32bit. Fortunately syscall-like insns can't be probed so it actually works, but it would be better to rename and use is_ia32_frame(). and goes all the way back to: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Oh well. 7+ years until someone actually tried a uretprobe on a 32bit process on a 64bit kernel.... Fixes: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Signed-off-by: Sebastian Mayr <me@sam.st> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Dmitry Safonov <dsafonov@virtuozzo.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190728152617.7308-1-me@sam.st
2019-07-28 15:26:17 +00:00
if (copy_to_user((void __user *)new_sp, &val, sizeof_long(regs)))
return -EFAULT;
regs->sp = new_sp;
return 0;
}
uprobes/x86: Fix scratch register selection for rip-relative fixups Before this patch, instructions such as div, mul, shifts with count in CL, cmpxchg are mishandled. This patch adds vex prefix handling. In particular, it avoids colliding with register operand encoded in vex.vvvv field. Since we need to avoid two possible register operands, the selection of scratch register needs to be from at least three registers. After looking through a lot of CPU docs, it looks like the safest choice is SI,DI,BX. Selecting BX needs care to not collide with implicit use of BX by cmpxchg8b. Test-case: #include <stdio.h> static const char *const pass[] = { "FAIL", "pass" }; long two = 2; void test1(void) { long ax = 0, dx = 0; asm volatile("\n" " xor %%edx,%%edx\n" " lea 2(%%edx),%%eax\n" // We divide 2 by 2. Result (in eax) should be 1: " probe1: .globl probe1\n" " divl two(%%rip)\n" // If we have a bug (eax mangled on entry) the result will be 2, // because eax gets restored by probe machinery. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[ax == 1] ); } long val2 = 0; void test2(void) { long old_val = val2; long ax = 0, dx = 0; asm volatile("\n" " mov val2,%%eax\n" // eax := val2 " lea 1(%%eax),%%edx\n" // edx := eax+1 // eax is equal to val2. cmpxchg should store edx to val2: " probe2: .globl probe2\n" " cmpxchg %%edx,val2(%%rip)\n" // If we have a bug (eax mangled on entry), val2 will stay unchanged : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val2 == old_val + 1] ); } long val3[2] = {0,0}; void test3(void) { long old_val = val3[0]; long ax = 0, dx = 0; asm volatile("\n" " mov val3,%%eax\n" // edx:eax := val3 " mov val3+4,%%edx\n" " mov %%eax,%%ebx\n" // ecx:ebx := edx:eax + 1 " mov %%edx,%%ecx\n" " add $1,%%ebx\n" " adc $0,%%ecx\n" // edx:eax is equal to val3. cmpxchg8b should store ecx:ebx to val3: " probe3: .globl probe3\n" " cmpxchg8b val3(%%rip)\n" // If we have a bug (edx:eax mangled on entry), val3 will stay unchanged. // If ecx:edx in mangled, val3 will get wrong value. : "=a" (ax), "=d" (dx) /*out*/ : "0" (ax), "1" (dx) /*in*/ : "cx", "bx", "memory" /*clobber*/ ); dprintf(2, "%s: %s\n", __func__, pass[val3[0] == old_val + 1 && val3[1] == 0] ); } int main(int argc, char **argv) { test1(); test2(); test3(); return 0; } Before this change all tests fail if probe{1,2,3} are probed. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2014-05-02 15:04:00 +00:00
/*
* We have to fix things up as follows:
*
* Typically, the new ip is relative to the copied instruction. We need
* to make it relative to the original instruction (FIX_IP). Exceptions
* are return instructions and absolute or indirect jump or call instructions.
*
* If the single-stepped instruction was a call, the return address that
* is atop the stack is the address following the copied instruction. We
* need to make it the address following the original instruction (FIX_CALL).
*
* If the original instruction was a rip-relative instruction such as
* "movl %edx,0xnnnn(%rip)", we have instead executed an equivalent
* instruction using a scratch register -- e.g., "movl %edx,0xnnnn(%rsi)".
* We need to restore the contents of the scratch register
* (FIX_RIP_reg).
*/
static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
riprel_post_xol(auprobe, regs);
if (auprobe->defparam.fixups & UPROBE_FIX_IP) {
long correction = utask->vaddr - utask->xol_vaddr;
regs->ip += correction;
} else if (auprobe->defparam.fixups & UPROBE_FIX_CALL) {
uprobes/x86: Fix detection of 32-bit user mode 32-bit processes running on a 64-bit kernel are not always detected correctly, causing the process to crash when uretprobes are installed. The reason for the crash is that in_ia32_syscall() is used to determine the process's mode, which only works correctly when called from a syscall. In the case of uretprobes, however, the function is called from a exception and always returns 'false' on a 64-bit kernel. In consequence this leads to corruption of the process's return address. Fix this by using user_64bit_mode() instead of in_ia32_syscall(), which is correct in any situation. [ tglx: Add a comment and the following historical info ] This should have been detected by the rename which happened in commit abfb9498ee13 ("x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()") which states in the changelog: The is_ia32_task()/is_x32_task() function names are a big misnomer: they suggests that the compat-ness of a system call is a task property, which is not true, the compatness of a system call purely depends on how it was invoked through the system call layer. ..... and then it went and blindly renamed every call site. Sadly enough this was already mentioned here: 8faaed1b9f50 ("uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and arch_uretprobe_hijack_return_addr()") where the changelog says: TODO: is_ia32_task() is not what we actually want, TS_COMPAT does not necessarily mean 32bit. Fortunately syscall-like insns can't be probed so it actually works, but it would be better to rename and use is_ia32_frame(). and goes all the way back to: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Oh well. 7+ years until someone actually tried a uretprobe on a 32bit process on a 64bit kernel.... Fixes: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Signed-off-by: Sebastian Mayr <me@sam.st> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Dmitry Safonov <dsafonov@virtuozzo.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190728152617.7308-1-me@sam.st
2019-07-28 15:26:17 +00:00
regs->sp += sizeof_long(regs); /* Pop incorrect return address */
uprobes/x86: Emulate push insns for uprobe on x86 Uprobe is a tracing mechanism for userspace programs. Typical uprobe will incur overhead of two traps. First trap is caused by replaced trap insn, and the second trap is to execute the original displaced insn in user space. To reduce the overhead, kernel provides hooks for architectures to emulate the original insn and skip the second trap. In x86, emulation is done for certain branch insns. This patch extends the emulation to "push <reg>" insns. These insns are typical in the beginning of the function. For example, bcc in https://github.com/iovisor/bcc repo provides tools to measure funclantency, detect memleak, etc. The tools will place uprobes in the beginning of function and possibly uretprobes at the end of function. This patch is able to reduce the trap overhead for uprobe from 2 to 1. Without this patch, uretprobe will typically incur three traps. With this patch, if the function starts with "push" insn, the number of traps can be reduced from 3 to 2. An experiment was conducted on two local VMs, fedora 26 64-bit VM and 32-bit VM, both 4 processors and 4GB memory, booted with latest tip repo (and this patch). The host is MacBook with intel i7 processor. The test program looks like: #include <stdio.h> #include <stdlib.h> #include <time.h> #include <sys/time.h> static void test() __attribute__((noinline)); void test() {} int main() { struct timeval start, end; gettimeofday(&start, NULL); for (int i = 0; i < 1000000; i++) { test(); } gettimeofday(&end, NULL); printf("%ld\n", ((end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec * 1000000 + start.tv_usec))); return 0; } The program is compiled without optimization, and the first insn for function "test" is "push %rbp". The host is relatively idle. Before the test run, the uprobe is inserted as below for uprobe: echo 'p <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable and for uretprobe: echo 'r <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable Unit: microsecond(usec) per loop iteration x86_64 W/ this patch W/O this patch uprobe 1.55 3.1 uretprobe 2.0 3.6 x86_32 W/ this patch W/O this patch uprobe 1.41 3.5 uretprobe 1.75 4.0 You can see that this patch significantly reduced the overhead, 50% for uprobe and 44% for uretprobe on x86_64, and even more on x86_32. Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-team@fb.com Link: http://lkml.kernel.org/r/20171201001202.3706564-1-yhs@fb.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-01 00:12:02 +00:00
if (emulate_push_stack(regs, utask->vaddr + auprobe->defparam.ilen))
return -ERESTART;
}
/* popf; tell the caller to not touch TF */
if (auprobe->defparam.fixups & UPROBE_FIX_SETF)
utask->autask.saved_tf = true;
return 0;
}
static void default_abort_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
riprel_post_xol(auprobe, regs);
}
static const struct uprobe_xol_ops default_xol_ops = {
.pre_xol = default_pre_xol_op,
.post_xol = default_post_xol_op,
.abort = default_abort_op,
};
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
static bool branch_is_call(struct arch_uprobe *auprobe)
{
return auprobe->branch.opc1 == 0xe8;
}
#define CASE_COND \
COND(70, 71, XF(OF)) \
COND(72, 73, XF(CF)) \
COND(74, 75, XF(ZF)) \
COND(78, 79, XF(SF)) \
COND(7a, 7b, XF(PF)) \
COND(76, 77, XF(CF) || XF(ZF)) \
COND(7c, 7d, XF(SF) != XF(OF)) \
COND(7e, 7f, XF(ZF) || XF(SF) != XF(OF))
#define COND(op_y, op_n, expr) \
case 0x ## op_y: DO((expr) != 0) \
case 0x ## op_n: DO((expr) == 0)
#define XF(xf) (!!(flags & X86_EFLAGS_ ## xf))
static bool is_cond_jmp_opcode(u8 opcode)
{
switch (opcode) {
#define DO(expr) \
return true;
CASE_COND
#undef DO
default:
return false;
}
}
static bool check_jmp_cond(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
unsigned long flags = regs->flags;
switch (auprobe->branch.opc1) {
#define DO(expr) \
return expr;
CASE_COND
#undef DO
default: /* not a conditional jmp */
return true;
}
}
#undef XF
#undef COND
#undef CASE_COND
static bool branch_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
unsigned long new_ip = regs->ip += auprobe->branch.ilen;
unsigned long offs = (long)auprobe->branch.offs;
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
if (branch_is_call(auprobe)) {
/*
* If it fails we execute this (mangled, see the comment in
* branch_clear_offset) insn out-of-line. In the likely case
* this should trigger the trap, and the probed application
* should die or restart the same insn after it handles the
* signal, arch_uprobe_post_xol() won't be even called.
*
* But there is corner case, see the comment in ->post_xol().
*/
uprobes/x86: Emulate push insns for uprobe on x86 Uprobe is a tracing mechanism for userspace programs. Typical uprobe will incur overhead of two traps. First trap is caused by replaced trap insn, and the second trap is to execute the original displaced insn in user space. To reduce the overhead, kernel provides hooks for architectures to emulate the original insn and skip the second trap. In x86, emulation is done for certain branch insns. This patch extends the emulation to "push <reg>" insns. These insns are typical in the beginning of the function. For example, bcc in https://github.com/iovisor/bcc repo provides tools to measure funclantency, detect memleak, etc. The tools will place uprobes in the beginning of function and possibly uretprobes at the end of function. This patch is able to reduce the trap overhead for uprobe from 2 to 1. Without this patch, uretprobe will typically incur three traps. With this patch, if the function starts with "push" insn, the number of traps can be reduced from 3 to 2. An experiment was conducted on two local VMs, fedora 26 64-bit VM and 32-bit VM, both 4 processors and 4GB memory, booted with latest tip repo (and this patch). The host is MacBook with intel i7 processor. The test program looks like: #include <stdio.h> #include <stdlib.h> #include <time.h> #include <sys/time.h> static void test() __attribute__((noinline)); void test() {} int main() { struct timeval start, end; gettimeofday(&start, NULL); for (int i = 0; i < 1000000; i++) { test(); } gettimeofday(&end, NULL); printf("%ld\n", ((end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec * 1000000 + start.tv_usec))); return 0; } The program is compiled without optimization, and the first insn for function "test" is "push %rbp". The host is relatively idle. Before the test run, the uprobe is inserted as below for uprobe: echo 'p <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable and for uretprobe: echo 'r <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable Unit: microsecond(usec) per loop iteration x86_64 W/ this patch W/O this patch uprobe 1.55 3.1 uretprobe 2.0 3.6 x86_32 W/ this patch W/O this patch uprobe 1.41 3.5 uretprobe 1.75 4.0 You can see that this patch significantly reduced the overhead, 50% for uprobe and 44% for uretprobe on x86_64, and even more on x86_32. Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-team@fb.com Link: http://lkml.kernel.org/r/20171201001202.3706564-1-yhs@fb.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-01 00:12:02 +00:00
if (emulate_push_stack(regs, new_ip))
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
return false;
} else if (!check_jmp_cond(auprobe, regs)) {
offs = 0;
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
}
regs->ip = new_ip + offs;
return true;
}
uprobes/x86: Emulate push insns for uprobe on x86 Uprobe is a tracing mechanism for userspace programs. Typical uprobe will incur overhead of two traps. First trap is caused by replaced trap insn, and the second trap is to execute the original displaced insn in user space. To reduce the overhead, kernel provides hooks for architectures to emulate the original insn and skip the second trap. In x86, emulation is done for certain branch insns. This patch extends the emulation to "push <reg>" insns. These insns are typical in the beginning of the function. For example, bcc in https://github.com/iovisor/bcc repo provides tools to measure funclantency, detect memleak, etc. The tools will place uprobes in the beginning of function and possibly uretprobes at the end of function. This patch is able to reduce the trap overhead for uprobe from 2 to 1. Without this patch, uretprobe will typically incur three traps. With this patch, if the function starts with "push" insn, the number of traps can be reduced from 3 to 2. An experiment was conducted on two local VMs, fedora 26 64-bit VM and 32-bit VM, both 4 processors and 4GB memory, booted with latest tip repo (and this patch). The host is MacBook with intel i7 processor. The test program looks like: #include <stdio.h> #include <stdlib.h> #include <time.h> #include <sys/time.h> static void test() __attribute__((noinline)); void test() {} int main() { struct timeval start, end; gettimeofday(&start, NULL); for (int i = 0; i < 1000000; i++) { test(); } gettimeofday(&end, NULL); printf("%ld\n", ((end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec * 1000000 + start.tv_usec))); return 0; } The program is compiled without optimization, and the first insn for function "test" is "push %rbp". The host is relatively idle. Before the test run, the uprobe is inserted as below for uprobe: echo 'p <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable and for uretprobe: echo 'r <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable Unit: microsecond(usec) per loop iteration x86_64 W/ this patch W/O this patch uprobe 1.55 3.1 uretprobe 2.0 3.6 x86_32 W/ this patch W/O this patch uprobe 1.41 3.5 uretprobe 1.75 4.0 You can see that this patch significantly reduced the overhead, 50% for uprobe and 44% for uretprobe on x86_64, and even more on x86_32. Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-team@fb.com Link: http://lkml.kernel.org/r/20171201001202.3706564-1-yhs@fb.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-01 00:12:02 +00:00
static bool push_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
unsigned long *src_ptr = (void *)regs + auprobe->push.reg_offset;
if (emulate_push_stack(regs, *src_ptr))
return false;
regs->ip += auprobe->push.ilen;
return true;
}
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
static int branch_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
BUG_ON(!branch_is_call(auprobe));
/*
* We can only get here if branch_emulate_op() failed to push the ret
* address _and_ another thread expanded our stack before the (mangled)
* "call" insn was executed out-of-line. Just restore ->sp and restart.
* We could also restore ->ip and try to call branch_emulate_op() again.
*/
uprobes/x86: Fix detection of 32-bit user mode 32-bit processes running on a 64-bit kernel are not always detected correctly, causing the process to crash when uretprobes are installed. The reason for the crash is that in_ia32_syscall() is used to determine the process's mode, which only works correctly when called from a syscall. In the case of uretprobes, however, the function is called from a exception and always returns 'false' on a 64-bit kernel. In consequence this leads to corruption of the process's return address. Fix this by using user_64bit_mode() instead of in_ia32_syscall(), which is correct in any situation. [ tglx: Add a comment and the following historical info ] This should have been detected by the rename which happened in commit abfb9498ee13 ("x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()") which states in the changelog: The is_ia32_task()/is_x32_task() function names are a big misnomer: they suggests that the compat-ness of a system call is a task property, which is not true, the compatness of a system call purely depends on how it was invoked through the system call layer. ..... and then it went and blindly renamed every call site. Sadly enough this was already mentioned here: 8faaed1b9f50 ("uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and arch_uretprobe_hijack_return_addr()") where the changelog says: TODO: is_ia32_task() is not what we actually want, TS_COMPAT does not necessarily mean 32bit. Fortunately syscall-like insns can't be probed so it actually works, but it would be better to rename and use is_ia32_frame(). and goes all the way back to: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Oh well. 7+ years until someone actually tried a uretprobe on a 32bit process on a 64bit kernel.... Fixes: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Signed-off-by: Sebastian Mayr <me@sam.st> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Dmitry Safonov <dsafonov@virtuozzo.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190728152617.7308-1-me@sam.st
2019-07-28 15:26:17 +00:00
regs->sp += sizeof_long(regs);
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
return -ERESTART;
}
static void branch_clear_offset(struct arch_uprobe *auprobe, struct insn *insn)
{
/*
* Turn this insn into "call 1f; 1:", this is what we will execute
* out-of-line if ->emulate() fails. We only need this to generate
* a trap, so that the probed task receives the correct signal with
* the properly filled siginfo.
*
* But see the comment in ->post_xol(), in the unlikely case it can
* succeed. So we need to ensure that the new ->ip can not fall into
* the non-canonical area and trigger #GP.
*
* We could turn it into (say) "pushf", but then we would need to
* divorce ->insn[] and ->ixol[]. We need to preserve the 1st byte
* of ->insn[] for set_orig_insn().
*/
memset(auprobe->insn + insn_offset_immediate(insn),
0, insn->immediate.nbytes);
}
static const struct uprobe_xol_ops branch_xol_ops = {
.emulate = branch_emulate_op,
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
.post_xol = branch_post_xol_op,
};
uprobes/x86: Emulate push insns for uprobe on x86 Uprobe is a tracing mechanism for userspace programs. Typical uprobe will incur overhead of two traps. First trap is caused by replaced trap insn, and the second trap is to execute the original displaced insn in user space. To reduce the overhead, kernel provides hooks for architectures to emulate the original insn and skip the second trap. In x86, emulation is done for certain branch insns. This patch extends the emulation to "push <reg>" insns. These insns are typical in the beginning of the function. For example, bcc in https://github.com/iovisor/bcc repo provides tools to measure funclantency, detect memleak, etc. The tools will place uprobes in the beginning of function and possibly uretprobes at the end of function. This patch is able to reduce the trap overhead for uprobe from 2 to 1. Without this patch, uretprobe will typically incur three traps. With this patch, if the function starts with "push" insn, the number of traps can be reduced from 3 to 2. An experiment was conducted on two local VMs, fedora 26 64-bit VM and 32-bit VM, both 4 processors and 4GB memory, booted with latest tip repo (and this patch). The host is MacBook with intel i7 processor. The test program looks like: #include <stdio.h> #include <stdlib.h> #include <time.h> #include <sys/time.h> static void test() __attribute__((noinline)); void test() {} int main() { struct timeval start, end; gettimeofday(&start, NULL); for (int i = 0; i < 1000000; i++) { test(); } gettimeofday(&end, NULL); printf("%ld\n", ((end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec * 1000000 + start.tv_usec))); return 0; } The program is compiled without optimization, and the first insn for function "test" is "push %rbp". The host is relatively idle. Before the test run, the uprobe is inserted as below for uprobe: echo 'p <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable and for uretprobe: echo 'r <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable Unit: microsecond(usec) per loop iteration x86_64 W/ this patch W/O this patch uprobe 1.55 3.1 uretprobe 2.0 3.6 x86_32 W/ this patch W/O this patch uprobe 1.41 3.5 uretprobe 1.75 4.0 You can see that this patch significantly reduced the overhead, 50% for uprobe and 44% for uretprobe on x86_64, and even more on x86_32. Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-team@fb.com Link: http://lkml.kernel.org/r/20171201001202.3706564-1-yhs@fb.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-01 00:12:02 +00:00
static const struct uprobe_xol_ops push_xol_ops = {
.emulate = push_emulate_op,
};
/* Returns -ENOSYS if branch_xol_ops doesn't handle this insn */
static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
{
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
u8 opc1 = OPCODE1(insn);
int i;
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
switch (opc1) {
case 0xeb: /* jmp 8 */
case 0xe9: /* jmp 32 */
case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */
break;
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
case 0xe8: /* call relative */
branch_clear_offset(auprobe, insn);
break;
case 0x0f:
if (insn->opcode.nbytes != 2)
return -ENOSYS;
/*
* If it is a "near" conditional jmp, OPCODE2() - 0x10 matches
* OPCODE1() of the "short" jmp which checks the same condition.
*/
opc1 = OPCODE2(insn) - 0x10;
fallthrough;
default:
if (!is_cond_jmp_opcode(opc1))
return -ENOSYS;
}
/*
* 16-bit overrides such as CALLW (66 e8 nn nn) are not supported.
* Intel and AMD behavior differ in 64-bit mode: Intel ignores 66 prefix.
* No one uses these insns, reject any branch insns with such prefix.
*/
for (i = 0; i < insn->prefixes.nbytes; i++) {
if (insn->prefixes.bytes[i] == 0x66)
return -ENOTSUPP;
}
uprobes/x86: Emulate relative call's See the previous "Emulate unconditional relative jmp's" which explains why we can not execute "jmp" out-of-line, the same applies to "call". Emulating of rip-relative call is trivial, we only need to additionally push the ret-address. If this fails, we execute this instruction out of line and this should trigger the trap, the probed application should die or the same insn will be restarted if a signal handler expands the stack. We do not even need ->post_xol() for this case. But there is a corner (and almost theoretical) case: another thread can expand the stack right before we execute this insn out of line. In this case it hit the same problem we are trying to solve. So we simply turn the probed insn into "call 1f; 1:" and add ->post_xol() which restores ->sp and restarts. Many thanks to Jonathan who finally found the standalone reproducer, otherwise I would never resolve the "random SIGSEGV's under systemtap" bug-report. Now that the problem is clear we can write the simplified test-case: void probe_func(void), callee(void); int failed = 1; asm ( ".text\n" ".align 4096\n" ".globl probe_func\n" "probe_func:\n" "call callee\n" "ret" ); /* * This assumes that: * * - &probe_func = 0x401000 + a_bit, aligned = 0x402000 * * - xol_vma->vm_start = TASK_SIZE_MAX - PAGE_SIZE = 0x7fffffffe000 * as xol_add_vma() asks; the 1st slot = 0x7fffffffe080 * * so we can target the non-canonical address from xol_vma using * the simple math below, 100 * 4096 is just the random offset */ asm (".org . + 0x800000000000 - 0x7fffffffe080 - 5 - 1 + 100 * 4096\n"); void callee(void) { failed = 0; } int main(void) { probe_func(); return failed; } It SIGSEGV's if you probe "probe_func" (although this is not very reliable, randomize_va_space/etc can change the placement of xol area). Note: as Denys Vlasenko pointed out, amd and intel treat "callw" (0x66 0xe8) differently. This patch relies on lib/insn.c and thus implements the intel's behaviour: 0x66 is simply ignored. Fortunately nothing sane should ever use this insn, so we postpone the fix until we decide what should we do; emulate or not, support or not, etc. Reported-by: Jonathan Lebon <jlebon@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
2014-04-06 16:11:02 +00:00
auprobe->branch.opc1 = opc1;
auprobe->branch.ilen = insn->length;
auprobe->branch.offs = insn->immediate.value;
auprobe->ops = &branch_xol_ops;
return 0;
}
uprobes/x86: Emulate push insns for uprobe on x86 Uprobe is a tracing mechanism for userspace programs. Typical uprobe will incur overhead of two traps. First trap is caused by replaced trap insn, and the second trap is to execute the original displaced insn in user space. To reduce the overhead, kernel provides hooks for architectures to emulate the original insn and skip the second trap. In x86, emulation is done for certain branch insns. This patch extends the emulation to "push <reg>" insns. These insns are typical in the beginning of the function. For example, bcc in https://github.com/iovisor/bcc repo provides tools to measure funclantency, detect memleak, etc. The tools will place uprobes in the beginning of function and possibly uretprobes at the end of function. This patch is able to reduce the trap overhead for uprobe from 2 to 1. Without this patch, uretprobe will typically incur three traps. With this patch, if the function starts with "push" insn, the number of traps can be reduced from 3 to 2. An experiment was conducted on two local VMs, fedora 26 64-bit VM and 32-bit VM, both 4 processors and 4GB memory, booted with latest tip repo (and this patch). The host is MacBook with intel i7 processor. The test program looks like: #include <stdio.h> #include <stdlib.h> #include <time.h> #include <sys/time.h> static void test() __attribute__((noinline)); void test() {} int main() { struct timeval start, end; gettimeofday(&start, NULL); for (int i = 0; i < 1000000; i++) { test(); } gettimeofday(&end, NULL); printf("%ld\n", ((end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec * 1000000 + start.tv_usec))); return 0; } The program is compiled without optimization, and the first insn for function "test" is "push %rbp". The host is relatively idle. Before the test run, the uprobe is inserted as below for uprobe: echo 'p <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable and for uretprobe: echo 'r <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable Unit: microsecond(usec) per loop iteration x86_64 W/ this patch W/O this patch uprobe 1.55 3.1 uretprobe 2.0 3.6 x86_32 W/ this patch W/O this patch uprobe 1.41 3.5 uretprobe 1.75 4.0 You can see that this patch significantly reduced the overhead, 50% for uprobe and 44% for uretprobe on x86_64, and even more on x86_32. Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-team@fb.com Link: http://lkml.kernel.org/r/20171201001202.3706564-1-yhs@fb.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-01 00:12:02 +00:00
/* Returns -ENOSYS if push_xol_ops doesn't handle this insn */
static int push_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
{
u8 opc1 = OPCODE1(insn), reg_offset = 0;
if (opc1 < 0x50 || opc1 > 0x57)
return -ENOSYS;
if (insn->length > 2)
return -ENOSYS;
if (insn->length == 2) {
/* only support rex_prefix 0x41 (x64 only) */
#ifdef CONFIG_X86_64
if (insn->rex_prefix.nbytes != 1 ||
insn->rex_prefix.bytes[0] != 0x41)
return -ENOSYS;
switch (opc1) {
case 0x50:
reg_offset = offsetof(struct pt_regs, r8);
break;
case 0x51:
reg_offset = offsetof(struct pt_regs, r9);
break;
case 0x52:
reg_offset = offsetof(struct pt_regs, r10);
break;
case 0x53:
reg_offset = offsetof(struct pt_regs, r11);
break;
case 0x54:
reg_offset = offsetof(struct pt_regs, r12);
break;
case 0x55:
reg_offset = offsetof(struct pt_regs, r13);
break;
case 0x56:
reg_offset = offsetof(struct pt_regs, r14);
break;
case 0x57:
reg_offset = offsetof(struct pt_regs, r15);
break;
}
#else
return -ENOSYS;
#endif
} else {
switch (opc1) {
case 0x50:
reg_offset = offsetof(struct pt_regs, ax);
break;
case 0x51:
reg_offset = offsetof(struct pt_regs, cx);
break;
case 0x52:
reg_offset = offsetof(struct pt_regs, dx);
break;
case 0x53:
reg_offset = offsetof(struct pt_regs, bx);
break;
case 0x54:
reg_offset = offsetof(struct pt_regs, sp);
break;
case 0x55:
reg_offset = offsetof(struct pt_regs, bp);
break;
case 0x56:
reg_offset = offsetof(struct pt_regs, si);
break;
case 0x57:
reg_offset = offsetof(struct pt_regs, di);
break;
}
}
auprobe->push.reg_offset = reg_offset;
auprobe->push.ilen = insn->length;
auprobe->ops = &push_xol_ops;
return 0;
}
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
/**
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
* arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
* @auprobe: the probepoint information.
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
* @mm: the probed address space.
* @addr: virtual address at which to install the probepoint
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
* Return 0 on success or a -ve number on error.
*/
int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr)
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
{
struct insn insn;
u8 fix_ip_or_call = UPROBE_FIX_IP;
int ret;
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
ret = uprobe_init_insn(auprobe, &insn, is_64bit_mm(mm));
if (ret)
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
return ret;
ret = branch_setup_xol_ops(auprobe, &insn);
if (ret != -ENOSYS)
return ret;
uprobes/x86: Emulate push insns for uprobe on x86 Uprobe is a tracing mechanism for userspace programs. Typical uprobe will incur overhead of two traps. First trap is caused by replaced trap insn, and the second trap is to execute the original displaced insn in user space. To reduce the overhead, kernel provides hooks for architectures to emulate the original insn and skip the second trap. In x86, emulation is done for certain branch insns. This patch extends the emulation to "push <reg>" insns. These insns are typical in the beginning of the function. For example, bcc in https://github.com/iovisor/bcc repo provides tools to measure funclantency, detect memleak, etc. The tools will place uprobes in the beginning of function and possibly uretprobes at the end of function. This patch is able to reduce the trap overhead for uprobe from 2 to 1. Without this patch, uretprobe will typically incur three traps. With this patch, if the function starts with "push" insn, the number of traps can be reduced from 3 to 2. An experiment was conducted on two local VMs, fedora 26 64-bit VM and 32-bit VM, both 4 processors and 4GB memory, booted with latest tip repo (and this patch). The host is MacBook with intel i7 processor. The test program looks like: #include <stdio.h> #include <stdlib.h> #include <time.h> #include <sys/time.h> static void test() __attribute__((noinline)); void test() {} int main() { struct timeval start, end; gettimeofday(&start, NULL); for (int i = 0; i < 1000000; i++) { test(); } gettimeofday(&end, NULL); printf("%ld\n", ((end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec * 1000000 + start.tv_usec))); return 0; } The program is compiled without optimization, and the first insn for function "test" is "push %rbp". The host is relatively idle. Before the test run, the uprobe is inserted as below for uprobe: echo 'p <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable and for uretprobe: echo 'r <binary>:<test_func_offset>' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable Unit: microsecond(usec) per loop iteration x86_64 W/ this patch W/O this patch uprobe 1.55 3.1 uretprobe 2.0 3.6 x86_32 W/ this patch W/O this patch uprobe 1.41 3.5 uretprobe 1.75 4.0 You can see that this patch significantly reduced the overhead, 50% for uprobe and 44% for uretprobe on x86_64, and even more on x86_32. Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-team@fb.com Link: http://lkml.kernel.org/r/20171201001202.3706564-1-yhs@fb.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-01 00:12:02 +00:00
ret = push_setup_xol_ops(auprobe, &insn);
if (ret != -ENOSYS)
return ret;
/*
* Figure out which fixups default_post_xol_op() will need to perform,
* and annotate defparam->fixups accordingly.
*/
switch (OPCODE1(&insn)) {
case 0x9d: /* popf */
auprobe->defparam.fixups |= UPROBE_FIX_SETF;
break;
case 0xc3: /* ret or lret -- ip is correct */
case 0xcb:
case 0xc2:
case 0xca:
case 0xea: /* jmp absolute -- ip is correct */
fix_ip_or_call = 0;
break;
case 0x9a: /* call absolute - Fix return addr, not ip */
fix_ip_or_call = UPROBE_FIX_CALL;
break;
case 0xff:
switch (MODRM_REG(&insn)) {
case 2: case 3: /* call or lcall, indirect */
fix_ip_or_call = UPROBE_FIX_CALL;
break;
case 4: case 5: /* jmp or ljmp, indirect */
fix_ip_or_call = 0;
break;
}
fallthrough;
default:
riprel_analyze(auprobe, &insn);
}
auprobe->defparam.ilen = insn.length;
auprobe->defparam.fixups |= fix_ip_or_call;
auprobe->ops = &default_xol_ops;
uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-09 09:26:42 +00:00
return 0;
}
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
/*
* arch_uprobe_pre_xol - prepare to execute out of line.
* @auprobe: the probepoint information.
* @regs: reflects the saved user state of current task.
*/
int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
if (auprobe->ops->pre_xol) {
int err = auprobe->ops->pre_xol(auprobe, regs);
if (err)
return err;
}
regs->ip = utask->xol_vaddr;
utask->autask.saved_trap_nr = current->thread.trap_nr;
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
current->thread.trap_nr = UPROBE_TRAP_NR;
utask->autask.saved_tf = !!(regs->flags & X86_EFLAGS_TF);
regs->flags |= X86_EFLAGS_TF;
if (test_tsk_thread_flag(current, TIF_BLOCKSTEP))
set_task_blockstep(current, false);
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
return 0;
}
/*
* If xol insn itself traps and generates a signal(Say,
* SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
* instruction jumps back to its own address. It is assumed that anything
* like do_page_fault/do_trap/etc sets thread.trap_nr != -1.
*
* arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
* arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
* UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
*/
bool arch_uprobe_xol_was_trapped(struct task_struct *t)
{
if (t->thread.trap_nr != UPROBE_TRAP_NR)
return true;
return false;
}
/*
* Called after single-stepping. To avoid the SMP problems that can
* occur when we temporarily put back the original opcode to
* single-step, we single-stepped a copy of the instruction.
*
* This function prepares to resume execution after the single-step.
*/
int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
bool send_sigtrap = utask->autask.saved_tf;
int err = 0;
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
current->thread.trap_nr = utask->autask.saved_trap_nr;
if (auprobe->ops->post_xol) {
err = auprobe->ops->post_xol(auprobe, regs);
if (err) {
/*
* Restore ->ip for restart or post mortem analysis.
* ->post_xol() must not return -ERESTART unless this
* is really possible.
*/
regs->ip = utask->vaddr;
if (err == -ERESTART)
err = 0;
send_sigtrap = false;
}
}
/*
* arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP
* so we can get an extra SIGTRAP if we do not clear TF. We need
* to examine the opcode to make it right.
*/
if (send_sigtrap)
send_sig(SIGTRAP, current, 0);
if (!utask->autask.saved_tf)
regs->flags &= ~X86_EFLAGS_TF;
return err;
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
}
/* callback routine for handling exceptions. */
int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
{
struct die_args *args = data;
struct pt_regs *regs = args->regs;
int ret = NOTIFY_DONE;
/* We are only interested in userspace traps */
if (regs && !user_mode(regs))
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
return NOTIFY_DONE;
switch (val) {
case DIE_INT3:
if (uprobe_pre_sstep_notifier(regs))
ret = NOTIFY_STOP;
break;
case DIE_DEBUG:
if (uprobe_post_sstep_notifier(regs))
ret = NOTIFY_STOP;
default:
break;
}
return ret;
}
/*
* This function gets called when XOL instruction either gets trapped or
* the thread has a fatal signal. Reset the instruction pointer to its
* probed address for the potential restart or for post mortem analysis.
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
*/
void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
if (auprobe->ops->abort)
auprobe->ops->abort(auprobe, regs);
current->thread.trap_nr = utask->autask.saved_trap_nr;
regs->ip = utask->vaddr;
/* clear TF if it was set by us in arch_uprobe_pre_xol() */
if (!utask->autask.saved_tf)
regs->flags &= ~X86_EFLAGS_TF;
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
}
static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
{
if (auprobe->ops->emulate)
return auprobe->ops->emulate(auprobe, regs);
uprobes/core: Handle breakpoint and singlestep exceptions Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 18:00:11 +00:00
return false;
}
bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
bool ret = __skip_sstep(auprobe, regs);
if (ret && (regs->flags & X86_EFLAGS_TF))
send_sig(SIGTRAP, current, 0);
return ret;
}
unsigned long
arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs)
{
uprobes/x86: Fix detection of 32-bit user mode 32-bit processes running on a 64-bit kernel are not always detected correctly, causing the process to crash when uretprobes are installed. The reason for the crash is that in_ia32_syscall() is used to determine the process's mode, which only works correctly when called from a syscall. In the case of uretprobes, however, the function is called from a exception and always returns 'false' on a 64-bit kernel. In consequence this leads to corruption of the process's return address. Fix this by using user_64bit_mode() instead of in_ia32_syscall(), which is correct in any situation. [ tglx: Add a comment and the following historical info ] This should have been detected by the rename which happened in commit abfb9498ee13 ("x86/entry: Rename is_{ia32,x32}_task() to in_{ia32,x32}_syscall()") which states in the changelog: The is_ia32_task()/is_x32_task() function names are a big misnomer: they suggests that the compat-ness of a system call is a task property, which is not true, the compatness of a system call purely depends on how it was invoked through the system call layer. ..... and then it went and blindly renamed every call site. Sadly enough this was already mentioned here: 8faaed1b9f50 ("uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and arch_uretprobe_hijack_return_addr()") where the changelog says: TODO: is_ia32_task() is not what we actually want, TS_COMPAT does not necessarily mean 32bit. Fortunately syscall-like insns can't be probed so it actually works, but it would be better to rename and use is_ia32_frame(). and goes all the way back to: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Oh well. 7+ years until someone actually tried a uretprobe on a 32bit process on a 64bit kernel.... Fixes: 0326f5a94dde ("uprobes/core: Handle breakpoint and singlestep exceptions") Signed-off-by: Sebastian Mayr <me@sam.st> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Dmitry Safonov <dsafonov@virtuozzo.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190728152617.7308-1-me@sam.st
2019-07-28 15:26:17 +00:00
int rasize = sizeof_long(regs), nleft;
unsigned long orig_ret_vaddr = 0; /* clear high bits for 32-bit apps */
if (copy_from_user(&orig_ret_vaddr, (void __user *)regs->sp, rasize))
return -1;
/* check whether address has been already hijacked */
if (orig_ret_vaddr == trampoline_vaddr)
return orig_ret_vaddr;
nleft = copy_to_user((void __user *)regs->sp, &trampoline_vaddr, rasize);
if (likely(!nleft))
return orig_ret_vaddr;
if (nleft != rasize) {
pr_err("return address clobbered: pid=%d, %%sp=%#lx, %%ip=%#lx\n",
current->pid, regs->sp, regs->ip);
force_sig(SIGSEGV);
}
return -1;
}
bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
struct pt_regs *regs)
{
uprobes/x86: Make arch_uretprobe_is_alive(RP_CHECK_CALL) more clever The previous change documents that cleanup_return_instances() can't always detect the dead frames, the stack can grow. But there is one special case which imho worth fixing: arch_uretprobe_is_alive() can return true when the stack didn't actually grow, but the next "call" insn uses the already invalidated frame. Test-case: #include <stdio.h> #include <setjmp.h> jmp_buf jmp; int nr = 1024; void func_2(void) { if (--nr == 0) return; longjmp(jmp, 1); } void func_1(void) { setjmp(jmp); func_2(); } int main(void) { func_1(); return 0; } If you ret-probe func_1() and func_2() prepare_uretprobe() hits the MAX_URETPROBE_DEPTH limit and "return" from func_2() is not reported. When we know that the new call is not chained, we can do the more strict check. In this case "sp" points to the new ret-addr, so every frame which uses the same "sp" must be dead. The only complication is that arch_uretprobe_is_alive() needs to know was it chained or not, so we add the new RP_CHECK_CHAIN_CALL enum and change prepare_uretprobe() to pass RP_CHECK_CALL only if !chained. Note: arch_uretprobe_is_alive() could also re-read *sp and check if this word is still trampoline_vaddr. This could obviously improve the logic, but I would like to avoid another copy_from_user() especially in the case when we can't avoid the false "alive == T" positives. Tested-by: Pratyush Anand <panand@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134028.GA4786@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-07-21 13:40:28 +00:00
if (ctx == RP_CHECK_CALL) /* sp was just decremented by "call" insn */
return regs->sp < ret->stack;
else
return regs->sp <= ret->stack;
}