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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>
57 lines
1.9 KiB
C
57 lines
1.9 KiB
C
#ifndef _ASM_UPROBES_H
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#define _ASM_UPROBES_H
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/*
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* User-space Probes (UProbes) for x86
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2008-2011
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* Authors:
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* Srikar Dronamraju
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* Jim Keniston
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*/
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#include <linux/notifier.h>
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typedef u8 uprobe_opcode_t;
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#define MAX_UINSN_BYTES 16
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#define UPROBE_XOL_SLOT_BYTES 128 /* to keep it cache aligned */
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#define UPROBE_SWBP_INSN 0xcc
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#define UPROBE_SWBP_INSN_SIZE 1
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struct arch_uprobe {
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u16 fixups;
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u8 insn[MAX_UINSN_BYTES];
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#ifdef CONFIG_X86_64
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unsigned long rip_rela_target_address;
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#endif
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};
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struct arch_uprobe_task {
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unsigned long saved_trap_nr;
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#ifdef CONFIG_X86_64
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unsigned long saved_scratch_register;
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#endif
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};
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extern int arch_uprobe_analyze_insn(struct arch_uprobe *aup, struct mm_struct *mm);
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extern int arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs);
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extern int arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs);
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extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
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extern int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
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extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
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#endif /* _ASM_UPROBES_H */
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