linux-stable/mm/Kconfig.debug

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# SPDX-License-Identifier: GPL-2.0-only
mm/page_ext: resurrect struct page extending code for debugging When we debug something, we'd like to insert some information to every page. For this purpose, we sometimes modify struct page itself. But, this has drawbacks. First, it requires re-compile. This makes us hesitate to use the powerful debug feature so development process is slowed down. And, second, sometimes it is impossible to rebuild the kernel due to third party module dependency. At third, system behaviour would be largely different after re-compile, because it changes size of struct page greatly and this structure is accessed by every part of kernel. Keeping this as it is would be better to reproduce errornous situation. This feature is intended to overcome above mentioned problems. This feature allocates memory for extended data per page in certain place rather than the struct page itself. This memory can be accessed by the accessor functions provided by this code. During the boot process, it checks whether allocation of huge chunk of memory is needed or not. If not, it avoids allocating memory at all. With this advantage, we can include this feature into the kernel in default and can avoid rebuild and solve related problems. Until now, memcg uses this technique. But, now, memcg decides to embed their variable to struct page itself and it's code to extend struct page has been removed. I'd like to use this code to develop debug feature, so this patch resurrect it. To help these things to work well, this patch introduces two callbacks for clients. One is the need callback which is mandatory if user wants to avoid useless memory allocation at boot-time. The other is optional, init callback, which is used to do proper initialization after memory is allocated. Detailed explanation about purpose of these functions is in code comment. Please refer it. Others are completely same with previous extension code in memcg. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Dave Hansen <dave@sr71.net> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Jungsoo Son <jungsoo.son@lge.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 00:55:46 +00:00
config PAGE_EXTENSION
bool "Extend memmap on extra space for more information on page"
help
mm/page_ext: resurrect struct page extending code for debugging When we debug something, we'd like to insert some information to every page. For this purpose, we sometimes modify struct page itself. But, this has drawbacks. First, it requires re-compile. This makes us hesitate to use the powerful debug feature so development process is slowed down. And, second, sometimes it is impossible to rebuild the kernel due to third party module dependency. At third, system behaviour would be largely different after re-compile, because it changes size of struct page greatly and this structure is accessed by every part of kernel. Keeping this as it is would be better to reproduce errornous situation. This feature is intended to overcome above mentioned problems. This feature allocates memory for extended data per page in certain place rather than the struct page itself. This memory can be accessed by the accessor functions provided by this code. During the boot process, it checks whether allocation of huge chunk of memory is needed or not. If not, it avoids allocating memory at all. With this advantage, we can include this feature into the kernel in default and can avoid rebuild and solve related problems. Until now, memcg uses this technique. But, now, memcg decides to embed their variable to struct page itself and it's code to extend struct page has been removed. I'd like to use this code to develop debug feature, so this patch resurrect it. To help these things to work well, this patch introduces two callbacks for clients. One is the need callback which is mandatory if user wants to avoid useless memory allocation at boot-time. The other is optional, init callback, which is used to do proper initialization after memory is allocated. Detailed explanation about purpose of these functions is in code comment. Please refer it. Others are completely same with previous extension code in memcg. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Dave Hansen <dave@sr71.net> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Jungsoo Son <jungsoo.son@lge.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 00:55:46 +00:00
Extend memmap on extra space for more information on page. This
could be used for debugging features that need to insert extra
field for every page. This extension enables us to save memory
by not allocating this extra memory according to boottime
configuration.
config DEBUG_PAGEALLOC
bool "Debug page memory allocations"
depends on DEBUG_KERNEL
depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
help
Unmap pages from the kernel linear mapping after free_pages().
Depending on runtime enablement, this results in a small or large
slowdown, but helps to find certain types of memory corruption.
mm, page_alloc: more extensive free page checking with debug_pagealloc The page allocator checks struct pages for expected state (mapcount, flags etc) as pages are being allocated (check_new_page()) and freed (free_pages_check()) to provide some defense against errors in page allocator users. Prior commits 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP") and 4db7548ccbd9 ("mm, page_alloc: defer debugging checks of freed pages until a PCP drain") this has happened for order-0 pages as they were allocated from or freed to the per-cpu caches (pcplists). Since those are fast paths, the checks are now performed only when pages are moved between pcplists and global free lists. This however lowers the chances of catching errors soon enough. In order to increase the chances of the checks to catch errors, the kernel has to be rebuilt with CONFIG_DEBUG_VM, which also enables multiple other internal debug checks (VM_BUG_ON() etc), which is suboptimal when the goal is to catch errors in mm users, not in mm code itself. To catch some wrong users of the page allocator we have CONFIG_DEBUG_PAGEALLOC, which is designed to have virtually no overhead unless enabled at boot time. Memory corruptions when writing to freed pages have often the same underlying errors (use-after-free, double free) as corrupting the corresponding struct pages, so this existing debugging functionality is a good fit to extend by also perform struct page checks at least as often as if CONFIG_DEBUG_VM was enabled. Specifically, after this patch, when debug_pagealloc is enabled on boot, and CONFIG_DEBUG_VM disabled, pages are checked when allocated from or freed to the pcplists *in addition* to being moved between pcplists and free lists. When both debug_pagealloc and CONFIG_DEBUG_VM are enabled, pages are checked when being moved between pcplists and free lists *in addition* to when allocated from or freed to the pcplists. When debug_pagealloc is not enabled on boot, the overhead in fast paths should be virtually none thanks to the use of static key. Link: http://lkml.kernel.org/r/20190603143451.27353-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-12 03:55:09 +00:00
Also, the state of page tracking structures is checked more often as
pages are being allocated and freed, as unexpected state changes
often happen for same reasons as memory corruption (e.g. double free,
mm, page_owner, debug_pagealloc: save and dump freeing stack trace The debug_pagealloc functionality is useful to catch buggy page allocator users that cause e.g. use after free or double free. When page inconsistency is detected, debugging is often simpler by knowing the call stack of process that last allocated and freed the page. When page_owner is also enabled, we record the allocation stack trace, but not freeing. This patch therefore adds recording of freeing process stack trace to page owner info, if both page_owner and debug_pagealloc are configured and enabled. With only page_owner enabled, this info is not useful for the memory leak debugging use case. dump_page() is adjusted to print the info. An example result of calling __free_pages() twice may look like this (note the page last free stack trace): BUG: Bad page state in process bash pfn:13d8f8 page:ffffc31984f63e00 refcount:-1 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x1affff800000000() raw: 01affff800000000 dead000000000100 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 ffffffffffffffff 0000000000000000 page dumped because: nonzero _refcount page_owner tracks the page as freed page last allocated via order 0, migratetype Unmovable, gfp_mask 0xcc0(GFP_KERNEL) prep_new_page+0x143/0x150 get_page_from_freelist+0x289/0x380 __alloc_pages_nodemask+0x13c/0x2d0 khugepaged+0x6e/0xc10 kthread+0xf9/0x130 ret_from_fork+0x3a/0x50 page last free stack trace: free_pcp_prepare+0x134/0x1e0 free_unref_page+0x18/0x90 khugepaged+0x7b/0xc10 kthread+0xf9/0x130 ret_from_fork+0x3a/0x50 Modules linked in: CPU: 3 PID: 271 Comm: bash Not tainted 5.3.0-rc4-2.g07a1a73-default+ #57 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack+0x85/0xc0 bad_page.cold+0xba/0xbf rmqueue_pcplist.isra.0+0x6c5/0x6d0 rmqueue+0x2d/0x810 get_page_from_freelist+0x191/0x380 __alloc_pages_nodemask+0x13c/0x2d0 __get_free_pages+0xd/0x30 __pud_alloc+0x2c/0x110 copy_page_range+0x4f9/0x630 dup_mmap+0x362/0x480 dup_mm+0x68/0x110 copy_process+0x19e1/0x1b40 _do_fork+0x73/0x310 __x64_sys_clone+0x75/0x80 do_syscall_64+0x6e/0x1e0 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f10af854a10 ... Link: http://lkml.kernel.org/r/20190820131828.22684-5-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-09-23 22:34:42 +00:00
use-after-free). The error reports for these checks can be augmented
with stack traces of last allocation and freeing of the page, when
PAGE_OWNER is also selected and enabled on boot.
mm, page_alloc: more extensive free page checking with debug_pagealloc The page allocator checks struct pages for expected state (mapcount, flags etc) as pages are being allocated (check_new_page()) and freed (free_pages_check()) to provide some defense against errors in page allocator users. Prior commits 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP") and 4db7548ccbd9 ("mm, page_alloc: defer debugging checks of freed pages until a PCP drain") this has happened for order-0 pages as they were allocated from or freed to the per-cpu caches (pcplists). Since those are fast paths, the checks are now performed only when pages are moved between pcplists and global free lists. This however lowers the chances of catching errors soon enough. In order to increase the chances of the checks to catch errors, the kernel has to be rebuilt with CONFIG_DEBUG_VM, which also enables multiple other internal debug checks (VM_BUG_ON() etc), which is suboptimal when the goal is to catch errors in mm users, not in mm code itself. To catch some wrong users of the page allocator we have CONFIG_DEBUG_PAGEALLOC, which is designed to have virtually no overhead unless enabled at boot time. Memory corruptions when writing to freed pages have often the same underlying errors (use-after-free, double free) as corrupting the corresponding struct pages, so this existing debugging functionality is a good fit to extend by also perform struct page checks at least as often as if CONFIG_DEBUG_VM was enabled. Specifically, after this patch, when debug_pagealloc is enabled on boot, and CONFIG_DEBUG_VM disabled, pages are checked when allocated from or freed to the pcplists *in addition* to being moved between pcplists and free lists. When both debug_pagealloc and CONFIG_DEBUG_VM are enabled, pages are checked when being moved between pcplists and free lists *in addition* to when allocated from or freed to the pcplists. When debug_pagealloc is not enabled on boot, the overhead in fast paths should be virtually none thanks to the use of static key. Link: http://lkml.kernel.org/r/20190603143451.27353-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-12 03:55:09 +00:00
For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
fill the pages with poison patterns after free_pages() and verify
mm, page_alloc: more extensive free page checking with debug_pagealloc The page allocator checks struct pages for expected state (mapcount, flags etc) as pages are being allocated (check_new_page()) and freed (free_pages_check()) to provide some defense against errors in page allocator users. Prior commits 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP") and 4db7548ccbd9 ("mm, page_alloc: defer debugging checks of freed pages until a PCP drain") this has happened for order-0 pages as they were allocated from or freed to the per-cpu caches (pcplists). Since those are fast paths, the checks are now performed only when pages are moved between pcplists and global free lists. This however lowers the chances of catching errors soon enough. In order to increase the chances of the checks to catch errors, the kernel has to be rebuilt with CONFIG_DEBUG_VM, which also enables multiple other internal debug checks (VM_BUG_ON() etc), which is suboptimal when the goal is to catch errors in mm users, not in mm code itself. To catch some wrong users of the page allocator we have CONFIG_DEBUG_PAGEALLOC, which is designed to have virtually no overhead unless enabled at boot time. Memory corruptions when writing to freed pages have often the same underlying errors (use-after-free, double free) as corrupting the corresponding struct pages, so this existing debugging functionality is a good fit to extend by also perform struct page checks at least as often as if CONFIG_DEBUG_VM was enabled. Specifically, after this patch, when debug_pagealloc is enabled on boot, and CONFIG_DEBUG_VM disabled, pages are checked when allocated from or freed to the pcplists *in addition* to being moved between pcplists and free lists. When both debug_pagealloc and CONFIG_DEBUG_VM are enabled, pages are checked when being moved between pcplists and free lists *in addition* to when allocated from or freed to the pcplists. When debug_pagealloc is not enabled on boot, the overhead in fast paths should be virtually none thanks to the use of static key. Link: http://lkml.kernel.org/r/20190603143451.27353-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-12 03:55:09 +00:00
the patterns before alloc_pages(). Additionally, this option cannot
be enabled in combination with hibernation as that would result in
incorrect warnings of memory corruption after a resume because free
pages are not saved to the suspend image.
By default this option will have a small overhead, e.g. by not
allowing the kernel mapping to be backed by large pages on some
architectures. Even bigger overhead comes when the debugging is
enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc
command line parameter.
config DEBUG_PAGEALLOC_ENABLE_DEFAULT
bool "Enable debug page memory allocations by default?"
depends on DEBUG_PAGEALLOC
help
Enable debug page memory allocations by default? This value
can be overridden by debug_pagealloc=off|on.
config PAGE_OWNER
bool "Track page owner"
depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
select DEBUG_FS
select STACKTRACE
select STACKDEPOT
select PAGE_EXTENSION
help
This keeps track of what call chain is the owner of a page, may
help to find bare alloc_page(s) leaks. Even if you include this
feature on your build, it is disabled in default. You should pass
"page_owner=on" to boot parameter in order to enable it. Eats
a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
for user-space helper.
If unsure, say N.
config PAGE_POISONING
bool "Poison pages after freeing"
help
Fill the pages with poison patterns after free_pages() and verify
the patterns before alloc_pages. The filling of the memory helps
reduce the risk of information leaks from freed data. This does
have a potential performance impact if enabled with the
"page_poison=1" kernel boot option.
Note that "poison" here is not the same thing as the "HWPoison"
for CONFIG_MEMORY_FAILURE. This is software poisoning only.
If you are only interested in sanitization of freed pages without
checking the poison pattern on alloc, you can boot the kernel with
"init_on_free=1" instead of enabling this.
If unsure, say N
mm/page_ref: add tracepoint to track down page reference manipulation CMA allocation should be guaranteed to succeed by definition, but, unfortunately, it would be failed sometimes. It is hard to track down the problem, because it is related to page reference manipulation and we don't have any facility to analyze it. This patch adds tracepoints to track down page reference manipulation. With it, we can find exact reason of failure and can fix the problem. Following is an example of tracepoint output. (note: this example is stale version that printing flags as the number. Recent version will print it as human readable string.) <...>-9018 [004] 92.678375: page_ref_set: pfn=0x17ac9 flags=0x0 count=1 mapcount=0 mapping=(nil) mt=4 val=1 <...>-9018 [004] 92.678378: kernel_stack: => get_page_from_freelist (ffffffff81176659) => __alloc_pages_nodemask (ffffffff81176d22) => alloc_pages_vma (ffffffff811bf675) => handle_mm_fault (ffffffff8119e693) => __do_page_fault (ffffffff810631ea) => trace_do_page_fault (ffffffff81063543) => do_async_page_fault (ffffffff8105c40a) => async_page_fault (ffffffff817581d8) [snip] <...>-9018 [004] 92.678379: page_ref_mod: pfn=0x17ac9 flags=0x40048 count=2 mapcount=1 mapping=0xffff880015a78dc1 mt=4 val=1 [snip] ... ... <...>-9131 [001] 93.174468: test_pages_isolated: start_pfn=0x17800 end_pfn=0x17c00 fin_pfn=0x17ac9 ret=fail [snip] <...>-9018 [004] 93.174843: page_ref_mod_and_test: pfn=0x17ac9 flags=0x40068 count=0 mapcount=0 mapping=0xffff880015a78dc1 mt=4 val=-1 ret=1 => release_pages (ffffffff8117c9e4) => free_pages_and_swap_cache (ffffffff811b0697) => tlb_flush_mmu_free (ffffffff81199616) => tlb_finish_mmu (ffffffff8119a62c) => exit_mmap (ffffffff811a53f7) => mmput (ffffffff81073f47) => do_exit (ffffffff810794e9) => do_group_exit (ffffffff81079def) => SyS_exit_group (ffffffff81079e74) => entry_SYSCALL_64_fastpath (ffffffff817560b6) This output shows that problem comes from exit path. In exit path, to improve performance, pages are not freed immediately. They are gathered and processed by batch. During this process, migration cannot be possible and CMA allocation is failed. This problem is hard to find without this page reference tracepoint facility. Enabling this feature bloat kernel text 30 KB in my configuration. text data bss dec hex filename 12127327 2243616 1507328 15878271 f2487f vmlinux_disabled 12157208 2258880 1507328 15923416 f2f8d8 vmlinux_enabled Note that, due to header file dependency problem between mm.h and tracepoint.h, this feature has to open code the static key functions for tracepoints. Proposed by Steven Rostedt in following link. https://lkml.org/lkml/2015/12/9/699 [arnd@arndb.de: crypto/async_pq: use __free_page() instead of put_page()] [iamjoonsoo.kim@lge.com: fix build failure for xtensa] [akpm@linux-foundation.org: tweak Kconfig text, per Vlastimil] Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-17 21:19:29 +00:00
config DEBUG_PAGE_REF
bool "Enable tracepoint to track down page reference manipulation"
depends on DEBUG_KERNEL
depends on TRACEPOINTS
help
mm/page_ref: add tracepoint to track down page reference manipulation CMA allocation should be guaranteed to succeed by definition, but, unfortunately, it would be failed sometimes. It is hard to track down the problem, because it is related to page reference manipulation and we don't have any facility to analyze it. This patch adds tracepoints to track down page reference manipulation. With it, we can find exact reason of failure and can fix the problem. Following is an example of tracepoint output. (note: this example is stale version that printing flags as the number. Recent version will print it as human readable string.) <...>-9018 [004] 92.678375: page_ref_set: pfn=0x17ac9 flags=0x0 count=1 mapcount=0 mapping=(nil) mt=4 val=1 <...>-9018 [004] 92.678378: kernel_stack: => get_page_from_freelist (ffffffff81176659) => __alloc_pages_nodemask (ffffffff81176d22) => alloc_pages_vma (ffffffff811bf675) => handle_mm_fault (ffffffff8119e693) => __do_page_fault (ffffffff810631ea) => trace_do_page_fault (ffffffff81063543) => do_async_page_fault (ffffffff8105c40a) => async_page_fault (ffffffff817581d8) [snip] <...>-9018 [004] 92.678379: page_ref_mod: pfn=0x17ac9 flags=0x40048 count=2 mapcount=1 mapping=0xffff880015a78dc1 mt=4 val=1 [snip] ... ... <...>-9131 [001] 93.174468: test_pages_isolated: start_pfn=0x17800 end_pfn=0x17c00 fin_pfn=0x17ac9 ret=fail [snip] <...>-9018 [004] 93.174843: page_ref_mod_and_test: pfn=0x17ac9 flags=0x40068 count=0 mapcount=0 mapping=0xffff880015a78dc1 mt=4 val=-1 ret=1 => release_pages (ffffffff8117c9e4) => free_pages_and_swap_cache (ffffffff811b0697) => tlb_flush_mmu_free (ffffffff81199616) => tlb_finish_mmu (ffffffff8119a62c) => exit_mmap (ffffffff811a53f7) => mmput (ffffffff81073f47) => do_exit (ffffffff810794e9) => do_group_exit (ffffffff81079def) => SyS_exit_group (ffffffff81079e74) => entry_SYSCALL_64_fastpath (ffffffff817560b6) This output shows that problem comes from exit path. In exit path, to improve performance, pages are not freed immediately. They are gathered and processed by batch. During this process, migration cannot be possible and CMA allocation is failed. This problem is hard to find without this page reference tracepoint facility. Enabling this feature bloat kernel text 30 KB in my configuration. text data bss dec hex filename 12127327 2243616 1507328 15878271 f2487f vmlinux_disabled 12157208 2258880 1507328 15923416 f2f8d8 vmlinux_enabled Note that, due to header file dependency problem between mm.h and tracepoint.h, this feature has to open code the static key functions for tracepoints. Proposed by Steven Rostedt in following link. https://lkml.org/lkml/2015/12/9/699 [arnd@arndb.de: crypto/async_pq: use __free_page() instead of put_page()] [iamjoonsoo.kim@lge.com: fix build failure for xtensa] [akpm@linux-foundation.org: tweak Kconfig text, per Vlastimil] Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-17 21:19:29 +00:00
This is a feature to add tracepoint for tracking down page reference
manipulation. This tracking is useful to diagnose functional failure
due to migration failures caused by page reference mismatches. Be
careful when enabling this feature because it adds about 30 KB to the
kernel code. However the runtime performance overhead is virtually
nil until the tracepoints are actually enabled.
config DEBUG_RODATA_TEST
bool "Testcase for the marking rodata read-only"
depends on STRICT_KERNEL_RWX
help
This option enables a testcase for the setting rodata read-only.
mm: add generic ptdump Add a generic version of page table dumping that architectures can opt-in to. Link: http://lkml.kernel.org/r/20191218162402.45610-20-steven.price@arm.com Signed-off-by: Steven Price <steven.price@arm.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexandre Ghiti <alex@ghiti.fr> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David S. Miller <davem@davemloft.net> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Hogan <jhogan@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Liang, Kan" <kan.liang@linux.intel.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Burton <paul.burton@mips.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Will Deacon <will@kernel.org> Cc: Zong Li <zong.li@sifive.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-02-04 01:36:20 +00:00
mm: add DEBUG_WX support Patch series "Extract DEBUG_WX to shared use". Some architectures support DEBUG_WX function, it's verbatim from each others, so extract to mm/Kconfig.debug for shared use. PPC and ARM ports don't support generic page dumper yet, so we only refine x86 and arm64 port in this patch series. For RISC-V port, the DEBUG_WX support depends on other patches which be merged already: - RISC-V page table dumper - Support strict kernel memory permissions for security This patch (of 4): Some architectures support DEBUG_WX function, it's verbatim from each others. Extract to mm/Kconfig.debug for shared use. [akpm@linux-foundation.org: reword text, per Will Deacon & Zong Li] Link: http://lkml.kernel.org/r/20200427194245.oxRJKj3fn%25akpm@linux-foundation.org [zong.li@sifive.com: remove the specific name of arm64] Link: http://lkml.kernel.org/r/3a6a92ecedc54e1d0fc941398e63d504c2cd5611.1589178399.git.zong.li@sifive.com [zong.li@sifive.com: add MMU dependency for DEBUG_WX] Link: http://lkml.kernel.org/r/4a674ac7863ff39ca91847b10e51209771f99416.1589178399.git.zong.li@sifive.com Suggested-by: Palmer Dabbelt <palmer@dabbelt.com> Signed-off-by: Zong Li <zong.li@sifive.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Link: http://lkml.kernel.org/r/cover.1587455584.git.zong.li@sifive.com Link: http://lkml.kernel.org/r/23980cd0f0e5d79e24a92169116407c75bcc650d.1587455584.git.zong.li@sifive.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-03 23:03:52 +00:00
config ARCH_HAS_DEBUG_WX
bool
config DEBUG_WX
bool "Warn on W+X mappings at boot"
depends on ARCH_HAS_DEBUG_WX
depends on MMU
select PTDUMP_CORE
help
Generate a warning if any W+X mappings are found at boot.
This is useful for discovering cases where the kernel is leaving W+X
mappings after applying NX, as such mappings are a security risk.
Look for a message in dmesg output like this:
<arch>/mm: Checked W+X mappings: passed, no W+X pages found.
or like this, if the check failed:
<arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
Note that even if the check fails, your kernel is possibly
still fine, as W+X mappings are not a security hole in
themselves, what they do is that they make the exploitation
of other unfixed kernel bugs easier.
There is no runtime or memory usage effect of this option
once the kernel has booted up - it's a one time check.
If in doubt, say "Y".
mm: add generic ptdump Add a generic version of page table dumping that architectures can opt-in to. Link: http://lkml.kernel.org/r/20191218162402.45610-20-steven.price@arm.com Signed-off-by: Steven Price <steven.price@arm.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexandre Ghiti <alex@ghiti.fr> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David S. Miller <davem@davemloft.net> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Hogan <jhogan@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Liang, Kan" <kan.liang@linux.intel.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Burton <paul.burton@mips.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Will Deacon <will@kernel.org> Cc: Zong Li <zong.li@sifive.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-02-04 01:36:20 +00:00
config GENERIC_PTDUMP
bool
config PTDUMP_CORE
bool
config PTDUMP_DEBUGFS
bool "Export kernel pagetable layout to userspace via debugfs"
depends on DEBUG_KERNEL
depends on DEBUG_FS
depends on GENERIC_PTDUMP
select PTDUMP_CORE
help
Say Y here if you want to show the kernel pagetable layout in a
debugfs file. This information is only useful for kernel developers
who are working in architecture specific areas of the kernel.
It is probably not a good idea to enable this feature in a production
kernel.
If in doubt, say N.