linux_dsm_epyc7002/mm/Kconfig.debug
Vlastimil Babka 8974558f49 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+ 
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>
2019-09-24 15:54:08 -07:00

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# SPDX-License-Identifier: GPL-2.0-only
config PAGE_EXTENSION
bool "Extend memmap on extra space for more information on page"
---help---
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.
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,
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.
For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
fill the pages with poison patterns after free_pages() and verify
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"
select PAGE_POISONING_NO_SANITY if HIBERNATION
---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 unsure, say N
config PAGE_POISONING_NO_SANITY
depends on PAGE_POISONING
bool "Only poison, don't sanity check"
---help---
Skip the sanity checking on alloc, only fill the pages with
poison on free. This reduces some of the overhead of the
poisoning feature.
If you are only interested in sanitization, say Y. Otherwise
say N.
config PAGE_POISONING_ZERO
bool "Use zero for poisoning instead of debugging value"
depends on PAGE_POISONING
---help---
Instead of using the existing poison value, fill the pages with
zeros. This makes it harder to detect when errors are occurring
due to sanitization but the zeroing at free means that it is
no longer necessary to write zeros when GFP_ZERO is used on
allocation.
If unsure, say N
config DEBUG_PAGE_REF
bool "Enable tracepoint to track down page reference manipulation"
depends on DEBUG_KERNEL
depends on TRACEPOINTS
---help---
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.