# SPDX-License-Identifier: GPL-2.0-only
config [31mCONFIG_PAGE_EXTENSION[0m
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 [31mCONFIG_DEBUG_PAGEALLOC[0m
bool "Debug page memory allocations"
depends on [31mCONFIG_DEBUG_KERNEL[0m
depends on ![31mCONFIG_HIBERNATION[0m || [31mCONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC[0m && ![31mCONFIG_PPC[0m && ![31mCONFIG_SPARC[0m
select [31mCONFIG_PAGE_POISONING[0m if ![31mCONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC[0m
---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
[31mCONFIG_PAGE_OWNER[0m is also selected and enabled on boot.
For architectures which don't enable [31mCONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC[0m,
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 [31mCONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT[0m or the debug_pagealloc
command line parameter.
config [31mCONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT[0m
bool "Enable debug page memory allocations by default?"
depends on [31mCONFIG_DEBUG_PAGEALLOC[0m
---help---
Enable debug page memory allocations by default? This value
can be overridden by debug_pagealloc=off|on.
config [31mCONFIG_PAGE_OWNER[0m
bool "Track page owner"
depends on [31mCONFIG_DEBUG_KERNEL[0m && [31mCONFIG_STACKTRACE_SUPPORT[0m
select [31mCONFIG_DEBUG_FS[0m
select [31mCONFIG_STACKTRACE[0m
select [31mCONFIG_STACKDEPOT[0m
select [31mCONFIG_PAGE_EXTENSION[0m
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 [31mCONFIG_PAGE_POISONING[0m
bool "Poison pages after freeing"
select [31mCONFIG_PAGE_POISONING_NO_SANITY[0m if [31mCONFIG_HIBERNATION[0m
---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 [31mCONFIG_PAGE_POISONING_NO_SANITY[0m
depends on [31mCONFIG_PAGE_POISONING[0m
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 [31mCONFIG_PAGE_POISONING_ZERO[0m
bool "Use zero for poisoning instead of debugging value"
depends on [31mCONFIG_PAGE_POISONING[0m
---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 [31mCONFIG_DEBUG_PAGE_REF[0m
bool "Enable tracepoint to track down page reference manipulation"
depends on [31mCONFIG_DEBUG_KERNEL[0m
depends on [31mCONFIG_TRACEPOINTS[0m
---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 [31mCONFIG_DEBUG_RODATA_TEST[0m
bool "Testcase for the marking rodata read-only"
depends on [31mCONFIG_STRICT_KERNEL_RWX[0m
---help---
This option enables a testcase for the setting rodata read-only.