# 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_PINNER
|
bool "Track page pinner"
|
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 pinner of a page, may
|
help to find page migration failures. Even if you include this
|
feature in your build, it is disabled by default. You should pass
|
"page_pinner=on" to boot parameter in order to enable it. Eats
|
a fair amount of memory if enabled.
|
|
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
|
|
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.
|
|
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".
|
|
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.
|
