# 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.

  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.