mm/Kconfig.debug

   1 config PAGE_EXTENSION
   2         bool "Extend memmap on extra space for more information on page"
   3         ---help---
   4           Extend memmap on extra space for more information on page. This
   5           could be used for debugging features that need to insert extra
   6           field for every page. This extension enables us to save memory
   7           by not allocating this extra memory according to boottime
   8           configuration.
   9
  10 config DEBUG_PAGEALLOC
  11         bool "Debug page memory allocations"
  12         depends on DEBUG_KERNEL
  13         depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
  14         depends on !KMEMCHECK
  15         select PAGE_EXTENSION
  16         select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
  17         ---help---
  18           Unmap pages from the kernel linear mapping after free_pages().
  19           Depending on runtime enablement, this results in a small or large
  20           slowdown, but helps to find certain types of memory corruption.
  21
  22           For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
  23           fill the pages with poison patterns after free_pages() and verify
  24           the patterns before alloc_pages().  Additionally,
  25           this option cannot be enabled in combination with hibernation as
  26           that would result in incorrect warnings of memory corruption after
  27           a resume because free pages are not saved to the suspend image.
  28
  29           By default this option will have a small overhead, e.g. by not
  30           allowing the kernel mapping to be backed by large pages on some
  31           architectures. Even bigger overhead comes when the debugging is
  32           enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc
  33           command line parameter.
  34
  35 config DEBUG_PAGEALLOC_ENABLE_DEFAULT
  36         bool "Enable debug page memory allocations by default?"
  37         default n
  38         depends on DEBUG_PAGEALLOC
  39         ---help---
  40           Enable debug page memory allocations by default? This value
  41           can be overridden by debug_pagealloc=off|on.
  42
  43 config PAGE_POISONING
  44         bool "Poison pages after freeing"
  45         select PAGE_EXTENSION
  46         select PAGE_POISONING_NO_SANITY if HIBERNATION
  47         ---help---
  48           Fill the pages with poison patterns after free_pages() and verify
  49           the patterns before alloc_pages. The filling of the memory helps
  50           reduce the risk of information leaks from freed data. This does
  51           have a potential performance impact.
  52
  53           Note that "poison" here is not the same thing as the "HWPoison"
  54           for CONFIG_MEMORY_FAILURE. This is software poisoning only.
  55
  56           If unsure, say N
  57
  58 config PAGE_POISONING_NO_SANITY
  59         depends on PAGE_POISONING
  60         bool "Only poison, don't sanity check"
  61         ---help---
  62            Skip the sanity checking on alloc, only fill the pages with
  63            poison on free. This reduces some of the overhead of the
  64            poisoning feature.
  65
  66            If you are only interested in sanitization, say Y. Otherwise
  67            say N.
  68
  69 config PAGE_POISONING_ZERO
  70         bool "Use zero for poisoning instead of random data"
  71         depends on PAGE_POISONING
  72         ---help---
  73            Instead of using the existing poison value, fill the pages with
  74            zeros. This makes it harder to detect when errors are occurring
  75            due to sanitization but the zeroing at free means that it is
  76            no longer necessary to write zeros when GFP_ZERO is used on
  77            allocation.
  78
  79            If unsure, say N
  80         bool
  81
  82 config DEBUG_PAGE_REF
  83         bool "Enable tracepoint to track down page reference manipulation"
  84         depends on DEBUG_KERNEL
  85         depends on TRACEPOINTS
  86         ---help---
  87           This is a feature to add tracepoint for tracking down page reference
  88           manipulation. This tracking is useful to diagnose functional failure
  89           due to migration failures caused by page reference mismatches.  Be
  90           careful when enabling this feature because it adds about 30 KB to the
  91           kernel code.  However the runtime performance overhead is virtually
  92           nil until the tracepoints are actually enabled.