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Linux/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            Enabling page poisoning with this option will disable hibernation
 80 
 81            If unsure, say N
 82         bool
 83 
 84 config DEBUG_PAGE_REF
 85         bool "Enable tracepoint to track down page reference manipulation"
 86         depends on DEBUG_KERNEL
 87         depends on TRACEPOINTS
 88         ---help---
 89           This is a feature to add tracepoint for tracking down page reference
 90           manipulation. This tracking is useful to diagnose functional failure
 91           due to migration failures caused by page reference mismatches.  Be
 92           careful when enabling this feature because it adds about 30 KB to the
 93           kernel code.  However the runtime performance overhead is virtually
 94           nil until the tracepoints are actually enabled.

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