mm/Kconfig.debug

   1 # SPDX-License-Identifier: GPL-2.0-only
   2 config PAGE_EXTENSION
   3         bool "Extend memmap on extra space for more information on page"
   4         help
   5           Extend memmap on extra space for more information on page. This
   6           could be used for debugging features that need to insert extra
   7           field for every page. This extension enables us to save memory
   8           by not allocating this extra memory according to boottime
   9           configuration.
  10
  11 config DEBUG_PAGEALLOC
  12         bool "Debug page memory allocations"
  13         depends on DEBUG_KERNEL
  14         depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
  15         select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
  16         help
  17           Unmap pages from the kernel linear mapping after free_pages().
  18           Depending on runtime enablement, this results in a small or large
  19           slowdown, but helps to find certain types of memory corruption.
  20
  21           Also, the state of page tracking structures is checked more often as
  22           pages are being allocated and freed, as unexpected state changes
  23           often happen for same reasons as memory corruption (e.g. double free,
  24           use-after-free). The error reports for these checks can be augmented
  25           with stack traces of last allocation and freeing of the page, when
  26           PAGE_OWNER is also selected and enabled on boot.
  27
  28           For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
  29           fill the pages with poison patterns after free_pages() and verify
  30           the patterns before alloc_pages(). Additionally, this option cannot
  31           be enabled in combination with hibernation as that would result in
  32           incorrect warnings of memory corruption after a resume because free
  33           pages are not saved to the suspend image.
  34
  35           By default this option will have a small overhead, e.g. by not
  36           allowing the kernel mapping to be backed by large pages on some
  37           architectures. Even bigger overhead comes when the debugging is
  38           enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc
  39           command line parameter.
  40
  41 config DEBUG_PAGEALLOC_ENABLE_DEFAULT
  42         bool "Enable debug page memory allocations by default?"
  43         depends on DEBUG_PAGEALLOC
  44         help
  45           Enable debug page memory allocations by default? This value
  46           can be overridden by debug_pagealloc=off|on.
  47
  48 config PAGE_OWNER
  49         bool "Track page owner"
  50         depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
  51         select DEBUG_FS
  52         select STACKTRACE
  53         select STACKDEPOT
  54         select PAGE_EXTENSION
  55         help
  56           This keeps track of what call chain is the owner of a page, may
  57           help to find bare alloc_page(s) leaks. Even if you include this
  58           feature on your build, it is disabled in default. You should pass
  59           "page_owner=on" to boot parameter in order to enable it. Eats
  60           a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
  61           for user-space helper.
  62
  63           If unsure, say N.
  64
  65 config PAGE_POISONING
  66         bool "Poison pages after freeing"
  67         help
  68           Fill the pages with poison patterns after free_pages() and verify
  69           the patterns before alloc_pages. The filling of the memory helps
  70           reduce the risk of information leaks from freed data. This does
  71           have a potential performance impact if enabled with the
  72           "page_poison=1" kernel boot option.
  73
  74           Note that "poison" here is not the same thing as the "HWPoison"
  75           for CONFIG_MEMORY_FAILURE. This is software poisoning only.
  76
  77           If you are only interested in sanitization of freed pages without
  78           checking the poison pattern on alloc, you can boot the kernel with
  79           "init_on_free=1" instead of enabling this.
  80
  81           If unsure, say N
  82
  83 config DEBUG_PAGE_REF
  84         bool "Enable tracepoint to track down page reference manipulation"
  85         depends on DEBUG_KERNEL
  86         depends on TRACEPOINTS
  87         help
  88           This is a feature to add tracepoint for tracking down page reference
  89           manipulation. This tracking is useful to diagnose functional failure
  90           due to migration failures caused by page reference mismatches.  Be
  91           careful when enabling this feature because it adds about 30 KB to the
  92           kernel code.  However the runtime performance overhead is virtually
  93           nil until the tracepoints are actually enabled.
  94
  95 config DEBUG_RODATA_TEST
  96     bool "Testcase for the marking rodata read-only"
  97     depends on STRICT_KERNEL_RWX
  98         help
  99       This option enables a testcase for the setting rodata read-only.
 100
 101 config ARCH_HAS_DEBUG_WX
 102         bool
 103
 104 config DEBUG_WX
 105         bool "Warn on W+X mappings at boot"
 106         depends on ARCH_HAS_DEBUG_WX
 107         depends on MMU
 108         select PTDUMP_CORE
 109         help
 110           Generate a warning if any W+X mappings are found at boot.
 111
 112           This is useful for discovering cases where the kernel is leaving W+X
 113           mappings after applying NX, as such mappings are a security risk.
 114
 115           Look for a message in dmesg output like this:
 116
 117             <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
 118
 119           or like this, if the check failed:
 120
 121             <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
 122
 123           Note that even if the check fails, your kernel is possibly
 124           still fine, as W+X mappings are not a security hole in
 125           themselves, what they do is that they make the exploitation
 126           of other unfixed kernel bugs easier.
 127
 128           There is no runtime or memory usage effect of this option
 129           once the kernel has booted up - it's a one time check.
 130
 131           If in doubt, say "Y".
 132
 133 config GENERIC_PTDUMP
 134         bool
 135
 136 config PTDUMP_CORE
 137         bool
 138
 139 config PTDUMP_DEBUGFS
 140         bool "Export kernel pagetable layout to userspace via debugfs"
 141         depends on DEBUG_KERNEL
 142         depends on DEBUG_FS
 143         depends on GENERIC_PTDUMP
 144         select PTDUMP_CORE
 145         help
 146           Say Y here if you want to show the kernel pagetable layout in a
 147           debugfs file. This information is only useful for kernel developers
 148           who are working in architecture specific areas of the kernel.
 149           It is probably not a good idea to enable this feature in a production
 150           kernel.
 151
 152           If in doubt, say N.