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         select PAGE_POISONING_NO_SANITY if HIBERNATION
  68         help
  69           Fill the pages with poison patterns after free_pages() and verify
  70           the patterns before alloc_pages. The filling of the memory helps
  71           reduce the risk of information leaks from freed data. This does
  72           have a potential performance impact if enabled with the
  73           "page_poison=1" kernel boot option.
  74
  75           Note that "poison" here is not the same thing as the "HWPoison"
  76           for CONFIG_MEMORY_FAILURE. This is software poisoning only.
  77
  78           If unsure, say N
  79
  80 config PAGE_POISONING_NO_SANITY
  81         depends on PAGE_POISONING
  82         bool "Only poison, don't sanity check"
  83         help
  84            Skip the sanity checking on alloc, only fill the pages with
  85            poison on free. This reduces some of the overhead of the
  86            poisoning feature.
  87
  88            If you are only interested in sanitization, say Y. Otherwise
  89            say N.
  90
  91 config PAGE_POISONING_ZERO
  92         bool "Use zero for poisoning instead of debugging value"
  93         depends on PAGE_POISONING
  94         help
  95            Instead of using the existing poison value, fill the pages with
  96            zeros. This makes it harder to detect when errors are occurring
  97            due to sanitization but the zeroing at free means that it is
  98            no longer necessary to write zeros when GFP_ZERO is used on
  99            allocation.
 100
 101            If unsure, say N
 102
 103 config DEBUG_PAGE_REF
 104         bool "Enable tracepoint to track down page reference manipulation"
 105         depends on DEBUG_KERNEL
 106         depends on TRACEPOINTS
 107         help
 108           This is a feature to add tracepoint for tracking down page reference
 109           manipulation. This tracking is useful to diagnose functional failure
 110           due to migration failures caused by page reference mismatches.  Be
 111           careful when enabling this feature because it adds about 30 KB to the
 112           kernel code.  However the runtime performance overhead is virtually
 113           nil until the tracepoints are actually enabled.
 114
 115 config DEBUG_RODATA_TEST
 116     bool "Testcase for the marking rodata read-only"
 117     depends on STRICT_KERNEL_RWX
 118         help
 119       This option enables a testcase for the setting rodata read-only.
 120
 121 config ARCH_HAS_DEBUG_WX
 122         bool
 123
 124 config DEBUG_WX
 125         bool "Warn on W+X mappings at boot"
 126         depends on ARCH_HAS_DEBUG_WX
 127         depends on MMU
 128         select PTDUMP_CORE
 129         help
 130           Generate a warning if any W+X mappings are found at boot.
 131
 132           This is useful for discovering cases where the kernel is leaving W+X
 133           mappings after applying NX, as such mappings are a security risk.
 134
 135           Look for a message in dmesg output like this:
 136
 137             <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
 138
 139           or like this, if the check failed:
 140
 141             <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
 142
 143           Note that even if the check fails, your kernel is possibly
 144           still fine, as W+X mappings are not a security hole in
 145           themselves, what they do is that they make the exploitation
 146           of other unfixed kernel bugs easier.
 147
 148           There is no runtime or memory usage effect of this option
 149           once the kernel has booted up - it's a one time check.
 150
 151           If in doubt, say "Y".
 152
 153 config GENERIC_PTDUMP
 154         bool
 155
 156 config PTDUMP_CORE
 157         bool
 158
 159 config PTDUMP_DEBUGFS
 160         bool "Export kernel pagetable layout to userspace via debugfs"
 161         depends on DEBUG_KERNEL
 162         depends on DEBUG_FS
 163         depends on GENERIC_PTDUMP
 164         select PTDUMP_CORE
 165         help
 166           Say Y here if you want to show the kernel pagetable layout in a
 167           debugfs file. This information is only useful for kernel developers
 168           who are working in architecture specific areas of the kernel.
 169           It is probably not a good idea to enable this feature in a production
 170           kernel.
 171
 172           If in doubt, say N.