linux/mm/Kconfig.debug
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   1# SPDX-License-Identifier: GPL-2.0-only
   2config 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
  11config 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
  41config 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
  48config 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
  65config 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
  83config 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
  95config 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
 101config ARCH_HAS_DEBUG_WX
 102        bool
 103
 104config 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
 133config GENERIC_PTDUMP
 134        bool
 135
 136config PTDUMP_CORE
 137        bool
 138
 139config 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.
 153
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