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 SLUB_DEBUG
  49         default y
  50         bool "Enable SLUB debugging support" if EXPERT
  51         depends on SYSFS && !SLUB_TINY
  52         select STACKDEPOT if STACKTRACE_SUPPORT
  53         help
  54           SLUB has extensive debug support features. Disabling these can
  55           result in significant savings in code size. While /sys/kernel/slab
  56           will still exist (with SYSFS enabled), it will not provide e.g. cache
  57           validation.
  58
  59 config SLUB_DEBUG_ON
  60         bool "SLUB debugging on by default"
  61         depends on SLUB_DEBUG
  62         select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT
  63         default n
  64         help
  65           Boot with debugging on by default. SLUB boots by default with
  66           the runtime debug capabilities switched off. Enabling this is
  67           equivalent to specifying the "slab_debug" parameter on boot.
  68           There is no support for more fine grained debug control like
  69           possible with slab_debug=xxx. SLUB debugging may be switched
  70           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
  71           "slab_debug=-".
  72
  73 config PAGE_OWNER
  74         bool "Track page owner"
  75         depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
  76         select DEBUG_FS
  77         select STACKTRACE
  78         select STACKDEPOT
  79         select PAGE_EXTENSION
  80         help
  81           This keeps track of what call chain is the owner of a page, may
  82           help to find bare alloc_page(s) leaks. Even if you include this
  83           feature on your build, it is disabled in default. You should pass
  84           "page_owner=on" to boot parameter in order to enable it. Eats
  85           a fair amount of memory if enabled. See tools/mm/page_owner_sort.c
  86           for user-space helper.
  87
  88           If unsure, say N.
  89
  90 config PAGE_TABLE_CHECK
  91         bool "Check for invalid mappings in user page tables"
  92         depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK
  93         depends on EXCLUSIVE_SYSTEM_RAM
  94         select PAGE_EXTENSION
  95         help
  96           Check that anonymous page is not being mapped twice with read write
  97           permissions. Check that anonymous and file pages are not being
  98           erroneously shared. Since the checking is performed at the time
  99           entries are added and removed to user page tables, leaking, corruption
 100           and double mapping problems are detected synchronously.
 101
 102           If unsure say "n".
 103
 104 config PAGE_TABLE_CHECK_ENFORCED
 105         bool "Enforce the page table checking by default"
 106         depends on PAGE_TABLE_CHECK
 107         help
 108           Always enable page table checking.  By default the page table checking
 109           is disabled, and can be optionally enabled via page_table_check=on
 110           kernel parameter. This config enforces that page table check is always
 111           enabled.
 112
 113           If unsure say "n".
 114
 115 config PAGE_POISONING
 116         bool "Poison pages after freeing"
 117         help
 118           Fill the pages with poison patterns after free_pages() and verify
 119           the patterns before alloc_pages. The filling of the memory helps
 120           reduce the risk of information leaks from freed data. This does
 121           have a potential performance impact if enabled with the
 122           "page_poison=1" kernel boot option.
 123
 124           Note that "poison" here is not the same thing as the "HWPoison"
 125           for CONFIG_MEMORY_FAILURE. This is software poisoning only.
 126
 127           If you are only interested in sanitization of freed pages without
 128           checking the poison pattern on alloc, you can boot the kernel with
 129           "init_on_free=1" instead of enabling this.
 130
 131           If unsure, say N
 132
 133 config DEBUG_PAGE_REF
 134         bool "Enable tracepoint to track down page reference manipulation"
 135         depends on DEBUG_KERNEL
 136         depends on TRACEPOINTS
 137         help
 138           This is a feature to add tracepoint for tracking down page reference
 139           manipulation. This tracking is useful to diagnose functional failure
 140           due to migration failures caused by page reference mismatches.  Be
 141           careful when enabling this feature because it adds about 30 KB to the
 142           kernel code.  However the runtime performance overhead is virtually
 143           nil until the tracepoints are actually enabled.
 144
 145 config DEBUG_RODATA_TEST
 146     bool "Testcase for the marking rodata read-only"
 147     depends on STRICT_KERNEL_RWX
 148         help
 149       This option enables a testcase for the setting rodata read-only.
 150
 151 config ARCH_HAS_DEBUG_WX
 152         bool
 153
 154 config DEBUG_WX
 155         bool "Warn on W+X mappings at boot"
 156         depends on ARCH_HAS_DEBUG_WX
 157         depends on MMU
 158         select PTDUMP_CORE
 159         help
 160           Generate a warning if any W+X mappings are found at boot.
 161
 162           This is useful for discovering cases where the kernel is leaving W+X
 163           mappings after applying NX, as such mappings are a security risk.
 164
 165           Look for a message in dmesg output like this:
 166
 167             <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
 168
 169           or like this, if the check failed:
 170
 171             <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
 172
 173           Note that even if the check fails, your kernel is possibly
 174           still fine, as W+X mappings are not a security hole in
 175           themselves, what they do is that they make the exploitation
 176           of other unfixed kernel bugs easier.
 177
 178           There is no runtime or memory usage effect of this option
 179           once the kernel has booted up - it's a one time check.
 180
 181           If in doubt, say "Y".
 182
 183 config GENERIC_PTDUMP
 184         bool
 185
 186 config PTDUMP_CORE
 187         bool
 188
 189 config PTDUMP_DEBUGFS
 190         bool "Export kernel pagetable layout to userspace via debugfs"
 191         depends on DEBUG_KERNEL
 192         depends on DEBUG_FS
 193         depends on GENERIC_PTDUMP
 194         select PTDUMP_CORE
 195         help
 196           Say Y here if you want to show the kernel pagetable layout in a
 197           debugfs file. This information is only useful for kernel developers
 198           who are working in architecture specific areas of the kernel.
 199           It is probably not a good idea to enable this feature in a production
 200           kernel.
 201
 202           If in doubt, say N.
 203
 204 config HAVE_DEBUG_KMEMLEAK
 205         bool
 206
 207 config DEBUG_KMEMLEAK
 208         bool "Kernel memory leak detector"
 209         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
 210         select DEBUG_FS
 211         select STACKTRACE if STACKTRACE_SUPPORT
 212         select KALLSYMS
 213         select CRC32
 214         select STACKDEPOT
 215         select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF
 216         help
 217           Say Y here if you want to enable the memory leak
 218           detector. The memory allocation/freeing is traced in a way
 219           similar to the Boehm's conservative garbage collector, the
 220           difference being that the orphan objects are not freed but
 221           only shown in /sys/kernel/debug/kmemleak. Enabling this
 222           feature will introduce an overhead to memory
 223           allocations. See Documentation/dev-tools/kmemleak.rst for more
 224           details.
 225
 226           Enabling SLUB_DEBUG may increase the chances of finding leaks
 227           due to the slab objects poisoning.
 228
 229           In order to access the kmemleak file, debugfs needs to be
 230           mounted (usually at /sys/kernel/debug).
 231
 232 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
 233         int "Kmemleak memory pool size"
 234         depends on DEBUG_KMEMLEAK
 235         range 200 1000000
 236         default 16000
 237         help
 238           Kmemleak must track all the memory allocations to avoid
 239           reporting false positives. Since memory may be allocated or
 240           freed before kmemleak is fully initialised, use a static pool
 241           of metadata objects to track such callbacks. After kmemleak is
 242           fully initialised, this memory pool acts as an emergency one
 243           if slab allocations fail.
 244
 245 config DEBUG_KMEMLEAK_DEFAULT_OFF
 246         bool "Default kmemleak to off"
 247         depends on DEBUG_KMEMLEAK
 248         help
 249           Say Y here to disable kmemleak by default. It can then be enabled
 250           on the command line via kmemleak=on.
 251
 252 config DEBUG_KMEMLEAK_AUTO_SCAN
 253         bool "Enable kmemleak auto scan thread on boot up"
 254         default y
 255         depends on DEBUG_KMEMLEAK
 256         help
 257           Depending on the cpu, kmemleak scan may be cpu intensive and can
 258           stall user tasks at times. This option enables/disables automatic
 259           kmemleak scan at boot up.
 260
 261           Say N here to disable kmemleak auto scan thread to stop automatic
 262           scanning. Disabling this option disables automatic reporting of
 263           memory leaks.
 264
 265           If unsure, say Y.
 266
 267 config PER_VMA_LOCK_STATS
 268         bool "Statistics for per-vma locks"
 269         depends on PER_VMA_LOCK
 270         help
 271           Say Y here to enable success, retry and failure counters of page
 272           faults handled under protection of per-vma locks. When enabled, the
 273           counters are exposed in /proc/vmstat. This information is useful for
 274           kernel developers to evaluate effectiveness of per-vma locks and to
 275           identify pathological cases. Counting these events introduces a small
 276           overhead in the page fault path.
 277
 278           If in doubt, say N.