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 DEBUG_SLAB
  49         bool "Debug slab memory allocations"
  50         depends on DEBUG_KERNEL && SLAB
  51         help
  52           Say Y here to have the kernel do limited verification on memory
  53           allocation as well as poisoning memory on free to catch use of freed
  54           memory. This can make kmalloc/kfree-intensive workloads much slower.
  55
  56 config SLUB_DEBUG
  57         default y
  58         bool "Enable SLUB debugging support" if EXPERT
  59         depends on SLUB && SYSFS && !SLUB_TINY
  60         select STACKDEPOT if STACKTRACE_SUPPORT
  61         help
  62           SLUB has extensive debug support features. Disabling these can
  63           result in significant savings in code size. While /sys/kernel/slab
  64           will still exist (with SYSFS enabled), it will not provide e.g. cache
  65           validation.
  66
  67 config SLUB_DEBUG_ON
  68         bool "SLUB debugging on by default"
  69         depends on SLUB && SLUB_DEBUG
  70         select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT
  71         default n
  72         help
  73           Boot with debugging on by default. SLUB boots by default with
  74           the runtime debug capabilities switched off. Enabling this is
  75           equivalent to specifying the "slub_debug" parameter on boot.
  76           There is no support for more fine grained debug control like
  77           possible with slub_debug=xxx. SLUB debugging may be switched
  78           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
  79           "slub_debug=-".
  80
  81 config PAGE_OWNER
  82         bool "Track page owner"
  83         depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
  84         select DEBUG_FS
  85         select STACKTRACE
  86         select STACKDEPOT
  87         select PAGE_EXTENSION
  88         help
  89           This keeps track of what call chain is the owner of a page, may
  90           help to find bare alloc_page(s) leaks. Even if you include this
  91           feature on your build, it is disabled in default. You should pass
  92           "page_owner=on" to boot parameter in order to enable it. Eats
  93           a fair amount of memory if enabled. See tools/mm/page_owner_sort.c
  94           for user-space helper.
  95
  96           If unsure, say N.
  97
  98 config PAGE_TABLE_CHECK
  99         bool "Check for invalid mappings in user page tables"
 100         depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK
 101         depends on EXCLUSIVE_SYSTEM_RAM
 102         select PAGE_EXTENSION
 103         help
 104           Check that anonymous page is not being mapped twice with read write
 105           permissions. Check that anonymous and file pages are not being
 106           erroneously shared. Since the checking is performed at the time
 107           entries are added and removed to user page tables, leaking, corruption
 108           and double mapping problems are detected synchronously.
 109
 110           If unsure say "n".
 111
 112 config PAGE_TABLE_CHECK_ENFORCED
 113         bool "Enforce the page table checking by default"
 114         depends on PAGE_TABLE_CHECK
 115         help
 116           Always enable page table checking.  By default the page table checking
 117           is disabled, and can be optionally enabled via page_table_check=on
 118           kernel parameter. This config enforces that page table check is always
 119           enabled.
 120
 121           If unsure say "n".
 122
 123 config PAGE_POISONING
 124         bool "Poison pages after freeing"
 125         help
 126           Fill the pages with poison patterns after free_pages() and verify
 127           the patterns before alloc_pages. The filling of the memory helps
 128           reduce the risk of information leaks from freed data. This does
 129           have a potential performance impact if enabled with the
 130           "page_poison=1" kernel boot option.
 131
 132           Note that "poison" here is not the same thing as the "HWPoison"
 133           for CONFIG_MEMORY_FAILURE. This is software poisoning only.
 134
 135           If you are only interested in sanitization of freed pages without
 136           checking the poison pattern on alloc, you can boot the kernel with
 137           "init_on_free=1" instead of enabling this.
 138
 139           If unsure, say N
 140
 141 config DEBUG_PAGE_REF
 142         bool "Enable tracepoint to track down page reference manipulation"
 143         depends on DEBUG_KERNEL
 144         depends on TRACEPOINTS
 145         help
 146           This is a feature to add tracepoint for tracking down page reference
 147           manipulation. This tracking is useful to diagnose functional failure
 148           due to migration failures caused by page reference mismatches.  Be
 149           careful when enabling this feature because it adds about 30 KB to the
 150           kernel code.  However the runtime performance overhead is virtually
 151           nil until the tracepoints are actually enabled.
 152
 153 config DEBUG_RODATA_TEST
 154     bool "Testcase for the marking rodata read-only"
 155     depends on STRICT_KERNEL_RWX
 156         help
 157       This option enables a testcase for the setting rodata read-only.
 158
 159 config ARCH_HAS_DEBUG_WX
 160         bool
 161
 162 config DEBUG_WX
 163         bool "Warn on W+X mappings at boot"
 164         depends on ARCH_HAS_DEBUG_WX
 165         depends on MMU
 166         select PTDUMP_CORE
 167         help
 168           Generate a warning if any W+X mappings are found at boot.
 169
 170           This is useful for discovering cases where the kernel is leaving W+X
 171           mappings after applying NX, as such mappings are a security risk.
 172
 173           Look for a message in dmesg output like this:
 174
 175             <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
 176
 177           or like this, if the check failed:
 178
 179             <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
 180
 181           Note that even if the check fails, your kernel is possibly
 182           still fine, as W+X mappings are not a security hole in
 183           themselves, what they do is that they make the exploitation
 184           of other unfixed kernel bugs easier.
 185
 186           There is no runtime or memory usage effect of this option
 187           once the kernel has booted up - it's a one time check.
 188
 189           If in doubt, say "Y".
 190
 191 config GENERIC_PTDUMP
 192         bool
 193
 194 config PTDUMP_CORE
 195         bool
 196
 197 config PTDUMP_DEBUGFS
 198         bool "Export kernel pagetable layout to userspace via debugfs"
 199         depends on DEBUG_KERNEL
 200         depends on DEBUG_FS
 201         depends on GENERIC_PTDUMP
 202         select PTDUMP_CORE
 203         help
 204           Say Y here if you want to show the kernel pagetable layout in a
 205           debugfs file. This information is only useful for kernel developers
 206           who are working in architecture specific areas of the kernel.
 207           It is probably not a good idea to enable this feature in a production
 208           kernel.
 209
 210           If in doubt, say N.
 211
 212 config HAVE_DEBUG_KMEMLEAK
 213         bool
 214
 215 config DEBUG_KMEMLEAK
 216         bool "Kernel memory leak detector"
 217         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
 218         select DEBUG_FS
 219         select STACKTRACE if STACKTRACE_SUPPORT
 220         select KALLSYMS
 221         select CRC32
 222         select STACKDEPOT
 223         select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF
 224         help
 225           Say Y here if you want to enable the memory leak
 226           detector. The memory allocation/freeing is traced in a way
 227           similar to the Boehm's conservative garbage collector, the
 228           difference being that the orphan objects are not freed but
 229           only shown in /sys/kernel/debug/kmemleak. Enabling this
 230           feature will introduce an overhead to memory
 231           allocations. See Documentation/dev-tools/kmemleak.rst for more
 232           details.
 233
 234           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
 235           of finding leaks due to the slab objects poisoning.
 236
 237           In order to access the kmemleak file, debugfs needs to be
 238           mounted (usually at /sys/kernel/debug).
 239
 240 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
 241         int "Kmemleak memory pool size"
 242         depends on DEBUG_KMEMLEAK
 243         range 200 1000000
 244         default 16000
 245         help
 246           Kmemleak must track all the memory allocations to avoid
 247           reporting false positives. Since memory may be allocated or
 248           freed before kmemleak is fully initialised, use a static pool
 249           of metadata objects to track such callbacks. After kmemleak is
 250           fully initialised, this memory pool acts as an emergency one
 251           if slab allocations fail.
 252
 253 config DEBUG_KMEMLEAK_DEFAULT_OFF
 254         bool "Default kmemleak to off"
 255         depends on DEBUG_KMEMLEAK
 256         help
 257           Say Y here to disable kmemleak by default. It can then be enabled
 258           on the command line via kmemleak=on.
 259
 260 config DEBUG_KMEMLEAK_AUTO_SCAN
 261         bool "Enable kmemleak auto scan thread on boot up"
 262         default y
 263         depends on DEBUG_KMEMLEAK
 264         help
 265           Depending on the cpu, kmemleak scan may be cpu intensive and can
 266           stall user tasks at times. This option enables/disables automatic
 267           kmemleak scan at boot up.
 268
 269           Say N here to disable kmemleak auto scan thread to stop automatic
 270           scanning. Disabling this option disables automatic reporting of
 271           memory leaks.
 272
 273           If unsure, say Y.
 274
 275 config PER_VMA_LOCK_STATS
 276         bool "Statistics for per-vma locks"
 277         depends on PER_VMA_LOCK
 278         help
 279           Say Y here to enable success, retry and failure counters of page
 280           faults handled under protection of per-vma locks. When enabled, the
 281           counters are exposed in /proc/vmstat. This information is useful for
 282           kernel developers to evaluate effectiveness of per-vma locks and to
 283           identify pathological cases. Counting these events introduces a small
 284           overhead in the page fault path.
 285
 286           If in doubt, say N.