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. This also disables
  64           SLUB sysfs support. /sys/slab will not exist and there will be
  65           no support for cache validation etc.
  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         select PAGE_EXTENSION
 102         help
 103           Check that anonymous page is not being mapped twice with read write
 104           permissions. Check that anonymous and file pages are not being
 105           erroneously shared. Since the checking is performed at the time
 106           entries are added and removed to user page tables, leaking, corruption
 107           and double mapping problems are detected synchronously.
 108
 109           If unsure say "n".
 110
 111 config PAGE_TABLE_CHECK_ENFORCED
 112         bool "Enforce the page table checking by default"
 113         depends on PAGE_TABLE_CHECK
 114         help
 115           Always enable page table checking.  By default the page table checking
 116           is disabled, and can be optionally enabled via page_table_check=on
 117           kernel parameter. This config enforces that page table check is always
 118           enabled.
 119
 120           If unsure say "n".
 121
 122 config PAGE_POISONING
 123         bool "Poison pages after freeing"
 124         help
 125           Fill the pages with poison patterns after free_pages() and verify
 126           the patterns before alloc_pages. The filling of the memory helps
 127           reduce the risk of information leaks from freed data. This does
 128           have a potential performance impact if enabled with the
 129           "page_poison=1" kernel boot option.
 130
 131           Note that "poison" here is not the same thing as the "HWPoison"
 132           for CONFIG_MEMORY_FAILURE. This is software poisoning only.
 133
 134           If you are only interested in sanitization of freed pages without
 135           checking the poison pattern on alloc, you can boot the kernel with
 136           "init_on_free=1" instead of enabling this.
 137
 138           If unsure, say N
 139
 140 config DEBUG_PAGE_REF
 141         bool "Enable tracepoint to track down page reference manipulation"
 142         depends on DEBUG_KERNEL
 143         depends on TRACEPOINTS
 144         help
 145           This is a feature to add tracepoint for tracking down page reference
 146           manipulation. This tracking is useful to diagnose functional failure
 147           due to migration failures caused by page reference mismatches.  Be
 148           careful when enabling this feature because it adds about 30 KB to the
 149           kernel code.  However the runtime performance overhead is virtually
 150           nil until the tracepoints are actually enabled.
 151
 152 config DEBUG_RODATA_TEST
 153     bool "Testcase for the marking rodata read-only"
 154     depends on STRICT_KERNEL_RWX
 155         help
 156       This option enables a testcase for the setting rodata read-only.
 157
 158 config ARCH_HAS_DEBUG_WX
 159         bool
 160
 161 config DEBUG_WX
 162         bool "Warn on W+X mappings at boot"
 163         depends on ARCH_HAS_DEBUG_WX
 164         depends on MMU
 165         select PTDUMP_CORE
 166         help
 167           Generate a warning if any W+X mappings are found at boot.
 168
 169           This is useful for discovering cases where the kernel is leaving W+X
 170           mappings after applying NX, as such mappings are a security risk.
 171
 172           Look for a message in dmesg output like this:
 173
 174             <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
 175
 176           or like this, if the check failed:
 177
 178             <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
 179
 180           Note that even if the check fails, your kernel is possibly
 181           still fine, as W+X mappings are not a security hole in
 182           themselves, what they do is that they make the exploitation
 183           of other unfixed kernel bugs easier.
 184
 185           There is no runtime or memory usage effect of this option
 186           once the kernel has booted up - it's a one time check.
 187
 188           If in doubt, say "Y".
 189
 190 config GENERIC_PTDUMP
 191         bool
 192
 193 config PTDUMP_CORE
 194         bool
 195
 196 config PTDUMP_DEBUGFS
 197         bool "Export kernel pagetable layout to userspace via debugfs"
 198         depends on DEBUG_KERNEL
 199         depends on DEBUG_FS
 200         depends on GENERIC_PTDUMP
 201         select PTDUMP_CORE
 202         help
 203           Say Y here if you want to show the kernel pagetable layout in a
 204           debugfs file. This information is only useful for kernel developers
 205           who are working in architecture specific areas of the kernel.
 206           It is probably not a good idea to enable this feature in a production
 207           kernel.
 208
 209           If in doubt, say N.
 210
 211 config HAVE_DEBUG_KMEMLEAK
 212         bool
 213
 214 config DEBUG_KMEMLEAK
 215         bool "Kernel memory leak detector"
 216         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
 217         select DEBUG_FS
 218         select STACKTRACE if STACKTRACE_SUPPORT
 219         select KALLSYMS
 220         select CRC32
 221         select STACKDEPOT
 222         select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF
 223         help
 224           Say Y here if you want to enable the memory leak
 225           detector. The memory allocation/freeing is traced in a way
 226           similar to the Boehm's conservative garbage collector, the
 227           difference being that the orphan objects are not freed but
 228           only shown in /sys/kernel/debug/kmemleak. Enabling this
 229           feature will introduce an overhead to memory
 230           allocations. See Documentation/dev-tools/kmemleak.rst for more
 231           details.
 232
 233           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
 234           of finding leaks due to the slab objects poisoning.
 235
 236           In order to access the kmemleak file, debugfs needs to be
 237           mounted (usually at /sys/kernel/debug).
 238
 239 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
 240         int "Kmemleak memory pool size"
 241         depends on DEBUG_KMEMLEAK
 242         range 200 1000000
 243         default 16000
 244         help
 245           Kmemleak must track all the memory allocations to avoid
 246           reporting false positives. Since memory may be allocated or
 247           freed before kmemleak is fully initialised, use a static pool
 248           of metadata objects to track such callbacks. After kmemleak is
 249           fully initialised, this memory pool acts as an emergency one
 250           if slab allocations fail.
 251
 252 config DEBUG_KMEMLEAK_TEST
 253         tristate "Simple test for the kernel memory leak detector"
 254         depends on DEBUG_KMEMLEAK && m
 255         help
 256           This option enables a module that explicitly leaks memory.
 257
 258           If unsure, say N.
 259
 260 config DEBUG_KMEMLEAK_DEFAULT_OFF
 261         bool "Default kmemleak to off"
 262         depends on DEBUG_KMEMLEAK
 263         help
 264           Say Y here to disable kmemleak by default. It can then be enabled
 265           on the command line via kmemleak=on.
 266
 267 config DEBUG_KMEMLEAK_AUTO_SCAN
 268         bool "Enable kmemleak auto scan thread on boot up"
 269         default y
 270         depends on DEBUG_KMEMLEAK
 271         help
 272           Depending on the cpu, kmemleak scan may be cpu intensive and can
 273           stall user tasks at times. This option enables/disables automatic
 274           kmemleak scan at boot up.
 275
 276           Say N here to disable kmemleak auto scan thread to stop automatic
 277           scanning. Disabling this option disables automatic reporting of
 278           memory leaks.
 279
 280           If unsure, say Y.
 281