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 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 59config 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 73config SLUB_RCU_DEBUG 74 bool "Enable UAF detection in TYPESAFE_BY_RCU caches (for KASAN)" 75 depends on SLUB_DEBUG 76 # SLUB_RCU_DEBUG should build fine without KASAN, but is currently useless 77 # without KASAN, so mark it as a dependency of KASAN for now. 78 depends on KASAN 79 default KASAN_GENERIC || KASAN_SW_TAGS 80 help 81 Make SLAB_TYPESAFE_BY_RCU caches behave approximately as if the cache 82 was not marked as SLAB_TYPESAFE_BY_RCU and every caller used 83 kfree_rcu() instead. 84 85 This is intended for use in combination with KASAN, to enable KASAN to 86 detect use-after-free accesses in such caches. 87 (KFENCE is able to do that independent of this flag.) 88 89 This might degrade performance. 90 Unfortunately this also prevents a very specific bug pattern from 91 triggering (insufficient checks against an object being recycled 92 within the RCU grace period); so this option can be turned off even on 93 KASAN builds, in case you want to test for such a bug. 94 95 If you're using this for testing bugs / fuzzing and care about 96 catching all the bugs WAY more than performance, you might want to 97 also turn on CONFIG_RCU_STRICT_GRACE_PERIOD. 98 99 WARNING: 100 This is designed as a debugging feature, not a security feature. 101 Objects are sometimes recycled without RCU delay under memory pressure. 102 103 If unsure, say N. 104 105config PAGE_OWNER 106 bool "Track page owner" 107 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 108 select DEBUG_FS 109 select STACKTRACE 110 select STACKDEPOT 111 select PAGE_EXTENSION 112 help 113 This keeps track of what call chain is the owner of a page, may 114 help to find bare alloc_page(s) leaks. Even if you include this 115 feature on your build, it is disabled in default. You should pass 116 "page_owner=on" to boot parameter in order to enable it. Eats 117 a fair amount of memory if enabled. See tools/mm/page_owner_sort.c 118 for user-space helper. 119 120 If unsure, say N. 121 122config PAGE_TABLE_CHECK 123 bool "Check for invalid mappings in user page tables" 124 depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK 125 depends on EXCLUSIVE_SYSTEM_RAM 126 select PAGE_EXTENSION 127 help 128 Check that anonymous page is not being mapped twice with read write 129 permissions. Check that anonymous and file pages are not being 130 erroneously shared. Since the checking is performed at the time 131 entries are added and removed to user page tables, leaking, corruption 132 and double mapping problems are detected synchronously. 133 134 If unsure say "n". 135 136config PAGE_TABLE_CHECK_ENFORCED 137 bool "Enforce the page table checking by default" 138 depends on PAGE_TABLE_CHECK 139 help 140 Always enable page table checking. By default the page table checking 141 is disabled, and can be optionally enabled via page_table_check=on 142 kernel parameter. This config enforces that page table check is always 143 enabled. 144 145 If unsure say "n". 146 147config PAGE_PINNER 148 bool "Track page pinner" 149 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 150 select DEBUG_FS 151 select STACKTRACE 152 select STACKDEPOT 153 select PAGE_EXTENSION 154 help 155 This keeps track of what call chain is the pinner of a page, may 156 help to find page migration failures. Even if you include this 157 feature in your build, it is disabled by default. You should pass 158 "page_pinner=on" to boot parameter in order to enable it. Eats 159 a fair amount of memory if enabled. 160 161 If unsure, say N. 162 163config PAGE_POISONING 164 bool "Poison pages after freeing" 165 help 166 Fill the pages with poison patterns after free_pages() and verify 167 the patterns before alloc_pages. The filling of the memory helps 168 reduce the risk of information leaks from freed data. This does 169 have a potential performance impact if enabled with the 170 "page_poison=1" kernel boot option. 171 172 Note that "poison" here is not the same thing as the "HWPoison" 173 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 174 175 If you are only interested in sanitization of freed pages without 176 checking the poison pattern on alloc, you can boot the kernel with 177 "init_on_free=1" instead of enabling this. 178 179 If unsure, say N 180 181config DEBUG_PAGE_REF 182 bool "Enable tracepoint to track down page reference manipulation" 183 depends on DEBUG_KERNEL 184 depends on TRACEPOINTS 185 help 186 This is a feature to add tracepoint for tracking down page reference 187 manipulation. This tracking is useful to diagnose functional failure 188 due to migration failures caused by page reference mismatches. Be 189 careful when enabling this feature because it adds about 30 KB to the 190 kernel code. However the runtime performance overhead is virtually 191 nil until the tracepoints are actually enabled. 192 193config DEBUG_RODATA_TEST 194 bool "Testcase for the marking rodata read-only" 195 depends on STRICT_KERNEL_RWX 196 help 197 This option enables a testcase for the setting rodata read-only. 198 199config ARCH_HAS_DEBUG_WX 200 bool 201 202config DEBUG_WX 203 bool "Warn on W+X mappings at boot" 204 depends on ARCH_HAS_DEBUG_WX 205 depends on MMU 206 select PTDUMP_CORE 207 help 208 Generate a warning if any W+X mappings are found at boot. 209 210 This is useful for discovering cases where the kernel is leaving W+X 211 mappings after applying NX, as such mappings are a security risk. 212 213 Look for a message in dmesg output like this: 214 215 <arch>/mm: Checked W+X mappings: passed, no W+X pages found. 216 217 or like this, if the check failed: 218 219 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found. 220 221 Note that even if the check fails, your kernel is possibly 222 still fine, as W+X mappings are not a security hole in 223 themselves, what they do is that they make the exploitation 224 of other unfixed kernel bugs easier. 225 226 There is no runtime or memory usage effect of this option 227 once the kernel has booted up - it's a one time check. 228 229 If in doubt, say "Y". 230 231config GENERIC_PTDUMP 232 bool 233 234config PTDUMP_CORE 235 bool 236 237config PTDUMP_DEBUGFS 238 bool "Export kernel pagetable layout to userspace via debugfs" 239 depends on DEBUG_KERNEL 240 depends on DEBUG_FS 241 depends on GENERIC_PTDUMP 242 select PTDUMP_CORE 243 help 244 Say Y here if you want to show the kernel pagetable layout in a 245 debugfs file. This information is only useful for kernel developers 246 who are working in architecture specific areas of the kernel. 247 It is probably not a good idea to enable this feature in a production 248 kernel. 249 250 If in doubt, say N. 251 252config HAVE_DEBUG_KMEMLEAK 253 bool 254 255config DEBUG_KMEMLEAK 256 bool "Kernel memory leak detector" 257 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 258 select DEBUG_FS 259 select STACKTRACE if STACKTRACE_SUPPORT 260 select KALLSYMS 261 select CRC32 262 select STACKDEPOT 263 select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF 264 help 265 Say Y here if you want to enable the memory leak 266 detector. The memory allocation/freeing is traced in a way 267 similar to the Boehm's conservative garbage collector, the 268 difference being that the orphan objects are not freed but 269 only shown in /sys/kernel/debug/kmemleak. Enabling this 270 feature will introduce an overhead to memory 271 allocations. See Documentation/dev-tools/kmemleak.rst for more 272 details. 273 274 Enabling SLUB_DEBUG may increase the chances of finding leaks 275 due to the slab objects poisoning. 276 277 In order to access the kmemleak file, debugfs needs to be 278 mounted (usually at /sys/kernel/debug). 279 280config DEBUG_KMEMLEAK_MEM_POOL_SIZE 281 int "Kmemleak memory pool size" 282 depends on DEBUG_KMEMLEAK 283 range 200 1000000 284 default 16000 285 help 286 Kmemleak must track all the memory allocations to avoid 287 reporting false positives. Since memory may be allocated or 288 freed before kmemleak is fully initialised, use a static pool 289 of metadata objects to track such callbacks. After kmemleak is 290 fully initialised, this memory pool acts as an emergency one 291 if slab allocations fail. 292 293config DEBUG_KMEMLEAK_DEFAULT_OFF 294 bool "Default kmemleak to off" 295 depends on DEBUG_KMEMLEAK 296 help 297 Say Y here to disable kmemleak by default. It can then be enabled 298 on the command line via kmemleak=on. 299 300config DEBUG_KMEMLEAK_AUTO_SCAN 301 bool "Enable kmemleak auto scan thread on boot up" 302 default y 303 depends on DEBUG_KMEMLEAK 304 help 305 Depending on the cpu, kmemleak scan may be cpu intensive and can 306 stall user tasks at times. This option enables/disables automatic 307 kmemleak scan at boot up. 308 309 Say N here to disable kmemleak auto scan thread to stop automatic 310 scanning. Disabling this option disables automatic reporting of 311 memory leaks. 312 313 If unsure, say Y. 314 315config PER_VMA_LOCK_STATS 316 bool "Statistics for per-vma locks" 317 depends on PER_VMA_LOCK 318 help 319 Say Y here to enable success, retry and failure counters of page 320 faults handled under protection of per-vma locks. When enabled, the 321 counters are exposed in /proc/vmstat. This information is useful for 322 kernel developers to evaluate effectiveness of per-vma locks and to 323 identify pathological cases. Counting these events introduces a small 324 overhead in the page fault path. 325 326 If in doubt, say N. 327