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 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. 104 105 config 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. 121 122 config 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". 135 136 config 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". 146 147 config PAGE_POISONING 148 bool "Poison pages after freeing" 149 help 150 Fill the pages with poison patterns after free_pages() and verify 151 the patterns before alloc_pages. The filling of the memory helps 152 reduce the risk of information leaks from freed data. This does 153 have a potential performance impact if enabled with the 154 "page_poison=1" kernel boot option. 155 156 Note that "poison" here is not the same thing as the "HWPoison" 157 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 158 159 If you are only interested in sanitization of freed pages without 160 checking the poison pattern on alloc, you can boot the kernel with 161 "init_on_free=1" instead of enabling this. 162 163 If unsure, say N 164 165 config DEBUG_PAGE_REF 166 bool "Enable tracepoint to track down page reference manipulation" 167 depends on DEBUG_KERNEL 168 depends on TRACEPOINTS 169 help 170 This is a feature to add tracepoint for tracking down page reference 171 manipulation. This tracking is useful to diagnose functional failure 172 due to migration failures caused by page reference mismatches. Be 173 careful when enabling this feature because it adds about 30 KB to the 174 kernel code. However the runtime performance overhead is virtually 175 nil until the tracepoints are actually enabled. 176 177 config DEBUG_RODATA_TEST 178 bool "Testcase for the marking rodata read-only" 179 depends on STRICT_KERNEL_RWX 180 help 181 This option enables a testcase for the setting rodata read-only. 182 183 config ARCH_HAS_DEBUG_WX 184 bool 185 186 config DEBUG_WX 187 bool "Warn on W+X mappings at boot" 188 depends on ARCH_HAS_DEBUG_WX 189 depends on MMU 190 select PTDUMP_CORE 191 help 192 Generate a warning if any W+X mappings are found at boot. 193 194 This is useful for discovering cases where the kernel is leaving W+X 195 mappings after applying NX, as such mappings are a security risk. 196 197 Look for a message in dmesg output like this: 198 199 <arch>/mm: Checked W+X mappings: passed, no W+X pages found. 200 201 or like this, if the check failed: 202 203 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found. 204 205 Note that even if the check fails, your kernel is possibly 206 still fine, as W+X mappings are not a security hole in 207 themselves, what they do is that they make the exploitation 208 of other unfixed kernel bugs easier. 209 210 There is no runtime or memory usage effect of this option 211 once the kernel has booted up - it's a one time check. 212 213 If in doubt, say "Y". 214 215 config GENERIC_PTDUMP 216 bool 217 218 config PTDUMP_CORE 219 bool 220 221 config PTDUMP_DEBUGFS 222 bool "Export kernel pagetable layout to userspace via debugfs" 223 depends on DEBUG_KERNEL 224 depends on DEBUG_FS 225 depends on GENERIC_PTDUMP 226 select PTDUMP_CORE 227 help 228 Say Y here if you want to show the kernel pagetable layout in a 229 debugfs file. This information is only useful for kernel developers 230 who are working in architecture specific areas of the kernel. 231 It is probably not a good idea to enable this feature in a production 232 kernel. 233 234 If in doubt, say N. 235 236 config HAVE_DEBUG_KMEMLEAK 237 bool 238 239 config DEBUG_KMEMLEAK 240 bool "Kernel memory leak detector" 241 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 242 select DEBUG_FS 243 select STACKTRACE if STACKTRACE_SUPPORT 244 select KALLSYMS 245 select CRC32 246 select STACKDEPOT 247 select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF 248 help 249 Say Y here if you want to enable the memory leak 250 detector. The memory allocation/freeing is traced in a way 251 similar to the Boehm's conservative garbage collector, the 252 difference being that the orphan objects are not freed but 253 only shown in /sys/kernel/debug/kmemleak. Enabling this 254 feature will introduce an overhead to memory 255 allocations. See Documentation/dev-tools/kmemleak.rst for more 256 details. 257 258 Enabling SLUB_DEBUG may increase the chances of finding leaks 259 due to the slab objects poisoning. 260 261 In order to access the kmemleak file, debugfs needs to be 262 mounted (usually at /sys/kernel/debug). 263 264 config DEBUG_KMEMLEAK_MEM_POOL_SIZE 265 int "Kmemleak memory pool size" 266 depends on DEBUG_KMEMLEAK 267 range 200 1000000 268 default 16000 269 help 270 Kmemleak must track all the memory allocations to avoid 271 reporting false positives. Since memory may be allocated or 272 freed before kmemleak is fully initialised, use a static pool 273 of metadata objects to track such callbacks. After kmemleak is 274 fully initialised, this memory pool acts as an emergency one 275 if slab allocations fail. 276 277 config DEBUG_KMEMLEAK_DEFAULT_OFF 278 bool "Default kmemleak to off" 279 depends on DEBUG_KMEMLEAK 280 help 281 Say Y here to disable kmemleak by default. It can then be enabled 282 on the command line via kmemleak=on. 283 284 config DEBUG_KMEMLEAK_AUTO_SCAN 285 bool "Enable kmemleak auto scan thread on boot up" 286 default y 287 depends on DEBUG_KMEMLEAK 288 help 289 Depending on the cpu, kmemleak scan may be cpu intensive and can 290 stall user tasks at times. This option enables/disables automatic 291 kmemleak scan at boot up. 292 293 Say N here to disable kmemleak auto scan thread to stop automatic 294 scanning. Disabling this option disables automatic reporting of 295 memory leaks. 296 297 If unsure, say Y. 298 299 config PER_VMA_LOCK_STATS 300 bool "Statistics for per-vma locks" 301 depends on PER_VMA_LOCK 302 help 303 Say Y here to enable success, retry and failure counters of page 304 faults handled under protection of per-vma locks. When enabled, the 305 counters are exposed in /proc/vmstat. This information is useful for 306 kernel developers to evaluate effectiveness of per-vma locks and to 307 identify pathological cases. Counting these events introduces a small 308 overhead in the page fault path. 309 310 If in doubt, say N. 311