1 # SPDX-License-Identifier: GPL-2.0-only 1 # SPDX-License-Identifier: GPL-2.0-only 2 config PAGE_EXTENSION 2 config PAGE_EXTENSION 3 bool "Extend memmap on extra space for 3 bool "Extend memmap on extra space for more information on page" 4 help 4 help 5 Extend memmap on extra space for mor 5 Extend memmap on extra space for more information on page. This 6 could be used for debugging features 6 could be used for debugging features that need to insert extra 7 field for every page. This extension 7 field for every page. This extension enables us to save memory 8 by not allocating this extra memory 8 by not allocating this extra memory according to boottime 9 configuration. 9 configuration. 10 10 11 config DEBUG_PAGEALLOC 11 config DEBUG_PAGEALLOC 12 bool "Debug page memory allocations" 12 bool "Debug page memory allocations" 13 depends on DEBUG_KERNEL 13 depends on DEBUG_KERNEL 14 depends on !HIBERNATION || ARCH_SUPPOR 14 depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC 15 select PAGE_POISONING if !ARCH_SUPPORT 15 select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC 16 help 16 help 17 Unmap pages from the kernel linear m 17 Unmap pages from the kernel linear mapping after free_pages(). 18 Depending on runtime enablement, thi 18 Depending on runtime enablement, this results in a small or large 19 slowdown, but helps to find certain 19 slowdown, but helps to find certain types of memory corruption. 20 20 21 Also, the state of page tracking str 21 Also, the state of page tracking structures is checked more often as 22 pages are being allocated and freed, 22 pages are being allocated and freed, as unexpected state changes 23 often happen for same reasons as mem 23 often happen for same reasons as memory corruption (e.g. double free, 24 use-after-free). The error reports f 24 use-after-free). The error reports for these checks can be augmented 25 with stack traces of last allocation 25 with stack traces of last allocation and freeing of the page, when 26 PAGE_OWNER is also selected and enab 26 PAGE_OWNER is also selected and enabled on boot. 27 27 28 For architectures which don't enable 28 For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC, 29 fill the pages with poison patterns 29 fill the pages with poison patterns after free_pages() and verify 30 the patterns before alloc_pages(). A 30 the patterns before alloc_pages(). Additionally, this option cannot 31 be enabled in combination with hiber 31 be enabled in combination with hibernation as that would result in 32 incorrect warnings of memory corrupt 32 incorrect warnings of memory corruption after a resume because free 33 pages are not saved to the suspend i 33 pages are not saved to the suspend image. 34 34 35 By default this option will have a s 35 By default this option will have a small overhead, e.g. by not 36 allowing the kernel mapping to be ba 36 allowing the kernel mapping to be backed by large pages on some 37 architectures. Even bigger overhead 37 architectures. Even bigger overhead comes when the debugging is 38 enabled by DEBUG_PAGEALLOC_ENABLE_DE 38 enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc 39 command line parameter. 39 command line parameter. 40 40 41 config DEBUG_PAGEALLOC_ENABLE_DEFAULT 41 config DEBUG_PAGEALLOC_ENABLE_DEFAULT 42 bool "Enable debug page memory allocat 42 bool "Enable debug page memory allocations by default?" 43 depends on DEBUG_PAGEALLOC 43 depends on DEBUG_PAGEALLOC 44 help 44 help 45 Enable debug page memory allocations 45 Enable debug page memory allocations by default? This value 46 can be overridden by debug_pagealloc 46 can be overridden by debug_pagealloc=off|on. 47 47 48 config SLUB_DEBUG 48 config SLUB_DEBUG 49 default y 49 default y 50 bool "Enable SLUB debugging support" i 50 bool "Enable SLUB debugging support" if EXPERT 51 depends on SYSFS && !SLUB_TINY 51 depends on SYSFS && !SLUB_TINY 52 select STACKDEPOT if STACKTRACE_SUPPOR 52 select STACKDEPOT if STACKTRACE_SUPPORT 53 help 53 help 54 SLUB has extensive debug support fea 54 SLUB has extensive debug support features. Disabling these can 55 result in significant savings in cod 55 result in significant savings in code size. While /sys/kernel/slab 56 will still exist (with SYSFS enabled 56 will still exist (with SYSFS enabled), it will not provide e.g. cache 57 validation. 57 validation. 58 58 59 config SLUB_DEBUG_ON 59 config SLUB_DEBUG_ON 60 bool "SLUB debugging on by default" 60 bool "SLUB debugging on by default" 61 depends on SLUB_DEBUG 61 depends on SLUB_DEBUG 62 select STACKDEPOT_ALWAYS_INIT if STACK 62 select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT 63 default n 63 default n 64 help 64 help 65 Boot with debugging on by default. S 65 Boot with debugging on by default. SLUB boots by default with 66 the runtime debug capabilities switc 66 the runtime debug capabilities switched off. Enabling this is 67 equivalent to specifying the "slab_d 67 equivalent to specifying the "slab_debug" parameter on boot. 68 There is no support for more fine gr 68 There is no support for more fine grained debug control like 69 possible with slab_debug=xxx. SLUB d 69 possible with slab_debug=xxx. SLUB debugging may be switched 70 off in a kernel built with CONFIG_SL 70 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 71 "slab_debug=-". 71 "slab_debug=-". 72 72 73 config PAGE_OWNER 73 config PAGE_OWNER 74 bool "Track page owner" 74 bool "Track page owner" 75 depends on DEBUG_KERNEL && STACKTRACE_ 75 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 76 select DEBUG_FS 76 select DEBUG_FS 77 select STACKTRACE 77 select STACKTRACE 78 select STACKDEPOT 78 select STACKDEPOT 79 select PAGE_EXTENSION 79 select PAGE_EXTENSION 80 help 80 help 81 This keeps track of what call chain 81 This keeps track of what call chain is the owner of a page, may 82 help to find bare alloc_page(s) leak 82 help to find bare alloc_page(s) leaks. Even if you include this 83 feature on your build, it is disable 83 feature on your build, it is disabled in default. You should pass 84 "page_owner=on" to boot parameter in 84 "page_owner=on" to boot parameter in order to enable it. Eats 85 a fair amount of memory if enabled. 85 a fair amount of memory if enabled. See tools/mm/page_owner_sort.c 86 for user-space helper. 86 for user-space helper. 87 87 88 If unsure, say N. 88 If unsure, say N. 89 89 90 config PAGE_TABLE_CHECK 90 config PAGE_TABLE_CHECK 91 bool "Check for invalid mappings in us 91 bool "Check for invalid mappings in user page tables" 92 depends on ARCH_SUPPORTS_PAGE_TABLE_CH 92 depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK 93 depends on EXCLUSIVE_SYSTEM_RAM 93 depends on EXCLUSIVE_SYSTEM_RAM 94 select PAGE_EXTENSION 94 select PAGE_EXTENSION 95 help 95 help 96 Check that anonymous page is not bei 96 Check that anonymous page is not being mapped twice with read write 97 permissions. Check that anonymous an 97 permissions. Check that anonymous and file pages are not being 98 erroneously shared. Since the checki 98 erroneously shared. Since the checking is performed at the time 99 entries are added and removed to use 99 entries are added and removed to user page tables, leaking, corruption 100 and double mapping problems are dete 100 and double mapping problems are detected synchronously. 101 101 102 If unsure say "n". 102 If unsure say "n". 103 103 104 config PAGE_TABLE_CHECK_ENFORCED 104 config PAGE_TABLE_CHECK_ENFORCED 105 bool "Enforce the page table checking 105 bool "Enforce the page table checking by default" 106 depends on PAGE_TABLE_CHECK 106 depends on PAGE_TABLE_CHECK 107 help 107 help 108 Always enable page table checking. 108 Always enable page table checking. By default the page table checking 109 is disabled, and can be optionally e 109 is disabled, and can be optionally enabled via page_table_check=on 110 kernel parameter. This config enforc 110 kernel parameter. This config enforces that page table check is always 111 enabled. 111 enabled. 112 112 113 If unsure say "n". 113 If unsure say "n". 114 114 115 config PAGE_POISONING 115 config PAGE_POISONING 116 bool "Poison pages after freeing" 116 bool "Poison pages after freeing" 117 help 117 help 118 Fill the pages with poison patterns 118 Fill the pages with poison patterns after free_pages() and verify 119 the patterns before alloc_pages. The 119 the patterns before alloc_pages. The filling of the memory helps 120 reduce the risk of information leaks 120 reduce the risk of information leaks from freed data. This does 121 have a potential performance impact 121 have a potential performance impact if enabled with the 122 "page_poison=1" kernel boot option. 122 "page_poison=1" kernel boot option. 123 123 124 Note that "poison" here is not the s 124 Note that "poison" here is not the same thing as the "HWPoison" 125 for CONFIG_MEMORY_FAILURE. This is s 125 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 126 126 127 If you are only interested in saniti 127 If you are only interested in sanitization of freed pages without 128 checking the poison pattern on alloc 128 checking the poison pattern on alloc, you can boot the kernel with 129 "init_on_free=1" instead of enabling 129 "init_on_free=1" instead of enabling this. 130 130 131 If unsure, say N 131 If unsure, say N 132 132 133 config DEBUG_PAGE_REF 133 config DEBUG_PAGE_REF 134 bool "Enable tracepoint to track down 134 bool "Enable tracepoint to track down page reference manipulation" 135 depends on DEBUG_KERNEL 135 depends on DEBUG_KERNEL 136 depends on TRACEPOINTS 136 depends on TRACEPOINTS 137 help 137 help 138 This is a feature to add tracepoint 138 This is a feature to add tracepoint for tracking down page reference 139 manipulation. This tracking is usefu 139 manipulation. This tracking is useful to diagnose functional failure 140 due to migration failures caused by 140 due to migration failures caused by page reference mismatches. Be 141 careful when enabling this feature b 141 careful when enabling this feature because it adds about 30 KB to the 142 kernel code. However the runtime pe 142 kernel code. However the runtime performance overhead is virtually 143 nil until the tracepoints are actual 143 nil until the tracepoints are actually enabled. 144 144 145 config DEBUG_RODATA_TEST 145 config DEBUG_RODATA_TEST 146 bool "Testcase for the marking rodata read 146 bool "Testcase for the marking rodata read-only" 147 depends on STRICT_KERNEL_RWX 147 depends on STRICT_KERNEL_RWX 148 help 148 help 149 This option enables a testcase for the s 149 This option enables a testcase for the setting rodata read-only. 150 150 151 config ARCH_HAS_DEBUG_WX 151 config ARCH_HAS_DEBUG_WX 152 bool 152 bool 153 153 154 config DEBUG_WX 154 config DEBUG_WX 155 bool "Warn on W+X mappings at boot" 155 bool "Warn on W+X mappings at boot" 156 depends on ARCH_HAS_DEBUG_WX 156 depends on ARCH_HAS_DEBUG_WX 157 depends on MMU 157 depends on MMU 158 select PTDUMP_CORE 158 select PTDUMP_CORE 159 help 159 help 160 Generate a warning if any W+X mappin 160 Generate a warning if any W+X mappings are found at boot. 161 161 162 This is useful for discovering cases 162 This is useful for discovering cases where the kernel is leaving W+X 163 mappings after applying NX, as such 163 mappings after applying NX, as such mappings are a security risk. 164 164 165 Look for a message in dmesg output l 165 Look for a message in dmesg output like this: 166 166 167 <arch>/mm: Checked W+X mappings: p 167 <arch>/mm: Checked W+X mappings: passed, no W+X pages found. 168 168 169 or like this, if the check failed: 169 or like this, if the check failed: 170 170 171 <arch>/mm: Checked W+X mappings: f 171 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found. 172 172 173 Note that even if the check fails, y 173 Note that even if the check fails, your kernel is possibly 174 still fine, as W+X mappings are not 174 still fine, as W+X mappings are not a security hole in 175 themselves, what they do is that the 175 themselves, what they do is that they make the exploitation 176 of other unfixed kernel bugs easier. 176 of other unfixed kernel bugs easier. 177 177 178 There is no runtime or memory usage 178 There is no runtime or memory usage effect of this option 179 once the kernel has booted up - it's 179 once the kernel has booted up - it's a one time check. 180 180 181 If in doubt, say "Y". 181 If in doubt, say "Y". 182 182 183 config GENERIC_PTDUMP 183 config GENERIC_PTDUMP 184 bool 184 bool 185 185 186 config PTDUMP_CORE 186 config PTDUMP_CORE 187 bool 187 bool 188 188 189 config PTDUMP_DEBUGFS 189 config PTDUMP_DEBUGFS 190 bool "Export kernel pagetable layout t 190 bool "Export kernel pagetable layout to userspace via debugfs" 191 depends on DEBUG_KERNEL 191 depends on DEBUG_KERNEL 192 depends on DEBUG_FS 192 depends on DEBUG_FS 193 depends on GENERIC_PTDUMP 193 depends on GENERIC_PTDUMP 194 select PTDUMP_CORE 194 select PTDUMP_CORE 195 help 195 help 196 Say Y here if you want to show the k 196 Say Y here if you want to show the kernel pagetable layout in a 197 debugfs file. This information is on 197 debugfs file. This information is only useful for kernel developers 198 who are working in architecture spec 198 who are working in architecture specific areas of the kernel. 199 It is probably not a good idea to en 199 It is probably not a good idea to enable this feature in a production 200 kernel. 200 kernel. 201 201 202 If in doubt, say N. 202 If in doubt, say N. 203 203 204 config HAVE_DEBUG_KMEMLEAK 204 config HAVE_DEBUG_KMEMLEAK 205 bool 205 bool 206 206 207 config DEBUG_KMEMLEAK 207 config DEBUG_KMEMLEAK 208 bool "Kernel memory leak detector" 208 bool "Kernel memory leak detector" 209 depends on DEBUG_KERNEL && HAVE_DEBUG_ 209 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 210 select DEBUG_FS 210 select DEBUG_FS 211 select STACKTRACE if STACKTRACE_SUPPOR 211 select STACKTRACE if STACKTRACE_SUPPORT 212 select KALLSYMS 212 select KALLSYMS 213 select CRC32 213 select CRC32 214 select STACKDEPOT 214 select STACKDEPOT 215 select STACKDEPOT_ALWAYS_INIT if !DEBU 215 select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF 216 help 216 help 217 Say Y here if you want to enable the 217 Say Y here if you want to enable the memory leak 218 detector. The memory allocation/free 218 detector. The memory allocation/freeing is traced in a way 219 similar to the Boehm's conservative 219 similar to the Boehm's conservative garbage collector, the 220 difference being that the orphan obj 220 difference being that the orphan objects are not freed but 221 only shown in /sys/kernel/debug/kmem 221 only shown in /sys/kernel/debug/kmemleak. Enabling this 222 feature will introduce an overhead t 222 feature will introduce an overhead to memory 223 allocations. See Documentation/dev-t 223 allocations. See Documentation/dev-tools/kmemleak.rst for more 224 details. 224 details. 225 225 226 Enabling SLUB_DEBUG may increase the 226 Enabling SLUB_DEBUG may increase the chances of finding leaks 227 due to the slab objects poisoning. 227 due to the slab objects poisoning. 228 228 229 In order to access the kmemleak file 229 In order to access the kmemleak file, debugfs needs to be 230 mounted (usually at /sys/kernel/debu 230 mounted (usually at /sys/kernel/debug). 231 231 232 config DEBUG_KMEMLEAK_MEM_POOL_SIZE 232 config DEBUG_KMEMLEAK_MEM_POOL_SIZE 233 int "Kmemleak memory pool size" 233 int "Kmemleak memory pool size" 234 depends on DEBUG_KMEMLEAK 234 depends on DEBUG_KMEMLEAK 235 range 200 1000000 235 range 200 1000000 236 default 16000 236 default 16000 237 help 237 help 238 Kmemleak must track all the memory a 238 Kmemleak must track all the memory allocations to avoid 239 reporting false positives. Since mem 239 reporting false positives. Since memory may be allocated or 240 freed before kmemleak is fully initi 240 freed before kmemleak is fully initialised, use a static pool 241 of metadata objects to track such ca 241 of metadata objects to track such callbacks. After kmemleak is 242 fully initialised, this memory pool 242 fully initialised, this memory pool acts as an emergency one 243 if slab allocations fail. 243 if slab allocations fail. 244 244 245 config DEBUG_KMEMLEAK_DEFAULT_OFF 245 config DEBUG_KMEMLEAK_DEFAULT_OFF 246 bool "Default kmemleak to off" 246 bool "Default kmemleak to off" 247 depends on DEBUG_KMEMLEAK 247 depends on DEBUG_KMEMLEAK 248 help 248 help 249 Say Y here to disable kmemleak by de 249 Say Y here to disable kmemleak by default. It can then be enabled 250 on the command line via kmemleak=on. 250 on the command line via kmemleak=on. 251 251 252 config DEBUG_KMEMLEAK_AUTO_SCAN 252 config DEBUG_KMEMLEAK_AUTO_SCAN 253 bool "Enable kmemleak auto scan thread 253 bool "Enable kmemleak auto scan thread on boot up" 254 default y 254 default y 255 depends on DEBUG_KMEMLEAK 255 depends on DEBUG_KMEMLEAK 256 help 256 help 257 Depending on the cpu, kmemleak scan 257 Depending on the cpu, kmemleak scan may be cpu intensive and can 258 stall user tasks at times. This opti 258 stall user tasks at times. This option enables/disables automatic 259 kmemleak scan at boot up. 259 kmemleak scan at boot up. 260 260 261 Say N here to disable kmemleak auto 261 Say N here to disable kmemleak auto scan thread to stop automatic 262 scanning. Disabling this option disa 262 scanning. Disabling this option disables automatic reporting of 263 memory leaks. 263 memory leaks. 264 264 265 If unsure, say Y. 265 If unsure, say Y. 266 266 267 config PER_VMA_LOCK_STATS 267 config PER_VMA_LOCK_STATS 268 bool "Statistics for per-vma locks" 268 bool "Statistics for per-vma locks" 269 depends on PER_VMA_LOCK 269 depends on PER_VMA_LOCK 270 help 270 help 271 Say Y here to enable success, retry 271 Say Y here to enable success, retry and failure counters of page 272 faults handled under protection of p 272 faults handled under protection of per-vma locks. When enabled, the 273 counters are exposed in /proc/vmstat 273 counters are exposed in /proc/vmstat. This information is useful for 274 kernel developers to evaluate effect 274 kernel developers to evaluate effectiveness of per-vma locks and to 275 identify pathological cases. Countin 275 identify pathological cases. Counting these events introduces a small 276 overhead in the page fault path. 276 overhead in the page fault path. 277 277 278 If in doubt, say N. 278 If in doubt, say N.
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