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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