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 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
48 config SLUB_DEBUG 56 config SLUB_DEBUG
49 default y 57 default y
50 bool "Enable SLUB debugging support" i 58 bool "Enable SLUB debugging support" if EXPERT
51 depends on SYSFS && !SLUB_TINY !! 59 depends on SLUB && SYSFS && !SLUB_TINY
52 select STACKDEPOT if STACKTRACE_SUPPOR 60 select STACKDEPOT if STACKTRACE_SUPPORT
53 help 61 help
54 SLUB has extensive debug support fea 62 SLUB has extensive debug support features. Disabling these can
55 result in significant savings in cod 63 result in significant savings in code size. While /sys/kernel/slab
56 will still exist (with SYSFS enabled 64 will still exist (with SYSFS enabled), it will not provide e.g. cache
57 validation. 65 validation.
58 66
59 config SLUB_DEBUG_ON 67 config SLUB_DEBUG_ON
60 bool "SLUB debugging on by default" 68 bool "SLUB debugging on by default"
61 depends on SLUB_DEBUG !! 69 depends on SLUB && SLUB_DEBUG
62 select STACKDEPOT_ALWAYS_INIT if STACK 70 select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT
63 default n 71 default n
64 help 72 help
65 Boot with debugging on by default. S 73 Boot with debugging on by default. SLUB boots by default with
66 the runtime debug capabilities switc 74 the runtime debug capabilities switched off. Enabling this is
67 equivalent to specifying the "slab_d !! 75 equivalent to specifying the "slub_debug" parameter on boot.
68 There is no support for more fine gr 76 There is no support for more fine grained debug control like
69 possible with slab_debug=xxx. SLUB d !! 77 possible with slub_debug=xxx. SLUB debugging may be switched
70 off in a kernel built with CONFIG_SL 78 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
71 "slab_debug=-". !! 79 "slub_debug=-".
72 80
73 config PAGE_OWNER 81 config PAGE_OWNER
74 bool "Track page owner" 82 bool "Track page owner"
75 depends on DEBUG_KERNEL && STACKTRACE_ 83 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
76 select DEBUG_FS 84 select DEBUG_FS
77 select STACKTRACE 85 select STACKTRACE
78 select STACKDEPOT 86 select STACKDEPOT
79 select PAGE_EXTENSION 87 select PAGE_EXTENSION
80 help 88 help
81 This keeps track of what call chain 89 This keeps track of what call chain is the owner of a page, may
82 help to find bare alloc_page(s) leak 90 help to find bare alloc_page(s) leaks. Even if you include this
83 feature on your build, it is disable 91 feature on your build, it is disabled in default. You should pass
84 "page_owner=on" to boot parameter in 92 "page_owner=on" to boot parameter in order to enable it. Eats
85 a fair amount of memory if enabled. 93 a fair amount of memory if enabled. See tools/mm/page_owner_sort.c
86 for user-space helper. 94 for user-space helper.
87 95
88 If unsure, say N. 96 If unsure, say N.
89 97
90 config PAGE_TABLE_CHECK 98 config PAGE_TABLE_CHECK
91 bool "Check for invalid mappings in us 99 bool "Check for invalid mappings in user page tables"
92 depends on ARCH_SUPPORTS_PAGE_TABLE_CH 100 depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK
93 depends on EXCLUSIVE_SYSTEM_RAM 101 depends on EXCLUSIVE_SYSTEM_RAM
94 select PAGE_EXTENSION 102 select PAGE_EXTENSION
95 help 103 help
96 Check that anonymous page is not bei 104 Check that anonymous page is not being mapped twice with read write
97 permissions. Check that anonymous an 105 permissions. Check that anonymous and file pages are not being
98 erroneously shared. Since the checki 106 erroneously shared. Since the checking is performed at the time
99 entries are added and removed to use 107 entries are added and removed to user page tables, leaking, corruption
100 and double mapping problems are dete 108 and double mapping problems are detected synchronously.
101 109
102 If unsure say "n". 110 If unsure say "n".
103 111
104 config PAGE_TABLE_CHECK_ENFORCED 112 config PAGE_TABLE_CHECK_ENFORCED
105 bool "Enforce the page table checking 113 bool "Enforce the page table checking by default"
106 depends on PAGE_TABLE_CHECK 114 depends on PAGE_TABLE_CHECK
107 help 115 help
108 Always enable page table checking. 116 Always enable page table checking. By default the page table checking
109 is disabled, and can be optionally e 117 is disabled, and can be optionally enabled via page_table_check=on
110 kernel parameter. This config enforc 118 kernel parameter. This config enforces that page table check is always
111 enabled. 119 enabled.
112 120
113 If unsure say "n". 121 If unsure say "n".
114 122
115 config PAGE_POISONING 123 config PAGE_POISONING
116 bool "Poison pages after freeing" 124 bool "Poison pages after freeing"
117 help 125 help
118 Fill the pages with poison patterns 126 Fill the pages with poison patterns after free_pages() and verify
119 the patterns before alloc_pages. The 127 the patterns before alloc_pages. The filling of the memory helps
120 reduce the risk of information leaks 128 reduce the risk of information leaks from freed data. This does
121 have a potential performance impact 129 have a potential performance impact if enabled with the
122 "page_poison=1" kernel boot option. 130 "page_poison=1" kernel boot option.
123 131
124 Note that "poison" here is not the s 132 Note that "poison" here is not the same thing as the "HWPoison"
125 for CONFIG_MEMORY_FAILURE. This is s 133 for CONFIG_MEMORY_FAILURE. This is software poisoning only.
126 134
127 If you are only interested in saniti 135 If you are only interested in sanitization of freed pages without
128 checking the poison pattern on alloc 136 checking the poison pattern on alloc, you can boot the kernel with
129 "init_on_free=1" instead of enabling 137 "init_on_free=1" instead of enabling this.
130 138
131 If unsure, say N 139 If unsure, say N
132 140
133 config DEBUG_PAGE_REF 141 config DEBUG_PAGE_REF
134 bool "Enable tracepoint to track down 142 bool "Enable tracepoint to track down page reference manipulation"
135 depends on DEBUG_KERNEL 143 depends on DEBUG_KERNEL
136 depends on TRACEPOINTS 144 depends on TRACEPOINTS
137 help 145 help
138 This is a feature to add tracepoint 146 This is a feature to add tracepoint for tracking down page reference
139 manipulation. This tracking is usefu 147 manipulation. This tracking is useful to diagnose functional failure
140 due to migration failures caused by 148 due to migration failures caused by page reference mismatches. Be
141 careful when enabling this feature b 149 careful when enabling this feature because it adds about 30 KB to the
142 kernel code. However the runtime pe 150 kernel code. However the runtime performance overhead is virtually
143 nil until the tracepoints are actual 151 nil until the tracepoints are actually enabled.
144 152
145 config DEBUG_RODATA_TEST 153 config DEBUG_RODATA_TEST
146 bool "Testcase for the marking rodata read 154 bool "Testcase for the marking rodata read-only"
147 depends on STRICT_KERNEL_RWX 155 depends on STRICT_KERNEL_RWX
148 help 156 help
149 This option enables a testcase for the s 157 This option enables a testcase for the setting rodata read-only.
150 158
151 config ARCH_HAS_DEBUG_WX 159 config ARCH_HAS_DEBUG_WX
152 bool 160 bool
153 161
154 config DEBUG_WX 162 config DEBUG_WX
155 bool "Warn on W+X mappings at boot" 163 bool "Warn on W+X mappings at boot"
156 depends on ARCH_HAS_DEBUG_WX 164 depends on ARCH_HAS_DEBUG_WX
157 depends on MMU 165 depends on MMU
158 select PTDUMP_CORE 166 select PTDUMP_CORE
159 help 167 help
160 Generate a warning if any W+X mappin 168 Generate a warning if any W+X mappings are found at boot.
161 169
162 This is useful for discovering cases 170 This is useful for discovering cases where the kernel is leaving W+X
163 mappings after applying NX, as such 171 mappings after applying NX, as such mappings are a security risk.
164 172
165 Look for a message in dmesg output l 173 Look for a message in dmesg output like this:
166 174
167 <arch>/mm: Checked W+X mappings: p 175 <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
168 176
169 or like this, if the check failed: 177 or like this, if the check failed:
170 178
171 <arch>/mm: Checked W+X mappings: f 179 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
172 180
173 Note that even if the check fails, y 181 Note that even if the check fails, your kernel is possibly
174 still fine, as W+X mappings are not 182 still fine, as W+X mappings are not a security hole in
175 themselves, what they do is that the 183 themselves, what they do is that they make the exploitation
176 of other unfixed kernel bugs easier. 184 of other unfixed kernel bugs easier.
177 185
178 There is no runtime or memory usage 186 There is no runtime or memory usage effect of this option
179 once the kernel has booted up - it's 187 once the kernel has booted up - it's a one time check.
180 188
181 If in doubt, say "Y". 189 If in doubt, say "Y".
182 190
183 config GENERIC_PTDUMP 191 config GENERIC_PTDUMP
184 bool 192 bool
185 193
186 config PTDUMP_CORE 194 config PTDUMP_CORE
187 bool 195 bool
188 196
189 config PTDUMP_DEBUGFS 197 config PTDUMP_DEBUGFS
190 bool "Export kernel pagetable layout t 198 bool "Export kernel pagetable layout to userspace via debugfs"
191 depends on DEBUG_KERNEL 199 depends on DEBUG_KERNEL
192 depends on DEBUG_FS 200 depends on DEBUG_FS
193 depends on GENERIC_PTDUMP 201 depends on GENERIC_PTDUMP
194 select PTDUMP_CORE 202 select PTDUMP_CORE
195 help 203 help
196 Say Y here if you want to show the k 204 Say Y here if you want to show the kernel pagetable layout in a
197 debugfs file. This information is on 205 debugfs file. This information is only useful for kernel developers
198 who are working in architecture spec 206 who are working in architecture specific areas of the kernel.
199 It is probably not a good idea to en 207 It is probably not a good idea to enable this feature in a production
200 kernel. 208 kernel.
201 209
202 If in doubt, say N. 210 If in doubt, say N.
203 211
204 config HAVE_DEBUG_KMEMLEAK 212 config HAVE_DEBUG_KMEMLEAK
205 bool 213 bool
206 214
207 config DEBUG_KMEMLEAK 215 config DEBUG_KMEMLEAK
208 bool "Kernel memory leak detector" 216 bool "Kernel memory leak detector"
209 depends on DEBUG_KERNEL && HAVE_DEBUG_ 217 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
210 select DEBUG_FS 218 select DEBUG_FS
211 select STACKTRACE if STACKTRACE_SUPPOR 219 select STACKTRACE if STACKTRACE_SUPPORT
212 select KALLSYMS 220 select KALLSYMS
213 select CRC32 221 select CRC32
214 select STACKDEPOT 222 select STACKDEPOT
215 select STACKDEPOT_ALWAYS_INIT if !DEBU 223 select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF
216 help 224 help
217 Say Y here if you want to enable the 225 Say Y here if you want to enable the memory leak
218 detector. The memory allocation/free 226 detector. The memory allocation/freeing is traced in a way
219 similar to the Boehm's conservative 227 similar to the Boehm's conservative garbage collector, the
220 difference being that the orphan obj 228 difference being that the orphan objects are not freed but
221 only shown in /sys/kernel/debug/kmem 229 only shown in /sys/kernel/debug/kmemleak. Enabling this
222 feature will introduce an overhead t 230 feature will introduce an overhead to memory
223 allocations. See Documentation/dev-t 231 allocations. See Documentation/dev-tools/kmemleak.rst for more
224 details. 232 details.
225 233
226 Enabling SLUB_DEBUG may increase the !! 234 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
227 due to the slab objects poisoning. !! 235 of finding leaks due to the slab objects poisoning.
228 236
229 In order to access the kmemleak file 237 In order to access the kmemleak file, debugfs needs to be
230 mounted (usually at /sys/kernel/debu 238 mounted (usually at /sys/kernel/debug).
231 239
232 config DEBUG_KMEMLEAK_MEM_POOL_SIZE 240 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
233 int "Kmemleak memory pool size" 241 int "Kmemleak memory pool size"
234 depends on DEBUG_KMEMLEAK 242 depends on DEBUG_KMEMLEAK
235 range 200 1000000 243 range 200 1000000
236 default 16000 244 default 16000
237 help 245 help
238 Kmemleak must track all the memory a 246 Kmemleak must track all the memory allocations to avoid
239 reporting false positives. Since mem 247 reporting false positives. Since memory may be allocated or
240 freed before kmemleak is fully initi 248 freed before kmemleak is fully initialised, use a static pool
241 of metadata objects to track such ca 249 of metadata objects to track such callbacks. After kmemleak is
242 fully initialised, this memory pool 250 fully initialised, this memory pool acts as an emergency one
243 if slab allocations fail. 251 if slab allocations fail.
244 252
245 config DEBUG_KMEMLEAK_DEFAULT_OFF 253 config DEBUG_KMEMLEAK_DEFAULT_OFF
246 bool "Default kmemleak to off" 254 bool "Default kmemleak to off"
247 depends on DEBUG_KMEMLEAK 255 depends on DEBUG_KMEMLEAK
248 help 256 help
249 Say Y here to disable kmemleak by de 257 Say Y here to disable kmemleak by default. It can then be enabled
250 on the command line via kmemleak=on. 258 on the command line via kmemleak=on.
251 259
252 config DEBUG_KMEMLEAK_AUTO_SCAN 260 config DEBUG_KMEMLEAK_AUTO_SCAN
253 bool "Enable kmemleak auto scan thread 261 bool "Enable kmemleak auto scan thread on boot up"
254 default y 262 default y
255 depends on DEBUG_KMEMLEAK 263 depends on DEBUG_KMEMLEAK
256 help 264 help
257 Depending on the cpu, kmemleak scan 265 Depending on the cpu, kmemleak scan may be cpu intensive and can
258 stall user tasks at times. This opti 266 stall user tasks at times. This option enables/disables automatic
259 kmemleak scan at boot up. 267 kmemleak scan at boot up.
260 268
261 Say N here to disable kmemleak auto 269 Say N here to disable kmemleak auto scan thread to stop automatic
262 scanning. Disabling this option disa 270 scanning. Disabling this option disables automatic reporting of
263 memory leaks. 271 memory leaks.
264 272
265 If unsure, say Y. 273 If unsure, say Y.
266 274
267 config PER_VMA_LOCK_STATS 275 config PER_VMA_LOCK_STATS
268 bool "Statistics for per-vma locks" 276 bool "Statistics for per-vma locks"
269 depends on PER_VMA_LOCK 277 depends on PER_VMA_LOCK
270 help 278 help
271 Say Y here to enable success, retry 279 Say Y here to enable success, retry and failure counters of page
272 faults handled under protection of p 280 faults handled under protection of per-vma locks. When enabled, the
273 counters are exposed in /proc/vmstat 281 counters are exposed in /proc/vmstat. This information is useful for
274 kernel developers to evaluate effect 282 kernel developers to evaluate effectiveness of per-vma locks and to
275 identify pathological cases. Countin 283 identify pathological cases. Counting these events introduces a small
276 overhead in the page fault path. 284 overhead in the page fault path.
277 285
278 If in doubt, say N. 286 If in doubt, say N.
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