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. This also disables
56 will still exist (with SYSFS enabled !! 64 SLUB sysfs support. /sys/slab will not exist and there will be
57 validation. !! 65 no support for cache validation etc.
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/vm/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 <<
94 select PAGE_EXTENSION 101 select PAGE_EXTENSION
95 help 102 help
96 Check that anonymous page is not bei 103 Check that anonymous page is not being mapped twice with read write
97 permissions. Check that anonymous an 104 permissions. Check that anonymous and file pages are not being
98 erroneously shared. Since the checki 105 erroneously shared. Since the checking is performed at the time
99 entries are added and removed to use 106 entries are added and removed to user page tables, leaking, corruption
100 and double mapping problems are dete 107 and double mapping problems are detected synchronously.
101 108
102 If unsure say "n". 109 If unsure say "n".
103 110
104 config PAGE_TABLE_CHECK_ENFORCED 111 config PAGE_TABLE_CHECK_ENFORCED
105 bool "Enforce the page table checking 112 bool "Enforce the page table checking by default"
106 depends on PAGE_TABLE_CHECK 113 depends on PAGE_TABLE_CHECK
107 help 114 help
108 Always enable page table checking. 115 Always enable page table checking. By default the page table checking
109 is disabled, and can be optionally e 116 is disabled, and can be optionally enabled via page_table_check=on
110 kernel parameter. This config enforc 117 kernel parameter. This config enforces that page table check is always
111 enabled. 118 enabled.
112 119
113 If unsure say "n". 120 If unsure say "n".
114 121
115 config PAGE_POISONING 122 config PAGE_POISONING
116 bool "Poison pages after freeing" 123 bool "Poison pages after freeing"
117 help 124 help
118 Fill the pages with poison patterns 125 Fill the pages with poison patterns after free_pages() and verify
119 the patterns before alloc_pages. The 126 the patterns before alloc_pages. The filling of the memory helps
120 reduce the risk of information leaks 127 reduce the risk of information leaks from freed data. This does
121 have a potential performance impact 128 have a potential performance impact if enabled with the
122 "page_poison=1" kernel boot option. 129 "page_poison=1" kernel boot option.
123 130
124 Note that "poison" here is not the s 131 Note that "poison" here is not the same thing as the "HWPoison"
125 for CONFIG_MEMORY_FAILURE. This is s 132 for CONFIG_MEMORY_FAILURE. This is software poisoning only.
126 133
127 If you are only interested in saniti 134 If you are only interested in sanitization of freed pages without
128 checking the poison pattern on alloc 135 checking the poison pattern on alloc, you can boot the kernel with
129 "init_on_free=1" instead of enabling 136 "init_on_free=1" instead of enabling this.
130 137
131 If unsure, say N 138 If unsure, say N
132 139
133 config DEBUG_PAGE_REF 140 config DEBUG_PAGE_REF
134 bool "Enable tracepoint to track down 141 bool "Enable tracepoint to track down page reference manipulation"
135 depends on DEBUG_KERNEL 142 depends on DEBUG_KERNEL
136 depends on TRACEPOINTS 143 depends on TRACEPOINTS
137 help 144 help
138 This is a feature to add tracepoint 145 This is a feature to add tracepoint for tracking down page reference
139 manipulation. This tracking is usefu 146 manipulation. This tracking is useful to diagnose functional failure
140 due to migration failures caused by 147 due to migration failures caused by page reference mismatches. Be
141 careful when enabling this feature b 148 careful when enabling this feature because it adds about 30 KB to the
142 kernel code. However the runtime pe 149 kernel code. However the runtime performance overhead is virtually
143 nil until the tracepoints are actual 150 nil until the tracepoints are actually enabled.
144 151
145 config DEBUG_RODATA_TEST 152 config DEBUG_RODATA_TEST
146 bool "Testcase for the marking rodata read 153 bool "Testcase for the marking rodata read-only"
147 depends on STRICT_KERNEL_RWX 154 depends on STRICT_KERNEL_RWX
148 help 155 help
149 This option enables a testcase for the s 156 This option enables a testcase for the setting rodata read-only.
150 157
151 config ARCH_HAS_DEBUG_WX 158 config ARCH_HAS_DEBUG_WX
152 bool 159 bool
153 160
154 config DEBUG_WX 161 config DEBUG_WX
155 bool "Warn on W+X mappings at boot" 162 bool "Warn on W+X mappings at boot"
156 depends on ARCH_HAS_DEBUG_WX 163 depends on ARCH_HAS_DEBUG_WX
157 depends on MMU 164 depends on MMU
158 select PTDUMP_CORE 165 select PTDUMP_CORE
159 help 166 help
160 Generate a warning if any W+X mappin 167 Generate a warning if any W+X mappings are found at boot.
161 168
162 This is useful for discovering cases 169 This is useful for discovering cases where the kernel is leaving W+X
163 mappings after applying NX, as such 170 mappings after applying NX, as such mappings are a security risk.
164 171
165 Look for a message in dmesg output l 172 Look for a message in dmesg output like this:
166 173
167 <arch>/mm: Checked W+X mappings: p 174 <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
168 175
169 or like this, if the check failed: 176 or like this, if the check failed:
170 177
171 <arch>/mm: Checked W+X mappings: f 178 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
172 179
173 Note that even if the check fails, y 180 Note that even if the check fails, your kernel is possibly
174 still fine, as W+X mappings are not 181 still fine, as W+X mappings are not a security hole in
175 themselves, what they do is that the 182 themselves, what they do is that they make the exploitation
176 of other unfixed kernel bugs easier. 183 of other unfixed kernel bugs easier.
177 184
178 There is no runtime or memory usage 185 There is no runtime or memory usage effect of this option
179 once the kernel has booted up - it's 186 once the kernel has booted up - it's a one time check.
180 187
181 If in doubt, say "Y". 188 If in doubt, say "Y".
182 189
183 config GENERIC_PTDUMP 190 config GENERIC_PTDUMP
184 bool 191 bool
185 192
186 config PTDUMP_CORE 193 config PTDUMP_CORE
187 bool 194 bool
188 195
189 config PTDUMP_DEBUGFS 196 config PTDUMP_DEBUGFS
190 bool "Export kernel pagetable layout t 197 bool "Export kernel pagetable layout to userspace via debugfs"
191 depends on DEBUG_KERNEL 198 depends on DEBUG_KERNEL
192 depends on DEBUG_FS 199 depends on DEBUG_FS
193 depends on GENERIC_PTDUMP 200 depends on GENERIC_PTDUMP
194 select PTDUMP_CORE 201 select PTDUMP_CORE
195 help 202 help
196 Say Y here if you want to show the k 203 Say Y here if you want to show the kernel pagetable layout in a
197 debugfs file. This information is on 204 debugfs file. This information is only useful for kernel developers
198 who are working in architecture spec 205 who are working in architecture specific areas of the kernel.
199 It is probably not a good idea to en 206 It is probably not a good idea to enable this feature in a production
200 kernel. 207 kernel.
201 <<
202 If in doubt, say N. <<
203 <<
204 config HAVE_DEBUG_KMEMLEAK <<
205 bool <<
206 <<
207 config DEBUG_KMEMLEAK <<
208 bool "Kernel memory leak detector" <<
209 depends on DEBUG_KERNEL && HAVE_DEBUG_ <<
210 select DEBUG_FS <<
211 select STACKTRACE if STACKTRACE_SUPPOR <<
212 select KALLSYMS <<
213 select CRC32 <<
214 select STACKDEPOT <<
215 select STACKDEPOT_ALWAYS_INIT if !DEBU <<
216 help <<
217 Say Y here if you want to enable the <<
218 detector. The memory allocation/free <<
219 similar to the Boehm's conservative <<
220 difference being that the orphan obj <<
221 only shown in /sys/kernel/debug/kmem <<
222 feature will introduce an overhead t <<
223 allocations. See Documentation/dev-t <<
224 details. <<
225 <<
226 Enabling SLUB_DEBUG may increase the <<
227 due to the slab objects poisoning. <<
228 <<
229 In order to access the kmemleak file <<
230 mounted (usually at /sys/kernel/debu <<
231 <<
232 config DEBUG_KMEMLEAK_MEM_POOL_SIZE <<
233 int "Kmemleak memory pool size" <<
234 depends on DEBUG_KMEMLEAK <<
235 range 200 1000000 <<
236 default 16000 <<
237 help <<
238 Kmemleak must track all the memory a <<
239 reporting false positives. Since mem <<
240 freed before kmemleak is fully initi <<
241 of metadata objects to track such ca <<
242 fully initialised, this memory pool <<
243 if slab allocations fail. <<
244 <<
245 config DEBUG_KMEMLEAK_DEFAULT_OFF <<
246 bool "Default kmemleak to off" <<
247 depends on DEBUG_KMEMLEAK <<
248 help <<
249 Say Y here to disable kmemleak by de <<
250 on the command line via kmemleak=on. <<
251 <<
252 config DEBUG_KMEMLEAK_AUTO_SCAN <<
253 bool "Enable kmemleak auto scan thread <<
254 default y <<
255 depends on DEBUG_KMEMLEAK <<
256 help <<
257 Depending on the cpu, kmemleak scan <<
258 stall user tasks at times. This opti <<
259 kmemleak scan at boot up. <<
260 <<
261 Say N here to disable kmemleak auto <<
262 scanning. Disabling this option disa <<
263 memory leaks. <<
264 <<
265 If unsure, say Y. <<
266 <<
267 config PER_VMA_LOCK_STATS <<
268 bool "Statistics for per-vma locks" <<
269 depends on PER_VMA_LOCK <<
270 help <<
271 Say Y here to enable success, retry <<
272 faults handled under protection of p <<
273 counters are exposed in /proc/vmstat <<
274 kernel developers to evaluate effect <<
275 identify pathological cases. Countin <<
276 overhead in the page fault path. <<
277 208
278 If in doubt, say N. 209 If in doubt, say N.
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