Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
1# SPDX-License-Identifier: GPL-2.0-only
2config 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
11config 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
41config 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
48config 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
59config 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
73config 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
105config 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
122config 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
136config 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
147config 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
165config 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
177config 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
183config ARCH_HAS_DEBUG_WX
184 bool
185
186config DEBUG_WX
187 bool "Warn on W+X mappings at boot"
188 depends on ARCH_HAS_DEBUG_WX
189 depends on ARCH_HAS_PTDUMP
190 depends on MMU
191 select PTDUMP
192 help
193 Generate a warning if any W+X mappings are found at boot.
194
195 This is useful for discovering cases where the kernel is leaving W+X
196 mappings after applying NX, as such mappings are a security risk.
197
198 Look for a message in dmesg output like this:
199
200 <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
201
202 or like this, if the check failed:
203
204 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
205
206 Note that even if the check fails, your kernel is possibly
207 still fine, as W+X mappings are not a security hole in
208 themselves, what they do is that they make the exploitation
209 of other unfixed kernel bugs easier.
210
211 There is no runtime or memory usage effect of this option
212 once the kernel has booted up - it's a one time check.
213
214 If in doubt, say "Y".
215
216config ARCH_HAS_PTDUMP
217 bool
218
219config PTDUMP
220 bool
221
222config PTDUMP_DEBUGFS
223 bool "Export kernel pagetable layout to userspace via debugfs"
224 depends on DEBUG_KERNEL
225 depends on DEBUG_FS
226 depends on ARCH_HAS_PTDUMP
227 select PTDUMP
228 help
229 Say Y here if you want to show the kernel pagetable layout in a
230 debugfs file. This information is only useful for kernel developers
231 who are working in architecture specific areas of the kernel.
232 It is probably not a good idea to enable this feature in a production
233 kernel.
234
235 If in doubt, say N.
236
237config HAVE_DEBUG_KMEMLEAK
238 bool
239
240config DEBUG_KMEMLEAK
241 bool "Kernel memory leak detector"
242 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
243 select DEBUG_FS
244 select STACKTRACE if STACKTRACE_SUPPORT
245 select KALLSYMS
246 select CRC32
247 select STACKDEPOT
248 select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF
249 help
250 Say Y here if you want to enable the memory leak
251 detector. The memory allocation/freeing is traced in a way
252 similar to the Boehm's conservative garbage collector, the
253 difference being that the orphan objects are not freed but
254 only shown in /sys/kernel/debug/kmemleak. Enabling this
255 feature will introduce an overhead to memory
256 allocations. See Documentation/dev-tools/kmemleak.rst for more
257 details.
258
259 Enabling SLUB_DEBUG may increase the chances of finding leaks
260 due to the slab objects poisoning.
261
262 In order to access the kmemleak file, debugfs needs to be
263 mounted (usually at /sys/kernel/debug).
264
265config DEBUG_KMEMLEAK_MEM_POOL_SIZE
266 int "Kmemleak memory pool size"
267 depends on DEBUG_KMEMLEAK
268 range 200 1000000
269 default 16000
270 help
271 Kmemleak must track all the memory allocations to avoid
272 reporting false positives. Since memory may be allocated or
273 freed before kmemleak is fully initialised, use a static pool
274 of metadata objects to track such callbacks. After kmemleak is
275 fully initialised, this memory pool acts as an emergency one
276 if slab allocations fail.
277
278config DEBUG_KMEMLEAK_DEFAULT_OFF
279 bool "Default kmemleak to off"
280 depends on DEBUG_KMEMLEAK
281 help
282 Say Y here to disable kmemleak by default. It can then be enabled
283 on the command line via kmemleak=on.
284
285config DEBUG_KMEMLEAK_AUTO_SCAN
286 bool "Enable kmemleak auto scan thread on boot up"
287 default y
288 depends on DEBUG_KMEMLEAK
289 help
290 Depending on the cpu, kmemleak scan may be cpu intensive and can
291 stall user tasks at times. This option enables/disables automatic
292 kmemleak scan at boot up.
293
294 Say N here to disable kmemleak auto scan thread to stop automatic
295 scanning. Disabling this option disables automatic reporting of
296 memory leaks.
297
298 If unsure, say Y.
299
300config PER_VMA_LOCK_STATS
301 bool "Statistics for per-vma locks"
302 depends on PER_VMA_LOCK
303 help
304 Say Y here to enable success, retry and failure counters of page
305 faults handled under protection of per-vma locks. When enabled, the
306 counters are exposed in /proc/vmstat. This information is useful for
307 kernel developers to evaluate effectiveness of per-vma locks and to
308 identify pathological cases. Counting these events introduces a small
309 overhead in the page fault path.
310
311 If in doubt, say N.