1config PAGE_EXTENSION
 2	bool "Extend memmap on extra space for more information on page"
 3	---help---
 4	  Extend memmap on extra space for more information on page. This
 5	  could be used for debugging features that need to insert extra
 6	  field for every page. This extension enables us to save memory
 7	  by not allocating this extra memory according to boottime
 8	  configuration.
 9
10config DEBUG_PAGEALLOC
11	bool "Debug page memory allocations"
12	depends on DEBUG_KERNEL
13	depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
14	select PAGE_EXTENSION
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	  For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
22	  fill the pages with poison patterns after free_pages() and verify
23	  the patterns before alloc_pages().  Additionally,
24	  this option cannot be enabled in combination with hibernation as
25	  that would result in incorrect warnings of memory corruption after
26	  a resume because free pages are not saved to the suspend image.
27
28	  By default this option will have a small overhead, e.g. by not
29	  allowing the kernel mapping to be backed by large pages on some
30	  architectures. Even bigger overhead comes when the debugging is
31	  enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc
32	  command line parameter.
33
34config DEBUG_PAGEALLOC_ENABLE_DEFAULT
35	bool "Enable debug page memory allocations by default?"
36	default n
37	depends on DEBUG_PAGEALLOC
38	---help---
39	  Enable debug page memory allocations by default? This value
40	  can be overridden by debug_pagealloc=off|on.
41
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
42config PAGE_POISONING
43	bool "Poison pages after freeing"
44	select PAGE_POISONING_NO_SANITY if HIBERNATION
45	---help---
46	  Fill the pages with poison patterns after free_pages() and verify
47	  the patterns before alloc_pages. The filling of the memory helps
48	  reduce the risk of information leaks from freed data. This does
49	  have a potential performance impact.
 
50
51	  Note that "poison" here is not the same thing as the "HWPoison"
52	  for CONFIG_MEMORY_FAILURE. This is software poisoning only.
53
54	  If unsure, say N
 
 
55
56config PAGE_POISONING_NO_SANITY
57	depends on PAGE_POISONING
58	bool "Only poison, don't sanity check"
59	---help---
60	   Skip the sanity checking on alloc, only fill the pages with
61	   poison on free. This reduces some of the overhead of the
62	   poisoning feature.
63
64	   If you are only interested in sanitization, say Y. Otherwise
65	   say N.
66
67config PAGE_POISONING_ZERO
68	bool "Use zero for poisoning instead of random data"
69	depends on PAGE_POISONING
70	---help---
71	   Instead of using the existing poison value, fill the pages with
72	   zeros. This makes it harder to detect when errors are occurring
73	   due to sanitization but the zeroing at free means that it is
74	   no longer necessary to write zeros when GFP_ZERO is used on
75	   allocation.
76
77	   If unsure, say N
78	bool
79
80config DEBUG_PAGE_REF
81	bool "Enable tracepoint to track down page reference manipulation"
82	depends on DEBUG_KERNEL
83	depends on TRACEPOINTS
84	---help---
85	  This is a feature to add tracepoint for tracking down page reference
86	  manipulation. This tracking is useful to diagnose functional failure
87	  due to migration failures caused by page reference mismatches.  Be
88	  careful when enabling this feature because it adds about 30 KB to the
89	  kernel code.  However the runtime performance overhead is virtually
90	  nil until the tracepoints are actually enabled.
91
92config DEBUG_RODATA_TEST
93    bool "Testcase for the marking rodata read-only"
94    depends on STRICT_KERNEL_RWX
95    ---help---
96      This option enables a testcase for the setting rodata read-only.

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