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