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 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
 56config SLUB_DEBUG
 57	default y
 58	bool "Enable SLUB debugging support" if EXPERT
 59	depends on SLUB && SYSFS && !SLUB_TINY
 60	select STACKDEPOT if STACKTRACE_SUPPORT
 61	help
 62	  SLUB has extensive debug support features. Disabling these can
 63	  result in significant savings in code size. This also disables
 64	  SLUB sysfs support. /sys/slab will not exist and there will be
 65	  no support for cache validation etc.
 66
 67config SLUB_DEBUG_ON
 68	bool "SLUB debugging on by default"
 69	depends on SLUB && SLUB_DEBUG
 70	select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT
 71	default n
 72	help
 73	  Boot with debugging on by default. SLUB boots by default with
 74	  the runtime debug capabilities switched off. Enabling this is
 75	  equivalent to specifying the "slub_debug" parameter on boot.
 76	  There is no support for more fine grained debug control like
 77	  possible with slub_debug=xxx. SLUB debugging may be switched
 78	  off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
 79	  "slub_debug=-".
 80
 81config PAGE_OWNER
 82	bool "Track page owner"
 83	depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
 84	select DEBUG_FS
 85	select STACKTRACE
 86	select STACKDEPOT
 87	select PAGE_EXTENSION
 88	help
 89	  This keeps track of what call chain is the owner of a page, may
 90	  help to find bare alloc_page(s) leaks. Even if you include this
 91	  feature on your build, it is disabled in default. You should pass
 92	  "page_owner=on" to boot parameter in order to enable it. Eats
 93	  a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
 94	  for user-space helper.
 95
 96	  If unsure, say N.
 97
 98config PAGE_TABLE_CHECK
 99	bool "Check for invalid mappings in user page tables"
100	depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK
101	select PAGE_EXTENSION
102	help
103	  Check that anonymous page is not being mapped twice with read write
104	  permissions. Check that anonymous and file pages are not being
105	  erroneously shared. Since the checking is performed at the time
106	  entries are added and removed to user page tables, leaking, corruption
107	  and double mapping problems are detected synchronously.
108
109	  If unsure say "n".
110
111config PAGE_TABLE_CHECK_ENFORCED
112	bool "Enforce the page table checking by default"
113	depends on PAGE_TABLE_CHECK
114	help
115	  Always enable page table checking.  By default the page table checking
116	  is disabled, and can be optionally enabled via page_table_check=on
117	  kernel parameter. This config enforces that page table check is always
118	  enabled.
119
120	  If unsure say "n".
121
122config PAGE_POISONING
123	bool "Poison pages after freeing"
124	help
 
125	  Fill the pages with poison patterns after free_pages() and verify
126	  the patterns before alloc_pages. The filling of the memory helps
127	  reduce the risk of information leaks from freed data. This does
128	  have a potential performance impact if enabled with the
129	  "page_poison=1" kernel boot option.
130
131	  Note that "poison" here is not the same thing as the "HWPoison"
132	  for CONFIG_MEMORY_FAILURE. This is software poisoning only.
133
134	  If you are only interested in sanitization of freed pages without
135	  checking the poison pattern on alloc, you can boot the kernel with
136	  "init_on_free=1" instead of enabling this.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
137
138	  If unsure, say N
 
139
140config DEBUG_PAGE_REF
141	bool "Enable tracepoint to track down page reference manipulation"
142	depends on DEBUG_KERNEL
143	depends on TRACEPOINTS
144	help
145	  This is a feature to add tracepoint for tracking down page reference
146	  manipulation. This tracking is useful to diagnose functional failure
147	  due to migration failures caused by page reference mismatches.  Be
148	  careful when enabling this feature because it adds about 30 KB to the
149	  kernel code.  However the runtime performance overhead is virtually
150	  nil until the tracepoints are actually enabled.
151
152config DEBUG_RODATA_TEST
153    bool "Testcase for the marking rodata read-only"
154    depends on STRICT_KERNEL_RWX
155	help
156      This option enables a testcase for the setting rodata read-only.
157
158config ARCH_HAS_DEBUG_WX
159	bool
160
161config DEBUG_WX
162	bool "Warn on W+X mappings at boot"
163	depends on ARCH_HAS_DEBUG_WX
164	depends on MMU
165	select PTDUMP_CORE
166	help
167	  Generate a warning if any W+X mappings are found at boot.
168
169	  This is useful for discovering cases where the kernel is leaving W+X
170	  mappings after applying NX, as such mappings are a security risk.
171
172	  Look for a message in dmesg output like this:
173
174	    <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
175
176	  or like this, if the check failed:
177
178	    <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
179
180	  Note that even if the check fails, your kernel is possibly
181	  still fine, as W+X mappings are not a security hole in
182	  themselves, what they do is that they make the exploitation
183	  of other unfixed kernel bugs easier.
184
185	  There is no runtime or memory usage effect of this option
186	  once the kernel has booted up - it's a one time check.
187
188	  If in doubt, say "Y".
189
190config GENERIC_PTDUMP
191	bool
192
193config PTDUMP_CORE
194	bool
195
196config PTDUMP_DEBUGFS
197	bool "Export kernel pagetable layout to userspace via debugfs"
198	depends on DEBUG_KERNEL
199	depends on DEBUG_FS
200	depends on GENERIC_PTDUMP
201	select PTDUMP_CORE
202	help
203	  Say Y here if you want to show the kernel pagetable layout in a
204	  debugfs file. This information is only useful for kernel developers
205	  who are working in architecture specific areas of the kernel.
206	  It is probably not a good idea to enable this feature in a production
207	  kernel.
208
209	  If in doubt, say N.