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 PAGE_OWNER
 49	bool "Track page owner"
 50	depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
 51	select DEBUG_FS
 52	select STACKTRACE
 53	select STACKDEPOT
 54	select PAGE_EXTENSION
 55	help
 56	  This keeps track of what call chain is the owner of a page, may
 57	  help to find bare alloc_page(s) leaks. Even if you include this
 58	  feature on your build, it is disabled in default. You should pass
 59	  "page_owner=on" to boot parameter in order to enable it. Eats
 60	  a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
 61	  for user-space helper.
 62
 63	  If unsure, say N.
 64
 65config PAGE_POISONING
 66	bool "Poison pages after freeing"
 67	select PAGE_POISONING_NO_SANITY if HIBERNATION
 68	help
 69	  Fill the pages with poison patterns after free_pages() and verify
 70	  the patterns before alloc_pages. The filling of the memory helps
 71	  reduce the risk of information leaks from freed data. This does
 72	  have a potential performance impact if enabled with the
 73	  "page_poison=1" kernel boot option.
 74
 75	  Note that "poison" here is not the same thing as the "HWPoison"
 76	  for CONFIG_MEMORY_FAILURE. This is software poisoning only.
 77
 78	  If unsure, say N
 79
 80config PAGE_POISONING_NO_SANITY
 81	depends on PAGE_POISONING
 82	bool "Only poison, don't sanity check"
 83	help
 84	   Skip the sanity checking on alloc, only fill the pages with
 85	   poison on free. This reduces some of the overhead of the
 86	   poisoning feature.
 87
 88	   If you are only interested in sanitization, say Y. Otherwise
 89	   say N.
 90
 91config PAGE_POISONING_ZERO
 92	bool "Use zero for poisoning instead of debugging value"
 93	depends on PAGE_POISONING
 94	help
 95	   Instead of using the existing poison value, fill the pages with
 96	   zeros. This makes it harder to detect when errors are occurring
 97	   due to sanitization but the zeroing at free means that it is
 98	   no longer necessary to write zeros when GFP_ZERO is used on
 99	   allocation.
100
101	   If unsure, say N
102
103config DEBUG_PAGE_REF
104	bool "Enable tracepoint to track down page reference manipulation"
105	depends on DEBUG_KERNEL
106	depends on TRACEPOINTS
107	help
108	  This is a feature to add tracepoint for tracking down page reference
109	  manipulation. This tracking is useful to diagnose functional failure
110	  due to migration failures caused by page reference mismatches.  Be
111	  careful when enabling this feature because it adds about 30 KB to the
112	  kernel code.  However the runtime performance overhead is virtually
113	  nil until the tracepoints are actually enabled.
114
115config DEBUG_RODATA_TEST
116    bool "Testcase for the marking rodata read-only"
117    depends on STRICT_KERNEL_RWX
118	help
119      This option enables a testcase for the setting rodata read-only.
120
121config ARCH_HAS_DEBUG_WX
122	bool
123
124config DEBUG_WX
125	bool "Warn on W+X mappings at boot"
126	depends on ARCH_HAS_DEBUG_WX
127	depends on MMU
128	select PTDUMP_CORE
129	help
130	  Generate a warning if any W+X mappings are found at boot.
131
132	  This is useful for discovering cases where the kernel is leaving W+X
133	  mappings after applying NX, as such mappings are a security risk.
134
135	  Look for a message in dmesg output like this:
136
137	    <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
138
139	  or like this, if the check failed:
140
141	    <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
142
143	  Note that even if the check fails, your kernel is possibly
144	  still fine, as W+X mappings are not a security hole in
145	  themselves, what they do is that they make the exploitation
146	  of other unfixed kernel bugs easier.
147
148	  There is no runtime or memory usage effect of this option
149	  once the kernel has booted up - it's a one time check.
150
151	  If in doubt, say "Y".
152
153config GENERIC_PTDUMP
154	bool
155
156config PTDUMP_CORE
157	bool
158
159config PTDUMP_DEBUGFS
160	bool "Export kernel pagetable layout to userspace via debugfs"
161	depends on DEBUG_KERNEL
162	depends on DEBUG_FS
163	depends on GENERIC_PTDUMP
164	select PTDUMP_CORE
165	help
166	  Say Y here if you want to show the kernel pagetable layout in a
167	  debugfs file. This information is only useful for kernel developers
168	  who are working in architecture specific areas of the kernel.
169	  It is probably not a good idea to enable this feature in a production
170	  kernel.
171
172	  If in doubt, say N.

 
 
 
 
 
 
 
 
 
 
 1config DEBUG_PAGEALLOC
 2	bool "Debug page memory allocations"
 3	depends on DEBUG_KERNEL
 4	depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
 5	depends on !KMEMCHECK
 6	select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
 7	---help---
 8	  Unmap pages from the kernel linear mapping after free_pages().
 9	  This results in a large slowdown, but helps to find certain types
10	  of memory corruption.
 
 
 
 
 
 
 
11
12	  For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
13	  fill the pages with poison patterns after free_pages() and verify
14	  the patterns before alloc_pages().  Additionally,
15	  this option cannot be enabled in combination with hibernation as
16	  that would result in incorrect warnings of memory corruption after
17	  a resume because free pages are not saved to the suspend image.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
18
19config WANT_PAGE_DEBUG_FLAGS
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
20	bool
21
22config PAGE_POISONING
23	bool
24	select WANT_PAGE_DEBUG_FLAGS