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 if enabled with the
50	  "page_poison=1" kernel boot option.
51
52	  Note that "poison" here is not the same thing as the "HWPoison"
53	  for CONFIG_MEMORY_FAILURE. This is software poisoning only.
54
55	  If unsure, say N
56
57config PAGE_POISONING_NO_SANITY
58	depends on PAGE_POISONING
59	bool "Only poison, don't sanity check"
60	---help---
61	   Skip the sanity checking on alloc, only fill the pages with
62	   poison on free. This reduces some of the overhead of the
63	   poisoning feature.
64
65	   If you are only interested in sanitization, say Y. Otherwise
66	   say N.
67
68config PAGE_POISONING_ZERO
69	bool "Use zero for poisoning instead of debugging value"
70	depends on PAGE_POISONING
71	---help---
72	   Instead of using the existing poison value, fill the pages with
73	   zeros. This makes it harder to detect when errors are occurring
74	   due to sanitization but the zeroing at free means that it is
75	   no longer necessary to write zeros when GFP_ZERO is used on
76	   allocation.
77
78	   If unsure, say N
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.
97