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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 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.