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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.
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 help
68 Fill the pages with poison patterns after free_pages() and verify
69 the patterns before alloc_pages. The filling of the memory helps
70 reduce the risk of information leaks from freed data. This does
71 have a potential performance impact if enabled with the
72 "page_poison=1" kernel boot option.
73
74 Note that "poison" here is not the same thing as the "HWPoison"
75 for CONFIG_MEMORY_FAILURE. This is software poisoning only.
76
77 If you are only interested in sanitization of freed pages without
78 checking the poison pattern on alloc, you can boot the kernel with
79 "init_on_free=1" instead of enabling this.
80
81 If unsure, say N
82
83config DEBUG_PAGE_REF
84 bool "Enable tracepoint to track down page reference manipulation"
85 depends on DEBUG_KERNEL
86 depends on TRACEPOINTS
87 help
88 This is a feature to add tracepoint for tracking down page reference
89 manipulation. This tracking is useful to diagnose functional failure
90 due to migration failures caused by page reference mismatches. Be
91 careful when enabling this feature because it adds about 30 KB to the
92 kernel code. However the runtime performance overhead is virtually
93 nil until the tracepoints are actually enabled.
94
95config DEBUG_RODATA_TEST
96 bool "Testcase for the marking rodata read-only"
97 depends on STRICT_KERNEL_RWX
98 help
99 This option enables a testcase for the setting rodata read-only.
100
101config ARCH_HAS_DEBUG_WX
102 bool
103
104config DEBUG_WX
105 bool "Warn on W+X mappings at boot"
106 depends on ARCH_HAS_DEBUG_WX
107 depends on MMU
108 select PTDUMP_CORE
109 help
110 Generate a warning if any W+X mappings are found at boot.
111
112 This is useful for discovering cases where the kernel is leaving W+X
113 mappings after applying NX, as such mappings are a security risk.
114
115 Look for a message in dmesg output like this:
116
117 <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
118
119 or like this, if the check failed:
120
121 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
122
123 Note that even if the check fails, your kernel is possibly
124 still fine, as W+X mappings are not a security hole in
125 themselves, what they do is that they make the exploitation
126 of other unfixed kernel bugs easier.
127
128 There is no runtime or memory usage effect of this option
129 once the kernel has booted up - it's a one time check.
130
131 If in doubt, say "Y".
132
133config GENERIC_PTDUMP
134 bool
135
136config PTDUMP_CORE
137 bool
138
139config PTDUMP_DEBUGFS
140 bool "Export kernel pagetable layout to userspace via debugfs"
141 depends on DEBUG_KERNEL
142 depends on DEBUG_FS
143 depends on GENERIC_PTDUMP
144 select PTDUMP_CORE
145 help
146 Say Y here if you want to show the kernel pagetable layout in a
147 debugfs file. This information is only useful for kernel developers
148 who are working in architecture specific areas of the kernel.
149 It is probably not a good idea to enable this feature in a production
150 kernel.
151
152 If in doubt, say N.