1 # SPDX-License-Identifier: GPL-2.0-only
3 bool "Extend memmap on extra space for more information on page"
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
11 config 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
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.
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.
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.
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.
41 config DEBUG_PAGEALLOC_ENABLE_DEFAULT
42 bool "Enable debug page memory allocations by default?"
43 depends on DEBUG_PAGEALLOC
45 Enable debug page memory allocations by default? This value
46 can be overridden by debug_pagealloc=off|on.
49 bool "Track page owner"
50 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
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.
66 bool "Poison pages after freeing"
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.
74 Note that "poison" here is not the same thing as the "HWPoison"
75 for CONFIG_MEMORY_FAILURE. This is software poisoning only.
79 config PAGE_POISONING_NO_SANITY
80 depends on PAGE_POISONING
81 bool "Only poison, don't sanity check"
83 Skip the sanity checking on alloc, only fill the pages with
84 poison on free. This reduces some of the overhead of the
87 If you are only interested in sanitization, say Y. Otherwise
90 config PAGE_POISONING_ZERO
91 bool "Use zero for poisoning instead of debugging value"
92 depends on PAGE_POISONING
94 Instead of using the existing poison value, fill the pages with
95 zeros. This makes it harder to detect when errors are occurring
96 due to sanitization but the zeroing at free means that it is
97 no longer necessary to write zeros when GFP_ZERO is used on
102 config DEBUG_PAGE_REF
103 bool "Enable tracepoint to track down page reference manipulation"
104 depends on DEBUG_KERNEL
105 depends on TRACEPOINTS
107 This is a feature to add tracepoint for tracking down page reference
108 manipulation. This tracking is useful to diagnose functional failure
109 due to migration failures caused by page reference mismatches. Be
110 careful when enabling this feature because it adds about 30 KB to the
111 kernel code. However the runtime performance overhead is virtually
112 nil until the tracepoints are actually enabled.
114 config DEBUG_RODATA_TEST
115 bool "Testcase for the marking rodata read-only"
116 depends on STRICT_KERNEL_RWX
118 This option enables a testcase for the setting rodata read-only.
120 config ARCH_HAS_DEBUG_WX
124 bool "Warn on W+X mappings at boot"
125 depends on ARCH_HAS_DEBUG_WX
129 Generate a warning if any W+X mappings are found at boot.
131 This is useful for discovering cases where the kernel is leaving W+X
132 mappings after applying NX, as such mappings are a security risk.
134 Look for a message in dmesg output like this:
136 <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
138 or like this, if the check failed:
140 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
142 Note that even if the check fails, your kernel is possibly
143 still fine, as W+X mappings are not a security hole in
144 themselves, what they do is that they make the exploitation
145 of other unfixed kernel bugs easier.
147 There is no runtime or memory usage effect of this option
148 once the kernel has booted up - it's a one time check.
150 If in doubt, say "Y".
152 config GENERIC_PTDUMP
158 config PTDUMP_DEBUGFS
159 bool "Export kernel pagetable layout to userspace via debugfs"
160 depends on DEBUG_KERNEL
162 depends on GENERIC_PTDUMP
165 Say Y here if you want to show the kernel pagetable layout in a
166 debugfs file. This information is only useful for kernel developers
167 who are working in architecture specific areas of the kernel.
168 It is probably not a good idea to enable this feature in a production