0001 # SPDX-License-Identifier: GPL-2.0-only
0002 config PAGE_EXTENSION
0003 bool "Extend memmap on extra space for more information on page"
0004 help
0005 Extend memmap on extra space for more information on page. This
0006 could be used for debugging features that need to insert extra
0007 field for every page. This extension enables us to save memory
0008 by not allocating this extra memory according to boottime
0009 configuration.
0010
0011 config DEBUG_PAGEALLOC
0012 bool "Debug page memory allocations"
0013 depends on DEBUG_KERNEL
0014 depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
0015 select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
0016 help
0017 Unmap pages from the kernel linear mapping after free_pages().
0018 Depending on runtime enablement, this results in a small or large
0019 slowdown, but helps to find certain types of memory corruption.
0020
0021 Also, the state of page tracking structures is checked more often as
0022 pages are being allocated and freed, as unexpected state changes
0023 often happen for same reasons as memory corruption (e.g. double free,
0024 use-after-free). The error reports for these checks can be augmented
0025 with stack traces of last allocation and freeing of the page, when
0026 PAGE_OWNER is also selected and enabled on boot.
0027
0028 For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
0029 fill the pages with poison patterns after free_pages() and verify
0030 the patterns before alloc_pages(). Additionally, this option cannot
0031 be enabled in combination with hibernation as that would result in
0032 incorrect warnings of memory corruption after a resume because free
0033 pages are not saved to the suspend image.
0034
0035 By default this option will have a small overhead, e.g. by not
0036 allowing the kernel mapping to be backed by large pages on some
0037 architectures. Even bigger overhead comes when the debugging is
0038 enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc
0039 command line parameter.
0040
0041 config DEBUG_PAGEALLOC_ENABLE_DEFAULT
0042 bool "Enable debug page memory allocations by default?"
0043 depends on DEBUG_PAGEALLOC
0044 help
0045 Enable debug page memory allocations by default? This value
0046 can be overridden by debug_pagealloc=off|on.
0047
0048 config DEBUG_SLAB
0049 bool "Debug slab memory allocations"
0050 depends on DEBUG_KERNEL && SLAB
0051 help
0052 Say Y here to have the kernel do limited verification on memory
0053 allocation as well as poisoning memory on free to catch use of freed
0054 memory. This can make kmalloc/kfree-intensive workloads much slower.
0055
0056 config SLUB_DEBUG
0057 default y
0058 bool "Enable SLUB debugging support" if EXPERT
0059 depends on SLUB && SYSFS
0060 select STACKDEPOT if STACKTRACE_SUPPORT
0061 help
0062 SLUB has extensive debug support features. Disabling these can
0063 result in significant savings in code size. This also disables
0064 SLUB sysfs support. /sys/slab will not exist and there will be
0065 no support for cache validation etc.
0066
0067 config SLUB_DEBUG_ON
0068 bool "SLUB debugging on by default"
0069 depends on SLUB && SLUB_DEBUG
0070 select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT
0071 default n
0072 help
0073 Boot with debugging on by default. SLUB boots by default with
0074 the runtime debug capabilities switched off. Enabling this is
0075 equivalent to specifying the "slub_debug" parameter on boot.
0076 There is no support for more fine grained debug control like
0077 possible with slub_debug=xxx. SLUB debugging may be switched
0078 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
0079 "slub_debug=-".
0080
0081 config PAGE_OWNER
0082 bool "Track page owner"
0083 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
0084 select DEBUG_FS
0085 select STACKTRACE
0086 select STACKDEPOT
0087 select PAGE_EXTENSION
0088 help
0089 This keeps track of what call chain is the owner of a page, may
0090 help to find bare alloc_page(s) leaks. Even if you include this
0091 feature on your build, it is disabled in default. You should pass
0092 "page_owner=on" to boot parameter in order to enable it. Eats
0093 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
0094 for user-space helper.
0095
0096 If unsure, say N.
0097
0098 config PAGE_TABLE_CHECK
0099 bool "Check for invalid mappings in user page tables"
0100 depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK
0101 select PAGE_EXTENSION
0102 help
0103 Check that anonymous page is not being mapped twice with read write
0104 permissions. Check that anonymous and file pages are not being
0105 erroneously shared. Since the checking is performed at the time
0106 entries are added and removed to user page tables, leaking, corruption
0107 and double mapping problems are detected synchronously.
0108
0109 If unsure say "n".
0110
0111 config PAGE_TABLE_CHECK_ENFORCED
0112 bool "Enforce the page table checking by default"
0113 depends on PAGE_TABLE_CHECK
0114 help
0115 Always enable page table checking. By default the page table checking
0116 is disabled, and can be optionally enabled via page_table_check=on
0117 kernel parameter. This config enforces that page table check is always
0118 enabled.
0119
0120 If unsure say "n".
0121
0122 config PAGE_POISONING
0123 bool "Poison pages after freeing"
0124 help
0125 Fill the pages with poison patterns after free_pages() and verify
0126 the patterns before alloc_pages. The filling of the memory helps
0127 reduce the risk of information leaks from freed data. This does
0128 have a potential performance impact if enabled with the
0129 "page_poison=1" kernel boot option.
0130
0131 Note that "poison" here is not the same thing as the "HWPoison"
0132 for CONFIG_MEMORY_FAILURE. This is software poisoning only.
0133
0134 If you are only interested in sanitization of freed pages without
0135 checking the poison pattern on alloc, you can boot the kernel with
0136 "init_on_free=1" instead of enabling this.
0137
0138 If unsure, say N
0139
0140 config DEBUG_PAGE_REF
0141 bool "Enable tracepoint to track down page reference manipulation"
0142 depends on DEBUG_KERNEL
0143 depends on TRACEPOINTS
0144 help
0145 This is a feature to add tracepoint for tracking down page reference
0146 manipulation. This tracking is useful to diagnose functional failure
0147 due to migration failures caused by page reference mismatches. Be
0148 careful when enabling this feature because it adds about 30 KB to the
0149 kernel code. However the runtime performance overhead is virtually
0150 nil until the tracepoints are actually enabled.
0151
0152 config DEBUG_RODATA_TEST
0153 bool "Testcase for the marking rodata read-only"
0154 depends on STRICT_KERNEL_RWX
0155 help
0156 This option enables a testcase for the setting rodata read-only.
0157
0158 config ARCH_HAS_DEBUG_WX
0159 bool
0160
0161 config DEBUG_WX
0162 bool "Warn on W+X mappings at boot"
0163 depends on ARCH_HAS_DEBUG_WX
0164 depends on MMU
0165 select PTDUMP_CORE
0166 help
0167 Generate a warning if any W+X mappings are found at boot.
0168
0169 This is useful for discovering cases where the kernel is leaving W+X
0170 mappings after applying NX, as such mappings are a security risk.
0171
0172 Look for a message in dmesg output like this:
0173
0174 <arch>/mm: Checked W+X mappings: passed, no W+X pages found.
0175
0176 or like this, if the check failed:
0177
0178 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found.
0179
0180 Note that even if the check fails, your kernel is possibly
0181 still fine, as W+X mappings are not a security hole in
0182 themselves, what they do is that they make the exploitation
0183 of other unfixed kernel bugs easier.
0184
0185 There is no runtime or memory usage effect of this option
0186 once the kernel has booted up - it's a one time check.
0187
0188 If in doubt, say "Y".
0189
0190 config GENERIC_PTDUMP
0191 bool
0192
0193 config PTDUMP_CORE
0194 bool
0195
0196 config PTDUMP_DEBUGFS
0197 bool "Export kernel pagetable layout to userspace via debugfs"
0198 depends on DEBUG_KERNEL
0199 depends on DEBUG_FS
0200 depends on GENERIC_PTDUMP
0201 select PTDUMP_CORE
0202 help
0203 Say Y here if you want to show the kernel pagetable layout in a
0204 debugfs file. This information is only useful for kernel developers
0205 who are working in architecture specific areas of the kernel.
0206 It is probably not a good idea to enable this feature in a production
0207 kernel.
0208
0209 If in doubt, say N.
