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 DEBUG_SLAB 49 bool "Debug slab memory allocations" 50 depends on DEBUG_KERNEL && SLAB 51 help 52 Say Y here to have the kernel do limited verification on memory 53 allocation as well as poisoning memory on free to catch use of freed 54 memory. This can make kmalloc/kfree-intensive workloads much slower. 55 56config SLUB_DEBUG 57 default y 58 bool "Enable SLUB debugging support" if EXPERT 59 depends on SLUB && SYSFS 60 select STACKDEPOT if STACKTRACE_SUPPORT 61 help 62 SLUB has extensive debug support features. Disabling these can 63 result in significant savings in code size. This also disables 64 SLUB sysfs support. /sys/slab will not exist and there will be 65 no support for cache validation etc. 66 67config SLUB_DEBUG_ON 68 bool "SLUB debugging on by default" 69 depends on SLUB && SLUB_DEBUG 70 select STACKDEPOT_ALWAYS_INIT if STACKTRACE_SUPPORT 71 default n 72 help 73 Boot with debugging on by default. SLUB boots by default with 74 the runtime debug capabilities switched off. Enabling this is 75 equivalent to specifying the "slub_debug" parameter on boot. 76 There is no support for more fine grained debug control like 77 possible with slub_debug=xxx. SLUB debugging may be switched 78 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 79 "slub_debug=-". 80 81config PAGE_OWNER 82 bool "Track page owner" 83 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 84 select DEBUG_FS 85 select STACKTRACE 86 select STACKDEPOT 87 select PAGE_EXTENSION 88 help 89 This keeps track of what call chain is the owner of a page, may 90 help to find bare alloc_page(s) leaks. Even if you include this 91 feature on your build, it is disabled in default. You should pass 92 "page_owner=on" to boot parameter in order to enable it. Eats 93 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 94 for user-space helper. 95 96 If unsure, say N. 97 98config PAGE_TABLE_CHECK 99 bool "Check for invalid mappings in user page tables" 100 depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK 101 select PAGE_EXTENSION 102 help 103 Check that anonymous page is not being mapped twice with read write 104 permissions. Check that anonymous and file pages are not being 105 erroneously shared. Since the checking is performed at the time 106 entries are added and removed to user page tables, leaking, corruption 107 and double mapping problems are detected synchronously. 108 109 If unsure say "n". 110 111config PAGE_TABLE_CHECK_ENFORCED 112 bool "Enforce the page table checking by default" 113 depends on PAGE_TABLE_CHECK 114 help 115 Always enable page table checking. By default the page table checking 116 is disabled, and can be optionally enabled via page_table_check=on 117 kernel parameter. This config enforces that page table check is always 118 enabled. 119 120 If unsure say "n". 121 122config PAGE_POISONING 123 bool "Poison pages after freeing" 124 help 125 Fill the pages with poison patterns after free_pages() and verify 126 the patterns before alloc_pages. The filling of the memory helps 127 reduce the risk of information leaks from freed data. This does 128 have a potential performance impact if enabled with the 129 "page_poison=1" kernel boot option. 130 131 Note that "poison" here is not the same thing as the "HWPoison" 132 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 133 134 If you are only interested in sanitization of freed pages without 135 checking the poison pattern on alloc, you can boot the kernel with 136 "init_on_free=1" instead of enabling this. 137 138 If unsure, say N 139 140config DEBUG_PAGE_REF 141 bool "Enable tracepoint to track down page reference manipulation" 142 depends on DEBUG_KERNEL 143 depends on TRACEPOINTS 144 help 145 This is a feature to add tracepoint for tracking down page reference 146 manipulation. This tracking is useful to diagnose functional failure 147 due to migration failures caused by page reference mismatches. Be 148 careful when enabling this feature because it adds about 30 KB to the 149 kernel code. However the runtime performance overhead is virtually 150 nil until the tracepoints are actually enabled. 151 152config DEBUG_RODATA_TEST 153 bool "Testcase for the marking rodata read-only" 154 depends on STRICT_KERNEL_RWX 155 help 156 This option enables a testcase for the setting rodata read-only. 157 158config ARCH_HAS_DEBUG_WX 159 bool 160 161config DEBUG_WX 162 bool "Warn on W+X mappings at boot" 163 depends on ARCH_HAS_DEBUG_WX 164 depends on MMU 165 select PTDUMP_CORE 166 help 167 Generate a warning if any W+X mappings are found at boot. 168 169 This is useful for discovering cases where the kernel is leaving W+X 170 mappings after applying NX, as such mappings are a security risk. 171 172 Look for a message in dmesg output like this: 173 174 <arch>/mm: Checked W+X mappings: passed, no W+X pages found. 175 176 or like this, if the check failed: 177 178 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found. 179 180 Note that even if the check fails, your kernel is possibly 181 still fine, as W+X mappings are not a security hole in 182 themselves, what they do is that they make the exploitation 183 of other unfixed kernel bugs easier. 184 185 There is no runtime or memory usage effect of this option 186 once the kernel has booted up - it's a one time check. 187 188 If in doubt, say "Y". 189 190config GENERIC_PTDUMP 191 bool 192 193config PTDUMP_CORE 194 bool 195 196config PTDUMP_DEBUGFS 197 bool "Export kernel pagetable layout to userspace via debugfs" 198 depends on DEBUG_KERNEL 199 depends on DEBUG_FS 200 depends on GENERIC_PTDUMP 201 select PTDUMP_CORE 202 help 203 Say Y here if you want to show the kernel pagetable layout in a 204 debugfs file. This information is only useful for kernel developers 205 who are working in architecture specific areas of the kernel. 206 It is probably not a good idea to enable this feature in a production 207 kernel. 208 209 If in doubt, say N. 210