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_PINNER 66 bool "Track page pinner" 67 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 68 select DEBUG_FS 69 select STACKTRACE 70 select STACKDEPOT 71 select PAGE_EXTENSION 72 help 73 This keeps track of what call chain is the pinner of a page, may 74 help to find page migration failures. Even if you include this 75 feature in your build, it is disabled by default. You should pass 76 "page_pinner=on" to boot parameter in order to enable it. Eats 77 a fair amount of memory if enabled. 78 79 If unsure, say N. 80 81config PAGE_POISONING 82 bool "Poison pages after freeing" 83 help 84 Fill the pages with poison patterns after free_pages() and verify 85 the patterns before alloc_pages. The filling of the memory helps 86 reduce the risk of information leaks from freed data. This does 87 have a potential performance impact if enabled with the 88 "page_poison=1" kernel boot option. 89 90 Note that "poison" here is not the same thing as the "HWPoison" 91 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 92 93 If you are only interested in sanitization of freed pages without 94 checking the poison pattern on alloc, you can boot the kernel with 95 "init_on_free=1" instead of enabling this. 96 97 If unsure, say N 98 99config DEBUG_PAGE_REF 100 bool "Enable tracepoint to track down page reference manipulation" 101 depends on DEBUG_KERNEL 102 depends on TRACEPOINTS 103 help 104 This is a feature to add tracepoint for tracking down page reference 105 manipulation. This tracking is useful to diagnose functional failure 106 due to migration failures caused by page reference mismatches. Be 107 careful when enabling this feature because it adds about 30 KB to the 108 kernel code. However the runtime performance overhead is virtually 109 nil until the tracepoints are actually enabled. 110 111config DEBUG_RODATA_TEST 112 bool "Testcase for the marking rodata read-only" 113 depends on STRICT_KERNEL_RWX 114 help 115 This option enables a testcase for the setting rodata read-only. 116 117config ARCH_HAS_DEBUG_WX 118 bool 119 120config DEBUG_WX 121 bool "Warn on W+X mappings at boot" 122 depends on ARCH_HAS_DEBUG_WX 123 depends on MMU 124 select PTDUMP_CORE 125 help 126 Generate a warning if any W+X mappings are found at boot. 127 128 This is useful for discovering cases where the kernel is leaving W+X 129 mappings after applying NX, as such mappings are a security risk. 130 131 Look for a message in dmesg output like this: 132 133 <arch>/mm: Checked W+X mappings: passed, no W+X pages found. 134 135 or like this, if the check failed: 136 137 <arch>/mm: Checked W+X mappings: failed, <N> W+X pages found. 138 139 Note that even if the check fails, your kernel is possibly 140 still fine, as W+X mappings are not a security hole in 141 themselves, what they do is that they make the exploitation 142 of other unfixed kernel bugs easier. 143 144 There is no runtime or memory usage effect of this option 145 once the kernel has booted up - it's a one time check. 146 147 If in doubt, say "Y". 148 149config GENERIC_PTDUMP 150 bool 151 152config PTDUMP_CORE 153 bool 154 155config PTDUMP_DEBUGFS 156 bool "Export kernel pagetable layout to userspace via debugfs" 157 depends on DEBUG_KERNEL 158 depends on DEBUG_FS 159 depends on GENERIC_PTDUMP 160 select PTDUMP_CORE 161 help 162 Say Y here if you want to show the kernel pagetable layout in a 163 debugfs file. This information is only useful for kernel developers 164 who are working in architecture specific areas of the kernel. 165 It is probably not a good idea to enable this feature in a production 166 kernel. 167 168 If in doubt, say N. 169 170config SPECULATIVE_PAGE_FAULT_STATS 171 bool "Additional statistics for speculative page faults" 172 depends on SPECULATIVE_PAGE_FAULT 173 help 174 Additional statistics for speculative page faults. 175 If in doubt, say N. 176