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). 25 26 For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC, 27 fill the pages with poison patterns after free_pages() and verify 28 the patterns before alloc_pages(). Additionally, this option cannot 29 be enabled in combination with hibernation as that would result in 30 incorrect warnings of memory corruption after a resume because free 31 pages are not saved to the suspend image. 32 33 By default this option will have a small overhead, e.g. by not 34 allowing the kernel mapping to be backed by large pages on some 35 architectures. Even bigger overhead comes when the debugging is 36 enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc 37 command line parameter. 38 39config DEBUG_PAGEALLOC_ENABLE_DEFAULT 40 bool "Enable debug page memory allocations by default?" 41 depends on DEBUG_PAGEALLOC 42 ---help--- 43 Enable debug page memory allocations by default? This value 44 can be overridden by debug_pagealloc=off|on. 45 46config PAGE_OWNER 47 bool "Track page owner" 48 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 49 select DEBUG_FS 50 select STACKTRACE 51 select STACKDEPOT 52 select PAGE_EXTENSION 53 help 54 This keeps track of what call chain is the owner of a page, may 55 help to find bare alloc_page(s) leaks. Even if you include this 56 feature on your build, it is disabled in default. You should pass 57 "page_owner=on" to boot parameter in order to enable it. Eats 58 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 59 for user-space helper. 60 61 If unsure, say N. 62 63config PAGE_POISONING 64 bool "Poison pages after freeing" 65 select PAGE_POISONING_NO_SANITY if HIBERNATION 66 ---help--- 67 Fill the pages with poison patterns after free_pages() and verify 68 the patterns before alloc_pages. The filling of the memory helps 69 reduce the risk of information leaks from freed data. This does 70 have a potential performance impact if enabled with the 71 "page_poison=1" kernel boot option. 72 73 Note that "poison" here is not the same thing as the "HWPoison" 74 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 75 76 If unsure, say N 77 78config PAGE_POISONING_NO_SANITY 79 depends on PAGE_POISONING 80 bool "Only poison, don't sanity check" 81 ---help--- 82 Skip the sanity checking on alloc, only fill the pages with 83 poison on free. This reduces some of the overhead of the 84 poisoning feature. 85 86 If you are only interested in sanitization, say Y. Otherwise 87 say N. 88 89config PAGE_POISONING_ZERO 90 bool "Use zero for poisoning instead of debugging value" 91 depends on PAGE_POISONING 92 ---help--- 93 Instead of using the existing poison value, fill the pages with 94 zeros. This makes it harder to detect when errors are occurring 95 due to sanitization but the zeroing at free means that it is 96 no longer necessary to write zeros when GFP_ZERO is used on 97 allocation. 98 99 If unsure, say N 100 101config DEBUG_PAGE_REF 102 bool "Enable tracepoint to track down page reference manipulation" 103 depends on DEBUG_KERNEL 104 depends on TRACEPOINTS 105 ---help--- 106 This is a feature to add tracepoint for tracking down page reference 107 manipulation. This tracking is useful to diagnose functional failure 108 due to migration failures caused by page reference mismatches. Be 109 careful when enabling this feature because it adds about 30 KB to the 110 kernel code. However the runtime performance overhead is virtually 111 nil until the tracepoints are actually enabled. 112 113config DEBUG_RODATA_TEST 114 bool "Testcase for the marking rodata read-only" 115 depends on STRICT_KERNEL_RWX 116 ---help--- 117 This option enables a testcase for the setting rodata read-only. 118