1config PAGE_EXTENSION 2 bool "Extend memmap on extra space for more information on page" 3 ---help--- 4 Extend memmap on extra space for more information on page. This 5 could be used for debugging features that need to insert extra 6 field for every page. This extension enables us to save memory 7 by not allocating this extra memory according to boottime 8 configuration. 9 10config DEBUG_PAGEALLOC 11 bool "Debug page memory allocations" 12 depends on DEBUG_KERNEL 13 depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC 14 select PAGE_EXTENSION 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 For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC, 22 fill the pages with poison patterns after free_pages() and verify 23 the patterns before alloc_pages(). Additionally, 24 this option cannot be enabled in combination with hibernation as 25 that would result in incorrect warnings of memory corruption after 26 a resume because free pages are not saved to the suspend image. 27 28 By default this option will have a small overhead, e.g. by not 29 allowing the kernel mapping to be backed by large pages on some 30 architectures. Even bigger overhead comes when the debugging is 31 enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc 32 command line parameter. 33 34config DEBUG_PAGEALLOC_ENABLE_DEFAULT 35 bool "Enable debug page memory allocations by default?" 36 depends on DEBUG_PAGEALLOC 37 ---help--- 38 Enable debug page memory allocations by default? This value 39 can be overridden by debug_pagealloc=off|on. 40 41config PAGE_OWNER 42 bool "Track page owner" 43 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 44 select DEBUG_FS 45 select STACKTRACE 46 select STACKDEPOT 47 select PAGE_EXTENSION 48 help 49 This keeps track of what call chain is the owner of a page, may 50 help to find bare alloc_page(s) leaks. Even if you include this 51 feature on your build, it is disabled in default. You should pass 52 "page_owner=on" to boot parameter in order to enable it. Eats 53 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 54 for user-space helper. 55 56 If unsure, say N. 57 58config PAGE_POISONING 59 bool "Poison pages after freeing" 60 select PAGE_POISONING_NO_SANITY if HIBERNATION 61 ---help--- 62 Fill the pages with poison patterns after free_pages() and verify 63 the patterns before alloc_pages. The filling of the memory helps 64 reduce the risk of information leaks from freed data. This does 65 have a potential performance impact if enabled with the 66 "page_poison=1" kernel boot option. 67 68 Note that "poison" here is not the same thing as the "HWPoison" 69 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 70 71 If unsure, say N 72 73config PAGE_POISONING_NO_SANITY 74 depends on PAGE_POISONING 75 bool "Only poison, don't sanity check" 76 ---help--- 77 Skip the sanity checking on alloc, only fill the pages with 78 poison on free. This reduces some of the overhead of the 79 poisoning feature. 80 81 If you are only interested in sanitization, say Y. Otherwise 82 say N. 83 84config PAGE_POISONING_ZERO 85 bool "Use zero for poisoning instead of debugging value" 86 depends on PAGE_POISONING 87 ---help--- 88 Instead of using the existing poison value, fill the pages with 89 zeros. This makes it harder to detect when errors are occurring 90 due to sanitization but the zeroing at free means that it is 91 no longer necessary to write zeros when GFP_ZERO is used on 92 allocation. 93 94 If unsure, say N 95 96config DEBUG_PAGE_REF 97 bool "Enable tracepoint to track down page reference manipulation" 98 depends on DEBUG_KERNEL 99 depends on TRACEPOINTS 100 ---help--- 101 This is a feature to add tracepoint for tracking down page reference 102 manipulation. This tracking is useful to diagnose functional failure 103 due to migration failures caused by page reference mismatches. Be 104 careful when enabling this feature because it adds about 30 KB to the 105 kernel code. However the runtime performance overhead is virtually 106 nil until the tracepoints are actually enabled. 107 108config DEBUG_RODATA_TEST 109 bool "Testcase for the marking rodata read-only" 110 depends on STRICT_KERNEL_RWX 111 ---help--- 112 This option enables a testcase for the setting rodata read-only. 113