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 default n 37 depends on DEBUG_PAGEALLOC 38 ---help--- 39 Enable debug page memory allocations by default? This value 40 can be overridden by debug_pagealloc=off|on. 41 42config PAGE_POISONING 43 bool "Poison pages after freeing" 44 select PAGE_POISONING_NO_SANITY if HIBERNATION 45 ---help--- 46 Fill the pages with poison patterns after free_pages() and verify 47 the patterns before alloc_pages. The filling of the memory helps 48 reduce the risk of information leaks from freed data. This does 49 have a potential performance impact. 50 51 Note that "poison" here is not the same thing as the "HWPoison" 52 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 53 54 If unsure, say N 55 56config PAGE_POISONING_NO_SANITY 57 depends on PAGE_POISONING 58 bool "Only poison, don't sanity check" 59 ---help--- 60 Skip the sanity checking on alloc, only fill the pages with 61 poison on free. This reduces some of the overhead of the 62 poisoning feature. 63 64 If you are only interested in sanitization, say Y. Otherwise 65 say N. 66 67config PAGE_POISONING_ZERO 68 bool "Use zero for poisoning instead of random data" 69 depends on PAGE_POISONING 70 ---help--- 71 Instead of using the existing poison value, fill the pages with 72 zeros. This makes it harder to detect when errors are occurring 73 due to sanitization but the zeroing at free means that it is 74 no longer necessary to write zeros when GFP_ZERO is used on 75 allocation. 76 77 If unsure, say N 78 bool 79 80config DEBUG_PAGE_REF 81 bool "Enable tracepoint to track down page reference manipulation" 82 depends on DEBUG_KERNEL 83 depends on TRACEPOINTS 84 ---help--- 85 This is a feature to add tracepoint for tracking down page reference 86 manipulation. This tracking is useful to diagnose functional failure 87 due to migration failures caused by page reference mismatches. Be 88 careful when enabling this feature because it adds about 30 KB to the 89 kernel code. However the runtime performance overhead is virtually 90 nil until the tracepoints are actually enabled. 91 92config DEBUG_RODATA_TEST 93 bool "Testcase for the marking rodata read-only" 94 depends on STRICT_KERNEL_RWX 95 ---help--- 96 This option enables a testcase for the setting rodata read-only. 97