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 depends on !KMEMCHECK 15 select PAGE_EXTENSION 16 select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC 17 ---help--- 18 Unmap pages from the kernel linear mapping after free_pages(). 19 Depending on runtime enablement, this results in a small or large 20 slowdown, but helps to find certain types of memory corruption. 21 22 For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC, 23 fill the pages with poison patterns after free_pages() and verify 24 the patterns before alloc_pages(). Additionally, 25 this option cannot be enabled in combination with hibernation as 26 that would result in incorrect warnings of memory corruption after 27 a resume because free pages are not saved to the suspend image. 28 29 By default this option will have a small overhead, e.g. by not 30 allowing the kernel mapping to be backed by large pages on some 31 architectures. Even bigger overhead comes when the debugging is 32 enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc 33 command line parameter. 34 35config DEBUG_PAGEALLOC_ENABLE_DEFAULT 36 bool "Enable debug page memory allocations by default?" 37 default n 38 depends on DEBUG_PAGEALLOC 39 ---help--- 40 Enable debug page memory allocations by default? This value 41 can be overridden by debug_pagealloc=off|on. 42 43config PAGE_POISONING 44 bool "Poison pages after freeing" 45 select PAGE_POISONING_NO_SANITY if HIBERNATION 46 ---help--- 47 Fill the pages with poison patterns after free_pages() and verify 48 the patterns before alloc_pages. The filling of the memory helps 49 reduce the risk of information leaks from freed data. This does 50 have a potential performance impact. 51 52 Note that "poison" here is not the same thing as the "HWPoison" 53 for CONFIG_MEMORY_FAILURE. This is software poisoning only. 54 55 If unsure, say N 56 57config PAGE_POISONING_NO_SANITY 58 depends on PAGE_POISONING 59 bool "Only poison, don't sanity check" 60 ---help--- 61 Skip the sanity checking on alloc, only fill the pages with 62 poison on free. This reduces some of the overhead of the 63 poisoning feature. 64 65 If you are only interested in sanitization, say Y. Otherwise 66 say N. 67 68config PAGE_POISONING_ZERO 69 bool "Use zero for poisoning instead of random data" 70 depends on PAGE_POISONING 71 ---help--- 72 Instead of using the existing poison value, fill the pages with 73 zeros. This makes it harder to detect when errors are occurring 74 due to sanitization but the zeroing at free means that it is 75 no longer necessary to write zeros when GFP_ZERO is used on 76 allocation. 77 78 If unsure, say N 79 bool 80 81config DEBUG_PAGE_REF 82 bool "Enable tracepoint to track down page reference manipulation" 83 depends on DEBUG_KERNEL 84 depends on TRACEPOINTS 85 ---help--- 86 This is a feature to add tracepoint for tracking down page reference 87 manipulation. This tracking is useful to diagnose functional failure 88 due to migration failures caused by page reference mismatches. Be 89 careful when enabling this feature because it adds about 30 KB to the 90 kernel code. However the runtime performance overhead is virtually 91 nil until the tracepoints are actually enabled. 92 93config DEBUG_RODATA_TEST 94 bool "Testcase for the marking rodata read-only" 95 depends on STRICT_KERNEL_RWX 96 ---help--- 97 This option enables a testcase for the setting rodata read-only. 98