1# This config refers to the generic KASAN mode. 2config HAVE_ARCH_KASAN 3 bool 4 5config HAVE_ARCH_KASAN_SW_TAGS 6 bool 7 8config CC_HAS_KASAN_GENERIC 9 def_bool $(cc-option, -fsanitize=kernel-address) 10 11config CC_HAS_KASAN_SW_TAGS 12 def_bool $(cc-option, -fsanitize=kernel-hwaddress) 13 14config KASAN 15 bool "KASAN: runtime memory debugger" 16 depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \ 17 (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS) 18 depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) 19 help 20 Enables KASAN (KernelAddressSANitizer) - runtime memory debugger, 21 designed to find out-of-bounds accesses and use-after-free bugs. 22 See Documentation/dev-tools/kasan.rst for details. 23 24choice 25 prompt "KASAN mode" 26 depends on KASAN 27 default KASAN_GENERIC 28 help 29 KASAN has two modes: generic KASAN (similar to userspace ASan, 30 x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and 31 software tag-based KASAN (a version based on software memory 32 tagging, arm64 only, similar to userspace HWASan, enabled with 33 CONFIG_KASAN_SW_TAGS). 34 Both generic and tag-based KASAN are strictly debugging features. 35 36config KASAN_GENERIC 37 bool "Generic mode" 38 depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC 39 depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) 40 select SLUB_DEBUG if SLUB 41 select CONSTRUCTORS 42 select STACKDEPOT 43 help 44 Enables generic KASAN mode. 45 Supported in both GCC and Clang. With GCC it requires version 4.9.2 46 or later for basic support and version 5.0 or later for detection of 47 out-of-bounds accesses for stack and global variables and for inline 48 instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires 49 version 3.7.0 or later and it doesn't support detection of 50 out-of-bounds accesses for global variables yet. 51 This mode consumes about 1/8th of available memory at kernel start 52 and introduces an overhead of ~x1.5 for the rest of the allocations. 53 The performance slowdown is ~x3. 54 For better error detection enable CONFIG_STACKTRACE. 55 Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB 56 (the resulting kernel does not boot). 57 58config KASAN_SW_TAGS 59 bool "Software tag-based mode" 60 depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS 61 depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) 62 select SLUB_DEBUG if SLUB 63 select CONSTRUCTORS 64 select STACKDEPOT 65 help 66 Enables software tag-based KASAN mode. 67 This mode requires Top Byte Ignore support by the CPU and therefore 68 is only supported for arm64. 69 This mode requires Clang version 7.0.0 or later. 70 This mode consumes about 1/16th of available memory at kernel start 71 and introduces an overhead of ~20% for the rest of the allocations. 72 This mode may potentially introduce problems relating to pointer 73 casting and comparison, as it embeds tags into the top byte of each 74 pointer. 75 For better error detection enable CONFIG_STACKTRACE. 76 Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB 77 (the resulting kernel does not boot). 78 79endchoice 80 81choice 82 prompt "Instrumentation type" 83 depends on KASAN 84 default KASAN_OUTLINE 85 86config KASAN_OUTLINE 87 bool "Outline instrumentation" 88 help 89 Before every memory access compiler insert function call 90 __asan_load*/__asan_store*. These functions performs check 91 of shadow memory. This is slower than inline instrumentation, 92 however it doesn't bloat size of kernel's .text section so 93 much as inline does. 94 95config KASAN_INLINE 96 bool "Inline instrumentation" 97 help 98 Compiler directly inserts code checking shadow memory before 99 memory accesses. This is faster than outline (in some workloads 100 it gives about x2 boost over outline instrumentation), but 101 make kernel's .text size much bigger. 102 For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later. 103 104endchoice 105 106config KASAN_STACK_ENABLE 107 bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST 108 default !(CLANG_VERSION < 90000) 109 depends on KASAN 110 help 111 The LLVM stack address sanitizer has a know problem that 112 causes excessive stack usage in a lot of functions, see 113 https://bugs.llvm.org/show_bug.cgi?id=38809 114 Disabling asan-stack makes it safe to run kernels build 115 with clang-8 with KASAN enabled, though it loses some of 116 the functionality. 117 This feature is always disabled when compile-testing with clang-8 118 or earlier to avoid cluttering the output in stack overflow 119 warnings, but clang-8 users can still enable it for builds without 120 CONFIG_COMPILE_TEST. On gcc and later clang versions it is 121 assumed to always be safe to use and enabled by default. 122 123config KASAN_STACK 124 int 125 default 1 if KASAN_STACK_ENABLE || CC_IS_GCC 126 default 0 127 128config KASAN_S390_4_LEVEL_PAGING 129 bool "KASan: use 4-level paging" 130 depends on KASAN && S390 131 help 132 Compiling the kernel with KASan disables automatic 3-level vs 133 4-level paging selection. 3-level paging is used by default (up 134 to 3TB of RAM with KASan enabled). This options allows to force 135 4-level paging instead. 136 137config TEST_KASAN 138 tristate "Module for testing KASAN for bug detection" 139 depends on m && KASAN 140 help 141 This is a test module doing various nasty things like 142 out of bounds accesses, use after free. It is useful for testing 143 kernel debugging features like KASAN. 144