1# SPDX-License-Identifier: GPL-2.0-only 2# This config refers to the generic KASAN mode. 3config HAVE_ARCH_KASAN 4 bool 5 6config HAVE_ARCH_KASAN_SW_TAGS 7 bool 8 9config HAVE_ARCH_KASAN_HW_TAGS 10 bool 11 12config HAVE_ARCH_KASAN_VMALLOC 13 bool 14 15config CC_HAS_KASAN_GENERIC 16 def_bool $(cc-option, -fsanitize=kernel-address) 17 18config CC_HAS_KASAN_SW_TAGS 19 def_bool $(cc-option, -fsanitize=kernel-hwaddress) 20 21# This option is only required for software KASAN modes. 22# Old GCC versions don't have proper support for no_sanitize_address. 23# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89124 for details. 24config CC_HAS_WORKING_NOSANITIZE_ADDRESS 25 def_bool !CC_IS_GCC || GCC_VERSION >= 80300 26 27menuconfig KASAN 28 bool "KASAN: runtime memory debugger" 29 depends on (((HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \ 30 (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)) && \ 31 CC_HAS_WORKING_NOSANITIZE_ADDRESS) || \ 32 HAVE_ARCH_KASAN_HW_TAGS 33 depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) 34 select STACKDEPOT 35 help 36 Enables KASAN (KernelAddressSANitizer) - runtime memory debugger, 37 designed to find out-of-bounds accesses and use-after-free bugs. 38 See Documentation/dev-tools/kasan.rst for details. 39 40if KASAN 41 42choice 43 prompt "KASAN mode" 44 default KASAN_GENERIC 45 help 46 KASAN has three modes: 47 1. generic KASAN (similar to userspace ASan, 48 x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC), 49 2. software tag-based KASAN (arm64 only, based on software 50 memory tagging (similar to userspace HWASan), enabled with 51 CONFIG_KASAN_SW_TAGS), and 52 3. hardware tag-based KASAN (arm64 only, based on hardware 53 memory tagging, enabled with CONFIG_KASAN_HW_TAGS). 54 55 All KASAN modes are strictly debugging features. 56 57 For better error reports enable CONFIG_STACKTRACE. 58 59config KASAN_GENERIC 60 bool "Generic mode" 61 depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC 62 select SLUB_DEBUG if SLUB 63 select CONSTRUCTORS 64 help 65 Enables generic KASAN mode. 66 67 This mode is supported in both GCC and Clang. With GCC it requires 68 version 8.3.0 or later. Any supported Clang version is compatible, 69 but detection of out-of-bounds accesses for global variables is 70 supported only since Clang 11. 71 72 This mode consumes about 1/8th of available memory at kernel start 73 and introduces an overhead of ~x1.5 for the rest of the allocations. 74 The performance slowdown is ~x3. 75 76 Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB 77 (the resulting kernel does not boot). 78 79config KASAN_SW_TAGS 80 bool "Software tag-based mode" 81 depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS 82 select SLUB_DEBUG if SLUB 83 select CONSTRUCTORS 84 help 85 Enables software tag-based KASAN mode. 86 87 This mode require software memory tagging support in the form of 88 HWASan-like compiler instrumentation. 89 90 Currently this mode is only implemented for arm64 CPUs and relies on 91 Top Byte Ignore. This mode requires Clang. 92 93 This mode consumes about 1/16th of available memory at kernel start 94 and introduces an overhead of ~20% for the rest of the allocations. 95 This mode may potentially introduce problems relating to pointer 96 casting and comparison, as it embeds tags into the top byte of each 97 pointer. 98 99 Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB 100 (the resulting kernel does not boot). 101 102config KASAN_HW_TAGS 103 bool "Hardware tag-based mode" 104 depends on HAVE_ARCH_KASAN_HW_TAGS 105 depends on SLUB 106 help 107 Enables hardware tag-based KASAN mode. 108 109 This mode requires hardware memory tagging support, and can be used 110 by any architecture that provides it. 111 112 Currently this mode is only implemented for arm64 CPUs starting from 113 ARMv8.5 and relies on Memory Tagging Extension and Top Byte Ignore. 114 115endchoice 116 117choice 118 prompt "Instrumentation type" 119 depends on KASAN_GENERIC || KASAN_SW_TAGS 120 default KASAN_OUTLINE 121 122config KASAN_OUTLINE 123 bool "Outline instrumentation" 124 help 125 Before every memory access compiler insert function call 126 __asan_load*/__asan_store*. These functions performs check 127 of shadow memory. This is slower than inline instrumentation, 128 however it doesn't bloat size of kernel's .text section so 129 much as inline does. 130 131config KASAN_INLINE 132 bool "Inline instrumentation" 133 help 134 Compiler directly inserts code checking shadow memory before 135 memory accesses. This is faster than outline (in some workloads 136 it gives about x2 boost over outline instrumentation), but 137 make kernel's .text size much bigger. 138 139endchoice 140 141config KASAN_STACK_ENABLE 142 bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST 143 depends on KASAN_GENERIC || KASAN_SW_TAGS 144 help 145 The LLVM stack address sanitizer has a know problem that 146 causes excessive stack usage in a lot of functions, see 147 https://bugs.llvm.org/show_bug.cgi?id=38809 148 Disabling asan-stack makes it safe to run kernels build 149 with clang-8 with KASAN enabled, though it loses some of 150 the functionality. 151 This feature is always disabled when compile-testing with clang 152 to avoid cluttering the output in stack overflow warnings, 153 but clang users can still enable it for builds without 154 CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe 155 to use and enabled by default. 156 157config KASAN_STACK 158 int 159 default 1 if KASAN_STACK_ENABLE || CC_IS_GCC 160 default 0 161 162config KASAN_SW_TAGS_IDENTIFY 163 bool "Enable memory corruption identification" 164 depends on KASAN_SW_TAGS 165 help 166 This option enables best-effort identification of bug type 167 (use-after-free or out-of-bounds) at the cost of increased 168 memory consumption. 169 170config KASAN_VMALLOC 171 bool "Back mappings in vmalloc space with real shadow memory" 172 depends on KASAN_GENERIC && HAVE_ARCH_KASAN_VMALLOC 173 help 174 By default, the shadow region for vmalloc space is the read-only 175 zero page. This means that KASAN cannot detect errors involving 176 vmalloc space. 177 178 Enabling this option will hook in to vmap/vmalloc and back those 179 mappings with real shadow memory allocated on demand. This allows 180 for KASAN to detect more sorts of errors (and to support vmapped 181 stacks), but at the cost of higher memory usage. 182 183config KASAN_KUNIT_TEST 184 tristate "KUnit-compatible tests of KASAN bug detection capabilities" if !KUNIT_ALL_TESTS 185 depends on KASAN && KUNIT 186 default KUNIT_ALL_TESTS 187 help 188 This is a KUnit test suite doing various nasty things like 189 out of bounds and use after free accesses. It is useful for testing 190 kernel debugging features like KASAN. 191 192 For more information on KUnit and unit tests in general, please refer 193 to the KUnit documentation in Documentation/dev-tools/kunit. 194 195config TEST_KASAN_MODULE 196 tristate "KUnit-incompatible tests of KASAN bug detection capabilities" 197 depends on m && KASAN && !KASAN_HW_TAGS 198 help 199 This is a part of the KASAN test suite that is incompatible with 200 KUnit. Currently includes tests that do bad copy_from/to_user 201 accesses. 202 203endif # KASAN 204