| # SPDX-License-Identifier: GPL-2.0-only | |
| # This config refers to the generic KASAN mode. | |
| config HAVE_ARCH_KASAN | |
| bool | |
| config HAVE_ARCH_KASAN_SW_TAGS | |
| bool | |
| config CC_HAS_KASAN_GENERIC | |
| def_bool $(cc-option, -fsanitize=kernel-address) | |
| config CC_HAS_KASAN_SW_TAGS | |
| def_bool $(cc-option, -fsanitize=kernel-hwaddress) | |
| config KASAN | |
| bool "KASAN: runtime memory debugger" | |
| depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \ | |
| (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS) | |
| depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) | |
| help | |
| Enables KASAN (KernelAddressSANitizer) - runtime memory debugger, | |
| designed to find out-of-bounds accesses and use-after-free bugs. | |
| See Documentation/dev-tools/kasan.rst for details. | |
| choice | |
| prompt "KASAN mode" | |
| depends on KASAN | |
| default KASAN_GENERIC | |
| help | |
| KASAN has two modes: generic KASAN (similar to userspace ASan, | |
| x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and | |
| software tag-based KASAN (a version based on software memory | |
| tagging, arm64 only, similar to userspace HWASan, enabled with | |
| CONFIG_KASAN_SW_TAGS). | |
| Both generic and tag-based KASAN are strictly debugging features. | |
| config KASAN_GENERIC | |
| bool "Generic mode" | |
| depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC | |
| depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) | |
| select SLUB_DEBUG if SLUB | |
| select CONSTRUCTORS | |
| select STACKDEPOT | |
| help | |
| Enables generic KASAN mode. | |
| Supported in both GCC and Clang. With GCC it requires version 4.9.2 | |
| or later for basic support and version 5.0 or later for detection of | |
| out-of-bounds accesses for stack and global variables and for inline | |
| instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires | |
| version 3.7.0 or later and it doesn't support detection of | |
| out-of-bounds accesses for global variables yet. | |
| This mode consumes about 1/8th of available memory at kernel start | |
| and introduces an overhead of ~x1.5 for the rest of the allocations. | |
| The performance slowdown is ~x3. | |
| For better error detection enable CONFIG_STACKTRACE. | |
| Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB | |
| (the resulting kernel does not boot). | |
| config KASAN_SW_TAGS | |
| bool "Software tag-based mode" | |
| depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS | |
| depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) | |
| select SLUB_DEBUG if SLUB | |
| select CONSTRUCTORS | |
| select STACKDEPOT | |
| help | |
| Enables software tag-based KASAN mode. | |
| This mode requires Top Byte Ignore support by the CPU and therefore | |
| is only supported for arm64. | |
| This mode requires Clang version 7.0.0 or later. | |
| This mode consumes about 1/16th of available memory at kernel start | |
| and introduces an overhead of ~20% for the rest of the allocations. | |
| This mode may potentially introduce problems relating to pointer | |
| casting and comparison, as it embeds tags into the top byte of each | |
| pointer. | |
| For better error detection enable CONFIG_STACKTRACE. | |
| Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB | |
| (the resulting kernel does not boot). | |
| endchoice | |
| choice | |
| prompt "Instrumentation type" | |
| depends on KASAN | |
| default KASAN_OUTLINE | |
| config KASAN_OUTLINE | |
| bool "Outline instrumentation" | |
| help | |
| Before every memory access compiler insert function call | |
| __asan_load*/__asan_store*. These functions performs check | |
| of shadow memory. This is slower than inline instrumentation, | |
| however it doesn't bloat size of kernel's .text section so | |
| much as inline does. | |
| config KASAN_INLINE | |
| bool "Inline instrumentation" | |
| help | |
| Compiler directly inserts code checking shadow memory before | |
| memory accesses. This is faster than outline (in some workloads | |
| it gives about x2 boost over outline instrumentation), but | |
| make kernel's .text size much bigger. | |
| For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later. | |
| endchoice | |
| config KASAN_STACK_ENABLE | |
| bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST | |
| default !(CLANG_VERSION < 90000) | |
| depends on KASAN | |
| help | |
| The LLVM stack address sanitizer has a know problem that | |
| causes excessive stack usage in a lot of functions, see | |
| https://bugs.llvm.org/show_bug.cgi?id=38809 | |
| Disabling asan-stack makes it safe to run kernels build | |
| with clang-8 with KASAN enabled, though it loses some of | |
| the functionality. | |
| This feature is always disabled when compile-testing with clang-8 | |
| or earlier to avoid cluttering the output in stack overflow | |
| warnings, but clang-8 users can still enable it for builds without | |
| CONFIG_COMPILE_TEST. On gcc and later clang versions it is | |
| assumed to always be safe to use and enabled by default. | |
| config KASAN_STACK | |
| int | |
| default 1 if KASAN_STACK_ENABLE || CC_IS_GCC | |
| default 0 | |
| config KASAN_S390_4_LEVEL_PAGING | |
| bool "KASan: use 4-level paging" | |
| depends on KASAN && S390 | |
| help | |
| Compiling the kernel with KASan disables automatic 3-level vs | |
| 4-level paging selection. 3-level paging is used by default (up | |
| to 3TB of RAM with KASan enabled). This options allows to force | |
| 4-level paging instead. | |
| config TEST_KASAN | |
| tristate "Module for testing KASAN for bug detection" | |
| depends on m && KASAN | |
| help | |
| This is a test module doing various nasty things like | |
| out of bounds accesses, use after free. It is useful for testing | |
| kernel debugging features like KASAN. |