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name : Kconfig.kasan # 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 HAVE_ARCH_KASAN_HW_TAGS bool config HAVE_ARCH_KASAN_VMALLOC bool config ARCH_DISABLE_KASAN_INLINE bool help An architecture might not support inline instrumentation. When this option is selected, inline and stack instrumentation are disabled. 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) # This option is only required for software KASAN modes. # Old GCC versions don't have proper support for no_sanitize_address. # See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89124 for details. config CC_HAS_WORKING_NOSANITIZE_ADDRESS def_bool !CC_IS_GCC || GCC_VERSION >= 80300 menuconfig 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)) && \ CC_HAS_WORKING_NOSANITIZE_ADDRESS) || \ HAVE_ARCH_KASAN_HW_TAGS depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) select STACKDEPOT 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. if KASAN choice prompt "KASAN mode" default KASAN_GENERIC help KASAN has three modes: 1. generic KASAN (similar to userspace ASan, x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC), 2. software tag-based KASAN (arm64 only, based on software memory tagging (similar to userspace HWASan), enabled with CONFIG_KASAN_SW_TAGS), and 3. hardware tag-based KASAN (arm64 only, based on hardware memory tagging, enabled with CONFIG_KASAN_HW_TAGS). All KASAN modes are strictly debugging features. For better error reports enable CONFIG_STACKTRACE. config KASAN_GENERIC bool "Generic mode" depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS select SLUB_DEBUG if SLUB select CONSTRUCTORS help Enables generic KASAN mode. This mode is supported in both GCC and Clang. With GCC it requires version 8.3.0 or later. Any supported Clang version is compatible, but detection of out-of-bounds accesses for global variables is supported only since Clang 11. 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. 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 CC_HAS_WORKING_NOSANITIZE_ADDRESS select SLUB_DEBUG if SLUB select CONSTRUCTORS help Enables software tag-based KASAN mode. This mode require software memory tagging support in the form of HWASan-like compiler instrumentation. Currently this mode is only implemented for arm64 CPUs and relies on Top Byte Ignore. This mode requires Clang. 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. Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB (the resulting kernel does not boot). config KASAN_HW_TAGS bool "Hardware tag-based mode" depends on HAVE_ARCH_KASAN_HW_TAGS depends on SLUB help Enables hardware tag-based KASAN mode. This mode requires hardware memory tagging support, and can be used by any architecture that provides it. Currently this mode is only implemented for arm64 CPUs starting from ARMv8.5 and relies on Memory Tagging Extension and Top Byte Ignore. endchoice choice prompt "Instrumentation type" depends on KASAN_GENERIC || KASAN_SW_TAGS 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" depends on !ARCH_DISABLE_KASAN_INLINE 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. endchoice config KASAN_STACK bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST depends on KASAN_GENERIC || KASAN_SW_TAGS depends on !ARCH_DISABLE_KASAN_INLINE default y if CC_IS_GCC 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 to avoid cluttering the output in stack overflow warnings, but clang users can still enable it for builds without CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe to use and enabled by default. If the architecture disables inline instrumentation, stack instrumentation is also disabled as it adds inline-style instrumentation that is run unconditionally. config KASAN_TAGS_IDENTIFY bool "Enable memory corruption identification" depends on KASAN_SW_TAGS || KASAN_HW_TAGS help This option enables best-effort identification of bug type (use-after-free or out-of-bounds) at the cost of increased memory consumption. config KASAN_VMALLOC bool "Back mappings in vmalloc space with real shadow memory" depends on KASAN_GENERIC && HAVE_ARCH_KASAN_VMALLOC help By default, the shadow region for vmalloc space is the read-only zero page. This means that KASAN cannot detect errors involving vmalloc space. Enabling this option will hook in to vmap/vmalloc and back those mappings with real shadow memory allocated on demand. This allows for KASAN to detect more sorts of errors (and to support vmapped stacks), but at the cost of higher memory usage. config KASAN_KUNIT_TEST tristate "KUnit-compatible tests of KASAN bug detection capabilities" if !KUNIT_ALL_TESTS depends on KASAN && KUNIT default KUNIT_ALL_TESTS help This is a KUnit test suite doing various nasty things like out of bounds and use after free accesses. It is useful for testing kernel debugging features like KASAN. For more information on KUnit and unit tests in general, please refer to the KUnit documentation in Documentation/dev-tools/kunit. config KASAN_MODULE_TEST tristate "KUnit-incompatible tests of KASAN bug detection capabilities" depends on m && KASAN && !KASAN_HW_TAGS help This is a part of the KASAN test suite that is incompatible with KUnit. Currently includes tests that do bad copy_from/to_user accesses. endif # KASAN