diff options
Diffstat (limited to 'lib/Kconfig.kasan')
| -rw-r--r-- | lib/Kconfig.kasan | 39 |
1 files changed, 23 insertions, 16 deletions
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index 34b84bcbd3d9..047b53dbfd58 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -18,7 +18,7 @@ config CC_HAS_KASAN_SW_TAGS config CC_HAS_WORKING_NOSANITIZE_ADDRESS def_bool !CC_IS_GCC || GCC_VERSION >= 80300 -config KASAN +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) @@ -29,9 +29,10 @@ config KASAN 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" - depends on KASAN default KASAN_GENERIC help KASAN has two modes: generic KASAN (similar to userspace ASan, @@ -39,6 +40,7 @@ choice 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 @@ -50,16 +52,18 @@ config KASAN_GENERIC 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 is supported in both GCC and Clang. With GCC it requires + version 8.3.0 or later. With Clang it requires version 7.0.0 or + later, 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. + For better error detection enable CONFIG_STACKTRACE. + Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB (the resulting kernel does not boot). @@ -72,15 +76,19 @@ config KASAN_SW_TAGS 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. + 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). @@ -88,7 +96,6 @@ endchoice choice prompt "Instrumentation type" - depends on KASAN default KASAN_OUTLINE config KASAN_OUTLINE @@ -107,13 +114,11 @@ config KASAN_INLINE 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 - depends on KASAN help The LLVM stack address sanitizer has a know problem that causes excessive stack usage in a lot of functions, see @@ -134,7 +139,7 @@ config KASAN_STACK config KASAN_S390_4_LEVEL_PAGING bool "KASan: use 4-level paging" - depends on KASAN && S390 + depends on S390 help Compiling the kernel with KASan disables automatic 3-level vs 4-level paging selection. 3-level paging is used by default (up @@ -151,7 +156,7 @@ config KASAN_SW_TAGS_IDENTIFY config KASAN_VMALLOC bool "Back mappings in vmalloc space with real shadow memory" - depends on KASAN && HAVE_ARCH_KASAN_VMALLOC + depends on 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 @@ -164,8 +169,10 @@ config KASAN_VMALLOC config TEST_KASAN tristate "Module for testing KASAN for bug detection" - depends on m && KASAN + depends on m 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. + +endif # KASAN |