diff options
| -rw-r--r-- | Documentation/dev-tools/kasan.rst | 7 | ||||
| -rw-r--r-- | lib/Kconfig.kasan | 24 |
2 files changed, 17 insertions, 14 deletions
diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index c652d740735d..15a2a53e77b0 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -13,11 +13,8 @@ KASAN uses compile-time instrumentation to insert validity checks before every memory access, and therefore requires a compiler version that supports that. Generic KASAN is 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 (see the Usage section). With Clang it requires version -7.0.0 or later and it doesn't support detection of out-of-bounds accesses for -global variables yet. +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 only supported since Clang 11. Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later. diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index 89053defc0d9..047b53dbfd58 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -40,6 +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 @@ -51,16 +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). @@ -73,15 +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). @@ -107,7 +114,6 @@ 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 |