Tag-based KASAN uses 1 shadow byte for 16 bytes of kernel memory, so it requires 1/16th of the kernel virtual address space for the shadow memory. This commit sets KASAN_SHADOW_SCALE_SHIFT to 4 when the tag-based KASAN mode is enabled. Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> --- arch/arm64/Makefile | 11 ++++++++++- arch/arm64/include/asm/memory.h | 7 +++---- 2 files changed, 13 insertions(+), 5 deletions(-) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 6cb9fc7e9382..99e7d08c6083 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -91,10 +91,19 @@ else TEXT_OFFSET := 0x00080000 endif +ifeq ($(CONFIG_KASAN_SW_TAGS), y) +KASAN_SHADOW_SCALE_SHIFT := 4 +else +KASAN_SHADOW_SCALE_SHIFT := 3 +endif + +KBUILD_CFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT) +KBUILD_CPPFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT) +KBUILD_AFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT) + # KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT)) # - (1 << (64 - KASAN_SHADOW_SCALE_SHIFT)) # in 32-bit arithmetic -KASAN_SHADOW_SCALE_SHIFT := 3 KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \ (0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 32))) \ + (1 << ($(CONFIG_ARM64_VA_BITS) - 32 - $(KASAN_SHADOW_SCALE_SHIFT))) \ diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index b96442960aea..05fbc7ffcd31 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -74,12 +74,11 @@ #define KERNEL_END _end /* - * KASAN requires 1/8th of the kernel virtual address space for the shadow - * region. KASAN can bloat the stack significantly, so double the (minimum) - * stack size when KASAN is in use. + * Generic and tag-based KASAN require 1/8th and 1/16th of the kernel virtual + * address space for the shadow region respectively. They can bloat the stack + * significantly, so double the (minimum) stack size when they are in use. */ #ifdef CONFIG_KASAN -#define KASAN_SHADOW_SCALE_SHIFT 3 #define KASAN_SHADOW_SIZE (UL(1) << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT)) #define KASAN_THREAD_SHIFT 1 #else -- 2.20.0.rc1.387.gf8505762e3-goog
