[PATCH v6 04/18] khwasan, arm64: adjust shadow size for CONFIG_KASAN_HW
From: dvyukov@google.com (Dmitry Vyukov)
Date: 2018-09-12 14:54:31
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On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov [off-list ref] wrote:
quoted hunk ↗ jump to hunk
KWHASAN 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 KHWASAN is enabled. Signed-off-by: Andrey Konovalov <redacted> --- arch/arm64/Makefile | 2 +- arch/arm64/include/asm/memory.h | 13 +++++++++---- 2 files changed, 10 insertions(+), 5 deletions(-)diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 106039d25e2f..17047b8ab984 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile@@ -94,7 +94,7 @@ endif # 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_SCALE_SHIFT := $(if $(CONFIG_KASAN_HW), 4, 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..f5e262ee76c1 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h@@ -74,12 +74,17 @@ #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. + * KASAN and KHWASAN require 1/8th and 1/16th of the kernel virtual address
I am somewhat confused by the terminology. "KASAN" is not actually "CONFIG_KASAN" below, it is actually "CONFIG_KASAN_GENERIC". While "KHWASAN" translates to "KASAN_HW" few lines later. I think we need some consistent terminology for comments and config names until it's too late.
+ * 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 +#ifdef CONFIG_KASAN_GENERIC #define KASAN_SHADOW_SCALE_SHIFT 3 +#endif +#ifdef CONFIG_KASAN_HW +#define KASAN_SHADOW_SCALE_SHIFT 4 +#endif +#ifdef CONFIG_KASAN #define KASAN_SHADOW_SIZE (UL(1) << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT)) #define KASAN_THREAD_SHIFT 1 #else -- 2.19.0.rc0.228.g281dcd1b4d0-goog