Commit b2f557ea authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

kasan, arm64: adjust shadow size for tag-based mode 

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.

Link: http://lkml.kernel.org/r/308b6bd49f756bb5e533be93c6f085ba99b30339.1544099024.git.andreyknvl@google.com


Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2bd926b4

arch/arm64/Makefile

+10 −1
Original line number Diff line number Diff line
@@ -101,10 +101,19 @@ 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))) \

arch/arm64/include/asm/memory.h

+3 −5
Original line number Diff line number Diff line
@@ -74,13 +74,11 @@ 
#endif



/*

 * 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, and then double it again if KASAN_EXTRA is

 * on.

 * 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))

#ifdef CONFIG_KASAN_EXTRA

#define KASAN_THREAD_SHIFT	2

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