diff options
Diffstat (limited to 'arch/arm64/include/asm/memory.h')
| -rw-r--r-- | arch/arm64/include/asm/memory.h | 38 |
1 files changed, 32 insertions, 6 deletions
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 56d1e6f14861..d82305ab420f 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -65,15 +65,41 @@ #define KERNEL_END _end /* - * 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. + * Generic and Software Tag-Based KASAN modes require 1/8th and 1/16th of the + * kernel virtual address space for storing the shadow memory respectively. + * + * The mapping between a virtual memory address and its corresponding shadow + * memory address is defined based on the formula: + * + * shadow_addr = (addr >> KASAN_SHADOW_SCALE_SHIFT) + KASAN_SHADOW_OFFSET + * + * where KASAN_SHADOW_SCALE_SHIFT is the order of the number of bits that map + * to a single shadow byte and KASAN_SHADOW_OFFSET is a constant that offsets + * the mapping. Note that KASAN_SHADOW_OFFSET does not point to the start of + * the shadow memory region. + * + * Based on this mapping, we define two constants: + * + * KASAN_SHADOW_START: the start of the shadow memory region; + * KASAN_SHADOW_END: the end of the shadow memory region. + * + * KASAN_SHADOW_END is defined first as the shadow address that corresponds to + * the upper bound of possible virtual kernel memory addresses UL(1) << 64 + * according to the mapping formula. + * + * KASAN_SHADOW_START is defined second based on KASAN_SHADOW_END. The shadow + * memory start must map to the lowest possible kernel virtual memory address + * and thus it depends on the actual bitness of the address space. + * + * As KASAN inserts redzones between stack variables, this increases the stack + * memory usage significantly. Thus, we double the (minimum) stack size. */ #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) -#define KASAN_SHADOW_END ((UL(1) << (64 - KASAN_SHADOW_SCALE_SHIFT)) \ - + KASAN_SHADOW_OFFSET) -#define PAGE_END (KASAN_SHADOW_END - (1UL << (vabits_actual - KASAN_SHADOW_SCALE_SHIFT))) +#define KASAN_SHADOW_END ((UL(1) << (64 - KASAN_SHADOW_SCALE_SHIFT)) + KASAN_SHADOW_OFFSET) +#define _KASAN_SHADOW_START(va) (KASAN_SHADOW_END - (UL(1) << ((va) - KASAN_SHADOW_SCALE_SHIFT))) +#define KASAN_SHADOW_START _KASAN_SHADOW_START(vabits_actual) +#define PAGE_END KASAN_SHADOW_START #define KASAN_THREAD_SHIFT 1 #else #define KASAN_THREAD_SHIFT 0 |