From 3d0cca0b02ac98eac9157b26cf3951997db68b37 Mon Sep 17 00:00:00 2001 From: Evgenii Stepanov Date: Thu, 20 May 2021 18:00:23 -0700 Subject: [PATCH] kasan: speed up mte_set_mem_tag_range Use DC GVA / DC GZVA to speed up KASan memory tagging in HW tags mode. The first cacheline is always tagged using STG/STZG even if the address is cacheline-aligned, as benchmarks show it is faster than a conditional branch. Signed-off-by: Evgenii Stepanov Co-developed-by: Peter Collingbourne Signed-off-by: Peter Collingbourne Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20210521010023.3244784-1-eugenis@google.com Signed-off-by: Will Deacon --- arch/arm64/include/asm/mte-kasan.h | 93 +++++++++++++++++++++++++++----------- 1 file changed, 67 insertions(+), 26 deletions(-) diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h index ddd4d17..d952352 100644 --- a/arch/arm64/include/asm/mte-kasan.h +++ b/arch/arm64/include/asm/mte-kasan.h @@ -48,43 +48,84 @@ static inline u8 mte_get_random_tag(void) return mte_get_ptr_tag(addr); } +static inline u64 __stg_post(u64 p) +{ + asm volatile(__MTE_PREAMBLE "stg %0, [%0], #16" + : "+r"(p) + : + : "memory"); + return p; +} + +static inline u64 __stzg_post(u64 p) +{ + asm volatile(__MTE_PREAMBLE "stzg %0, [%0], #16" + : "+r"(p) + : + : "memory"); + return p; +} + +static inline void __dc_gva(u64 p) +{ + asm volatile(__MTE_PREAMBLE "dc gva, %0" : : "r"(p) : "memory"); +} + +static inline void __dc_gzva(u64 p) +{ + asm volatile(__MTE_PREAMBLE "dc gzva, %0" : : "r"(p) : "memory"); +} + /* * Assign allocation tags for a region of memory based on the pointer tag. * Note: The address must be non-NULL and MTE_GRANULE_SIZE aligned and - * size must be non-zero and MTE_GRANULE_SIZE aligned. + * size must be MTE_GRANULE_SIZE aligned. */ -static inline void mte_set_mem_tag_range(void *addr, size_t size, - u8 tag, bool init) +static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag, + bool init) { - u64 curr, end; + u64 curr, mask, dczid_bs, end1, end2, end3; - if (!size) - return; + /* Read DC G(Z)VA block size from the system register. */ + dczid_bs = 4ul << (read_cpuid(DCZID_EL0) & 0xf); curr = (u64)__tag_set(addr, tag); - end = curr + size; + mask = dczid_bs - 1; + /* STG/STZG up to the end of the first block. */ + end1 = curr | mask; + end3 = curr + size; + /* DC GVA / GZVA in [end1, end2) */ + end2 = end3 & ~mask; /* - * 'asm volatile' is required to prevent the compiler to move - * the statement outside of the loop. + * The following code uses STG on the first DC GVA block even if the + * start address is aligned - it appears to be faster than an alignment + * check + conditional branch. Also, if the range size is at least 2 DC + * GVA blocks, the first two loops can use post-condition to save one + * branch each. */ - if (init) { - do { - asm volatile(__MTE_PREAMBLE "stzg %0, [%0]" - : - : "r" (curr) - : "memory"); - curr += MTE_GRANULE_SIZE; - } while (curr != end); - } else { - do { - asm volatile(__MTE_PREAMBLE "stg %0, [%0]" - : - : "r" (curr) - : "memory"); - curr += MTE_GRANULE_SIZE; - } while (curr != end); - } +#define SET_MEMTAG_RANGE(stg_post, dc_gva) \ + do { \ + if (size >= 2 * dczid_bs) { \ + do { \ + curr = stg_post(curr); \ + } while (curr < end1); \ + \ + do { \ + dc_gva(curr); \ + curr += dczid_bs; \ + } while (curr < end2); \ + } \ + \ + while (curr < end3) \ + curr = stg_post(curr); \ + } while (0) + + if (init) + SET_MEMTAG_RANGE(__stzg_post, __dc_gzva); + else + SET_MEMTAG_RANGE(__stg_post, __dc_gva); +#undef SET_MEMTAG_RANGE } void mte_enable_kernel_sync(void); -- 2.7.4