From 5add8248556a3c1006018d7d8e601c9572b280a9 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Thu, 25 Jun 2020 20:31:24 -0700 Subject: [PATCH] target/arm: Implement helper_mte_checkN Fill out the stub that was added earlier. Reviewed-by: Peter Maydell Signed-off-by: Richard Henderson Message-id: 20200626033144.790098-27-richard.henderson@linaro.org Signed-off-by: Peter Maydell --- target/arm/internals.h | 2 + target/arm/mte_helper.c | 165 +++++++++++++++++++++++++++++++++++++++- 2 files changed, 166 insertions(+), 1 deletion(-) diff --git a/target/arm/internals.h b/target/arm/internals.h index 807830cc40..c763a23dfb 100644 --- a/target/arm/internals.h +++ b/target/arm/internals.h @@ -1321,6 +1321,8 @@ FIELD(MTEDESC, TSIZE, 14, 10) /* mte_checkN only */ bool mte_probe1(CPUARMState *env, uint32_t desc, uint64_t ptr); uint64_t mte_check1(CPUARMState *env, uint32_t desc, uint64_t ptr, uintptr_t ra); +uint64_t mte_checkN(CPUARMState *env, uint32_t desc, + uint64_t ptr, uintptr_t ra); static inline int allocation_tag_from_addr(uint64_t ptr) { diff --git a/target/arm/mte_helper.c b/target/arm/mte_helper.c index c8a5e7c0ed..abe6af6b79 100644 --- a/target/arm/mte_helper.c +++ b/target/arm/mte_helper.c @@ -500,7 +500,170 @@ uint64_t HELPER(mte_check1)(CPUARMState *env, uint32_t desc, uint64_t ptr) /* * Perform an MTE checked access for multiple logical accesses. */ + +/** + * checkN: + * @tag: tag memory to test + * @odd: true to begin testing at tags at odd nibble + * @cmp: the tag to compare against + * @count: number of tags to test + * + * Return the number of successful tests. + * Thus a return value < @count indicates a failure. + * + * A note about sizes: count is expected to be small. + * + * The most common use will be LDP/STP of two integer registers, + * which means 16 bytes of memory touching at most 2 tags, but + * often the access is aligned and thus just 1 tag. + * + * Using AdvSIMD LD/ST (multiple), one can access 64 bytes of memory, + * touching at most 5 tags. SVE LDR/STR (vector) with the default + * vector length is also 64 bytes; the maximum architectural length + * is 256 bytes touching at most 9 tags. + * + * The loop below uses 7 logical operations and 1 memory operation + * per tag pair. An implementation that loads an aligned word and + * uses masking to ignore adjacent tags requires 18 logical operations + * and thus does not begin to pay off until 6 tags. + * Which, according to the survey above, is unlikely to be common. + */ +static int checkN(uint8_t *mem, int odd, int cmp, int count) +{ + int n = 0, diff; + + /* Replicate the test tag and compare. */ + cmp *= 0x11; + diff = *mem++ ^ cmp; + + if (odd) { + goto start_odd; + } + + while (1) { + /* Test even tag. */ + if (unlikely((diff) & 0x0f)) { + break; + } + if (++n == count) { + break; + } + + start_odd: + /* Test odd tag. */ + if (unlikely((diff) & 0xf0)) { + break; + } + if (++n == count) { + break; + } + + diff = *mem++ ^ cmp; + } + return n; +} + +uint64_t mte_checkN(CPUARMState *env, uint32_t desc, + uint64_t ptr, uintptr_t ra) +{ + int mmu_idx, ptr_tag, bit55; + uint64_t ptr_last, ptr_end, prev_page, next_page; + uint64_t tag_first, tag_end; + uint64_t tag_byte_first, tag_byte_end; + uint32_t esize, total, tag_count, tag_size, n, c; + uint8_t *mem1, *mem2; + MMUAccessType type; + + bit55 = extract64(ptr, 55, 1); + + /* If TBI is disabled, the access is unchecked, and ptr is not dirty. */ + if (unlikely(!tbi_check(desc, bit55))) { + return ptr; + } + + ptr_tag = allocation_tag_from_addr(ptr); + + if (tcma_check(desc, bit55, ptr_tag)) { + goto done; + } + + mmu_idx = FIELD_EX32(desc, MTEDESC, MIDX); + type = FIELD_EX32(desc, MTEDESC, WRITE) ? MMU_DATA_STORE : MMU_DATA_LOAD; + esize = FIELD_EX32(desc, MTEDESC, ESIZE); + total = FIELD_EX32(desc, MTEDESC, TSIZE); + + /* Find the addr of the end of the access, and of the last element. */ + ptr_end = ptr + total; + ptr_last = ptr_end - esize; + + /* Round the bounds to the tag granule, and compute the number of tags. */ + tag_first = QEMU_ALIGN_DOWN(ptr, TAG_GRANULE); + tag_end = QEMU_ALIGN_UP(ptr_last, TAG_GRANULE); + tag_count = (tag_end - tag_first) / TAG_GRANULE; + + /* Round the bounds to twice the tag granule, and compute the bytes. */ + tag_byte_first = QEMU_ALIGN_DOWN(ptr, 2 * TAG_GRANULE); + tag_byte_end = QEMU_ALIGN_UP(ptr_last, 2 * TAG_GRANULE); + + /* Locate the page boundaries. */ + prev_page = ptr & TARGET_PAGE_MASK; + next_page = prev_page + TARGET_PAGE_SIZE; + + if (likely(tag_end - prev_page <= TARGET_PAGE_SIZE)) { + /* Memory access stays on one page. */ + tag_size = (tag_byte_end - tag_byte_first) / (2 * TAG_GRANULE); + mem1 = allocation_tag_mem(env, mmu_idx, ptr, type, total, + MMU_DATA_LOAD, tag_size, ra); + if (!mem1) { + goto done; + } + /* Perform all of the comparisons. */ + n = checkN(mem1, ptr & TAG_GRANULE, ptr_tag, tag_count); + } else { + /* Memory access crosses to next page. */ + tag_size = (next_page - tag_byte_first) / (2 * TAG_GRANULE); + mem1 = allocation_tag_mem(env, mmu_idx, ptr, type, next_page - ptr, + MMU_DATA_LOAD, tag_size, ra); + + tag_size = (tag_byte_end - next_page) / (2 * TAG_GRANULE); + mem2 = allocation_tag_mem(env, mmu_idx, next_page, type, + ptr_end - next_page, + MMU_DATA_LOAD, tag_size, ra); + + /* + * Perform all of the comparisons. + * Note the possible but unlikely case of the operation spanning + * two pages that do not both have tagging enabled. + */ + n = c = (next_page - tag_first) / TAG_GRANULE; + if (mem1) { + n = checkN(mem1, ptr & TAG_GRANULE, ptr_tag, c); + } + if (n == c) { + if (!mem2) { + goto done; + } + n += checkN(mem2, 0, ptr_tag, tag_count - c); + } + } + + /* + * If we failed, we know which granule. Compute the element that + * is first in that granule, and signal failure on that element. + */ + if (unlikely(n < tag_count)) { + uint64_t fail_ofs; + + fail_ofs = tag_first + n * TAG_GRANULE - ptr; + fail_ofs = ROUND_UP(fail_ofs, esize); + mte_check_fail(env, mmu_idx, ptr + fail_ofs, ra); + } + + done: + return useronly_clean_ptr(ptr); +} + uint64_t HELPER(mte_checkN)(CPUARMState *env, uint32_t desc, uint64_t ptr) { - return ptr; + return mte_checkN(env, desc, ptr, GETPC()); } -- 2.39.2