[{"id":3687086,"web_url":"http://patchwork.ozlabs.org/comment/3687086/","msgid":"<39d0700c-4185-4683-8249-1d014c579c59@linaro.org>","list_archive_url":null,"date":"2026-05-06T13:44:07","subject":"Re: [PATCH v5 07/15] target/arm: add canonical tag check, mtx helpers","submitter":{"id":72104,"url":"http://patchwork.ozlabs.org/api/people/72104/","name":"Richard Henderson","email":"richard.henderson@linaro.org"},"content":"On 5/4/26 10:50, Gabriel Brookman wrote:\n> Add a helper that checks whether mtx is active from MTEDESC and a\n> helper that checks whether a tag matches the selector bit. These\n> helpers will be used for the subsequent commits.\n> \n> Signed-off-by: Gabriel Brookman \n> ---\n> target/arm/internals.h | 14 +++++++++++++-\n> 1 file changed, 13 insertions(+), 1 deletion(-)\n> \n> diff --git a/target/arm/internals.h b/target/arm/internals.h\n> index 6df2c547c5..779eafabc8 100644\n> --- a/target/arm/internals.h\n> +++ b/target/arm/internals.h\n> @@ -1629,6 +1629,12 @@ static inline uint64_t address_with_allocation_tag(uint64_t ptr, int rtag)\n> return deposit64(ptr, 56, 4, rtag);\n> }\n> \n> +/* Return true if mtx bits mean that the access is canonically checked. */\n> +static inline bool mtx_check(uint32_t desc, int bit55)\n> +{\n> + return (desc >> (R_MTEDESC_MTX_SHIFT + bit55)) & 1;\n> +}\n\nUnused, so belongs to some other patch.\n\n\nOtherwise,\nReviewed-by: Richard Henderson \n\n\nr~\n\n> +\n> /* Return true if tbi or mtx bits mean that the access is tag checked. */\n> static inline bool tbi_or_mtx_check(uint32_t desc, int bit55)\n> {\n> @@ -1636,6 +1642,12 @@ static inline bool tbi_or_mtx_check(uint32_t desc, int bit55)\n> return desc & (mask << bit55);\n> }\n> \n> +/* Return whether or not the second nibble of a VA matches bit 55. */\n> +static inline bool tag_is_canonical(int ptr_tag, int bit55)\n> +{\n> + return ((ptr_tag + bit55) & 0xf) == 0;\n> +}\n> +\n> /* Return true if tcma bits mean that the access is unchecked. */\n> static inline bool tcma_check(uint32_t desc, int bit55, int ptr_tag)\n> {\n> @@ -1643,7 +1655,7 @@ static inline bool tcma_check(uint32_t desc, int bit55, int ptr_tag)\n> * We had extracted bit55 and ptr_tag for other reasons, so fold\n> * (ptr<59:55> == 00000 || ptr<59:55> == 11111) into a single test.\n> */\n> - bool match = ((ptr_tag + bit55) & 0xf) == 0;\n> + bool match = tag_is_canonical(ptr_tag, bit55);\n> bool tcma = (desc >> (R_MTEDESC_TCMA_SHIFT + bit55)) & 1;\n> return tcma && match;\n> }\n>","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=IGHK3FCn;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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