linux-kernel - Re: [PATCH v4 0/7] support FEAT_MTE_STORE

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Message-ID: <aCroCLuvhwnrnfjR@e129823.arm.com>
Date: Mon, 19 May 2025 09:12:56 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: catalin.marinas@....com, pcc@...gle.com, will@...nel.org,
	broonie@...nel.org, anshuman.khandual@....com, joey.gouly@....com,
	maz@...nel.org, oliver.upton@...ux.dev, frederic@...nel.org,
	james.morse@....com, hardevsinh.palaniya@...iconsignals.io,
	huangxiaojia2@...wei.com, mark.rutland@....com,
	samuel.holland@...ive.com, palmer@...osinc.com,
	charlie@...osinc.com, thiago.bauermann@...aro.org,
	bgray@...ux.ibm.com, tglx@...utronix.de, puranjay@...nel.org,
	david@...hat.com, yang@...amperecomputing.com, mbenes@...e.cz,
	joel.granados@...nel.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/7] support FEAT_MTE_STORE_ONLY feature

Gentle ping in case of forgoten...

> ARMv8.5 based processors introduce the Memory Tagging Extension (MTE) feature.
> MTE is built on top of the ARMv8.0 virtual address tagging TBI
> (Top Byte Ignore) feature and allows software to access a 4-bit
> allocation tag for each 16-byte granule in the physical address space.
> A logical tag is derived from bits 59-56 of the virtual
> address used for the memory access. A CPU with MTE enabled will compare
> the logical tag against the allocation tag and potentially raise an
> tag check fault on mismatch, subject to system registers configuration.
>
> Since ARMv8.9, FEAT_MTE_STORE_ONLY can be used to restrict raise of tag
> check fault on store operation only.
> For this, application can use PR_MTE_STORE_ONLY flag
> when it sets the MTE setting with prctl().
>
> This feature omits tag check for fetch/read operation.
> So it might be used not only debugging purpose but also be used
> by application requiring strong memory safty in normal env.
>
> Patch Sequences
> ================
>
> Patch #1 adds cpufeature FEAT_MTE_STORE_ONLY
>
> Patch #2 introduce new flag -- PR_MTE_STORE_ONLY
>
> Patch #3 support MTE_STORE_ONLY feature
>
> Patch #4 add HWCAP for MTE_STORE_ONLY
>
> Patch #5 adds mte store-only hwcap test
>
> Patch #6 preparation for adding mte store-only testcase
>
> Patch #7 adds mte store-only testcases
>
> Patch History
> ================
>
> v3 to v4:
>   - separate cpufeature and hwcap commit.
>   - add mte store-only testcases in check_mmap_options
>   - https://lore.kernel.org/linux-arm-kernel/aApBk8eGA2Eo57fq@e129823.arm.com/
>
> v2 to v3:
>   - rebase to 6.15-rc1
>   - https://lore.kernel.org/linux-arm-kernel/20250403174701.74312-1-yeoreum.yun@arm.com/
>
> v1 to v2:
>   - add doc to elf_hwcaps.rst
>   - add MTE_STORE_ONLY hwcap test
>   - https://lore.kernel.org/linux-arm-kernel/20250403142707.26397-1-yeoreum.yun@arm.com/
>
> Note:
>   This patch based on
>     https://lore.kernel.org/linux-arm-kernel/20250507095757.1663684-1-yeoreum.yun@arm.com/
>
> Yeoreum Yun (7):
>   arm64/cpufeature: add MTE_STORE_ONLY feature
>   prtcl: introduce PR_MTE_STORE_ONLY
>   arm64/kernel: support store-only mte tag check
>   arm64/hwcaps: add MTE_STORE_ONLY hwcaps
>   tools/kselftest: add MTE_STORE_ONLY feature hwcap test
>   kselftest/arm64/mte: preparation for mte store only test
>   kselftest/arm64/mte: add MTE_STORE_ONLY testcases
>
>  Documentation/arch/arm64/elf_hwcaps.rst       |   3 +
>  arch/arm64/include/asm/hwcap.h                |   1 +
>  arch/arm64/include/asm/processor.h            |   2 +
>  arch/arm64/include/uapi/asm/hwcap.h           |   1 +
>  arch/arm64/kernel/cpufeature.c                |   9 ++
>  arch/arm64/kernel/cpuinfo.c                   |   1 +
>  arch/arm64/kernel/mte.c                       |  11 +-
>  arch/arm64/kernel/process.c                   |   6 +-
>  arch/arm64/tools/cpucaps                      |   1 +
>  include/uapi/linux/prctl.h                    |   2 +
>  tools/testing/selftests/arm64/abi/hwcap.c     |   6 +
>  .../selftests/arm64/mte/check_buffer_fill.c   |  10 +-
>  .../selftests/arm64/mte/check_child_memory.c  |   4 +-
>  .../arm64/mte/check_hugetlb_options.c         |   6 +-
>  .../selftests/arm64/mte/check_ksm_options.c   |   2 +-
>  .../selftests/arm64/mte/check_mmap_options.c  | 116 ++++++++++++------
>  .../testing/selftests/arm64/mte/check_prctl.c |  25 ++--
>  .../arm64/mte/check_tags_inclusion.c          |   8 +-
>  .../selftests/arm64/mte/check_user_mem.c      |   2 +-
>  .../selftests/arm64/mte/mte_common_util.c     |  14 ++-
>  .../selftests/arm64/mte/mte_common_util.h     |   3 +-
>  21 files changed, 167 insertions(+), 66 deletions(-)
>
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>

--
Sincerely,
Yeoreum Yun