[PATCH v3 0/4] support FEAT_MTE_STORE_ONLY feature

[Yeoreum Yun]

Gentle ping in case of forgotten.

> 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.
>
> Since v1:
>   - add doc to elf_hwcaps.rst
>   - add MTE_STORE_ONLY hwcap test
>
> Since v2:
>   - Rebase to 6.15.-rc1
>
> NOTE:
>   This patches based on https://lore.kernel.org/all/20250410074721.947380-1-yeoreum.yun@arm.com/
>
> Yeoreum Yun (4):
>   arm64/feature: add MTE_STORE_ONLY feature
>   prtcl: introduce PR_MTE_STORE_ONLY
>   arm64/kernel: support store-only mte tag check
>   tools/kselftest: add MTE_STORE_ONLY feature hwcap test
>
>  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 ++++++
>  11 files changed, 41 insertions(+), 2 deletions(-)
>
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>

--
Sincerely,
Yeoreum Yun