linux-kernel - Re: [PATCH v3 2/4] prtcl: introduce PR_MTE_STORE

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Message-ID: <390f3d5e-8da6-4286-b8a9-72eabcc3abd5@redhat.com>
Date: Thu, 24 Apr 2025 22:34:57 +0200
From: David Hildenbrand <david@...hat.com>
To: Yeoreum Yun <yeoreum.yun@....com>, catalin.marinas@....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, shameerali.kolothum.thodi@...wei.com,
 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,
 yang@...amperecomputing.com, mbenes@...e.cz, joel.granados@...nel.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 nd@....com
Subject: Re: [PATCH v3 2/4] prtcl: introduce PR_MTE_STORE_ONLY

On 10.04.25 10:07, Yeoreum Yun wrote:
> PR_MTE_STORE_ONLY is used to restrict the MTE tag check for store
> opeartion only.
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
> ---
>   include/uapi/linux/prctl.h | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
> index 15c18ef4eb11..83ac566251d8 100644
> --- a/include/uapi/linux/prctl.h
> +++ b/include/uapi/linux/prctl.h
> @@ -244,6 +244,8 @@ struct prctl_mm_map {
>   # define PR_MTE_TAG_MASK		(0xffffUL << PR_MTE_TAG_SHIFT)
>   /* Unused; kept only for source compatibility */
>   # define PR_MTE_TCF_SHIFT		1
> +/* MTE tag check store only */
> +# define PR_MTE_STORE_ONLY		(1UL << 19)

That is the next available bit after PR_MTE_TAG_MASK, correct?

Would we want to leave some space to grow PR_MTE_TAG_MASK in the future 
(could that happen?)?

-- 
Cheers,

David / dhildenb