From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C2BD269833; Fri, 2 May 2025 17:08:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746205708; cv=none; b=se27+DpRsozJVN6xyen6hPrGwAYlOJ3uO36QrRtoeU1PJXowj2J1Yt2UZ29sYkmAy4SMgExXz6LZGfUj5W1VgF3/ObwISL/SBgNENc9PoiaL5SdobvPZrfLi3se2YQpDh9NPNXAlVYiBBbcUYLUuZ+p4jgaZPTR1oaegY1wZ21s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746205708; c=relaxed/simple; bh=MHsz2Fi2k9mv6IeTOC5g4/8EDZf7CKvhbnjjpQI7eu0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lt3q6vfMETuZHCzg8dLY7m0IcmFrqPYEFiwxvTOeU7aFK4TNR1SwRkM+rgL+Mn0/PsVBvau+CpPLYO1UEz+Rixhd62v50pMNYKRV2GK8Posn1rrXyk4tbZsuDn3KC9/9h6oZ5fmvv74Ln4Gq+apxY4E4rn6/Sdj7MFjjgiM0L64= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3984C4CEF2; Fri, 2 May 2025 17:08:23 +0000 (UTC) Date: Fri, 2 May 2025 18:08:21 +0100 From: Catalin Marinas To: Yeoreum Yun , Peter Collingbourne Cc: will@kernel.org, broonie@kernel.org, anshuman.khandual@arm.com, joey.gouly@arm.com, yury.khrustalev@arm.com, maz@kernel.org, oliver.upton@linux.dev, frederic@kernel.org, shmeerali.kolothum.thodi@huawei.com, james.morse@arm.com, mark.rutland@arm.com, huangxiaojia2@huawei.com, akpm@linux-foundation.org, surenb@google.com, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, nd@arm.com Subject: Re: [PATCH v3 2/3] arm64/mm/fault: use original FAR_EL1 value when ARM64_MTE_FAR is supported Message-ID: References: <20250410074721.947380-1-yeoreum.yun@arm.com> <20250410074721.947380-3-yeoreum.yun@arm.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250410074721.947380-3-yeoreum.yun@arm.com> + Peter Collingbourne as he added the SA_EXPOSE_TAGBITS flag. On Thu, Apr 10, 2025 at 08:47:20AM +0100, Yeoreum Yun wrote: > Use the original FAR_EL1 value when an MTE tag check fault occurs, > if ARM64_MTE_FAR is supported. > This allows reports to include not only the logical tag (memory tag) > but also the address tag information. > > Applications that require this information should install a signal handler with > the SA_EXPOSE_TAGBITS flag. > While this introduces a minor ABI change, > most applications do not set this flag and therefore will not be affected. It is indeed a minor ABI in that a tag check fault resulting in a signal will report the bits 63:60 as well, not just 59:56 of the address (if the signal handler was registered with SA_EXPOSE_TAGBITS). I don't think user-space would notice but asking Peter. > Signed-off-by: Yeoreum Yun > --- > arch/arm64/mm/fault.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index ec0a337891dd..f21d972f99b1 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -837,9 +837,12 @@ static int do_tag_check_fault(unsigned long far, unsigned long esr, > /* > * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN > * for tag check faults. Set them to corresponding bits in the untagged > - * address. > + * address if ARM64_MTE_FAR isn't supported. > + * Otherwise, bits 63:60 of FAR_EL1 are KNOWN. > */ > - far = (__untagged_addr(far) & ~MTE_TAG_MASK) | (far & MTE_TAG_MASK); > + if (!cpus_have_cap(ARM64_MTE_FAR)) > + far = (__untagged_addr(far) & ~MTE_TAG_MASK) | (far & MTE_TAG_MASK); > + > do_bad_area(far, esr, regs); > return 0; > } > -- > LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}