From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B14A2C43334 for ; Fri, 17 Jun 2022 09:07:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380558AbiFQJHJ (ORCPT ); Fri, 17 Jun 2022 05:07:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53146 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1381479AbiFQJHD (ORCPT ); Fri, 17 Jun 2022 05:07:03 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 75E6650472 for ; Fri, 17 Jun 2022 02:07:02 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3D6D612FC; Fri, 17 Jun 2022 02:07:02 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.39.168]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A27AD3F792; Fri, 17 Jun 2022 02:06:58 -0700 (PDT) Date: Fri, 17 Jun 2022 10:06:54 +0100 From: Mark Rutland To: Tong Tiangen Cc: James Morse , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Robin Murphy , Dave Hansen , Catalin Marinas , Will Deacon , Alexander Viro , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , x86@kernel.org, "H . Peter Anvin" , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Kefeng Wang , Xie XiuQi , Guohanjun Subject: Re: [PATCH -next v5 7/8] arm64: add uaccess to machine check safe Message-ID: References: <20220528065056.1034168-1-tongtiangen@huawei.com> <20220528065056.1034168-8-tongtiangen@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220528065056.1034168-8-tongtiangen@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 28, 2022 at 06:50:55AM +0000, Tong Tiangen wrote: > If user access fail due to hardware memory error, only the relevant > processes are affected, so killing the user process and isolate the > error page with hardware memory errors is a more reasonable choice > than kernel panic. > > Signed-off-by: Tong Tiangen > --- > arch/arm64/lib/copy_from_user.S | 8 ++++---- > arch/arm64/lib/copy_to_user.S | 8 ++++---- All of these changes are to the *kernel* accesses performed as part of copy to/from user, and have nothing to do with userspace, so it does not make sense to mark these as UACCESS. Do we *actually* need to recover from failues on these accesses? Looking at _copy_from_user(), the kernel will immediately follow this up with a memset() to the same address which will be fatal anyway, so this is only punting the failure for a few instructions. If we really need to recover from certain accesses to kernel memory we should add a new EX_TYPE_KACCESS_ERR_ZERO_MC or similar, but we need a strong rationale as to why that's useful. As things stand I do not beleive it makes sense for copy to/from user specifically. > arch/arm64/mm/extable.c | 8 ++++---- > 3 files changed, 12 insertions(+), 12 deletions(-) > > diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S > index 34e317907524..402dd48a4f93 100644 > --- a/arch/arm64/lib/copy_from_user.S > +++ b/arch/arm64/lib/copy_from_user.S > @@ -25,7 +25,7 @@ > .endm > > .macro strb1 reg, ptr, val > - strb \reg, [\ptr], \val > + USER(9998f, strb \reg, [\ptr], \val) > .endm > > .macro ldrh1 reg, ptr, val > @@ -33,7 +33,7 @@ > .endm > > .macro strh1 reg, ptr, val > - strh \reg, [\ptr], \val > + USER(9998f, strh \reg, [\ptr], \val) > .endm > > .macro ldr1 reg, ptr, val > @@ -41,7 +41,7 @@ > .endm > > .macro str1 reg, ptr, val > - str \reg, [\ptr], \val > + USER(9998f, str \reg, [\ptr], \val) > .endm > > .macro ldp1 reg1, reg2, ptr, val > @@ -49,7 +49,7 @@ > .endm > > .macro stp1 reg1, reg2, ptr, val > - stp \reg1, \reg2, [\ptr], \val > + USER(9998f, stp \reg1, \reg2, [\ptr], \val) > .endm > > end .req x5 > diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S > index 802231772608..4134bdb3a8b0 100644 > --- a/arch/arm64/lib/copy_to_user.S > +++ b/arch/arm64/lib/copy_to_user.S > @@ -20,7 +20,7 @@ > * x0 - bytes not copied > */ > .macro ldrb1 reg, ptr, val > - ldrb \reg, [\ptr], \val > + USER(9998f, ldrb \reg, [\ptr], \val) > .endm > > .macro strb1 reg, ptr, val > @@ -28,7 +28,7 @@ > .endm > > .macro ldrh1 reg, ptr, val > - ldrh \reg, [\ptr], \val > + USER(9998f, ldrh \reg, [\ptr], \val) > .endm > > .macro strh1 reg, ptr, val > @@ -36,7 +36,7 @@ > .endm > > .macro ldr1 reg, ptr, val > - ldr \reg, [\ptr], \val > + USER(9998f, ldr \reg, [\ptr], \val) > .endm > > .macro str1 reg, ptr, val > @@ -44,7 +44,7 @@ > .endm > > .macro ldp1 reg1, reg2, ptr, val > - ldp \reg1, \reg2, [\ptr], \val > + USER(9998f, ldp \reg1, \reg2, [\ptr], \val) > .endm > > .macro stp1 reg1, reg2, ptr, val > diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c > index c301dcf6335f..8ca8d9639f9f 100644 > --- a/arch/arm64/mm/extable.c > +++ b/arch/arm64/mm/extable.c > @@ -86,10 +86,10 @@ bool fixup_exception_mc(struct pt_regs *regs) > if (!ex) > return false; > > - /* > - * This is not complete, More Machine check safe extable type can > - * be processed here. > - */ > + switch (ex->type) { > + case EX_TYPE_UACCESS_ERR_ZERO: > + return ex_handler_uaccess_err_zero(ex, regs); > + } This addition specifically makes sense to me, so can you split this into a separate patch? Thanks, Mark.