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 C7CF6CCA473 for ; Sat, 18 Jun 2022 09:27:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233802AbiFRJ1x (ORCPT ); Sat, 18 Jun 2022 05:27:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33844 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230508AbiFRJ1v (ORCPT ); Sat, 18 Jun 2022 05:27:51 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BACA20BCA for ; Sat, 18 Jun 2022 02:27:50 -0700 (PDT) Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4LQ9XH59BYzYrnK; Sat, 18 Jun 2022 17:26:39 +0800 (CST) Received: from kwepemm600017.china.huawei.com (7.193.23.234) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 18 Jun 2022 17:27:47 +0800 Received: from [10.174.179.234] (10.174.179.234) by kwepemm600017.china.huawei.com (7.193.23.234) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 18 Jun 2022 17:27:46 +0800 Message-ID: Date: Sat, 18 Jun 2022 17:27:45 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH -next v5 7/8] arm64: add uaccess to machine check safe To: Mark Rutland 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 , , "H . Peter Anvin" , , , , , Kefeng Wang , Xie XiuQi , Guohanjun References: <20220528065056.1034168-1-tongtiangen@huawei.com> <20220528065056.1034168-8-tongtiangen@huawei.com> From: Tong Tiangen In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/6/17 17:06, Mark Rutland 写道: > 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. You have a point. so there is no need to modify copy_from/to_user.S in this patch set. > > 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 recovery success, The task will be killed and there will be no subsequent memset(). > > 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? According to my understanding of the above, only the modification of extable.c is retained. So what do you mean which part is made into a separate patch? Thanks, Tong. > > Thanks, > Mark. > > .