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 941E1C433EF for ; Wed, 6 Apr 2022 13:48:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233534AbiDFNug (ORCPT ); Wed, 6 Apr 2022 09:50:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42160 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233947AbiDFNt5 (ORCPT ); Wed, 6 Apr 2022 09:49:57 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id DC3096D8DD2 for ; Wed, 6 Apr 2022 04:19:54 -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 529C223A; Wed, 6 Apr 2022 04:19:54 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.10.98]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 24FC43F718; Wed, 6 Apr 2022 04:19:52 -0700 (PDT) Date: Wed, 6 Apr 2022 12:19:48 +0100 From: Mark Rutland To: Tong Tiangen Cc: Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Catalin Marinas , Will Deacon , Alexander Viro , x86@kernel.org, "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH -next V2 4/7] arm64: add copy_from_user to machine check safe Message-ID: References: <20220406091311.3354723-1-tongtiangen@huawei.com> <20220406091311.3354723-5-tongtiangen@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220406091311.3354723-5-tongtiangen@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 06, 2022 at 09:13:08AM +0000, Tong Tiangen wrote: > Add scenarios copy_from_user to machine check safe. > > The data copied is user data and is machine check safe, so just kill > the user process and isolate the error page, not necessary panic. > > Signed-off-by: Tong Tiangen > --- > arch/arm64/include/asm/asm-uaccess.h | 16 ++++++++++++++++ > arch/arm64/lib/copy_from_user.S | 11 ++++++----- > 2 files changed, 22 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h > index 0557af834e03..f31c8978e1af 100644 > --- a/arch/arm64/include/asm/asm-uaccess.h > +++ b/arch/arm64/include/asm/asm-uaccess.h > @@ -92,4 +92,20 @@ alternative_else_nop_endif > > _asm_extable 8888b,\l; > .endm > + > + .macro user_ldp_mc l, reg1, reg2, addr, post_inc > +8888: ldtr \reg1, [\addr]; > +8889: ldtr \reg2, [\addr, #8]; > + add \addr, \addr, \post_inc; > + > + _asm_extable_mc 8888b, \l; > + _asm_extable_mc 8889b, \l; > + .endm > + > + .macro user_ldst_mc l, inst, reg, addr, post_inc > +8888: \inst \reg, [\addr]; > + add \addr, \addr, \post_inc; > + > + _asm_extable_mc 8888b, \l; > + .endm > #endif > diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S > index 34e317907524..d9d7c5291871 100644 > --- a/arch/arm64/lib/copy_from_user.S > +++ b/arch/arm64/lib/copy_from_user.S > @@ -21,7 +21,7 @@ > */ > > .macro ldrb1 reg, ptr, val > - user_ldst 9998f, ldtrb, \reg, \ptr, \val > + user_ldst_mc 9998f, ldtrb, \reg, \ptr, \val > .endm > > .macro strb1 reg, ptr, val > @@ -29,7 +29,7 @@ > .endm > > .macro ldrh1 reg, ptr, val > - user_ldst 9997f, ldtrh, \reg, \ptr, \val > + user_ldst_mc 9997f, ldtrh, \reg, \ptr, \val > .endm > > .macro strh1 reg, ptr, val > @@ -37,7 +37,7 @@ > .endm > > .macro ldr1 reg, ptr, val > - user_ldst 9997f, ldtr, \reg, \ptr, \val > + user_ldst_mc 9997f, ldtr, \reg, \ptr, \val > .endm > > .macro str1 reg, ptr, val > @@ -45,7 +45,7 @@ > .endm > > .macro ldp1 reg1, reg2, ptr, val > - user_ldp 9997f, \reg1, \reg2, \ptr, \val > + user_ldp_mc 9997f, \reg1, \reg2, \ptr, \val > .endm > > .macro stp1 reg1, reg2, ptr, val > @@ -62,7 +62,8 @@ SYM_FUNC_START(__arch_copy_from_user) > ret > > // Exception fixups > -9997: cmp dst, dstin > +9997: cbz x0, 9998f // Check machine check exception > + cmp dst, dstin > b.ne 9998f If you look at the copy template, you'd see that `dstin` *is* x0. Consier if we took a non-SEA fault. The the fixup handler will overwrite x0, it's likely `dst` != `dstin`, and we'll branch to the byte-by-byte copy. Or if we're doing something odd and mmap_min_addr is 0, we can do the wrong thing the other way around and *not* branch to the byte-by-byte copy when we should. So this is at best confusing, but likely broken too. Thanks, Mark. > // Before being absolutely sure we couldn't copy anything, try harder > USER(9998f, ldtrb tmp1w, [srcin]) > -- > 2.18.0.huawei.25 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel