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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9B68BC43334 for ; Sat, 18 Jun 2022 12:41:16 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4LQFrp6FT0z3cjF for ; Sat, 18 Jun 2022 22:41:14 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=mark.rutland@arm.com; receiver=) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4LQFrK262bz2yZc for ; Sat, 18 Jun 2022 22:40:45 +1000 (AEST) 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 1EF68113E; Sat, 18 Jun 2022 05:40:13 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.35.139]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6859A3F792; Sat, 18 Jun 2022 05:40:08 -0700 (PDT) Date: Sat, 18 Jun 2022 13:40:01 +0100 From: Mark Rutland To: Tong Tiangen Subject: Re: [PATCH -next v5 2/8] arm64: extable: make uaaccess helper use extable type EX_TYPE_UACCESS_ERR_ZERO Message-ID: References: <20220528065056.1034168-1-tongtiangen@huawei.com> <20220528065056.1034168-3-tongtiangen@huawei.com> <4371a7c9-8766-9fee-2558-e6f43f06ad19@huawei.com> <0da734f3-5743-3df3-3f90-d92e5bd585ce@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0da734f3-5743-3df3-3f90-d92e5bd585ce@huawei.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kefeng Wang , Dave Hansen , linux-mm@kvack.org, Paul Mackerras , Guohanjun , Will Deacon , "H . Peter Anvin" , x86@kernel.org, Ingo Molnar , Catalin Marinas , Xie XiuQi , Borislav Petkov , Alexander Viro , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Robin Murphy , linux-kernel@vger.kernel.org, James Morse , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Sat, Jun 18, 2022 at 04:42:06PM +0800, Tong Tiangen wrote: > > > > diff --git a/arch/arm64/include/asm/asm-extable.h > > > > b/arch/arm64/include/asm/asm-extable.h > > > > index 56ebe183e78b..9c94ac1f082c 100644 > > > > --- a/arch/arm64/include/asm/asm-extable.h > > > > +++ b/arch/arm64/include/asm/asm-extable.h > > > > @@ -28,6 +28,14 @@ > > > >       __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0) > > > >       .endm > > > > +/* > > > > + * Create an exception table entry for uaccess `insn`, which > > > > will branch to `fixup` > > > > + * when an unhandled fault is taken. > > > > + * ex->data = ~0 means both reg_err and reg_zero is set to wzr(x31). > > > > + */ > > > > +    .macro          _asm_extable_uaccess, insn, fixup > > > > +    __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_UACCESS_ERR_ZERO, ~0) > > > > +    .endm > > > > > > I'm not too keen on using `~0` here, since that also sets other bits > > > in the > > > data field, and its somewhat opaque. > > > > > > How painful is it to generate the data fields as with the C version > > > of this > > > macro, so that we can pass in wzr explciitly for the two sub-fields? > > > > > > Other than that, this looks good to me. > > > > > > Thanks, > > > Mark. > > > > ok, will fix next version. > > > > Thanks, > > Tong. > > I tried to using data filelds as with C version, but here assembly code we > can not using operator such as << and |, if we use lsl and orr instructions, > the gpr will be occupied. > > So how about using 0x3ff directly here? it means err register and zero > register both set to x31. I had a go at implementing this, and it seems simple enough. Please see: https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/extable/asm-uaccess Mark.