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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 176EFC1975A for ; Wed, 25 Mar 2020 12:03:32 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E0CEF20771 for ; Wed, 25 Mar 2020 12:03:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="RQTR6HI5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E0CEF20771 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=uyqoctrgyTB9LnJcuamZK2X4B4vLaG0GJxb2rELiO6o=; b=RQTR6HI5kBtGlm 3tsaFy5gWt139APGsaNUUmcxrskZdT8CGqo9JMtbVpi2bBuaDw2M2rASt3OvW8YnOjBcLvoW7TLhq PIhEqNZhXl3p0MWx7SNVtlwLJDGfS+p7PoUkCcTuMERXjZpvTqnelD3yMRKPGGbOPI9FmjL0yqd0p EeRzc1LdqFGlSGuvwL8I0v3Fp9uwClxZnrmBsF9nA+6zg0K3tWq1ag9+pklA4gNjYbGihw3M83eb/ +uLbEN2Fdk/KOQlVfMGSup/qVhPSYIEeai+CpTf6fCxEcWwrJ9CGTHzhVUCwqjMrIRB/UAVAa1COf aCyU0e7PD0utQAR7AUow==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jH4ks-0002LW-FC; Wed, 25 Mar 2020 12:03:30 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jH4kp-0002KZ-28 for linux-arm-kernel@lists.infradead.org; Wed, 25 Mar 2020 12:03:28 +0000 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 0D6DE31B; Wed, 25 Mar 2020 05:03:25 -0700 (PDT) Received: from C02TD0UTHF1T.local (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 61BDF3F71F; Wed, 25 Mar 2020 05:03:23 -0700 (PDT) Date: Wed, 25 Mar 2020 12:03:17 +0000 From: Mark Rutland To: Ard Biesheuvel Subject: Re: [PATCH 0/3] arm64: Open code .arch_extension Message-ID: <20200325120224.GA34330@C02TD0UTHF1T.local> References: <20200325114110.23491-1-broonie@kernel.org> <20200325115038.GD4346@sirena.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200325_050327_149350_B533E631 X-CRM114-Status: GOOD ( 13.55 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eric Biggers , Catalin Marinas , Mark Brown , linux-crypto@vger.kernel.org, Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Mar 25, 2020 at 12:54:10PM +0100, Ard Biesheuvel wrote: > On Wed, 25 Mar 2020 at 12:50, Mark Brown wrote: > > Since BTI is a mandatory feature of v8.5 there is no BTI arch_extension, > > you can only enable it by moving the base architecture to v8.5. You'd > > need to use .arch and that feels likely to find us sharp edges to run > > into. > > I think we should talk to the toolchain folks about this. Even if > .arch_extension today does not support the 'bti' argument, it *is* > most definitely an architecture extension, even it it is mandatory in > v8.5 (given that v8.5 is itself an architecture extension). It certianly seems unfortunate, as it goes against the premise of having HINT space instructions. Most software will want to enable HINT space instructions from ARMv8.x but nothing else to ensure binary compatibility with existing hardware. I see the same is true for pointer authentication judging by: https://sourceware.org/binutils/docs/as/AArch64-Extensions.html#AArch64-Extensions ... so worth raising with toolchain folk as a general principle even if we have to bodge around it for now. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel