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=-4.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 77A5CC433DB for ; Thu, 21 Jan 2021 11:50:23 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 10A4C2395B for ; Thu, 21 Jan 2021 11:50:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10A4C2395B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:To:Subject:Message-ID:Date:From:In-Reply-To: References:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=68godzE0dAumcrmCVL0GqMaMmjXqzR3Z+i88PIyLrhk=; b=VSsNaky4OaIMldm8pSsVnpO3O LDFhaTtOuutB0VPpespefo5VAGSjoYgWwSbV08eZJXetx7eJvSsWLs1zM7MZOYOXl2wIcM0sEjG6O +ldPMnM86gMFYeU2eFuwkgxxlqHJx+R4IKtM41KwtL3jThIspnwU0IX8GifX4lcY+BZLkP4rvLfBB VsERMNhIvuw63Dhpjd0pjDBMEZbaao3v2WKClXIZMCk8/1O7fTjuOJHP9N2xvvPBArQoA0TRRNuIi v5GSbeWS7XBMr2fTTBh5bjx0xfU1WkxnmJJygSyDta1FFgonezDZ1amSmg6godyi/2NEPtfQdvNz5 KYF5BSEdQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2YSQ-0006Vx-LX; Thu, 21 Jan 2021 11:48:58 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2YSO-0006VI-FQ for linux-arm-kernel@lists.infradead.org; Thu, 21 Jan 2021 11:48:57 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7F8BD23977 for ; Thu, 21 Jan 2021 11:48:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611229735; bh=4LoYAC73s65Y5H0iYwUuGzJLofq3OtSrbEyyV4z/Kog=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=oBpyGboZuZUjl523dwPWQwgTBZSYXSYF7piXJkDfjOhUnVt0mpF8tpsy6IyLDmxlw qEEdYZQyh7zk9SiuMR9gAne8ettknwKIH/ju5oblc2y0c8cPAUbRYfRSGNlkO0j1m5 2FEsgxre++Ar5NxlVBxnqODtLjLTLhKARflHZfGoN/TgbXUdsYgKdTh45LAroo4mZ1 KrNgaP/zIEMCm4OYGIAbJrPzRzEjpubHHEu8KTitI8Y9Di8C5W4rZvaOFat+emLEP9 CFszvu3uSFjl4ka4jogtXmDQEiwwvM0XQJx+6s9dFEcoSFPXRNu8TODLF5zOVsnT1c Zv/hYiVOlhZrQ== Received: by mail-ot1-f49.google.com with SMTP id k8so1297794otr.8 for ; Thu, 21 Jan 2021 03:48:55 -0800 (PST) X-Gm-Message-State: AOAM532JP0xuuI1guxPeKuIPB2kAenc0OIdJvPRUeFtLBGz03CdYZXYM woCurL0qdlFzi7coRyi722jYXsYbhn/FLi3F1+U= X-Google-Smtp-Source: ABdhPJwd56HgLproI09sgiWpE983hjJPCQ2fDWHVcfiofuOXt425n9x+OHdx1ZUjKLrj2FNAoQtyENmXNJ9zYiszajE= X-Received: by 2002:a05:6830:1e2a:: with SMTP id t10mr4636246otr.90.1611229734707; Thu, 21 Jan 2021 03:48:54 -0800 (PST) MIME-Version: 1.0 References: <20210120173800.1660730-1-jthierry@redhat.com> <186bb660-6e70-6bbf-4e96-1894799c79ce@redhat.com> In-Reply-To: From: Ard Biesheuvel Date: Thu, 21 Jan 2021 12:48:43 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 00/17] objtool: add base support for arm64 To: Peter Zijlstra X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_064856_686158_18145AED X-CRM114-Status: GOOD ( 20.99 ) 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: Mark Rutland , Michal Marek , Julien Thierry , linux-efi , Catalin Marinas , Masahiro Yamada , Linux Kernel Mailing List , Mark Brown , linux-hardening@vger.kernel.org, Josh Poimboeuf , Will Deacon , Linux ARM , Kees Cook Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 21 Jan 2021 at 12:23, Peter Zijlstra wrote: > > On Thu, Jan 21, 2021 at 12:08:23PM +0100, Ard Biesheuvel wrote: > > On Thu, 21 Jan 2021 at 11:26, Julien Thierry wrote: > > > > I'm not familiar with toolcahin code models, but would this approach be > > > able to validate assembly code (either inline or in assembly files?) > > > > > > > No, it would not. But those files are part of the code base, and can > > be reviewed and audited. > > x86 has a long history if failing at exactly that. That's a fair point. But on the flip side, maintaining objtool does not look like it has been a walk in the park either. What i am especially concerned about is things like 3193c0836f20, where we actually have to disable certain compiler optimizations because they interfere with objtool's ability to understand the resulting object code. Correctness and performance are challenging enough as requirements for generated code. Mind you, I am not saying it is not worth it *for x86*, where there is a lot of other stuff going on. But on arm64, we don't care about ORC, about -fomit-frame-pointer, about retpolines or about any of the other things objtool enables. On arm64, all it currently seems to provide is a way to capture the call stack accurately, and given that it needs a GCC plugin for this (which needs to be maintained as well, which is non-trivial, and also bars us from using objtool with Clang builds), my current position is simply that opening this can of worms at this point is just not worth it. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel