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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 0446BC6FA82 for ; Wed, 14 Sep 2022 14:01:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc: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=Mf0wB3MReD+6+CI1paRuDOdVQioewjBA7Jh4RcaRM18=; b=pYUjAU1bZrdDIA 0emvqU2z5PJ4vixQh+JfiJ8dSrInsc6F4+TbWXRFboONdR9SKN5Gk7oMupo2myzxbVSJfLZMlOmRU SUnAbGJqX9MlksWCZL8QeZXtdQEFnzmujBpZaxMSGraCkuNObm71HWAR6PwglKq+SqW5DM62hIlQH /XuECNQFwsSnrE0pu/hGKi52jL3GxQFZVxGZTXDnoFBIlhWV/666yUL2rCPMKiTFu6Sdv9s8F622H 4ne+DRIcqwRg9oxKqA/459xJmWSvMHC9TR5YgsBnCKqBj3497XPi8+IsQMCqnxLHfyV8nZTKe5LZN gdPEIAnEGD3RSnt6c/Mg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oYSwJ-001UFh-U9; Wed, 14 Sep 2022 14:00:32 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oYSwI-001U6v-Gk for linux-arm-kernel@bombadil.infradead.org; Wed, 14 Sep 2022 14:00:30 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=6QAWxLdMZL2HrdyA2qxKWv8rmsu40qWwB6+Piak/frU=; b=grvdlhiDJot2FEpq+aFmAKpbVL 618tCmlcl9TPnZnLX8PT4AhesK8/j7mmZuPujaIwSXumYee6m/OP3I9Z8QFflX21DFKDV/1eCyZSO 1tXouQhREH2V6O6uTrrhCur9gYWzcDGFuM3KczBsBLsHjAH+g6vjLnj4+SbI8pdwWgVG/nIGTDvyD DiHFFwPKYeMxg+uODtM74++NkL63AwP3uz/GHM1UJwCvDU+S0s8jHC8bfF+pJP8Ip02ArlO2XX031 PYJx514ksqOpuNFWFgGMNIp/Q19glVLvHb4u8/vmi0+mnjAgBbMDj0XzSWSfa/KX4gkD96/5qTrfO EMxpDi1g==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1oYSw9-000EDJ-E2; Wed, 14 Sep 2022 14:00:21 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id A70D43002AE; Wed, 14 Sep 2022 16:00:16 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8BBF52B8AD401; Wed, 14 Sep 2022 16:00:16 +0200 (CEST) Date: Wed, 14 Sep 2022 16:00:16 +0200 From: Peter Zijlstra To: Josh Poimboeuf Cc: Michael Matz , Borislav Petkov , linux-toolchains@vger.kernel.org, Indu Bhagat , Nick Desaulniers , linux-kernel@vger.kernel.org, "Jose E. Marchesi" , Miroslav Benes , Mark Rutland , Will Deacon , x86@kernel.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Ard Biesheuvel , Chen Zhongjin , Sathvika Vasireddy , Christophe Leroy , Mark Brown Subject: Re: [RFC] Objtool toolchain proposal: -fannotate-{jump-table,noreturn} Message-ID: References: <20220909180704.jwwed4zhwvin7uyi@treble> <20220914000416.daxbgccbxwpknn2q@treble> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220914000416.daxbgccbxwpknn2q@treble> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 Wed, Sep 14, 2022 at 01:04:16AM +0100, Josh Poimboeuf wrote: > > I will mention that objtool's existence is based on mistrust, of persons > > (not correctly annotating stuff) and of tools (not correctly heeding those > > annotations). The mistrust in persons is understandable and can be dealt > > with by tools, but the mistrust in tools can't be fixed by making tools > > more complicated by emitting even more information; there's no good reason > > to assume that one piece of info can be trusted more than other pieces. > > So, if you mistrust the tools you have already lost. That's somewhat > > philosophical, so I won't beat that horse much more either. > > Maybe this is semantics, but I wouldn't characterize objtool's existence > as being based on the mistrust of tools. It's main motivation is to > fill in the toolchain's blind spots in asm and inline-asm, which exist > by design. That and a fairly deep seated loathing for the regular CFI annotations and DWARF in general. Linus was fairly firm he didn't want anything to do with DWARF for in-kernel unwinding. That left us in a spot that we needed unwind information in a 'better' format than DWARF. Objtool was born out of those contraints. ORC not needing the CFI annotations and ORC being *much* faster at unwiding and generation (debug builds are slow) were all good. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel