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Wed, 03 Feb 2021 11:57:29 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 412043003D8; Wed, 3 Feb 2021 12:57:27 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2A5702364E363; Wed, 3 Feb 2021 12:57:27 +0100 (CET) Date: Wed, 3 Feb 2021 12:57:27 +0100 From: Peter Zijlstra To: Josh Poimboeuf Subject: Re: [RFC PATCH 12/17] gcc-plugins: objtool: Add plugin to detect switch table on arm64 Message-ID: References: <20210120173800.1660730-13-jthierry@redhat.com> <20210127221557.1119744-1-ndesaulniers@google.com> <20210127232651.rj3mo7c2oqh4ytsr@treble> <20210201214423.dhsma73k7ccscovm@treble> <671f1aa9-975e-1bda-6768-259adbdc24c8@redhat.com> <20210203001414.idjrcrki7wmhndre@treble> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210203001414.idjrcrki7wmhndre@treble> 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 , Bill Wendling , linux-efi , Julien Thierry , clang-built-linux , Catalin Marinas , Masahiro Yamada , Nick Desaulniers , LKML , Michal Marek , raphael.gault@arm.com, Mark Brown , linux-hardening@vger.kernel.org, swine@google.com, yonghyun@google.com, Will Deacon , Ard Biesheuvel , 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 Tue, Feb 02, 2021 at 06:14:14PM -0600, Josh Poimboeuf wrote: > > Sure, but this is what production unwinders do, and they don't require > > compiler plugins, right? > > What do you mean by "production unwinders"? Generally unwinders rely on > either frame pointers or DWARF, but (without validation) those aren't > robust enough for live patching in the kernel, so I'm not sure how this > is relevant. Not to mention that DWARF and consequently it's unders are horribly large, complex and above all fragile things. There's a reason ORC got invented, DWARF is simlpy unacceptable and inadequate. Now, one avenue that has been mentioned in the past, but I've not seen recently, is to have objtool use DWARF as input to help it understand the code. At least in userspace we can rely on DWARF libs. But I'm fairly sure people aren't jumping up and down for having to always build their kernel with DWARFs on, compile speed etc.. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel