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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27E03C433EF for ; Wed, 19 Jan 2022 21:07:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245730AbiASVHq (ORCPT ); Wed, 19 Jan 2022 16:07:46 -0500 Received: from mail-out.m-online.net ([212.18.0.9]:55296 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229564AbiASVHm (ORCPT ); Wed, 19 Jan 2022 16:07:42 -0500 Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 4JfJBN5hcHz1qwyD; Wed, 19 Jan 2022 22:07:40 +0100 (CET) Received: from localhost (dynscan1.mnet-online.de [192.168.6.70]) by mail.m-online.net (Postfix) with ESMTP id 4JfJBN54Cfz1qqkB; Wed, 19 Jan 2022 22:07:40 +0100 (CET) X-Virus-Scanned: amavisd-new at mnet-online.de Received: from mail.mnet-online.de ([192.168.8.182]) by localhost (dynscan1.mail.m-online.net [192.168.6.70]) (amavisd-new, port 10024) with ESMTP id fa2MReFuQDWV; Wed, 19 Jan 2022 22:07:39 +0100 (CET) X-Auth-Info: a+k5wgMBRWkntvg+3VX7x/EHIpisGRCFgjaQ+T+kj0Njbe4vckVflYo3aArUijhP Received: from igel.home (ppp-46-244-165-91.dynamic.mnet-online.de [46.244.165.91]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.mnet-online.de (Postfix) with ESMTPSA; Wed, 19 Jan 2022 22:07:39 +0100 (CET) Received: by igel.home (Postfix, from userid 1000) id 74A832C36EC; Wed, 19 Jan 2022 22:07:39 +0100 (CET) From: Andreas Schwab To: Jessica Clarke Cc: Changbin Du , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-riscv , linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: eliminate unreliable __builtin_frame_address(1) References: <20220117154433.3124-1-changbin.du@gmail.com> <87v8yg6lhf.fsf@igel.home> <8735lj78wu.fsf@igel.home> <8F8D535F-3637-4BC7-8853-B709EC5D14C9@jrtc27.com> X-Yow: Uh-oh!! I forgot to submit to COMPULSORY URINALYSIS! Date: Wed, 19 Jan 2022 22:07:39 +0100 In-Reply-To: <8F8D535F-3637-4BC7-8853-B709EC5D14C9@jrtc27.com> (Jessica Clarke's message of "Wed, 19 Jan 2022 20:48:48 +0000") Message-ID: <87y23b5t9g.fsf@igel.home> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.91 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Jan 19 2022, Jessica Clarke wrote: > My point is that the only thing that can possibly read the incoming > frame pointer of a leaf function is the leaf function itself, and since > it knows where it’s putting it then there is no ABI issue, it just > remembers where it put it and loads it from there. llvm sidesteps that issue by always saving ra when creating a frame, even in a leaf function, so it can use a constant offset. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1 "And now for something completely different."