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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 B9EF6C4332F for ; Thu, 15 Dec 2022 00:20:09 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4NXXtb53B7z3f5T for ; Thu, 15 Dec 2022 11:20:07 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4NXXt11DYMz2xVr for ; Thu, 15 Dec 2022 11:19:36 +1100 (AEDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 2BF0HSWb025354; Wed, 14 Dec 2022 18:17:28 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 2BF0HQ0c025352; Wed, 14 Dec 2022 18:17:26 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Wed, 14 Dec 2022 18:17:25 -0600 From: Segher Boessenkool To: Nicholas Piggin Subject: Re: [PATCH] powerpc/64: Implement arch_within_stack_frames Message-ID: <20221215001725.GS25951@gate.crashing.org> References: <20221214044252.1910657-1-nicholas@linux.ibm.com> <0dfbaab8-c962-9127-b56d-8f9989c095d8@csgroup.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linuxppc-dev@lists.ozlabs.org" , Nicholas Miehlbradt Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Dec 14, 2022 at 09:39:25PM +1000, Nicholas Piggin wrote: > What about just copying x86's implementation including using > __builtin_frame_address(1/2)? Are those builtins reliable for all > our targets and compiler versions? __builtin_frame_address(n) with n > 0 is specifically not supported, not on any architecture; it does not work in all situations on *any* arch, and not in *any* situation on some archs. This is clearly documented: Calling this function with a nonzero argument can have unpredictable effects, including crashing the calling program. As a result, calls that are considered unsafe are diagnosed when the '-Wframe-address' option is in effect. Such calls should only be made in debugging situations. (and that warning is enabled by -Wall). Segher