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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 AAB7DC433FF for ; Fri, 9 Aug 2019 08:55:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7302420B7C for ; Fri, 9 Aug 2019 08:55:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406036AbfHIIzZ (ORCPT ); Fri, 9 Aug 2019 04:55:25 -0400 Received: from foss.arm.com ([217.140.110.172]:43682 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405785AbfHIIzZ (ORCPT ); Fri, 9 Aug 2019 04:55:25 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7CA5D344; Fri, 9 Aug 2019 01:55:24 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5D9333F706; Fri, 9 Aug 2019 01:55:23 -0700 (PDT) Date: Fri, 9 Aug 2019 09:55:21 +0100 From: Mark Rutland To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Joel Fernandes , Jiping Ma , mingo@redhat.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/2 v2] tracing/arm64: Have max stack tracer handle the case of return address after data Message-ID: <20190809085520.GC48423@lakrids.cambridge.arm.com> References: <20190807172826.352574408@goodmis.org> <20190807172907.155165959@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190807172907.155165959@goodmis.org> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 07, 2019 at 01:28:27PM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (VMware)" > > Most archs (well at least x86) store the function call return address on the > stack before storing the local variables for the function. The max stack > tracer depends on this in its algorithm to display the stack size of each > function it finds in the back trace. > > Some archs (arm64), may store the return address (from its link register) > just before calling a nested function. There's no reason to save the link > register on leaf functions, as it wont be updated. This breaks the algorithm > of the max stack tracer. > > Add a new define ARCH_RET_ADDR_AFTER_LOCAL_VARS that an architecture may set > if it stores the return address (link register) after it stores the > function's local variables, and have the stack trace shift the values of the > mapped stack size to the appropriate functions. > > Link: 20190802094103.163576-1-jiping.ma2@windriver.com > > Reported-by: Jiping Ma > Signed-off-by: Steven Rostedt (VMware) > --- > arch/arm64/include/asm/ftrace.h | 13 +++++++++++++ > kernel/trace/trace_stack.c | 14 ++++++++++++++ > 2 files changed, 27 insertions(+) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 5ab5200b2bdc..961e98618db4 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -14,6 +14,19 @@ > #define MCOUNT_ADDR ((unsigned long)_mcount) > #define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE > > +/* > + * Currently, gcc tends to save the link register after the local variables > + * on the stack. This causes the max stack tracer to report the function > + * frame sizes for the wrong functions. By defining > + * ARCH_RET_ADDR_AFTER_LOCAL_VARS, it will tell the stack tracer to expect > + * to find the return address on the stack after the local variables have > + * been set up. > + * > + * Note, this may change in the future, and we will need to deal with that > + * if it were to happen. > + */ > +#define ARCH_RET_ADDR_AFTER_LOCAL_VARS 1 FWIW (with whatever this got renamed to): Acked-by: Mark Rutland Thanks, Mark.