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_2 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 9317BC32751 for ; Wed, 7 Aug 2019 19:29:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6E9982229C for ; Wed, 7 Aug 2019 19:29:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730559AbfHGT3T (ORCPT ); Wed, 7 Aug 2019 15:29:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:36582 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730407AbfHGT3S (ORCPT ); Wed, 7 Aug 2019 15:29:18 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3129D2086D; Wed, 7 Aug 2019 19:29:17 +0000 (UTC) Date: Wed, 7 Aug 2019 15:29:15 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Joel Fernandes , Jiping Ma , mingo@redhat.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-arm-kernel@lists.infradead.org, Mark Rutland Subject: Re: [PATCH 1/2 v2] tracing/arm64: Have max stack tracer handle the case of return address after data Message-ID: <20190807152915.6ee412b1@gandalf.local.home> In-Reply-To: <20190807172907.155165959@goodmis.org> References: <20190807172826.352574408@goodmis.org> <20190807172907.155165959@goodmis.org> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ I should have added Mark as Cc ] Dear ARM64 folks, Are you OK with this patch set? If so, please ACK. Should it be marked for stable? Hmm, I'm starting to think not. -- Steve On Wed, 07 Aug 2019 13:28:27 -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 > + > #ifndef __ASSEMBLY__ > #include > > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c > index 5d16f73898db..40e4a88eea8f 100644 > --- a/kernel/trace/trace_stack.c > +++ b/kernel/trace/trace_stack.c > @@ -158,6 +158,20 @@ static void check_stack(unsigned long ip, unsigned long *stack) > i++; > } > > +#ifdef ARCH_RET_ADDR_AFTER_LOCAL_VARS > + /* > + * Some archs will store the link register before calling > + * nested functions. This means the saved return address > + * comes after the local storage, and we need to shift > + * for that. > + */ > + if (x > 1) { > + memmove(&stack_trace_index[0], &stack_trace_index[1], > + sizeof(stack_trace_index[0]) * (x - 1)); > + x--; > + } > +#endif > + > stack_trace_nr_entries = x; > > if (task_stack_end_corrupted(current)) {