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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4533C433F5 for ; Fri, 22 Oct 2021 18:53:22 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8CEAB6108B for ; Fri, 22 Oct 2021 18:53:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8CEAB6108B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=DmJjrIClEne2Au91yl0ckuMJ3RNwM1/9ziKuWrYBsMk=; b=Lqh7Fdd0xPJpUU zbllazjSZZzvYIkFsdKQpkH2uOrgQH1GKgvrpW9wkr8M9hW+5TFr+UVvs+uEYGDOy5o+8BGxu9Izi hbvf/79UbblUGLzBkS2mpABVXJewvaWsPYW1rvxdbirVucCIWKwjqvDmcz/ekRvBAMjIJGijPvtRm IpVaFt7u48c2eKldB04nAxITX9zLOSC2kHkTGK0DinR4PLxhqzn2xzFdc0ORCfeOapWV9z3pTJqlb 07d/HBvVFGdQ64ijwq2HIOCbZ6cJYPu8AqxyVoYAKA9eH8yeaROzWVjCz3KDm13ApZlquOsA+gaG+ EJ5JQ6xj0g+MeYOupJmg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mdzeB-00BloC-9P; Fri, 22 Oct 2021 18:52:07 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mdze7-00BlnW-Gq for linux-arm-kernel@lists.infradead.org; Fri, 22 Oct 2021 18:52:05 +0000 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 A9AE61063; Fri, 22 Oct 2021 11:51:58 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.73.6]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3D4D83F73D; Fri, 22 Oct 2021 11:51:56 -0700 (PDT) Date: Fri, 22 Oct 2021 19:51:48 +0100 From: Mark Rutland To: madvenka@linux.microsoft.com Cc: broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v10 04/11] arm64: Make return_address() use arch_stack_walk() Message-ID: <20211022185148.GA91654@C02TD0UTHF1T.local> References: <20211015025847.17694-1-madvenka@linux.microsoft.com> <20211015025847.17694-5-madvenka@linux.microsoft.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211015025847.17694-5-madvenka@linux.microsoft.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211022_115203_651773_08B3123D X-CRM114-Status: GOOD ( 20.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 Thu, Oct 14, 2021 at 09:58:40PM -0500, madvenka@linux.microsoft.com wrote: > From: "Madhavan T. Venkataraman" > > Currently, return_address() in ARM64 code walks the stack using > start_backtrace() and walk_stackframe(). Make it use arch_stack_walk() > instead. This makes maintenance easier. > > Signed-off-by: Madhavan T. Venkataraman > --- > arch/arm64/kernel/return_address.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/arch/arm64/kernel/return_address.c b/arch/arm64/kernel/return_address.c > index a6d18755652f..92a0f4d434e4 100644 > --- a/arch/arm64/kernel/return_address.c > +++ b/arch/arm64/kernel/return_address.c > @@ -35,15 +35,11 @@ NOKPROBE_SYMBOL(save_return_addr); > void *return_address(unsigned int level) > { > struct return_address_data data; > - struct stackframe frame; > > data.level = level + 2; > data.addr = NULL; > > - start_backtrace(&frame, > - (unsigned long)__builtin_frame_address(0), > - (unsigned long)return_address); > - walk_stackframe(current, &frame, save_return_addr, &data); > + arch_stack_walk(save_return_addr, &data, current, NULL); This looks equivalent to me. Previously the arguments to start_backtrace() meant that walk_stackframe would report return_address(), then the caller of return_address(), and so on. As arch_stack_walk() starts from its immediate caller (i.e. return_address()), that should result in the same trace. It would be nice if we could note something to that effect in the commit message. I had a play with ftrace, which uses return_address(), and that all looks sound. > > if (!data.level) > return data.addr; The end of this function currently does: if (!data.level) return data.addr; else return NULL; ... but since we initialize data.addr to NULL, and save_return_addr() only writes to data.addr when called at the correct level, we can simplify that to: return data.addr; Regardles of that cleanup: Reviewed-by: Mark Rutland Tested-by: Mark Rutland I'll continue reviewing the series next week. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel