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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 0C065C4332D for ; Tue, 2 Mar 2021 23:35:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D13A764F3F for ; Tue, 2 Mar 2021 23:35:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1838191AbhCBXGB (ORCPT ); Tue, 2 Mar 2021 18:06:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:45870 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241902AbhCBWbv (ORCPT ); Tue, 2 Mar 2021 17:31:51 -0500 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 7979064F2D; Tue, 2 Mar 2021 22:31:00 +0000 (UTC) Date: Tue, 2 Mar 2021 17:30:58 -0500 From: Steven Rostedt To: Will Deacon Cc: Li Huafei , gregory.herrero@oracle.com, catalin.marinas@arm.com, christophe.leroy@csgroup.eu, linux-kernel@vger.kernel.org, zhangjinhao2@huawei.com, yangjihong1@huawei.com, xukuohai@huawei.com, linux-arm-kernel@lists.infradead.org, Chen Jun Subject: Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount() Message-ID: <20210302173058.28fd3d36@gandalf.local.home> In-Reply-To: <20210225160116.GA13604@willie-the-truck> References: <20210225140747.10818-1-lihuafei1@huawei.com> <20210225094426.7729b9cc@gandalf.local.home> <20210225160116.GA13604@willie-the-truck> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 25 Feb 2021 16:01:17 +0000 Will Deacon wrote: > On Thu, Feb 25, 2021 at 09:44:26AM -0500, Steven Rostedt wrote: > > This requires an acked-by from one of the ARM64 maintainers. > > > > -- Steve > > > > > > On Thu, 25 Feb 2021 22:07:47 +0800 > > Li Huafei wrote: > > > > > When cross-compiling the kernel, the endian of the target machine and > > > the local machine may not match, at this time the recordmcount tool > > > needs byte reversal when processing elf's variables to get the correct > > > value. w* callback function is used to solve this problem, w is used for > > > 4-byte variable processing, while w8 is used for 8-byte. > > > > > > arm64_is_fake_mcount() is used to filter '_mcount' relocations that are > > > not used by ftrace. In arm64_is_fake_mcount(), rp->info is 8 bytes in > > > size, but w is used. This causes arm64_is_fake_mcount() to get the wrong > > > type of relocation when we cross-compile the arm64_be kernel image on an > > > x86_le machine, and all valid '_mcount' is filtered out. The > > > recordmcount tool does not collect any mcount function call locations. > > > At kernel startup, the following ftrace log is seen: > > > > > > ftrace: No functions to be traced? > > > > > > and thus ftrace cannot be used. > > > > > > Using w8 to get the value of rp->r_info will fix the problem. > > > > > > Fixes: ea0eada45632 ("recordmcount: only record relocation of type > > > R_AARCH64_CALL26 on arm64") > > > Signed-off-by: Li Huafei > > > --- > > > scripts/recordmcount.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c > > > index b9c2ee7ab43f..cce12e1971d8 100644 > > > --- a/scripts/recordmcount.c > > > +++ b/scripts/recordmcount.c > > > @@ -438,7 +438,7 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp) > > > > > > static int arm64_is_fake_mcount(Elf64_Rel const *rp) > > > { > > > - return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26; > > > + return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26; > > Acked-by: Will Deacon > > But you know you could avoid these sorts of problems by moving to little > endian along with everybody else? ;) > I just realized that I received this patch twice, and thought it was the same patch! Chen was three days ahead of you, so he get's the credit ;-) https://lore.kernel.org/r/20210222135840.56250-1-chenjun102@huawei.com -- Steve