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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 D7C22C433E9 for ; Wed, 3 Mar 2021 11:12:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 97B9C64EE8 for ; Wed, 3 Mar 2021 11:12:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232335AbhCCLLJ (ORCPT ); Wed, 3 Mar 2021 06:11:09 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:13111 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240148AbhCCBZ7 (ORCPT ); Tue, 2 Mar 2021 20:25:59 -0500 Received: from DGGEMS401-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4Dqx8h5ljDz16FRB; Wed, 3 Mar 2021 09:23:32 +0800 (CST) Received: from [10.67.110.237] (10.67.110.237) by DGGEMS401-HUB.china.huawei.com (10.3.19.201) with Microsoft SMTP Server id 14.3.498.0; Wed, 3 Mar 2021 09:25:05 +0800 Subject: Re: [PATCH] recordmcount: Fix the wrong use of w* in arm64_is_fake_mcount() To: Steven Rostedt References: <20210225140747.10818-1-lihuafei1@huawei.com> <20210225094426.7729b9cc@gandalf.local.home> <20210225160116.GA13604@willie-the-truck> <20210302173058.28fd3d36@gandalf.local.home> From: Li Huafei CC: , , , , , Zhangjinhao , , , Message-ID: <54eb164c-695d-57c5-6bcd-51483b7998d3@huawei.com> Date: Wed, 3 Mar 2021 09:25:05 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210302173058.28fd3d36@gandalf.local.home> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.110.237] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/3/3 6:30, Steven Rostedt wrote: > 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 > . > That's fine, thanks Steve and Will! Huafei