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 161A5C4332F for ; Wed, 27 Oct 2021 08:58:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F01DB61040 for ; Wed, 27 Oct 2021 08:58:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241128AbhJ0JBF (ORCPT ); Wed, 27 Oct 2021 05:01:05 -0400 Received: from mxout01.lancloud.ru ([45.84.86.81]:46980 "EHLO mxout01.lancloud.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241123AbhJ0JBE (ORCPT ); Wed, 27 Oct 2021 05:01:04 -0400 Received: from LanCloud DKIM-Filter: OpenDKIM Filter v2.11.0 mxout01.lancloud.ru B793F20DE16B Received: from LanCloud Received: from LanCloud Received: from LanCloud Message-ID: <95ac8344-ff8c-d66f-00c7-06c43a61fca3@omp.ru> Date: Wed, 27 Oct 2021 11:58:31 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.2.1 Subject: Re: [for-next][PATCH 10/12] ftrace/sh: Add arch_ftrace_ops_list_func stub to have compressed image still link Content-Language: en-US To: Steven Rostedt , CC: Ingo Molnar , Andrew Morton , Yoshinori Sato , Rich Felker , References: <20211026162315.297389528@goodmis.org> <20211026162349.204017174@goodmis.org> From: Sergey Shtylyov Organization: Open Mobile Platform In-Reply-To: <20211026162349.204017174@goodmis.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.11.198] X-ClientProxiedBy: LFEXT02.lancloud.ru (fd00:f066::142) To LFEX1907.lancloud.ru (fd00:f066::207) Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org On 26.10.2021 19:23, Steven Rostedt wrote: > From: "linux-sh@vger.kernel.org" Collective author, really? :-) > Using the linker script to fix an issue where some archs call the > function tracer with just the ip (instruction pointer) and pip (parent > instruction pointer) where as more up to date archs also pass in the > associated ftrace_ops and the ftrace_regs pointer, the generic code > will be called either with two parameters or four. To avoid any C > undefined behavior of calling two parameters to four or four to two > parameter function, two functions are created, where a preprocessor > macro uses the one that matches the architecture. As the function > pointers for them may be different, a typecast is used. But this > triggers issues with newer compilers that will fail due to -Werror. > > A linker trick is now used to map the generic function to the function > that is used (note the generic function is only used to set the default > function callback). The linker trick defines ftrace_ops_list_func (the > generic function) to arch_ftrace_ops_list_func (the arch defined one). > > Link: https://lore.kernel.org/all/20200617165616.52241bde@oasis.local.home/ > > But this fails sh arch because their linker script is included in their > compressed image that does not define arch_ftrace_ops_list_func at all > > sh4-linux-ld:arch/sh/boot/compressed/../../kernel/vmlinux.lds:32: undefined symbol `arch_ftrace_ops_list_func' referenced in expression > > Included a stub by that name in the misc.c to allow the code to > compile and link, even though it's not used. > > This is similar to what was done for ftrace_stub: > > b83b43ffc6e4b ("fgraph: Fix function type mismatches of > ftrace_graph_return using ftrace_stub") > > Link: https://lkml.kernel.org/r/20211021221627.5d7270de@rorschach.local.home > > Cc: Yoshinori Sato > Cc: Rich Felker > Cc: linux-sh@vger.kernel.org > Signed-off-by: Steven Rostedt (VMware) [...] MBR, Sergey