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=-17.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 542DAC433E0 for ; Fri, 15 Jan 2021 08:10:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18F8B22287 for ; Fri, 15 Jan 2021 08:10:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732340AbhAOIKG (ORCPT ); Fri, 15 Jan 2021 03:10:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:54138 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726004AbhAOIKG (ORCPT ); Fri, 15 Jan 2021 03:10:06 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id ED103221E9; Fri, 15 Jan 2021 08:09:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610698165; bh=Mq/LTukrC0t3iHVpjub9KIF5jll7ihy+9U7R71ci734=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sciVsVPcKNtoAmAZUP47NaO7j3y4z02VjQlVZdZu5cGXUqlf+Xi1neW9JE++SfpWX wGhiuzgWWY98zuD8lYfyyXQI3MsXwVGoR48s8a7PBCVqG718XlpG/Qrxy9E30r6mKO Um/7+yBEwaSfRbQLnFqAWu3+nxZlAC73qaa1nuDPCVPr0d1gGGWXIYSYo7gHf9hWyv w/zqgMsgG2B6+OecEAVjo/LCIgU5dRak0ukKyaqunIZUjomYCqKem6DN5bofB5KAc5 Yberl18nHnF5npmPzcL0VBdh0xLD7sRUfpRNl/lYhpvOhmmJxjYIAkBPk9pKaqQyJU lZsfGczkkwxlQ== Date: Fri, 15 Jan 2021 09:09:20 +0100 From: Jessica Yu To: Nick Desaulniers Cc: Fangrui Song , LKML , clang-built-linux , Sam Ravnborg , Marco Elver Subject: Re: [PATCH v2] module: Ignore _GLOBAL_OFFSET_TABLE_ when warning for undefined symbols Message-ID: <20210115080920.GA9637@linux-8ccs> References: <20210114211840.GA5617@linux-8ccs> <20210114215416.993167-1-maskray@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: X-OS: Linux linux-8ccs 5.8.0-rc6-lp150.12.61-default+ x86_64 User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +++ Nick Desaulniers [14/01/21 14:01 -0800]: >On Thu, Jan 14, 2021 at 1:54 PM 'Fangrui Song' via Clang Built Linux > wrote: >> >> clang-12 -fno-pic (since >> https://github.com/llvm/llvm-project/commit/a084c0388e2a59b9556f2de0083333232da3f1d6) >> can emit `call __stack_chk_fail@PLT` instead of `call __stack_chk_fail` >> on x86. The two forms should have identical behaviors on x86-64 but the >> former causes GNU as<2.37 to produce an unreferenced undefined symbol >> _GLOBAL_OFFSET_TABLE_. >> >> (On x86-32, there is an R_386_PC32 vs R_386_PLT32 difference but the >> linker behavior is identical as far as Linux kernel is concerned.) >> >> Simply ignore _GLOBAL_OFFSET_TABLE_ for now, like what >> scripts/mod/modpost.c:ignore_undef_symbol does. This also fixes the >> problem for gcc/clang -fpie and -fpic, which may emit `call foo@PLT` for >> external function calls on x86. >> >> Note: ld -z defs and dynamic loaders do not error for unreferenced >> undefined symbols so the module loader is reading too much. If we ever >> need to ignore more symbols, the code should be refactored to ignore >> unreferenced symbols. >> >> Reported-by: Marco Elver >> Link: https://github.com/ClangBuiltLinux/linux/issues/1250 >> Signed-off-by: Fangrui Song > >Thanks for the patch. > >Reviewed-by: Nick Desaulniers > >Jessica, would you mind adding when applying: > >Cc: > >as I suspect we might want this fixed in stable tree's branches, too. >It might of interest to add: > >Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27178 > >too. Sure, will do! Thanks, Jessica