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=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 36E16C433E0 for ; Sun, 24 May 2020 22:13:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F33282076C for ; Sun, 24 May 2020 22:13:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ALJxHnzX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388407AbgEXWNc (ORCPT ); Sun, 24 May 2020 18:13:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387850AbgEXWNb (ORCPT ); Sun, 24 May 2020 18:13:31 -0400 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9E93C061A0E for ; Sun, 24 May 2020 15:13:31 -0700 (PDT) Received: by mail-pf1-x443.google.com with SMTP id n15so8060776pfd.0 for ; Sun, 24 May 2020 15:13:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=2tLotsYCPUeHq+EC4OZ2nCQeyCiq7TXwLeRalL2UPHk=; b=ALJxHnzXD6u3Xh9kh5uyarx37KeGNeq7fV7VYD4fxkXGvzCx1OEdUMQG4e+FN2iIpY ZMf6gFxhderJTO5gLY/bOYg6B5su2IzY8Hk/zEb5rd3PHLcSI5f9ZjPYnwGWdMLv/tQW jVg0uFbn4KJnhubHRVkTG37nd6RkkW+TW6kBjXVuKpGeEKjwTFAuqq1p3zjgtt5/+Ya0 DZ6lSOlQIz5BADOLOsIDzRgYB/uTVkacylLOBZq/mz0lv7LlRPsF6jWFdAQPjmHzGz2s CNMOzkpFBcb4udvFMgKS4uKNapy2ipLVmjEoUrC2cIbtSOjw4igN9O7ZyCcpteIPorg/ 356w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=2tLotsYCPUeHq+EC4OZ2nCQeyCiq7TXwLeRalL2UPHk=; b=S8MB2X9SYpYB8QF4EYgeDbWYWDzEfB2ORmAj/1QmHS9Cx/6kMONSk2VvlrO9tzBa1R XQKUNDnLaWqMSKxlKh4T9BFVLvWX34fVcBpfkm3hB8kR/lH8Yr4D3SAuVaElF1Ma8QM3 CMpMiSmC5SgDLOroeWPZpRGjgs9UT6+6hU+47+tf+4Kbqiro8KGqJQL5OsnBGAK4p799 X5Nyn1LgJqOVJj5GT5ydATmgBlHUd8V3Yf/osTKQUgCizF0Bz3RJqpUnxyFDxNGR0n2N ZlyE4P69F0E6u/0aSv76n6c4pwKp9sYP8/jMxyTzmafqC1GsIAQ0epN6bFMLq8Bw2RkR 2K8w== X-Gm-Message-State: AOAM531V1eiTKMcTJQ67C2mSCuVONm07iC0TMOMrInxeB/0Nxyu4HOZZ 4u2jti8iYhTbUV36YU2UFbk6KQ== X-Google-Smtp-Source: ABdhPJyD2ygP3HHWXFRI2ICeQgnbVaXMmbC3/r49TruM+KtN6I2ykB9NVBp+n18nUNz8uiAbWryagw== X-Received: by 2002:aa7:8483:: with SMTP id u3mr14642476pfn.223.1590358410725; Sun, 24 May 2020 15:13:30 -0700 (PDT) Received: from google.com ([2620:15c:2ce:0:9efe:9f1:9267:2b27]) by smtp.gmail.com with ESMTPSA id o190sm10706108pfb.178.2020.05.24.15.13.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 24 May 2020 15:13:30 -0700 (PDT) Date: Sun, 24 May 2020 15:13:26 -0700 From: Fangrui Song To: Arvind Sankar Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, Nick Desaulniers , Dmitry Golovin , clang-built-linux@googlegroups.com, Ard Biesheuvel , Masahiro Yamada , Daniel Kiper , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] x86/boot: Add .text.startup to setup.ld Message-ID: <20200524221326.zo6zthdqecm2ke5t@google.com> References: <20200524212816.243139-2-nivedita@alum.mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200524212816.243139-2-nivedita@alum.mit.edu> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-05-24, Arvind Sankar wrote: >gcc puts the main function into .text.startup when compiled with -Os (or >-O2). This results in arch/x86/boot/main.c having a .text.startup >section which is currently not included explicitly in the linker script >setup.ld in the same directory. > >The BFD linker places this orphan section immediately after .text, so >this still works. However, LLD git, since [1], is choosing to place it >immediately after the .bstext section instead (this is the first code >section). This plays havoc with the section layout that setup.elf >requires to create the setup header, for eg on 64-bit: > > LD arch/x86/boot/setup.elf > ld.lld: error: section .text.startup file range overlaps with .header > >>> .text.startup range is [0x200040, 0x2001FE] > >>> .header range is [0x2001EF, 0x20026B] > > ld.lld: error: section .header file range overlaps with .bsdata > >>> .header range is [0x2001EF, 0x20026B] > >>> .bsdata range is [0x2001FF, 0x200398] > > ld.lld: error: section .bsdata file range overlaps with .entrytext > >>> .bsdata range is [0x2001FF, 0x200398] > >>> .entrytext range is [0x20026C, 0x2002D3] > > ld.lld: error: section .text.startup virtual address range overlaps > with .header > >>> .text.startup range is [0x40, 0x1FE] > >>> .header range is [0x1EF, 0x26B] > > ld.lld: error: section .header virtual address range overlaps with > .bsdata > >>> .header range is [0x1EF, 0x26B] > >>> .bsdata range is [0x1FF, 0x398] > > ld.lld: error: section .bsdata virtual address range overlaps with > .entrytext > >>> .bsdata range is [0x1FF, 0x398] > >>> .entrytext range is [0x26C, 0x2D3] > > ld.lld: error: section .text.startup load address range overlaps with > .header > >>> .text.startup range is [0x40, 0x1FE] > >>> .header range is [0x1EF, 0x26B] > > ld.lld: error: section .header load address range overlaps with > .bsdata > >>> .header range is [0x1EF, 0x26B] > >>> .bsdata range is [0x1FF, 0x398] > > ld.lld: error: section .bsdata load address range overlaps with > .entrytext > >>> .bsdata range is [0x1FF, 0x398] > >>> .entrytext range is [0x26C, 0x2D3] > >Explicitly pull .text.startup into the .text output section to avoid >this. > >[1] https://reviews.llvm.org/D75225 > >Signed-off-by: Arvind Sankar >Reviewed-by: Fangrui Song >--- > arch/x86/boot/setup.ld | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld >index 24c95522f231..ed60abcdb089 100644 >--- a/arch/x86/boot/setup.ld >+++ b/arch/x86/boot/setup.ld >@@ -20,7 +20,7 @@ SECTIONS > .initdata : { *(.initdata) } > __end_init = .; > >- .text : { *(.text) } >+ .text : { *(.text.startup) *(.text) } > .text32 : { *(.text32) } > > . = ALIGN(16); >-- >2.26.2 Should .text.startup* be used instead? If -ffunction-sections is used, // a.c int main() {} gcc -O2 a.c # .text.startup gcc -Os a.c # .text.startup gcc -O2 -ffunction-sections a.c # .text.startup.main gcc -Os -ffunction-sections a.c # .text.startup.main ----- In case anyone wants to CC a GCC dev for the citation that main compiles to `.text.startup` in -Os or -O2 mode, I have a small request that `.text.startup.` probably makes more sense. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95095 I made an llvm change recently https://reviews.llvm.org/D79600