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=-22.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,NICE_REPLY_A,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 27EE9C47082 for ; Tue, 8 Jun 2021 16:58:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E1A36128D for ; Tue, 8 Jun 2021 16:58:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233010AbhFHRAB (ORCPT ); Tue, 8 Jun 2021 13:00:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:42866 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231278AbhFHQ77 (ORCPT ); Tue, 8 Jun 2021 12:59:59 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C85316128A; Tue, 8 Jun 2021 16:58:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1623171486; bh=Ja60BwzhwKaBB5iIiSXsEGAZVJfmAoDxNKFPZcXcG3I=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=tlP0ZO+WdQp8AVW+NfqrsB+lZ80F3LPab6qHr772OKPDFC38dIEdeO2QzkK0jVS3c zYqGZwwCh64jPTUTFJHODg1FMdgPVyQPG2pf6MyluRCvuEWIEpbFHD0xXw9Xjnvy46 iJRAmoAGRWMt3y5YzGlE55u1vIU97Aq58iaaZA9cKudIz7a9jPRy5wU/6lS4di+1qP WPeXsf5gQxavK9KZ6S5MvzVsTj22S9QidR3XZeSRDEQGRKoP3f6LU3ZM/14kElQFyB LYdlQ0bTssPLY1WJjw7UJY7i16bjJ3/jVyBSogr+ldKwOexr2oRFY3fdFrh852ozk3 5m6yOqs/c7K0Q== Subject: Re: [PATCH v3 16/16] objtool,x86: Rewrite retpoline thunk calls To: Nick Desaulniers , Peter Zijlstra Cc: =?UTF-8?B?RsSBbmctcnXDrCBTw7JuZw==?= , Josh Poimboeuf , lma@semihalf.com, Guenter Roeck , Juergen Gross , lb@semihalf.com, LKML , mbenes@suse.com, =?UTF-8?Q?Rados=c5=82aw_Biernacki?= , upstream@semihalf.com, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , clang-built-linux , Sami Tolvanen References: <20210604205018.2238778-1-ndesaulniers@google.com> <20210604235046.w3hazgcpsg4oefex@google.com> From: Nathan Chancellor Message-ID: Date: Tue, 8 Jun 2021 09:58:03 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/7/2021 1:54 PM, 'Nick Desaulniers' via Clang Built Linux wrote: > On Mon, Jun 7, 2021 at 2:46 AM Peter Zijlstra wrote: >> > > Thanks, the below diff resolves the linker error reported in > https://github.com/ClangBuiltLinux/linux/issues/1388 > > Both readelf implementations seem happy with the results, too. > > Tested-by: Nick Desaulniers > > Nathan, > Can you please test the below diff and see if that resolves your boot > issue reported in: > https://github.com/ClangBuiltLinux/linux/issues/1384 Unfortunately, it does not appear to resolve that issue. $ git log -2 --decorate=no --oneline eea6a9d6d277 Peter's fix 614124bea77e Linux 5.13-rc5 $ strings /mnt/c/Users/natec/Linux/kernel-investigation | grep microsoft 5.13.0-rc5-microsoft-standard-WSL2-00001-geea6a9d6d277 (nathan@archlinux-ax161) #3 SMP Tue Jun 8 09:46:19 MST 2021 My VM still never makes it to userspace. >> --- >> tools/objtool/elf.c | 25 ++++++++++++++++++++++++- >> 1 file changed, 24 insertions(+), 1 deletion(-) >> >> diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c >> index 743c2e9d0f56..41bca1d13d8e 100644 >> --- a/tools/objtool/elf.c >> +++ b/tools/objtool/elf.c >> @@ -717,7 +717,7 @@ static int elf_add_string(struct elf *elf, struct section *strtab, char *str) >> >> struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) >> { >> - struct section *symtab; >> + struct section *symtab, *symtab_shndx; >> struct symbol *sym; >> Elf_Data *data; >> Elf_Scn *s; >> @@ -769,6 +769,29 @@ struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) >> symtab->len += data->d_size; >> symtab->changed = true; >> >> + symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); >> + if (symtab_shndx) { >> + s = elf_getscn(elf->elf, symtab_shndx->idx); >> + if (!s) { >> + WARN_ELF("elf_getscn"); >> + return NULL; >> + } >> + >> + data = elf_newdata(s); >> + if (!data) { >> + WARN_ELF("elf_newdata"); >> + return NULL; >> + } >> + >> + data->d_buf = &sym->sym.st_size; /* conveniently 0 */ >> + data->d_size = sizeof(Elf32_Word); >> + data->d_align = 4; >> + data->d_type = ELF_T_WORD; >> + >> + symtab_shndx->len += 4; >> + symtab_shndx->changed = true; >> + } >> + >> sym->sec = find_section_by_index(elf, 0); >> >> elf_add_symbol(elf, sym); > > > The only thing that's still different is that the `file` command still > prints "no section header." > > $ find . -name \*.lto.o | xargs file | rev | cut -d , -f 1 | rev | > sort | uniq -c > 1 no section header > 8377 not stripped > 1 too many section headers (33683) > 1 too many section headers (50758) > $ file --version > file-5.39 > > That's drivers/gpu/drm/amd/amdgpu/amdgpu.lto.o, fs/xfs/xfs.lto.o, > drivers/gpu/drm/i915/i915.lto.o, respectively. I'm not sure that's a > problem, yet, and whether 9bc0bb50727c8ac69fbb33fb937431cf3518ff37 is > even related yet; those might just be huge drivers and figured it was > reporting somewhere in case it ever comes up again. CONFIG_LTO > implies -ffunction-sections -fdata-sections, and > CONFIG_LD_DEAD_CODE_DATA_ELIMINATION explicitly sets those, too. >