From patchwork Sat Oct 31 11:34:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 317418 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=-14.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 A2139C388F7 for ; Sat, 31 Oct 2020 11:39:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6EF7C20731 for ; Sat, 31 Oct 2020 11:39:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604144346; bh=Fc5d6HqYu1fwZuvx7GQkTaMz4kjMw5wdzWjqvAXE6nM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0tpYwmUy089UsxgMRlLB5eb8MvN8awhzycz6QgZ/glF1+fBvvsj2/LBPAj+2abbW/ TNd3+sUqVZW5SWd6u+9/ZvmJZ5tESCn2N+J6YngheKkBJ1IcC+ft+6YfvoTPBEnGbK hGlAmtTIZwfoN3qCnIGvFH5Korcqma3xplO6EstA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727052AbgJaLiy (ORCPT ); Sat, 31 Oct 2020 07:38:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:33792 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727118AbgJaLf4 (ORCPT ); Sat, 31 Oct 2020 07:35:56 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 341072074F; Sat, 31 Oct 2020 11:35:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604144154; bh=Fc5d6HqYu1fwZuvx7GQkTaMz4kjMw5wdzWjqvAXE6nM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ba9nYFkBlb8zxeHUYowgqInlfaDMRZQrSMVyTAKUJ/P4ewFvh41RSg51kj/Tl1Xbj Pc3xYRke7DhRMfGFWMgU+1EwfUNKaf0bZFgEadM8p9hzRhefIRoApDsh4JzKeaQZoy 4dDzpQUM/eU+XZ9z66UzX475XXjtfKcxZSH045XI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dmitry Golovin , Josh Poimboeuf , Borislav Petkov , Nathan Chancellor , Miroslav Benes , "Peter Zijlstra (Intel)" , Nick Desaulniers Subject: [PATCH 5.4 03/49] objtool: Support Clang non-section symbols in ORC generation Date: Sat, 31 Oct 2020 12:34:59 +0100 Message-Id: <20201031113455.615829187@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201031113455.439684970@linuxfoundation.org> References: <20201031113455.439684970@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Josh Poimboeuf commit e81e0724432542af8d8c702c31e9d82f57b1ff31 upstream. When compiling the kernel with AS=clang, objtool produces a lot of warnings: warning: objtool: missing symbol for section .text warning: objtool: missing symbol for section .init.text warning: objtool: missing symbol for section .ref.text It then fails to generate the ORC table. The problem is that objtool assumes text section symbols always exist. But the Clang assembler is aggressive about removing them. When generating relocations for the ORC table, objtool always tries to reference instructions by their section symbol offset. If the section symbol doesn't exist, it bails. Do a fallback: when a section symbol isn't available, reference a function symbol instead. Reported-by: Dmitry Golovin Signed-off-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Tested-by: Nathan Chancellor Reviewed-by: Miroslav Benes Acked-by: Peter Zijlstra (Intel) Link: https://github.com/ClangBuiltLinux/linux/issues/669 Link: https://lkml.kernel.org/r/9a9cae7fcf628843aabe5a086b1a3c5bf50f42e8.1585761021.git.jpoimboe@redhat.com Cc: Nick Desaulniers Signed-off-by: Greg Kroah-Hartman --- tools/objtool/orc_gen.c | 33 ++++++++++++++++++++++++++------- 1 file changed, 26 insertions(+), 7 deletions(-) --- a/tools/objtool/orc_gen.c +++ b/tools/objtool/orc_gen.c @@ -88,11 +88,6 @@ static int create_orc_entry(struct secti struct orc_entry *orc; struct rela *rela; - if (!insn_sec->sym) { - WARN("missing symbol for section %s", insn_sec->name); - return -1; - } - /* populate ORC data */ orc = (struct orc_entry *)u_sec->data->d_buf + idx; memcpy(orc, o, sizeof(*orc)); @@ -105,8 +100,32 @@ static int create_orc_entry(struct secti } memset(rela, 0, sizeof(*rela)); - rela->sym = insn_sec->sym; - rela->addend = insn_off; + if (insn_sec->sym) { + rela->sym = insn_sec->sym; + rela->addend = insn_off; + } else { + /* + * The Clang assembler doesn't produce section symbols, so we + * have to reference the function symbol instead: + */ + rela->sym = find_symbol_containing(insn_sec, insn_off); + if (!rela->sym) { + /* + * Hack alert. This happens when we need to reference + * the NOP pad insn immediately after the function. + */ + rela->sym = find_symbol_containing(insn_sec, + insn_off - 1); + } + if (!rela->sym) { + WARN("missing symbol for insn at offset 0x%lx\n", + insn_off); + return -1; + } + + rela->addend = insn_off - rela->sym->offset; + } + rela->type = R_X86_64_PC32; rela->offset = idx * sizeof(int);