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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 4FCC3C4321D for ; Thu, 23 Aug 2018 08:09:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14028206B2 for ; Thu, 23 Aug 2018 08:09:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 14028206B2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729301AbeHWLhs (ORCPT ); Thu, 23 Aug 2018 07:37:48 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:45158 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726481AbeHWLhs (ORCPT ); Thu, 23 Aug 2018 07:37:48 -0400 Received: from localhost (5355525A.cm-6-6b.dynamic.ziggo.nl [83.85.82.90]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 0267CC83; Thu, 23 Aug 2018 08:09:21 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Josh Poimboeuf , Allan Xavier , Andy Lutomirski , Borislav Petkov , Brian Gerst , Denys Vlasenko , "H. Peter Anvin" , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Sasha Levin Subject: [PATCH 4.9 068/130] objtool: Support GCC 8 -fnoreorder-functions Date: Thu, 23 Aug 2018 09:53:04 +0200 Message-Id: <20180823074931.813475899@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180823074927.161454870@linuxfoundation.org> References: <20180823074927.161454870@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Poimboeuf [ Upstream commit 08b393d01c88aff27347ed2b1b354eb4db2f1532 ] Since the following commit: cd77849a69cf ("objtool: Fix GCC 8 cold subfunction detection for aliased functions") ... if the kernel is built with EXTRA_CFLAGS='-fno-reorder-functions', objtool can get stuck in an infinite loop. That flag causes the new GCC 8 cold subfunctions to be placed in .text instead of .text.unlikely. But it also has an unfortunate quirk: in the symbol table, the subfunction (e.g., nmi_panic.cold.7) is nested inside the parent (nmi_panic). That function overlap confuses objtool, and causes it to get into an infinite loop in next_insn_same_func(). Here's Allan's description of the loop: "Objtool iterates through the instructions in nmi_panic using next_insn_same_func. Once it reaches the end of nmi_panic at 0x534 it jumps to 0x528 as that's the start of nmi_panic.cold.7. However, since the instructions starting at 0x528 are still associated with nmi_panic objtool will get stuck in a loop, continually jumping back to 0x528 after reaching 0x534." Fix it by shortening the length of the parent function so that the functions no longer overlap. Reported-and-analyzed-by: Allan Xavier Signed-off-by: Josh Poimboeuf Cc: Allan Xavier Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/9e704c52bee651129b036be14feda317ae5606ae.1530136978.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- tools/objtool/elf.c | 37 ++++++++++++++++++++++++++----------- 1 file changed, 26 insertions(+), 11 deletions(-) --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -302,19 +302,34 @@ static int read_symbols(struct elf *elf) continue; sym->pfunc = sym->cfunc = sym; coldstr = strstr(sym->name, ".cold."); - if (coldstr) { - coldstr[0] = '\0'; - pfunc = find_symbol_by_name(elf, sym->name); - coldstr[0] = '.'; + if (!coldstr) + continue; + + coldstr[0] = '\0'; + pfunc = find_symbol_by_name(elf, sym->name); + coldstr[0] = '.'; + + if (!pfunc) { + WARN("%s(): can't find parent function", + sym->name); + goto err; + } - if (!pfunc) { - WARN("%s(): can't find parent function", - sym->name); - goto err; - } + sym->pfunc = pfunc; + pfunc->cfunc = sym; - sym->pfunc = pfunc; - pfunc->cfunc = sym; + /* + * Unfortunately, -fnoreorder-functions puts the child + * inside the parent. Remove the overlap so we can + * have sane assumptions. + * + * Note that pfunc->len now no longer matches + * pfunc->sym.st_size. + */ + if (sym->sec == pfunc->sec && + sym->offset >= pfunc->offset && + sym->offset + sym->len == pfunc->offset + pfunc->len) { + pfunc->len -= sym->len; } } }