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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_NEOMUTT 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 F2342C0044C for ; Wed, 7 Nov 2018 17:09:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0BC92081D for ; Wed, 7 Nov 2018 17:09:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0BC92081D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1731422AbeKHCkS (ORCPT ); Wed, 7 Nov 2018 21:40:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57382 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727757AbeKHCkS (ORCPT ); Wed, 7 Nov 2018 21:40:18 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C4975307CDC2; Wed, 7 Nov 2018 17:09:02 +0000 (UTC) Received: from treble (ovpn-121-72.rdu2.redhat.com [10.10.121.72]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C64B118EC6; Wed, 7 Nov 2018 17:08:58 +0000 (UTC) Date: Wed, 7 Nov 2018 11:08:56 -0600 From: Josh Poimboeuf To: Artem Savkov Cc: Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH] objtool: fix .cold. functions parent symbols search Message-ID: <20181107170856.usgyzckfirem5qh7@treble> References: <20181107140559.28504-1-asavkov@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20181107140559.28504-1-asavkov@redhat.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 07 Nov 2018 17:09:02 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 07, 2018 at 03:05:59PM +0100, Artem Savkov wrote: > The way it is currently done it is possible for read_symbols() to find the > same symbol as parent for ".cold" functions. I seem to remember having this discussion for kpatch-build, but I forget the details. Can you explain how this can happen (and also add that detail to the commit message)? I haven't seen any bug reports, is it purely theoretical? > This leads to a bunch of > complications such as func length being set to 0 and a segfault in > add_switch_table(). Fix by copying the search string instead of modifying > it in place. > > Signed-off-by: Artem Savkov > --- > tools/objtool/elf.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c > index 6dbb9fae0f9d..781c8afb29b9 100644 > --- a/tools/objtool/elf.c > +++ b/tools/objtool/elf.c > @@ -298,6 +298,7 @@ static int read_symbols(struct elf *elf) > /* Create parent/child links for any cold subfunctions */ > list_for_each_entry(sec, &elf->sections, list) { > list_for_each_entry(sym, &sec->symbol_list, list) { > + char *pname; > if (sym->type != STT_FUNC) > continue; > sym->pfunc = sym->cfunc = sym; > @@ -305,9 +306,9 @@ static int read_symbols(struct elf *elf) > if (!coldstr) > continue; > > - coldstr[0] = '\0'; > - pfunc = find_symbol_by_name(elf, sym->name); > - coldstr[0] = '.'; > + pname = strndup(sym->name, coldstr - sym->name); > + pfunc = find_symbol_by_name(elf, pname); > + free(pname); > > if (!pfunc) { > WARN("%s(): can't find parent function", > -- > 2.17.2 > -- Josh