Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755952AbdGCOLD (ORCPT ); Mon, 3 Jul 2017 10:11:03 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:37816 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933222AbdGCNq2 (ORCPT ); Mon, 3 Jul 2017 09:46:28 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arnd Bergmann , Josh Poimboeuf , Denys Vlasenko , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.9 163/172] objtool: Fix another GCC jump table detection issue Date: Mon, 3 Jul 2017 15:35:43 +0200 Message-Id: <20170703133421.991167358@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170703133414.260777365@linuxfoundation.org> References: <20170703133414.260777365@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3677 Lines: 99 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Poimboeuf commit 5c51f4ae84df0f9df33ac08aa5be50061a8b4242 upstream. Arnd Bergmann reported a (false positive) objtool warning: drivers/infiniband/sw/rxe/rxe_resp.o: warning: objtool: rxe_responder()+0xfe: sibling call from callable instruction with changed frame pointer The issue is in find_switch_table(). It tries to find a switch statement's jump table by walking backwards from an indirect jump instruction, looking for a relocation to the .rodata section. In this case it stopped walking prematurely: the first .rodata relocation it encountered was for a variable (resp_state_name) instead of a jump table, so it just assumed there wasn't a jump table. The fix is to ignore any .rodata relocation which refers to an ELF object symbol. This works because the jump tables are anonymous and have no symbols associated with them. Reported-by: Arnd Bergmann Tested-by: Arnd Bergmann Signed-off-by: Josh Poimboeuf Cc: Denys Vlasenko Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 3732710ff6f2 ("objtool: Improve rare switch jump table pattern detection") Link: http://lkml.kernel.org/r/20170302225723.3ndbsnl4hkqbne7a@treble Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- tools/objtool/builtin-check.c | 15 ++++++++++++--- tools/objtool/elf.c | 12 ++++++++++++ tools/objtool/elf.h | 1 + 3 files changed, 25 insertions(+), 3 deletions(-) --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -757,11 +757,20 @@ static struct rela *find_switch_table(st insn->jump_dest->offset > orig_insn->offset)) break; + /* look for a relocation which references .rodata */ text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); - if (text_rela && text_rela->sym == file->rodata->sym) - return find_rela_by_dest(file->rodata, - text_rela->addend); + if (!text_rela || text_rela->sym != file->rodata->sym) + continue; + + /* + * Make sure the .rodata address isn't associated with a + * symbol. gcc jump tables are anonymous data. + */ + if (find_symbol_containing(file->rodata, text_rela->addend)) + continue; + + return find_rela_by_dest(file->rodata, text_rela->addend); } return NULL; --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -85,6 +85,18 @@ struct symbol *find_symbol_by_offset(str return NULL; } +struct symbol *find_symbol_containing(struct section *sec, unsigned long offset) +{ + struct symbol *sym; + + list_for_each_entry(sym, &sec->symbol_list, list) + if (sym->type != STT_SECTION && + offset >= sym->offset && offset < sym->offset + sym->len) + return sym; + + return NULL; +} + struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset, unsigned int len) { --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -79,6 +79,7 @@ struct elf { struct elf *elf_open(const char *name); struct section *find_section_by_name(struct elf *elf, const char *name); struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset); +struct symbol *find_symbol_containing(struct section *sec, unsigned long offset); struct rela *find_rela_by_dest(struct section *sec, unsigned long offset); struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset, unsigned int len);