From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752576AbcCIGIS (ORCPT ); Wed, 9 Mar 2016 01:08:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55116 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752358AbcCIGHx (ORCPT ); Wed, 9 Mar 2016 01:07:53 -0500 From: Josh Poimboeuf To: Ingo Molnar Cc: Arnaldo Carvalho de Melo , Thomas Gleixner , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, Michal Marek , Peter Zijlstra , Andy Lutomirski , Borislav Petkov , Linus Torvalds , Andi Kleen , Pedro Alves , Namhyung Kim , Bernd Petrovitsch , Chris J Arges , Andrew Morton , Jiri Slaby , Arnaldo Carvalho de Melo Subject: [PATCH 02/11] objtool: Detect infinite recursion Date: Wed, 9 Mar 2016 00:06:52 -0600 Message-Id: In-Reply-To: References: <20160308154909.GA20956@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I don't _think_ dead_end_function() can get into a recursive loop, but just in case, stop the loop and print a warning. Signed-off-by: Josh Poimboeuf --- tools/objtool/builtin-check.c | 45 +++++++++++++++++++++++++++++++------------ 1 file changed, 33 insertions(+), 12 deletions(-) diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c index 80d9ed9..51da270 100644 --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -121,8 +121,14 @@ static bool ignore_func(struct objtool_file *file, struct symbol *func) * * For local functions, we have to detect them manually by simply looking for * the lack of a return instruction. + * + * Returns: + * -1: error + * 0: no dead end + * 1: dead end */ -static bool dead_end_function(struct objtool_file *file, struct symbol *func) +static int __dead_end_function(struct objtool_file *file, struct symbol *func, + int recursion) { int i; struct instruction *insn, *func_insn; @@ -144,19 +150,19 @@ static bool dead_end_function(struct objtool_file *file, struct symbol *func) }; if (func->bind == STB_WEAK) - return false; + return 0; if (func->bind == STB_GLOBAL) for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) if (!strcmp(func->name, global_noreturns[i])) - return true; + return 1; if (!func->sec) - return false; + return 0; func_insn = find_instruction(file, func->sec, func->offset); if (!func_insn) - return false; + return 0; insn = func_insn; list_for_each_entry_from(insn, &file->insns, list) { @@ -167,11 +173,11 @@ static bool dead_end_function(struct objtool_file *file, struct symbol *func) empty = false; if (insn->type == INSN_RETURN) - return false; + return 0; } if (empty) - return false; + return 0; /* * A function can have a sibling call instead of a return. In that @@ -190,7 +196,7 @@ static bool dead_end_function(struct objtool_file *file, struct symbol *func) if (!dest) /* sibling call to another file */ - return false; + return 0; if (dest->sec != func->sec || dest->offset < func->offset || @@ -201,16 +207,28 @@ static bool dead_end_function(struct objtool_file *file, struct symbol *func) if (!dest_func) continue; - return dead_end_function(file, dest_func); + if (recursion == 5) { + WARN_FUNC("infinite recursion (objtool bug!)", + dest->sec, dest->offset); + return -1; + } + + return __dead_end_function(file, dest_func, + recursion + 1); } } if (insn->type == INSN_JUMP_DYNAMIC) /* sibling call */ - return false; + return 0; } - return true; + return 1; +} + +static int dead_end_function(struct objtool_file *file, struct symbol *func) +{ + return __dead_end_function(file, func, 0); } /* @@ -809,8 +827,11 @@ static int validate_branch(struct objtool_file *file, break; } - if (dead_end_function(file, insn->call_dest)) + ret = dead_end_function(file, insn->call_dest); + if (ret == 1) return warnings; + if (ret == -1) + warnings++; /* fallthrough */ case INSN_CALL_DYNAMIC: -- 2.4.3