From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932621Ab3HGQvS (ORCPT ); Wed, 7 Aug 2013 12:51:18 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:31426 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932395Ab3HGQvP (ORCPT ); Wed, 7 Aug 2013 12:51:15 -0400 X-Authority-Analysis: v=2.0 cv=KJ7Y/S5o c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=Z5wj0-MXZUkA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=n9eEBXj4wC8A:10 a=20KFwNOVAAAA:8 a=11smRfc0_RqT7KlUWkcA:9 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130807165114.147890467@goodmis.org> User-Agent: quilt/0.60-1 Date: Wed, 07 Aug 2013 12:49:38 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: "H. Peter Anvin" , Linus Torvalds , Ingo Molnar , Andrew Morton , Thomas Gleixner , Peter Zijlstra , Jason Baron Subject: [PATCH 4/4] x86/jump-label: Show where and what was wrong on errors References: <20130807164934.149920591@goodmis.org> Content-Disposition: inline; filename=0004-x86-jump-label-Show-where-and-what-was-wrong-on-erro.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt When modifying text sections for jump labels, a paranoid check is performed. If the check fails, the system "bugs". But why it failed is not shown. The BUG_ON()s in the jump label update code is replaced with bug_at(ip). This is a function that will show what pointer failed, and what was at the location of the failure that made jump label panic. Signed-off-by: Steven Rostedt --- arch/x86/kernel/jump_label.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index 24cf2b2..912a528 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -24,6 +24,18 @@ union jump_code_union { } __attribute__((packed)); }; +static void bug_at(unsigned char *ip, int line) +{ + /* + * The location is not an op that we were expecting. + * Something went wrong. Crash the box, as something could be + * corrupting the kernel. + */ + pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n", + ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line); + BUG(); +} + static void __jump_label_transform(struct jump_entry *entry, enum jump_label_type type, void *(*poker)(void *, const void *, size_t), @@ -37,7 +49,8 @@ static void __jump_label_transform(struct jump_entry *entry, * We are enabling this jump label. If it is not a nop * then something must have gone wrong. */ - BUG_ON(memcmp((void *)entry->code, ideal_nop, 5) != 0); + if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0)) + bug_at((void *)entry->code, __LINE__); code.jump = 0xe9; code.offset = entry->target - @@ -51,12 +64,14 @@ static void __jump_label_transform(struct jump_entry *entry, */ if (init) { const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP }; - BUG_ON(memcmp((void *)entry->code, default_nop, 5) != 0); + if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0)) + bug_at((void *)entry->code, __LINE__); } else { code.jump = 0xe9; code.offset = entry->target - (entry->code + JUMP_LABEL_NOP_SIZE); - BUG_ON(memcmp((void *)entry->code, &code, 5) != 0); + if (unlikely(memcmp((void *)entry->code, &code, 5) != 0)) + bug_at((void *)entry->code, __LINE__); } memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE); } -- 1.7.10.4