From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932570Ab3HGQvR (ORCPT ); Wed, 7 Aug 2013 12:51:17 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:18980 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932392Ab3HGQvP (ORCPT ); Wed, 7 Aug 2013 12:51:15 -0400 X-Authority-Analysis: v=2.0 cv=aqMw+FlV c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=if_WWjHuaHkA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=pLi8QA9iOc4A:10 a=20KFwNOVAAAA:8 a=oGMlB6cnAAAA:8 a=nTqW6CzA5JgN1M89fUwA:9 a=jEp0ucaQiEUA:10 a=CY6gl2JlH4YA:10 a=jeBq3FmKZ4MA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130807165113.974746364@goodmis.org> User-Agent: quilt/0.60-1 Date: Wed, 07 Aug 2013 12:49:37 -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 , Jason Baron Subject: [PATCH 3/4] x86/jump-label: Add safety checks to jump label conversions References: <20130807164934.149920591@goodmis.org> Content-Disposition: inline; filename=0003-x86-jump-label-Add-safety-checks-to-jump-label-conve.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt As with all modifying of kernel text, we need to be very paranoid. When converting the jump label locations to and from nops to jumps a check has been added to make sure what we are replacing is what we expect, otherwise we bug. Cc: H. Peter Anvin Cc: Jason Baron Signed-off-by: Steven Rostedt --- arch/x86/kernel/jump_label.c | 32 ++++++++++++++++++++++++++++---- 1 file changed, 28 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index ae3d8fb..24cf2b2 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -26,16 +26,40 @@ union jump_code_union { static void __jump_label_transform(struct jump_entry *entry, enum jump_label_type type, - void *(*poker)(void *, const void *, size_t)) + void *(*poker)(void *, const void *, size_t), + int init) { union jump_code_union code; + const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5]; if (type == JUMP_LABEL_ENABLE) { + /* + * 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); + code.jump = 0xe9; code.offset = entry->target - (entry->code + JUMP_LABEL_NOP_SIZE); - } else + } else { + /* + * We are disabling this jump label. If it is not what + * we think it is, then something must have gone wrong. + * If this is the first initialization call, then we + * are converting the default nop to the ideal nop. + */ + if (init) { + const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP }; + BUG_ON(memcmp((void *)entry->code, default_nop, 5) != 0); + } else { + code.jump = 0xe9; + code.offset = entry->target - + (entry->code + JUMP_LABEL_NOP_SIZE); + BUG_ON(memcmp((void *)entry->code, &code, 5) != 0); + } memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE); + } (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE); } @@ -45,7 +69,7 @@ void arch_jump_label_transform(struct jump_entry *entry, { get_online_cpus(); mutex_lock(&text_mutex); - __jump_label_transform(entry, type, text_poke_smp); + __jump_label_transform(entry, type, text_poke_smp, 0); mutex_unlock(&text_mutex); put_online_cpus(); } @@ -76,7 +100,7 @@ __init_or_module void arch_jump_label_transform_static(struct jump_entry *entry, jlstate = JL_STATE_NO_UPDATE; } if (jlstate == JL_STATE_UPDATE) - __jump_label_transform(entry, type, text_poke_early); + __jump_label_transform(entry, type, text_poke_early, 1); } #endif -- 1.7.10.4