Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030644AbbD1PPk (ORCPT ); Tue, 28 Apr 2015 11:15:40 -0400 Received: from cantor2.suse.de ([195.135.220.15]:54312 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030312AbbD1PPg (ORCPT ); Tue, 28 Apr 2015 11:15:36 -0400 Date: Tue, 28 Apr 2015 17:15:34 +0200 (CEST) From: Jiri Kosina To: x86@kernel.org, Borislav Petkov cc: Josh Poimboeuf , Kees Cook , Seth Jennings , Vojtech Pavlik , linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: [PATCH v2 1/2] x86: introduce kaslr_offset() In-Reply-To: <20150428120838.GA16487@treble.redhat.com> Message-ID: References: <20150428120838.GA16487@treble.redhat.com> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3079 Lines: 90 Offset that has been chosen for kaslr during kernel decompression can be easily computed as a difference between _text and __START_KERNEL. We are already making use of this in dump_kernel_offset() notifier and in arch_crash_save_vmcoreinfo(). Introduce kaslr_offset() that makes this computation instead of hard-coding it, so that other kernel code (such as live patching) can make use of it. Also convert existing users to make use of it. Signed-off-by: Jiri Kosina --- It'd be great to potentially have Ack from x86 guys for this patch so that I could take it through livepatching.git with the depending 2/2 patch. Thanks. v1 -> v2: convert arch_crash_save_vmcoreinfo(), as spotted by Josh Poimboeuf. arch/x86/include/asm/setup.h | 6 ++++++ arch/x86/kernel/machine_kexec_64.c | 3 ++- arch/x86/kernel/setup.c | 2 +- 3 files changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index f69e06b..785ac2f 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -65,12 +65,18 @@ static inline void x86_ce4100_early_setup(void) { } * This is set up by the setup-routine at boot-time */ extern struct boot_params boot_params; +extern char _text[]; static inline bool kaslr_enabled(void) { return !!(boot_params.hdr.loadflags & KASLR_FLAG); } +static inline unsigned long kaslr_offset(void) +{ + return (unsigned long)&_text - __START_KERNEL; +} + /* * Do NOT EVER look at the BIOS memory size location. * It does not work on many machines. diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index 415480d..e102963 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -25,6 +25,7 @@ #include #include #include +#include #ifdef CONFIG_KEXEC_FILE static struct kexec_file_ops *kexec_file_loaders[] = { @@ -334,7 +335,7 @@ void arch_crash_save_vmcoreinfo(void) VMCOREINFO_LENGTH(node_data, MAX_NUMNODES); #endif vmcoreinfo_append_str("KERNELOFFSET=%lx\n", - (unsigned long)&_text - __START_KERNEL); + kaslr_offset()); } /* arch-dependent functionality related to kexec file-based syscall */ diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index d74ac33..5056d3c 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -834,7 +834,7 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p) { if (kaslr_enabled()) { pr_emerg("Kernel Offset: 0x%lx from 0x%lx (relocation range: 0x%lx-0x%lx)\n", - (unsigned long)&_text - __START_KERNEL, + kaslr_offset(), __START_KERNEL, __START_KERNEL_map, MODULES_VADDR-1); -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/