From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756227AbZJ2BxQ (ORCPT ); Wed, 28 Oct 2009 21:53:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754925AbZJ2BxO (ORCPT ); Wed, 28 Oct 2009 21:53:14 -0400 Received: from mga09.intel.com ([134.134.136.24]:60455 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755033AbZJ2BxJ (ORCPT ); Wed, 28 Oct 2009 21:53:09 -0400 X-ExtLoop1: 1 Message-Id: <20091029024821.080941108@sbs-t61.sc.intel.com> User-Agent: quilt/0.47-1 Date: Wed, 28 Oct 2009 18:46:57 -0800 From: Suresh Siddha To: mingo@elte.hu, hpa@zytor.com, linux-kernel@vger.kernel.org Cc: Steven Rostedt , Suresh Siddha Subject: [patch 2/3] x86_64, ftrace: make ftrace use kernel identity mapping to modify code References: <20091029024820.996634347@sbs-t61.sc.intel.com> Content-Disposition: inline; filename=fix_ftrace_rodata.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On x86_64, kernel text mappings are mapped read-only with CONFIG_DEBUG_RODATA. So use the kernel identity mapping instead of the kernel text mapping to modify the kernel text. Acked-by: Steven Rostedt Tested-by: Steven Rostedt Signed-off-by: Suresh Siddha --- arch/x86/kernel/ftrace.c | 17 +++++++++++++++++ arch/x86/mm/pageattr.c | 3 +-- 2 files changed, 18 insertions(+), 2 deletions(-) Index: tip/arch/x86/kernel/ftrace.c =================================================================== --- tip.orig/arch/x86/kernel/ftrace.c +++ tip/arch/x86/kernel/ftrace.c @@ -189,9 +189,26 @@ static void wait_for_nmi(void) nmi_wait_count++; } +static inline int +within(unsigned long addr, unsigned long start, unsigned long end) +{ + return addr >= start && addr < end; +} + static int do_ftrace_mod_code(unsigned long ip, void *new_code) { + /* + * On x86_64, kernel text mappings are mapped read-only with + * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead + * of the kernel text mapping to modify the kernel text. + * + * For 32bit kernels, these mappings are same and we can use + * kernel identity mapping to modify code. + */ + if (within(ip, (unsigned long)_text, (unsigned long)_etext)) + ip = (unsigned long)__va(__pa(ip)); + mod_code_ip = (void *)ip; mod_code_newcode = new_code; Index: tip/arch/x86/mm/pageattr.c =================================================================== --- tip.orig/arch/x86/mm/pageattr.c +++ tip/arch/x86/mm/pageattr.c @@ -279,8 +279,7 @@ static inline pgprot_t static_protection __pa((unsigned long)__end_rodata) >> PAGE_SHIFT)) pgprot_val(forbidden) |= _PAGE_RW; -#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) && \ - !defined(CONFIG_DYNAMIC_FTRACE) +#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) /* * Once the kernel maps the text as RO (kernel_set_to_readonly is set), * kernel text mappings for the large page aligned text, rodata sections