From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760356AbYHTQzh (ORCPT ); Wed, 20 Aug 2008 12:55:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758712AbYHTQzK (ORCPT ); Wed, 20 Aug 2008 12:55:10 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:42755 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754867AbYHTQzI (ORCPT ); Wed, 20 Aug 2008 12:55:08 -0400 Date: Wed, 20 Aug 2008 12:55:07 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: LKML cc: Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Andrew Morton , Linus Torvalds , Benjamin Herrenschmidt Subject: [PATCH] ftrace: x86 use copy to and from user functions Message-ID: User-Agent: Alpine 1.10 (DEB 962 2008-03-14) 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 The modification of code is performed either by kstop_machine, before SMP starts, or on module code before the module is executed. There is no reason to do the modifications from assembly. The copy to and from user functions are sufficient and produces cleaner and easier to read code. Thanks to Benjamin Herrenschmidt for suggesting the idea. Signed-off-by: Steven Rostedt --- arch/x86/kernel/ftrace.c | 38 +++++++++++++------------------------- 1 file changed, 13 insertions(+), 25 deletions(-) Index: linux-tip.git/arch/x86/kernel/ftrace.c =================================================================== --- linux-tip.git.orig/arch/x86/kernel/ftrace.c 2008-08-20 12:39:41.000000000 -0400 +++ linux-tip.git/arch/x86/kernel/ftrace.c 2008-08-20 12:40:17.000000000 -0400 @@ -11,6 +11,7 @@ #include #include +#include #include #include #include @@ -60,11 +61,7 @@ notrace int ftrace_modify_code(unsigned long ip, unsigned char *old_code, unsigned char *new_code) { - unsigned replaced; - unsigned old = *(unsigned *)old_code; /* 4 bytes */ - unsigned new = *(unsigned *)new_code; /* 4 bytes */ - unsigned char newch = new_code[4]; - int faulted = 0; + unsigned char replaced[MCOUNT_INSN_SIZE]; /* * Note: Due to modules and __init, code can @@ -72,29 +69,20 @@ ftrace_modify_code(unsigned long ip, uns * as well as code changing. * * No real locking needed, this code is run through - * kstop_machine. + * kstop_machine, or before SMP starts. */ - asm volatile ( - "1: lock\n" - " cmpxchg %3, (%2)\n" - " jnz 2f\n" - " movb %b4, 4(%2)\n" - "2:\n" - ".section .fixup, \"ax\"\n" - "3: movl $1, %0\n" - " jmp 2b\n" - ".previous\n" - _ASM_EXTABLE(1b, 3b) - : "=r"(faulted), "=a"(replaced) - : "r"(ip), "r"(new), "c"(newch), - "0"(faulted), "a"(old) - : "memory"); - sync_core(); + if (__copy_from_user(replaced, (char __user *)ip, MCOUNT_INSN_SIZE)) + return 1; - if (replaced != old && replaced != new) - faulted = 2; + if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) + return 2; - return faulted; + WARN_ON_ONCE(__copy_to_user((char __user *)ip, new_code, + MCOUNT_INSN_SIZE)); + + sync_core(); + + return 0; } notrace int ftrace_update_ftrace_func(ftrace_func_t func)