From patchwork Sun Dec 6 02:02:57 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Li Bin X-Patchwork-Id: 7776171 X-Patchwork-Delegate: horms@verge.net.au Return-Path: X-Original-To: patchwork-linux-sh@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id A7EAA9F30B for ; Sun, 6 Dec 2015 02:01:27 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id DACEE20452 for ; Sun, 6 Dec 2015 02:01:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9230E20439 for ; Sun, 6 Dec 2015 02:01:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752378AbbLFCBZ (ORCPT ); Sat, 5 Dec 2015 21:01:25 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:57217 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751817AbbLFCBY (ORCPT ); Sat, 5 Dec 2015 21:01:24 -0500 Received: from 172.24.1.51 (EHLO szxeml426-hub.china.huawei.com) ([172.24.1.51]) by szxrg03-dlp.huawei.com (MOS 4.4.3-GA FastPath queued) with ESMTP id BSF09367; Sun, 06 Dec 2015 10:01:21 +0800 (CST) Received: from localhost.localdomain (10.175.100.166) by szxeml426-hub.china.huawei.com (10.82.67.181) with Microsoft SMTP Server id 14.3.235.1; Sun, 6 Dec 2015 10:01:11 +0800 From: Li Bin To: , CC: , Li Bin , Subject: [PATCH v2 4/5] sh: ftrace: fix the comments for ftrace_modify_code Date: Sun, 6 Dec 2015 10:02:57 +0800 Message-ID: <1449367378-29430-5-git-send-email-huawei.libin@huawei.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1449367378-29430-1-git-send-email-huawei.libin@huawei.com> References: <1449367378-29430-1-git-send-email-huawei.libin@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.100.166] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020204.566396F2.002A, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 4b265bbaba6fb235628731974250fc07 Sender: linux-sh-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP There is no need to worry about module and __init text disappearing case, because that ftrace has a module notifier that is called when a module is being unloaded and before the text goes away and this code grabs the ftrace_lock mutex and removes the module functions from the ftrace list, such that it will no longer do any modifications to that module's text, the update to make functions be traced or not is done under the ftrace_lock mutex as well. And by now, __init section codes should not been modified by ftrace, because it is black listed in recordmcount.c and ignored by ftrace. Cc: linux-sh@vger.kernel.org Suggested-by: Steven Rostedt Signed-off-by: Li Bin --- arch/sh/kernel/ftrace.c | 12 +++++------- 1 files changed, 5 insertions(+), 7 deletions(-) diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c index 079d70e..38993e0 100644 --- a/arch/sh/kernel/ftrace.c +++ b/arch/sh/kernel/ftrace.c @@ -212,13 +212,11 @@ static int ftrace_modify_code(unsigned long ip, unsigned char *old_code, unsigned char replaced[MCOUNT_INSN_SIZE]; /* - * Note: Due to modules and __init, code can - * disappear and change, we need to protect against faulting - * as well as code changing. We do this by using the - * probe_kernel_* functions. - * - * No real locking needed, this code is run through - * kstop_machine, or before SMP starts. + * Note: + * We are paranoid about modifying text, as if a bug was to happen, it + * could cause us to read or write to someplace that could cause harm. + * Carefully read and modify the code with probe_kernel_*(), and make + * sure what we read is what we expected it to be before modifying it. */ /* read the text we want to modify */