Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755226AbbLDH3G (ORCPT ); Fri, 4 Dec 2015 02:29:06 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:18776 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754912AbbLDH2Z (ORCPT ); Fri, 4 Dec 2015 02:28:25 -0500 From: Li Bin To: , CC: , Li Bin , "James Hogan" , Subject: [PATCH 2/5] metag: ftrace: fix the comments for ftrace_modify_code Date: Fri, 4 Dec 2015 15:27:44 +0800 Message-ID: <1449214067-12177-3-git-send-email-huawei.libin@huawei.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1449214067-12177-1-git-send-email-huawei.libin@huawei.com> References: <1449214067-12177-1-git-send-email-huawei.libin@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.100.166] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020202.5661408C.0048,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: 5701201c9a55cf44b57efc12df4254bb Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2037 Lines: 50 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: James Hogan Cc: linux-metag@vger.kernel.org Suggested-by: Steven Rostedt Signed-off-by: Li Bin --- arch/metag/kernel/ftrace.c | 12 ++++++------ 1 files changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/metag/kernel/ftrace.c b/arch/metag/kernel/ftrace.c index ed1d685..e5d71b1 100644 --- a/arch/metag/kernel/ftrace.c +++ b/arch/metag/kernel/ftrace.c @@ -54,12 +54,12 @@ static int ftrace_modify_code(unsigned long pc, 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. - * - * No real locking needed, this code is run through - * kstop_machine. + * Note: + * We are paranoid about modifying text, as if a bug were to happen, it + * could cause us to read or write to someplace that could cause harm. + * Carefully read and modify the code with aarch64_insn_*() which uses + * 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 */ -- 1.7.1 -- 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/