From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752708AbbCCFKR (ORCPT ); Tue, 3 Mar 2015 00:10:17 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:8097 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751327AbbCCFJu (ORCPT ); Tue, 3 Mar 2015 00:09:50 -0500 From: Wang Nan To: , , , , CC: , , , Subject: [PATCH 2/3] ftrace/x86: don't return error if other makes a same code change. Date: Tue, 3 Mar 2015 13:09:04 +0800 Message-ID: <1425359345-38714-3-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.4 In-Reply-To: <1425359345-38714-1-git-send-email-wangnan0@huawei.com> References: <1425306312-3437-1-git-send-email-wangnan0@huawei.com> <1425359345-38714-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.197.247] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In ftrace_modify_code_direct(), if the target instruction has already been modified by other to the desire instruction, don't return error. This patch is for early kprobe. If an early kprobe is unregistered before ftrace is ready, the instruction may have already been restored to NOP. Signed-off-by: Wang Nan --- arch/x86/kernel/ftrace.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 0a86c7c..fba1779 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -121,8 +121,13 @@ ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, return -EFAULT; /* Make sure it is what we expect it to be */ - if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) - return -EINVAL; + if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) { + /* Check if someone else has already done it */ + if (memcmp(replaced, new_code, MCOUNT_INSN_SIZE) != 0) + return -EINVAL; + else + return 0; + } ip = text_ip_addr(ip); -- 1.8.4