From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 661EBC433DF for ; Mon, 1 Jun 2020 12:28:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F109208A7 for ; Mon, 1 Jun 2020 12:28:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728114AbgFAM25 (ORCPT ); Mon, 1 Jun 2020 08:28:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:36950 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726201AbgFAM2I (ORCPT ); Mon, 1 Jun 2020 08:28:08 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1C54B207BC; Mon, 1 Jun 2020 12:28:08 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.93) (envelope-from ) id 1jfjXz-00274D-5X; Mon, 01 Jun 2020 08:28:07 -0400 Message-ID: <20200601122807.057114335@goodmis.org> User-Agent: quilt/0.66 Date: Mon, 01 Jun 2020 08:27:30 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Cheng Jian Subject: [for-next][PATCH 01/12] ftrace: show debugging information when panic_on_warn set References: <20200601122729.727113609@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Cheng Jian When an anomaly is detected in the function call modification code, ftrace_bug() is called to disable function tracing as well as give some warn and information that may help debug the problem. But currently, we call FTRACE_WARN_ON_ONCE() first in ftrace_bug(), so when panic_on_warn is set, we can't see the debugging information here. Call FTRACE_WARN_ON_ONCE() at the end of ftrace_bug() to ensure that the debugging information is displayed first. after this patch, the dmesg looks like: ------------[ ftrace bug ]------------ ftrace failed to modify [] bcm2835_handle_irq+0x4/0x58 actual: 1f:20:03:d5 Setting ftrace call site to call ftrace function ftrace record flags: 80000001 (1) expected tramp: ffff80001009d6f0 ------------[ cut here ]------------ WARNING: CPU: 2 PID: 1635 at kernel/trace/ftrace.c:2078 ftrace_bug+0x204/0x238 Kernel panic - not syncing: panic_on_warn set ... CPU: 2 PID: 1635 Comm: sh Not tainted 5.7.0-rc5-00033-gb922183867f5 #14 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x1b0 show_stack+0x20/0x30 dump_stack+0xc0/0x10c panic+0x16c/0x368 __warn+0x120/0x160 report_bug+0xc8/0x160 bug_handler+0x28/0x98 brk_handler+0x70/0xd0 do_debug_exception+0xcc/0x1ac el1_sync_handler+0xe4/0x120 el1_sync+0x7c/0x100 ftrace_bug+0x204/0x238 Link: https://lkml.kernel.org/r/20200515100828.7091-1-cj.chengjian@huawei.com Signed-off-by: Cheng Jian Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ftrace.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index bd030b1b9514..cd39cbf3631a 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2027,14 +2027,14 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec) { unsigned long ip = rec ? rec->ip : 0; + pr_info("------------[ ftrace bug ]------------\n"); + switch (failed) { case -EFAULT: - FTRACE_WARN_ON_ONCE(1); pr_info("ftrace faulted on modifying "); print_ip_sym(ip); break; case -EINVAL: - FTRACE_WARN_ON_ONCE(1); pr_info("ftrace failed to modify "); print_ip_sym(ip); print_ip_ins(" actual: ", (unsigned char *)ip); @@ -2045,12 +2045,10 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec) } break; case -EPERM: - FTRACE_WARN_ON_ONCE(1); pr_info("ftrace faulted on writing "); print_ip_sym(ip); break; default: - FTRACE_WARN_ON_ONCE(1); pr_info("ftrace faulted on unknown error "); print_ip_sym(ip); } @@ -2077,6 +2075,8 @@ void ftrace_bug(int failed, struct dyn_ftrace *rec) ip = ftrace_get_addr_curr(rec); pr_cont("\n expected tramp: %lx\n", ip); } + + FTRACE_WARN_ON_ONCE(1); } static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update) -- 2.26.2