From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761514AbXIZSXm (ORCPT ); Wed, 26 Sep 2007 14:23:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760288AbXIZSWu (ORCPT ); Wed, 26 Sep 2007 14:22:50 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:60566 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759967AbXIZSWs (ORCPT ); Wed, 26 Sep 2007 14:22:48 -0400 Subject: [patch 3/3] Trace sample From: "David J. Wilder" To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, randy.dunlap@oracle.com, hch@infradead.org, mathieu.desnoyers@polymtl.ca Content-Type: text/plain Date: Wed, 26 Sep 2007 11:22:43 -0700 Message-Id: <1190830963.1232.14.camel@lc4eb748232119.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-27.rhel4.6) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Trace example - Adds the trace example to samples/ Signed-off-by: David Wilder --- samples/Kconfig | 6 ++ samples/Makefile | 1 + samples/trace/Makefile | 4 + samples/trace/fork_trace.c | 132 ++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 143 insertions(+), 0 deletions(-) diff --git a/samples/Kconfig b/samples/Kconfig index 57bb223..e11c806 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -13,4 +13,10 @@ config SAMPLE_MARKERS help This build markers example modules. +config SAMPLE_TRACE + tristate "Build trace example -- loadable modules only" + depends on TRACE && m + help + This builds a trace example module. + endif # SAMPLES diff --git a/samples/Makefile b/samples/Makefile index 5a4f0b6..8f6d05b 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -1,3 +1,4 @@ # Makefile for Linux samples code obj-$(CONFIG_SAMPLES) += markers/ +obj-$(CONFIG_SAMPLES) += trace/ diff --git a/samples/trace/Makefile b/samples/trace/Makefile new file mode 100644 index 0000000..a2da8af --- /dev/null +++ b/samples/trace/Makefile @@ -0,0 +1,4 @@ +# builds the trace example kernel modules; +# then to use (as root): insmod + +obj-$(CONFIG_SAMPLE_TRACE) := fork_trace.o diff --git a/samples/trace/fork_trace.c b/samples/trace/fork_trace.c new file mode 100644 index 0000000..71c04c7 --- /dev/null +++ b/samples/trace/fork_trace.c @@ -0,0 +1,132 @@ +/* + * An example of using trace in a kprobes module + * + * Copyright (C) 2007 IBM Inc. + * + * David Wilder + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + * ------- + * This module creates a trace channel and places a kprobe + * on the function do_fork(). The value of current->pid is written to + * the trace channel each time the kprobe is hit.. + * + * How to run the example: + * $ mount -t debugfs /debug + * $ insmod fork_trace.ko + * + * To view the data produced by the module: + * $ cat /debug/trace_example/do_fork/trace0 + * + */ + +#include +#include +#include +#include + +#define USE_GLOBAL_BUFFERS 1 +#define USE_FLIGHT 1 + +#define PROBE_POINT "do_fork" + +static struct kprobe kp; +static struct trace_info *kprobes_trace; + +#ifdef USE_GLOBAL_BUFFERS +static DEFINE_SPINLOCK(trace_lock); +#endif + +/* + * Send formatted trace data to trace channel. + * @note Preemption must be disabled to use this. + */ +static void trace_printf(struct trace_info *trace, const char *format, ...) +{ + va_list ap, aq; + char *record; + unsigned long flags; + int len; + + if (!trace) + return; + +#ifdef USE_GLOBAL_BUFFERS + spin_lock_irqsave(&trace_lock, flags); +#endif + if (trace_running(trace)) { + va_start(ap, format); + va_copy(aq, ap); + len = vsnprintf(NULL, 0, format, aq); + va_end(aq); + record = relay_reserve(trace->rchan, ++len); + if (record) + vsnprintf(record, len, format, ap); + va_end(ap); + } +#ifdef USE_GLOBAL_BUFFERS + spin_unlock_irqrestore(&trace_lock, flags); +#endif +} + +static int handler_pre(struct kprobe *p, struct pt_regs *regs) +{ + rcu_read_lock(); + trace_printf(kprobes_trace, "%d\n", current->pid); + rcu_read_unlock(); + return 0; +} + +int init_module(void) +{ + int ret; + u32 flags = 0; + +#ifdef USE_GLOBAL_BUFFERS + flags |= TRACE_GLOBAL_CHANNEL; +#endif + +#ifdef USE_FLIGHT + flags |= TRACE_FLIGHT_CHANNEL; +#endif + + /* setup the trace */ + kprobes_trace = trace_setup("trace_example", PROBE_POINT, + 1024, 8, flags); + if (IS_ERR(kprobes_trace)) + return PTR_ERR(kprobes_trace); + + trace_start(kprobes_trace); + + /* setup the kprobe */ + kp.pre_handler = handler_pre; + kp.post_handler = NULL; + kp.fault_handler = NULL; + kp.symbol_name = PROBE_POINT; + ret = register_kprobe(&kp); + if (ret) { + printk(KERN_ERR "fork_trace: register_kprobe failed\n"); + return ret; + } + return 0; +} + +void cleanup_module(void) +{ + unregister_kprobe(&kp); + trace_stop(kprobes_trace); + trace_cleanup(kprobes_trace); +} +MODULE_LICENSE("GPL");