The patch titled
Trace sample
has been added to the -mm tree. Its filename is
trace-sample.patch
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------------------------------------------------------
Subject: Trace sample
From: "David J. Wilder" <dwilder@xxxxxxxxxx>
Add the trace example to samples/.
Signed-off-by: David Wilder <dwilder@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
samples/Kconfig | 6 +
samples/Makefile | 2
samples/trace/Makefile | 4 +
samples/trace/fork_trace.c | 132 +++++++++++++++++++++++++++++++++++
4 files changed, 143 insertions(+), 1 deletion(-)
diff -puN samples/Kconfig~trace-sample samples/Kconfig
--- a/samples/Kconfig~trace-sample
+++ a/samples/Kconfig
@@ -33,5 +33,11 @@ config SAMPLE_KRETPROBES
default m
depends on SAMPLE_KPROBES && KRETPROBES
+config SAMPLE_TRACE
+ tristate "Build trace example -- loadable modules only"
+ depends on TRACE && KPROBES && m
+ help
+ This builds a trace example module.
+
endif # SAMPLES
diff -puN samples/Makefile~trace-sample samples/Makefile
--- a/samples/Makefile~trace-sample
+++ a/samples/Makefile
@@ -1,3 +1,3 @@
# Makefile for Linux samples code
-obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/
+obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ trace/
diff -puN /dev/null samples/trace/Makefile
--- /dev/null
+++ a/samples/trace/Makefile
@@ -0,0 +1,4 @@
+# builds the trace example kernel modules;
+# then to use (as root): insmod <fork_trace.ko>
+
+obj-$(CONFIG_SAMPLE_TRACE) := fork_trace.o
diff -puN /dev/null samples/trace/fork_trace.c
--- /dev/null
+++ a/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 <dwilder@xxxxxxxxxx>
+ *
+ * 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 <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+#include <linux/trace.h>
+
+#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");
_
Patches currently in -mm which might be from dwilder@xxxxxxxxxx are
relay-reset-consumed.patch
trace-code-and-documentation.patch
trace-sample.patch
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