[PATCH 3/3] TEST PATCH - ftrace example patch for use of trace pipe headers

[Steven Rostedt]

DO NOT APPLY THIS PATCH!!!!!

This is an example of implementing a plugin for header for the trace_pipe
file.

DO NOT APPLY THIS PATCH!!!!! 

Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
---
 kernel/trace/trace_functions.c |   41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

Index: linux-sched-devel.git/kernel/trace/trace_functions.c
===================================================================
--- linux-sched-devel.git.orig/kernel/trace/trace_functions.c	2008-04-21 16:50:49.000000000 -0400
+++ linux-sched-devel.git/kernel/trace/trace_functions.c	2008-04-21 16:54:55.000000000 -0400
@@ -16,6 +16,45 @@
 
 #include "trace.h"
 
+static void function_pipe_open(struct trace_iterator *iter)
+{
+	int *traceme;
+
+	traceme = kzalloc(sizeof(int), GFP_KERNEL);
+	if (!traceme)
+		return;
+
+	iter->private = traceme;
+}
+
+static ssize_t function_read(struct trace_iterator *iter,
+			     struct file *filp, char __user *ubuf,
+			     size_t cnt, loff_t *ppos)
+{
+	unsigned char head[] = "Test header\n";
+	int *traced;
+	int ret;
+
+	if (!iter->private)
+		return 0;
+
+	traced = iter->private;
+	if (*traced >= sizeof(head)-1)
+		return 0;
+
+	if (cnt > sizeof(head)-1)
+		cnt = sizeof(head)-1;
+
+	ret = copy_to_user(ubuf, head + *traced, cnt);
+
+	*traced += cnt;
+
+	if (ret)
+		cnt = -EFAULT;
+
+	return cnt;
+}
+
 static void function_reset(struct trace_array *tr)
 {
 	int cpu;
@@ -68,6 +107,8 @@ static struct tracer function_trace __re
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest    = trace_selftest_startup_function,
 #endif
+	.pipe_open   = function_pipe_open,
+	.read        = function_read,
 };
 
 static __init int init_function_trace(void)

-- 
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