[PATCH 4/7] tracing: add format file to describe event struct fields
From: Steven Rostedt
Date: Mon Mar 02 2009 - 15:32:12 EST
From: Steven Rostedt <srostedt@xxxxxxxxxx>
This patch adds the "format" file to the trace point event directory.
This is based off of work by Tom Zanussi, in which a file is exported
to be tread from user land such that a user space app may read the
binary record stored in the ring buffer.
# cat /debug/tracing/events/sched/sched_switch/format
field:pid_t prev_pid; offset:12; size:4;
field:int prev_prio; offset:16; size:4;
field special:char next_comm[TASK_COMM_LEN]; offset:20; size:16;
field:pid_t next_pid; offset:36; size:4;
field:int next_prio; offset:40; size:4;
Idea-from: Tom Zanussi <tzanussi@xxxxxxxxx>
Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
---
kernel/trace/trace.h | 1 +
kernel/trace/trace_events.c | 56 ++++++++++++++++++++++++++++++++++-
kernel/trace/trace_events_stage_2.h | 52 ++++++++++++++++++++++++++++++++
kernel/trace/trace_events_stage_3.h | 2 +
4 files changed, 110 insertions(+), 1 deletions(-)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index cf6ba41..e606633 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -754,6 +754,7 @@ struct ftrace_event_call {
int (*raw_init)(void);
int (*raw_reg)(void);
void (*raw_unreg)(void);
+ int (*show_format)(struct trace_seq *s);
};
void event_trace_printk(unsigned long ip, const char *fmt, ...);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 26069fa..d57a772 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3,6 +3,9 @@
*
* Copyright (C) 2008 Red Hat Inc, Steven Rostedt <srostedt@xxxxxxxxxx>
*
+ * - Added format output of fields of the trace point.
+ * This was based off of work by Tom Zanussi <tzanussi@xxxxxxxxx>.
+ *
*/
#include <linux/debugfs.h>
@@ -444,6 +447,42 @@ event_available_types_read(struct file *filp, char __user *ubuf, size_t cnt,
return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}
+static ssize_t
+event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
+ loff_t *ppos)
+{
+ struct ftrace_event_call *call = filp->private_data;
+ struct trace_seq *s;
+ char *buf;
+ int r;
+
+ s = kmalloc(sizeof(*s), GFP_KERNEL);
+ if (!s)
+ return -ENOMEM;
+
+ trace_seq_init(s);
+
+ if (*ppos)
+ return 0;
+
+ r = call->show_format(s);
+ if (!r) {
+ /*
+ * ug! The format output is bigger than a PAGE!!
+ */
+ buf = "FORMAT TOO BIG\n";
+ r = simple_read_from_buffer(ubuf, cnt, ppos,
+ buf, strlen(buf));
+ goto out;
+ }
+
+ r = simple_read_from_buffer(ubuf, cnt, ppos,
+ s->buffer, s->len);
+ out:
+ kfree(s);
+ return r;
+}
+
static const struct seq_operations show_event_seq_ops = {
.start = t_start,
.next = t_next,
@@ -490,6 +529,11 @@ static const struct file_operations ftrace_available_types_fops = {
.read = event_available_types_read,
};
+static const struct file_operations ftrace_event_format_fops = {
+ .open = tracing_open_generic,
+ .read = event_format_read,
+};
+
static struct dentry *event_trace_events_dir(void)
{
static struct dentry *d_tracer;
@@ -602,7 +646,17 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
&ftrace_available_types_fops);
if (!entry)
pr_warning("Could not create debugfs "
- "'%s/type' available_types\n", call->name);
+ "'%s/available_types' entry\n", call->name);
+
+ /* A trace may not want to export its format */
+ if (!call->show_format)
+ return 0;
+
+ entry = debugfs_create_file("format", 0444, call->dir, call,
+ &ftrace_event_format_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs "
+ "'%s/format' entry\n", call->name);
return 0;
}
diff --git a/kernel/trace/trace_events_stage_2.h b/kernel/trace/trace_events_stage_2.h
index dc79fe3..3a80ea4 100644
--- a/kernel/trace/trace_events_stage_2.h
+++ b/kernel/trace/trace_events_stage_2.h
@@ -74,3 +74,55 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \
}
#include <trace/trace_event_types.h>
+
+/*
+ * Setup the showing format of trace point.
+ *
+ * int
+ * ftrace_format_##call(struct trace_seq *s)
+ * {
+ * struct ftrace_raw_##call field;
+ * int ret;
+ *
+ * ret = trace_seq_printf(s, #type " " #item ";"
+ * " size:%d; offset:%d;\n",
+ * sizeof(field.type),
+ * offsetof(struct ftrace_raw_##call,
+ * item));
+ *
+ * }
+ */
+
+#undef TRACE_FIELD
+#define TRACE_FIELD(type, item, assign) \
+ ret = trace_seq_printf(s, "\tfield:" #type " " #item ";\t" \
+ "offset:%lu;\tsize:%lu;\n", \
+ offsetof(typeof(field), item), \
+ sizeof(field.item)); \
+ if (!ret) \
+ return 0;
+
+
+#undef TRACE_FIELD_SPECIAL
+#define TRACE_FIELD_SPECIAL(type_item, item, cmd) \
+ ret = trace_seq_printf(s, "\tfield special:" #type_item ";\t" \
+ "offset:%lu;\tsize:%lu;\n", \
+ offsetof(typeof(field), item), \
+ sizeof(field.item)); \
+ if (!ret) \
+ return 0;
+
+#undef TRACE_EVENT_FORMAT
+#define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt) \
+int \
+ftrace_format_##call(struct trace_seq *s) \
+{ \
+ struct ftrace_raw_##call field; \
+ int ret; \
+ \
+ tstruct; \
+ \
+ return ret; \
+}
+
+#include <trace/trace_event_types.h>
diff --git a/kernel/trace/trace_events_stage_3.h b/kernel/trace/trace_events_stage_3.h
index 2ab65e9..c62a4d2 100644
--- a/kernel/trace/trace_events_stage_3.h
+++ b/kernel/trace/trace_events_stage_3.h
@@ -101,6 +101,7 @@
* .raw_init = ftrace_raw_init_event_<call>,
* .raw_reg = ftrace_raw_reg_event_<call>,
* .raw_unreg = ftrace_raw_unreg_event_<call>,
+ * .show_format = ftrace_format_<call>,
* }
*
*/
@@ -230,4 +231,5 @@ __attribute__((section("_ftrace_events"))) event_##call = { \
.raw_init = ftrace_raw_init_event_##call, \
.raw_reg = ftrace_raw_reg_event_##call, \
.raw_unreg = ftrace_raw_unreg_event_##call, \
+ .show_format = ftrace_format_##call, \
}
--
1.5.6.5
--
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