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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2013-04-30 15:46:14 -0400
committerSteven Rostedt <rostedt@goodmis.org>2013-06-11 18:38:46 -0400
commitad71d889b88055e61e3970a6744a271a51a94f42 (patch)
tree716f6e043847000a82449270e3b2d5dcdc9c4f79
parent317ddd256b9c24b0d78fa8018f80f1e495481a10 (diff)
tracing: Add function probe to trigger a ftrace dump to console
Add the "dump" command to have the ftrace buffer dumped to console if a function is hit. This is useful when debugging a tripple fault, where you have an idea of a function that is called just before the tripple fault occurs, and can tell ftrace to dump its content out to the console before it continues. Format is: <function>:dump echo 'bad_address:dump' > /debug/tracing/set_ftrace_filter To remove this: echo '!bad_address:dump' > /debug/tracing/set_ftrace_filter Requested-by: Luis Claudio R. Goncalves <lclaudio@uudg.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--Documentation/trace/ftrace.txt7
-rw-r--r--kernel/trace/trace_functions.c59
2 files changed, 61 insertions, 5 deletions
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index bfe8c29b1f1d..cc9ec57e157c 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -2430,6 +2430,13 @@ The following commands are supported:
echo '!schedule:disable_event:sched:sched_switch' > \
set_ftrace_filter
+- dump
+ When the function is hit, it will dump the contents of the ftrace
+ ring buffer to the console. This is useful if you need to debug
+ something, and want to dump the trace when a certain function
+ is hit. Perhaps its a function that is called before a tripple
+ fault happens and does not allow you to get a regular dump.
+
trace_pipe
----------
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index c4d6d7191988..d7c8719734b8 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -290,6 +290,13 @@ ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip, void **data)
trace_dump_stack(STACK_SKIP);
}
+static void
+ftrace_dump_probe(unsigned long ip, unsigned long parent_ip, void **data)
+{
+ if (update_count(data))
+ ftrace_dump(DUMP_ALL);
+}
+
static int
ftrace_probe_print(const char *name, struct seq_file *m,
unsigned long ip, void *data)
@@ -327,6 +334,13 @@ ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,
return ftrace_probe_print("stacktrace", m, ip, data);
}
+static int
+ftrace_dump_print(struct seq_file *m, unsigned long ip,
+ struct ftrace_probe_ops *ops, void *data)
+{
+ return ftrace_probe_print("dump", m, ip, data);
+}
+
static struct ftrace_probe_ops traceon_count_probe_ops = {
.func = ftrace_traceon_count,
.print = ftrace_traceon_print,
@@ -342,6 +356,11 @@ static struct ftrace_probe_ops stacktrace_count_probe_ops = {
.print = ftrace_stacktrace_print,
};
+static struct ftrace_probe_ops dump_probe_ops = {
+ .func = ftrace_dump_probe,
+ .print = ftrace_dump_print,
+};
+
static struct ftrace_probe_ops traceon_probe_ops = {
.func = ftrace_traceon,
.print = ftrace_traceon_print,
@@ -425,6 +444,19 @@ ftrace_stacktrace_callback(struct ftrace_hash *hash,
param, enable);
}
+static int
+ftrace_dump_callback(struct ftrace_hash *hash,
+ char *glob, char *cmd, char *param, int enable)
+{
+ struct ftrace_probe_ops *ops;
+
+ ops = &dump_probe_ops;
+
+ /* Only dump once. */
+ return ftrace_trace_probe_callback(ops, hash, glob, cmd,
+ "1", enable);
+}
+
static struct ftrace_func_command ftrace_traceon_cmd = {
.name = "traceon",
.func = ftrace_trace_onoff_callback,
@@ -440,6 +472,11 @@ static struct ftrace_func_command ftrace_stacktrace_cmd = {
.func = ftrace_stacktrace_callback,
};
+static struct ftrace_func_command ftrace_dump_cmd = {
+ .name = "dump",
+ .func = ftrace_dump_callback,
+};
+
static int __init init_func_cmd_traceon(void)
{
int ret;
@@ -450,13 +487,25 @@ static int __init init_func_cmd_traceon(void)
ret = register_ftrace_command(&ftrace_traceon_cmd);
if (ret)
- unregister_ftrace_command(&ftrace_traceoff_cmd);
+ goto out_free_traceoff;
ret = register_ftrace_command(&ftrace_stacktrace_cmd);
- if (ret) {
- unregister_ftrace_command(&ftrace_traceoff_cmd);
- unregister_ftrace_command(&ftrace_traceon_cmd);
- }
+ if (ret)
+ goto out_free_traceon;
+
+ ret = register_ftrace_command(&ftrace_dump_cmd);
+ if (ret)
+ goto out_free_stacktrace;
+
+ return 0;
+
+ out_free_stacktrace:
+ unregister_ftrace_command(&ftrace_stacktrace_cmd);
+ out_free_traceon:
+ unregister_ftrace_command(&ftrace_traceon_cmd);
+ out_free_traceoff:
+ unregister_ftrace_command(&ftrace_traceoff_cmd);
+
return ret;
}
#else