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>
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index c4d6d71..d7c8719 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -290,6 +290,13 @@
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 @@
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 @@
.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 @@
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 @@
.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 @@
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