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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>
This commit is contained in:
Steven Rostedt (Red Hat) 2013-04-30 15:46:14 -04:00 committed by Steven Rostedt
parent 317ddd256b
commit ad71d889b8
2 changed files with 61 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
Documentation/trace/ftrace.txt
View File

@ -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
----------

59
kernel/trace/trace_functions.c
View File

@ -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