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tracing: Add function probe to trigger a ftrace dump to console

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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
Download patch file Download diff file Expand all files Collapse all files

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