Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 99c621d7 authored by Michael Sartain's avatar Michael Sartain Committed by Steven Rostedt (VMware)
Browse files

tracing: Add saved_tgids file to show cached pid to tgid mappings 

Export the cached pid / tgid mappings in debugfs tracing saved_tgids file.
This allows user apps to translate the pids from a trace to their respective
thread group.

Example saved_tgids file with pid / tgid values separated by ' ':

  # cat saved_tgids
  1048 1048
  1047 1047
  7 7
  1049 1047
  1054 1047
  1053 1047

Link: http://lkml.kernel.org/r/20170630004023.064965233@goodmis.org
Link: http://lkml.kernel.org/r/20170706040713.unwkumbta5menygi@mikesart-cos



Reviewed-by: default avatarJoel Fernandes <joelaf@google.com>
Signed-off-by: default avatarMichael Sartain <mikesart@fastmail.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 69d71879

kernel/trace/trace.c

+73 −0
Original line number Diff line number Diff line
@@ -4688,6 +4688,76 @@ static const struct file_operations tracing_readme_fops = { 
	.llseek		= generic_file_llseek,

};



static void *saved_tgids_next(struct seq_file *m, void *v, loff_t *pos)

{

	int *ptr = v;



	if (*pos || m->count)

		ptr++;



	(*pos)++;



	for (; ptr <= &tgid_map[PID_MAX_DEFAULT]; ptr++) {

		if (trace_find_tgid(*ptr))

			return ptr;

	}



	return NULL;

}



static void *saved_tgids_start(struct seq_file *m, loff_t *pos)

{

	void *v;

	loff_t l = 0;



	if (!tgid_map)

		return NULL;



	v = &tgid_map[0];

	while (l <= *pos) {

		v = saved_tgids_next(m, v, &l);

		if (!v)

			return NULL;

	}



	return v;

}



static void saved_tgids_stop(struct seq_file *m, void *v)

{

}



static int saved_tgids_show(struct seq_file *m, void *v)

{

	int pid = (int *)v - tgid_map;



	seq_printf(m, "%d %d\n", pid, trace_find_tgid(pid));

	return 0;

}



static const struct seq_operations tracing_saved_tgids_seq_ops = {

	.start		= saved_tgids_start,

	.stop		= saved_tgids_stop,

	.next		= saved_tgids_next,

	.show		= saved_tgids_show,

};



static int tracing_saved_tgids_open(struct inode *inode, struct file *filp)

{

	if (tracing_disabled)

		return -ENODEV;



	return seq_open(filp, &tracing_saved_tgids_seq_ops);

}





static const struct file_operations tracing_saved_tgids_fops = {

	.open		= tracing_saved_tgids_open,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= seq_release,

};



static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)

{

	unsigned int *ptr = v;
@@ -7920,6 +7990,9 @@ static __init int tracer_init_tracefs(void) 
	trace_create_file("saved_cmdlines_size", 0644, d_tracer,

			  NULL, &tracing_saved_cmdlines_size_fops);



	trace_create_file("saved_tgids", 0444, d_tracer,

			NULL, &tracing_saved_tgids_fops);



	trace_eval_init();



	trace_create_eval_file(d_tracer);