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Commit eb9a7bf0 authored by Abhishek Sagar's avatar Abhishek Sagar Committed by Ingo Molnar
Browse files

ftrace: add debugfs entry 'failures' 



Identify functions which had their mcount call-site updates failed. This can
help us track functions which ftrace shouldn't fiddle with, and are thus not
being traced. If there is no race with any external agent which is modifying
the mcount call-site, then this file displays no entries (normal case).

Signed-off-by: default avatarAbhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 1d74f2a0

kernel/trace/ftrace.c

+39 −1
Original line number Diff line number Diff line
@@ -768,6 +768,7 @@ enum { 
	FTRACE_ITER_FILTER	= (1 << 0),

	FTRACE_ITER_CONT	= (1 << 1),

	FTRACE_ITER_NOTRACE	= (1 << 2),

	FTRACE_ITER_FAILURES	= (1 << 3),

};



#define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */
@@ -799,9 +800,16 @@ t_next(struct seq_file *m, void *v, loff_t *pos) 
		}

	} else {

		rec = &iter->pg->records[iter->idx++];

		if ((rec->flags & FTRACE_FL_FAILED) ||

		if ((!(iter->flags & FTRACE_ITER_FAILURES) &&

		     (rec->flags & FTRACE_FL_FAILED)) ||



		    ((iter->flags & FTRACE_ITER_FAILURES) &&

		     (!(rec->flags & FTRACE_FL_FAILED) ||

		      (rec->flags & FTRACE_FL_FREE))) ||



		    ((iter->flags & FTRACE_ITER_FILTER) &&

		     !(rec->flags & FTRACE_FL_FILTER)) ||



		    ((iter->flags & FTRACE_ITER_NOTRACE) &&

		     !(rec->flags & FTRACE_FL_NOTRACE))) {

			rec = NULL;
@@ -896,6 +904,24 @@ int ftrace_avail_release(struct inode *inode, struct file *file) 
	return 0;

}



static int

ftrace_failures_open(struct inode *inode, struct file *file)

{

	int ret;

	struct seq_file *m;

	struct ftrace_iterator *iter;



	ret = ftrace_avail_open(inode, file);

	if (!ret) {

		m = (struct seq_file *)file->private_data;

		iter = (struct ftrace_iterator *)m->private;

		iter->flags = FTRACE_ITER_FAILURES;

	}



	return ret;

}





static void ftrace_filter_reset(int enable)

{

	struct ftrace_page *pg;
@@ -1309,6 +1335,13 @@ static struct file_operations ftrace_avail_fops = { 
	.release = ftrace_avail_release,

};



static struct file_operations ftrace_failures_fops = {

	.open = ftrace_failures_open,

	.read = seq_read,

	.llseek = seq_lseek,

	.release = ftrace_avail_release,

};



static struct file_operations ftrace_filter_fops = {

	.open = ftrace_filter_open,

	.read = ftrace_regex_read,
@@ -1386,6 +1419,11 @@ static __init int ftrace_init_debugfs(void) 
		pr_warning("Could not create debugfs "

			   "'available_filter_functions' entry\n");



	entry = debugfs_create_file("failures", 0444,

				    d_tracer, NULL, &ftrace_failures_fops);

	if (!entry)

		pr_warning("Could not create debugfs 'failures' entry\n");



	entry = debugfs_create_file("set_ftrace_filter", 0644, d_tracer,

				    NULL, &ftrace_filter_fops);

	if (!entry)