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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This code exports profiling data as debugfs files to userspace.
4 *
5 * Copyright IBM Corp. 2009
6 * Author(s): Peter Oberparleiter <[email protected]>
7 *
8 * Uses gcc-internal data definitions.
9 * Based on the gcov-kernel patch by:
10 * Hubertus Franke <[email protected]>
11 * Nigel Hinds <[email protected]>
12 * Rajan Ravindran <[email protected]>
13 * Peter Oberparleiter <[email protected]>
14 * Paul Larson
15 * Yi CDL Yang
16 */
17
18#define pr_fmt(fmt) "gcov: " fmt
19
20#include <linux/init.h>
21#include <linux/module.h>
22#include <linux/debugfs.h>
23#include <linux/fs.h>
24#include <linux/list.h>
25#include <linux/string.h>
26#include <linux/slab.h>
27#include <linux/mutex.h>
28#include <linux/seq_file.h>
29#include <linux/mm.h>
30#include "gcov.h"
31
32/**
33 * struct gcov_node - represents a debugfs entry
34 * @list: list head for child node list
35 * @children: child nodes
36 * @all: list head for list of all nodes
37 * @parent: parent node
38 * @loaded_info: array of pointers to profiling data sets for loaded object
39 * files.
40 * @num_loaded: number of profiling data sets for loaded object files.
41 * @unloaded_info: accumulated copy of profiling data sets for unloaded
42 * object files. Used only when gcov_persist=1.
43 * @dentry: main debugfs entry, either a directory or data file
44 * @links: associated symbolic links
45 * @name: data file basename
46 *
47 * struct gcov_node represents an entity within the gcov/ subdirectory
48 * of debugfs. There are directory and data file nodes. The latter represent
49 * the actual synthesized data file plus any associated symbolic links which
50 * are needed by the gcov tool to work correctly.
51 */
52struct gcov_node {
53 struct list_head list;
54 struct list_head children;
55 struct list_head all;
56 struct gcov_node *parent;
57 struct gcov_info **loaded_info;
58 struct gcov_info *unloaded_info;
59 struct dentry *dentry;
60 struct dentry **links;
61 int num_loaded;
62 char name[];
63};
64
65static const char objtree[] = OBJTREE;
66static const char srctree[] = SRCTREE;
67static struct gcov_node root_node;
68static LIST_HEAD(all_head);
69static DEFINE_MUTEX(node_lock);
70
71/* If non-zero, keep copies of profiling data for unloaded modules. */
72static int gcov_persist = 1;
73
74static int __init gcov_persist_setup(char *str)
75{
76 unsigned long val;
77
78 if (kstrtoul(str, 0, &val)) {
79 pr_warn("invalid gcov_persist parameter '%s'\n", str);
80 return 0;
81 }
82 gcov_persist = val;
83 pr_info("setting gcov_persist to %d\n", gcov_persist);
84
85 return 1;
86}
87__setup("gcov_persist=", gcov_persist_setup);
88
89#define ITER_STRIDE PAGE_SIZE
90
91/**
92 * struct gcov_iterator - specifies current file position in logical records
93 * @info: associated profiling data
94 * @buffer: buffer containing file data
95 * @size: size of buffer
96 * @pos: current position in file
97 */
98struct gcov_iterator {
99 struct gcov_info *info;
100 size_t size;
101 loff_t pos;
102 char buffer[] __counted_by(size);
103};
104
105/**
106 * gcov_iter_new - allocate and initialize profiling data iterator
107 * @info: profiling data set to be iterated
108 *
109 * Return file iterator on success, %NULL otherwise.
110 */
111static struct gcov_iterator *gcov_iter_new(struct gcov_info *info)
112{
113 struct gcov_iterator *iter;
114 size_t size;
115
116 /* Dry-run to get the actual buffer size. */
117 size = convert_to_gcda(NULL, info);
118
119 iter = kvmalloc_flex(*iter, buffer, size);
120 if (!iter)
121 return NULL;
122
123 iter->info = info;
124 iter->size = size;
125 convert_to_gcda(iter->buffer, info);
126
127 return iter;
128}
129
130
131/**
132 * gcov_iter_free - free iterator data
133 * @iter: file iterator
134 */
135static void gcov_iter_free(struct gcov_iterator *iter)
136{
137 kvfree(iter);
138}
139
140/**
141 * gcov_iter_get_info - return profiling data set for given file iterator
142 * @iter: file iterator
143 */
144static struct gcov_info *gcov_iter_get_info(struct gcov_iterator *iter)
145{
146 return iter->info;
147}
148
149/**
150 * gcov_iter_start - reset file iterator to starting position
151 * @iter: file iterator
152 */
153static void gcov_iter_start(struct gcov_iterator *iter)
154{
155 iter->pos = 0;
156}
157
158/**
159 * gcov_iter_next - advance file iterator to next logical record
160 * @iter: file iterator
161 *
162 * Return zero if new position is valid, non-zero if iterator has reached end.
163 */
164static int gcov_iter_next(struct gcov_iterator *iter)
165{
166 if (iter->pos < iter->size)
167 iter->pos += ITER_STRIDE;
168
169 if (iter->pos >= iter->size)
170 return -EINVAL;
171
172 return 0;
173}
174
175/**
176 * gcov_iter_write - write data for current pos to seq_file
177 * @iter: file iterator
178 * @seq: seq_file handle
179 *
180 * Return zero on success, non-zero otherwise.
181 */
182static int gcov_iter_write(struct gcov_iterator *iter, struct seq_file *seq)
183{
184 size_t len;
185
186 if (iter->pos >= iter->size)
187 return -EINVAL;
188
189 len = ITER_STRIDE;
190 if (iter->pos + len > iter->size)
191 len = iter->size - iter->pos;
192
193 seq_write(seq, iter->buffer + iter->pos, len);
194
195 return 0;
196}
197
198/*
199 * seq_file.start() implementation for gcov data files. Note that the
200 * gcov_iterator interface is designed to be more restrictive than seq_file
201 * (no start from arbitrary position, etc.), to simplify the iterator
202 * implementation.
203 */
204static void *gcov_seq_start(struct seq_file *seq, loff_t *pos)
205{
206 loff_t i;
207
208 gcov_iter_start(seq->private);
209 for (i = 0; i < *pos; i++) {
210 if (gcov_iter_next(seq->private))
211 return NULL;
212 }
213 return seq->private;
214}
215
216/* seq_file.next() implementation for gcov data files. */
217static void *gcov_seq_next(struct seq_file *seq, void *data, loff_t *pos)
218{
219 struct gcov_iterator *iter = data;
220
221 (*pos)++;
222 if (gcov_iter_next(iter))
223 return NULL;
224
225 return iter;
226}
227
228/* seq_file.show() implementation for gcov data files. */
229static int gcov_seq_show(struct seq_file *seq, void *data)
230{
231 struct gcov_iterator *iter = data;
232
233 if (gcov_iter_write(iter, seq))
234 return -EINVAL;
235 return 0;
236}
237
238static void gcov_seq_stop(struct seq_file *seq, void *data)
239{
240 /* Unused. */
241}
242
243static const struct seq_operations gcov_seq_ops = {
244 .start = gcov_seq_start,
245 .next = gcov_seq_next,
246 .show = gcov_seq_show,
247 .stop = gcov_seq_stop,
248};
249
250/*
251 * Return a profiling data set associated with the given node. This is
252 * either a data set for a loaded object file or a data set copy in case
253 * all associated object files have been unloaded.
254 */
255static struct gcov_info *get_node_info(struct gcov_node *node)
256{
257 if (node->num_loaded > 0)
258 return node->loaded_info[0];
259
260 return node->unloaded_info;
261}
262
263/*
264 * Return a newly allocated profiling data set which contains the sum of
265 * all profiling data associated with the given node.
266 */
267static struct gcov_info *get_accumulated_info(struct gcov_node *node)
268{
269 struct gcov_info *info;
270 int i = 0;
271
272 if (node->unloaded_info)
273 info = gcov_info_dup(node->unloaded_info);
274 else
275 info = gcov_info_dup(node->loaded_info[i++]);
276 if (!info)
277 return NULL;
278 for (; i < node->num_loaded; i++)
279 gcov_info_add(info, node->loaded_info[i]);
280
281 return info;
282}
283
284/*
285 * open() implementation for gcov data files. Create a copy of the profiling
286 * data set and initialize the iterator and seq_file interface.
287 */
288static int gcov_seq_open(struct inode *inode, struct file *file)
289{
290 struct gcov_node *node = inode->i_private;
291 struct gcov_iterator *iter;
292 struct seq_file *seq;
293 struct gcov_info *info;
294 int rc = -ENOMEM;
295
296 mutex_lock(&node_lock);
297 /*
298 * Read from a profiling data copy to minimize reference tracking
299 * complexity and concurrent access and to keep accumulating multiple
300 * profiling data sets associated with one node simple.
301 */
302 info = get_accumulated_info(node);
303 if (!info)
304 goto out_unlock;
305 iter = gcov_iter_new(info);
306 if (!iter)
307 goto err_free_info;
308 rc = seq_open(file, &gcov_seq_ops);
309 if (rc)
310 goto err_free_iter_info;
311 seq = file->private_data;
312 seq->private = iter;
313out_unlock:
314 mutex_unlock(&node_lock);
315 return rc;
316
317err_free_iter_info:
318 gcov_iter_free(iter);
319err_free_info:
320 gcov_info_free(info);
321 goto out_unlock;
322}
323
324/*
325 * release() implementation for gcov data files. Release resources allocated
326 * by open().
327 */
328static int gcov_seq_release(struct inode *inode, struct file *file)
329{
330 struct gcov_iterator *iter;
331 struct gcov_info *info;
332 struct seq_file *seq;
333
334 seq = file->private_data;
335 iter = seq->private;
336 info = gcov_iter_get_info(iter);
337 gcov_iter_free(iter);
338 gcov_info_free(info);
339 seq_release(inode, file);
340
341 return 0;
342}
343
344/*
345 * Find a node by the associated data file name. Needs to be called with
346 * node_lock held.
347 */
348static struct gcov_node *get_node_by_name(const char *name)
349{
350 struct gcov_node *node;
351 struct gcov_info *info;
352
353 list_for_each_entry(node, &all_head, all) {
354 info = get_node_info(node);
355 if (info && (strcmp(gcov_info_filename(info), name) == 0))
356 return node;
357 }
358
359 return NULL;
360}
361
362/*
363 * Reset all profiling data associated with the specified node.
364 */
365static void reset_node(struct gcov_node *node)
366{
367 int i;
368
369 if (node->unloaded_info)
370 gcov_info_reset(node->unloaded_info);
371 for (i = 0; i < node->num_loaded; i++)
372 gcov_info_reset(node->loaded_info[i]);
373}
374
375static void remove_node(struct gcov_node *node);
376
377/*
378 * write() implementation for gcov data files. Reset profiling data for the
379 * corresponding file. If all associated object files have been unloaded,
380 * remove the debug fs node as well.
381 */
382static ssize_t gcov_seq_write(struct file *file, const char __user *addr,
383 size_t len, loff_t *pos)
384{
385 struct seq_file *seq;
386 struct gcov_info *info;
387 struct gcov_node *node;
388
389 seq = file->private_data;
390 info = gcov_iter_get_info(seq->private);
391 mutex_lock(&node_lock);
392 node = get_node_by_name(gcov_info_filename(info));
393 if (node) {
394 /* Reset counts or remove node for unloaded modules. */
395 if (node->num_loaded == 0)
396 remove_node(node);
397 else
398 reset_node(node);
399 }
400 /* Reset counts for open file. */
401 gcov_info_reset(info);
402 mutex_unlock(&node_lock);
403
404 return len;
405}
406
407/*
408 * Given a string <path> representing a file path of format:
409 * path/to/file.gcda
410 * construct and return a new string:
411 * <dir/>path/to/file.<ext>
412 */
413static char *link_target(const char *dir, const char *path, const char *ext)
414{
415 char *target;
416 char *old_ext;
417 char *copy;
418
419 copy = kstrdup(path, GFP_KERNEL);
420 if (!copy)
421 return NULL;
422 old_ext = strrchr(copy, '.');
423 if (old_ext)
424 *old_ext = '\0';
425 if (dir)
426 target = kasprintf(GFP_KERNEL, "%s/%s.%s", dir, copy, ext);
427 else
428 target = kasprintf(GFP_KERNEL, "%s.%s", copy, ext);
429 kfree(copy);
430
431 return target;
432}
433
434/*
435 * Construct a string representing the symbolic link target for the given
436 * gcov data file name and link type. Depending on the link type and the
437 * location of the data file, the link target can either point to a
438 * subdirectory of srctree, objtree or in an external location.
439 */
440static char *get_link_target(const char *filename, const struct gcov_link *ext)
441{
442 const char *rel;
443 char *result;
444
445 if (strncmp(filename, objtree, strlen(objtree)) == 0) {
446 rel = filename + strlen(objtree) + 1;
447 if (ext->dir == SRC_TREE)
448 result = link_target(srctree, rel, ext->ext);
449 else
450 result = link_target(objtree, rel, ext->ext);
451 } else {
452 /* External compilation. */
453 result = link_target(NULL, filename, ext->ext);
454 }
455
456 return result;
457}
458
459#define SKEW_PREFIX ".tmp_"
460
461/*
462 * For a filename .tmp_filename.ext return filename.ext. Needed to compensate
463 * for filename skewing caused by the mod-versioning mechanism.
464 */
465static const char *deskew(const char *basename)
466{
467 if (strncmp(basename, SKEW_PREFIX, sizeof(SKEW_PREFIX) - 1) == 0)
468 return basename + sizeof(SKEW_PREFIX) - 1;
469 return basename;
470}
471
472/*
473 * Create links to additional files (usually .c and .gcno files) which the
474 * gcov tool expects to find in the same directory as the gcov data file.
475 */
476static void add_links(struct gcov_node *node, struct dentry *parent)
477{
478 const char *basename;
479 char *target;
480 int num;
481 int i;
482
483 for (num = 0; gcov_link[num].ext; num++)
484 /* Nothing. */;
485 node->links = kzalloc_objs(struct dentry *, num);
486 if (!node->links)
487 return;
488 for (i = 0; i < num; i++) {
489 target = get_link_target(
490 gcov_info_filename(get_node_info(node)),
491 &gcov_link[i]);
492 if (!target)
493 goto out_err;
494 basename = kbasename(target);
495 if (basename == target)
496 goto out_err;
497 node->links[i] = debugfs_create_symlink(deskew(basename),
498 parent, target);
499 kfree(target);
500 }
501
502 return;
503out_err:
504 kfree(target);
505 while (i-- > 0)
506 debugfs_remove(node->links[i]);
507 kfree(node->links);
508 node->links = NULL;
509}
510
511static const struct file_operations gcov_data_fops = {
512 .open = gcov_seq_open,
513 .release = gcov_seq_release,
514 .read = seq_read,
515 .llseek = seq_lseek,
516 .write = gcov_seq_write,
517};
518
519/* Basic initialization of a new node. */
520static void init_node(struct gcov_node *node, struct gcov_info *info,
521 const char *name, struct gcov_node *parent)
522{
523 INIT_LIST_HEAD(&node->list);
524 INIT_LIST_HEAD(&node->children);
525 INIT_LIST_HEAD(&node->all);
526 if (node->loaded_info) {
527 node->loaded_info[0] = info;
528 node->num_loaded = 1;
529 }
530 node->parent = parent;
531 if (name)
532 strcpy(node->name, name);
533}
534
535/*
536 * Create a new node and associated debugfs entry. Needs to be called with
537 * node_lock held.
538 */
539static struct gcov_node *new_node(struct gcov_node *parent,
540 struct gcov_info *info, const char *name)
541{
542 struct gcov_node *node;
543
544 node = kzalloc(sizeof(struct gcov_node) + strlen(name) + 1, GFP_KERNEL);
545 if (!node)
546 goto err_nomem;
547 if (info) {
548 node->loaded_info = kzalloc_objs(struct gcov_info *, 1);
549 if (!node->loaded_info)
550 goto err_nomem;
551 }
552 init_node(node, info, name, parent);
553 /* Differentiate between gcov data file nodes and directory nodes. */
554 if (info) {
555 node->dentry = debugfs_create_file(deskew(node->name), 0600,
556 parent->dentry, node, &gcov_data_fops);
557 } else
558 node->dentry = debugfs_create_dir(node->name, parent->dentry);
559 if (info)
560 add_links(node, parent->dentry);
561 list_add(&node->list, &parent->children);
562 list_add(&node->all, &all_head);
563
564 return node;
565
566err_nomem:
567 kfree(node);
568 pr_warn("out of memory\n");
569 return NULL;
570}
571
572/* Remove symbolic links associated with node. */
573static void remove_links(struct gcov_node *node)
574{
575 int i;
576
577 if (!node->links)
578 return;
579 for (i = 0; gcov_link[i].ext; i++)
580 debugfs_remove(node->links[i]);
581 kfree(node->links);
582 node->links = NULL;
583}
584
585/*
586 * Remove node from all lists and debugfs and release associated resources.
587 * Needs to be called with node_lock held.
588 */
589static void release_node(struct gcov_node *node)
590{
591 list_del(&node->list);
592 list_del(&node->all);
593 debugfs_remove(node->dentry);
594 remove_links(node);
595 kfree(node->loaded_info);
596 if (node->unloaded_info)
597 gcov_info_free(node->unloaded_info);
598 kfree(node);
599}
600
601/* Release node and empty parents. Needs to be called with node_lock held. */
602static void remove_node(struct gcov_node *node)
603{
604 struct gcov_node *parent;
605
606 while ((node != &root_node) && list_empty(&node->children)) {
607 parent = node->parent;
608 release_node(node);
609 node = parent;
610 }
611}
612
613/*
614 * Find child node with given basename. Needs to be called with node_lock
615 * held.
616 */
617static struct gcov_node *get_child_by_name(struct gcov_node *parent,
618 const char *name)
619{
620 struct gcov_node *node;
621
622 list_for_each_entry(node, &parent->children, list) {
623 if (strcmp(node->name, name) == 0)
624 return node;
625 }
626
627 return NULL;
628}
629
630/*
631 * write() implementation for reset file. Reset all profiling data to zero
632 * and remove nodes for which all associated object files are unloaded.
633 */
634static ssize_t reset_write(struct file *file, const char __user *addr,
635 size_t len, loff_t *pos)
636{
637 struct gcov_node *node;
638
639 mutex_lock(&node_lock);
640restart:
641 list_for_each_entry(node, &all_head, all) {
642 if (node->num_loaded > 0)
643 reset_node(node);
644 else if (list_empty(&node->children)) {
645 remove_node(node);
646 /* Several nodes may have gone - restart loop. */
647 goto restart;
648 }
649 }
650 mutex_unlock(&node_lock);
651
652 return len;
653}
654
655/* read() implementation for reset file. Unused. */
656static ssize_t reset_read(struct file *file, char __user *addr, size_t len,
657 loff_t *pos)
658{
659 /* Allow read operation so that a recursive copy won't fail. */
660 return 0;
661}
662
663static const struct file_operations gcov_reset_fops = {
664 .write = reset_write,
665 .read = reset_read,
666 .llseek = noop_llseek,
667};
668
669/*
670 * Create a node for a given profiling data set and add it to all lists and
671 * debugfs. Needs to be called with node_lock held.
672 */
673static void add_node(struct gcov_info *info)
674{
675 char *filename;
676 char *curr;
677 char *next;
678 struct gcov_node *parent;
679 struct gcov_node *node;
680
681 filename = kstrdup(gcov_info_filename(info), GFP_KERNEL);
682 if (!filename)
683 return;
684 parent = &root_node;
685 /* Create directory nodes along the path. */
686 for (curr = filename; (next = strchr(curr, '/')); curr = next + 1) {
687 if (curr == next)
688 continue;
689 *next = 0;
690 if (strcmp(curr, ".") == 0)
691 continue;
692 if (strcmp(curr, "..") == 0) {
693 if (!parent->parent)
694 goto err_remove;
695 parent = parent->parent;
696 continue;
697 }
698 node = get_child_by_name(parent, curr);
699 if (!node) {
700 node = new_node(parent, NULL, curr);
701 if (!node)
702 goto err_remove;
703 }
704 parent = node;
705 }
706 /* Create file node. */
707 node = new_node(parent, info, curr);
708 if (!node)
709 goto err_remove;
710out:
711 kfree(filename);
712 return;
713
714err_remove:
715 remove_node(parent);
716 goto out;
717}
718
719/*
720 * Associate a profiling data set with an existing node. Needs to be called
721 * with node_lock held.
722 */
723static void add_info(struct gcov_node *node, struct gcov_info *info)
724{
725 struct gcov_info **loaded_info;
726 int num = node->num_loaded;
727
728 /*
729 * Prepare new array. This is done first to simplify cleanup in
730 * case the new data set is incompatible, the node only contains
731 * unloaded data sets and there's not enough memory for the array.
732 */
733 loaded_info = kzalloc_objs(struct gcov_info *, num + 1);
734 if (!loaded_info) {
735 pr_warn("could not add '%s' (out of memory)\n",
736 gcov_info_filename(info));
737 return;
738 }
739 memcpy(loaded_info, node->loaded_info,
740 num * sizeof(struct gcov_info *));
741 loaded_info[num] = info;
742 /* Check if the new data set is compatible. */
743 if (num == 0) {
744 /*
745 * A module was unloaded, modified and reloaded. The new
746 * data set replaces the copy of the last one.
747 */
748 if (!gcov_info_is_compatible(node->unloaded_info, info)) {
749 pr_warn("discarding saved data for %s "
750 "(incompatible version)\n",
751 gcov_info_filename(info));
752 gcov_info_free(node->unloaded_info);
753 node->unloaded_info = NULL;
754 }
755 } else {
756 /*
757 * Two different versions of the same object file are loaded.
758 * The initial one takes precedence.
759 */
760 if (!gcov_info_is_compatible(node->loaded_info[0], info)) {
761 pr_warn("could not add '%s' (incompatible "
762 "version)\n", gcov_info_filename(info));
763 kfree(loaded_info);
764 return;
765 }
766 }
767 /* Overwrite previous array. */
768 kfree(node->loaded_info);
769 node->loaded_info = loaded_info;
770 node->num_loaded = num + 1;
771}
772
773/*
774 * Return the index of a profiling data set associated with a node.
775 */
776static int get_info_index(struct gcov_node *node, struct gcov_info *info)
777{
778 int i;
779
780 for (i = 0; i < node->num_loaded; i++) {
781 if (node->loaded_info[i] == info)
782 return i;
783 }
784 return -ENOENT;
785}
786
787/*
788 * Save the data of a profiling data set which is being unloaded.
789 */
790static void save_info(struct gcov_node *node, struct gcov_info *info)
791{
792 if (node->unloaded_info)
793 gcov_info_add(node->unloaded_info, info);
794 else {
795 node->unloaded_info = gcov_info_dup(info);
796 if (!node->unloaded_info) {
797 pr_warn("could not save data for '%s' "
798 "(out of memory)\n",
799 gcov_info_filename(info));
800 }
801 }
802}
803
804/*
805 * Disassociate a profiling data set from a node. Needs to be called with
806 * node_lock held.
807 */
808static void remove_info(struct gcov_node *node, struct gcov_info *info)
809{
810 int i;
811
812 i = get_info_index(node, info);
813 if (i < 0) {
814 pr_warn("could not remove '%s' (not found)\n",
815 gcov_info_filename(info));
816 return;
817 }
818 if (gcov_persist)
819 save_info(node, info);
820 /* Shrink array. */
821 node->loaded_info[i] = node->loaded_info[node->num_loaded - 1];
822 node->num_loaded--;
823 if (node->num_loaded > 0)
824 return;
825 /* Last loaded data set was removed. */
826 kfree(node->loaded_info);
827 node->loaded_info = NULL;
828 node->num_loaded = 0;
829 if (!node->unloaded_info)
830 remove_node(node);
831}
832
833/*
834 * Callback to create/remove profiling files when code compiled with
835 * -fprofile-arcs is loaded/unloaded.
836 */
837void gcov_event(enum gcov_action action, struct gcov_info *info)
838{
839 struct gcov_node *node;
840
841 mutex_lock(&node_lock);
842 node = get_node_by_name(gcov_info_filename(info));
843 switch (action) {
844 case GCOV_ADD:
845 if (node)
846 add_info(node, info);
847 else
848 add_node(info);
849 break;
850 case GCOV_REMOVE:
851 if (node)
852 remove_info(node, info);
853 else {
854 pr_warn("could not remove '%s' (not found)\n",
855 gcov_info_filename(info));
856 }
857 break;
858 }
859 mutex_unlock(&node_lock);
860}
861
862/* Create debugfs entries. */
863static __init int gcov_fs_init(void)
864{
865 init_node(&root_node, NULL, NULL, NULL);
866 /*
867 * /sys/kernel/debug/gcov will be parent for the reset control file
868 * and all profiling files.
869 */
870 root_node.dentry = debugfs_create_dir("gcov", NULL);
871 /*
872 * Create reset file which resets all profiling counts when written
873 * to.
874 */
875 debugfs_create_file("reset", 0600, root_node.dentry, NULL,
876 &gcov_reset_fops);
877 /* Replay previous events to get our fs hierarchy up-to-date. */
878 gcov_enable_events();
879 return 0;
880}
881device_initcall(gcov_fs_init);