xref: /openbmc/linux/kernel/gcov/fs.c (revision 0a671dc5)
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 <oberpar@linux.vnet.ibm.com>
7   *
8   *    Uses gcc-internal data definitions.
9   *    Based on the gcov-kernel patch by:
10   *		 Hubertus Franke <frankeh@us.ibm.com>
11   *		 Nigel Hinds <nhinds@us.ibm.com>
12   *		 Rajan Ravindran <rajancr@us.ibm.com>
13   *		 Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
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 "gcov.h"
30  
31  /**
32   * struct gcov_node - represents a debugfs entry
33   * @list: list head for child node list
34   * @children: child nodes
35   * @all: list head for list of all nodes
36   * @parent: parent node
37   * @loaded_info: array of pointers to profiling data sets for loaded object
38   *   files.
39   * @num_loaded: number of profiling data sets for loaded object files.
40   * @unloaded_info: accumulated copy of profiling data sets for unloaded
41   *   object files. Used only when gcov_persist=1.
42   * @dentry: main debugfs entry, either a directory or data file
43   * @links: associated symbolic links
44   * @name: data file basename
45   *
46   * struct gcov_node represents an entity within the gcov/ subdirectory
47   * of debugfs. There are directory and data file nodes. The latter represent
48   * the actual synthesized data file plus any associated symbolic links which
49   * are needed by the gcov tool to work correctly.
50   */
51  struct gcov_node {
52  	struct list_head list;
53  	struct list_head children;
54  	struct list_head all;
55  	struct gcov_node *parent;
56  	struct gcov_info **loaded_info;
57  	struct gcov_info *unloaded_info;
58  	struct dentry *dentry;
59  	struct dentry **links;
60  	int num_loaded;
61  	char name[0];
62  };
63  
64  static const char objtree[] = OBJTREE;
65  static const char srctree[] = SRCTREE;
66  static struct gcov_node root_node;
67  static LIST_HEAD(all_head);
68  static DEFINE_MUTEX(node_lock);
69  
70  /* If non-zero, keep copies of profiling data for unloaded modules. */
71  static int gcov_persist = 1;
72  
73  static int __init gcov_persist_setup(char *str)
74  {
75  	unsigned long val;
76  
77  	if (kstrtoul(str, 0, &val)) {
78  		pr_warn("invalid gcov_persist parameter '%s'\n", str);
79  		return 0;
80  	}
81  	gcov_persist = val;
82  	pr_info("setting gcov_persist to %d\n", gcov_persist);
83  
84  	return 1;
85  }
86  __setup("gcov_persist=", gcov_persist_setup);
87  
88  /*
89   * seq_file.start() implementation for gcov data files. Note that the
90   * gcov_iterator interface is designed to be more restrictive than seq_file
91   * (no start from arbitrary position, etc.), to simplify the iterator
92   * implementation.
93   */
94  static void *gcov_seq_start(struct seq_file *seq, loff_t *pos)
95  {
96  	loff_t i;
97  
98  	gcov_iter_start(seq->private);
99  	for (i = 0; i < *pos; i++) {
100  		if (gcov_iter_next(seq->private))
101  			return NULL;
102  	}
103  	return seq->private;
104  }
105  
106  /* seq_file.next() implementation for gcov data files. */
107  static void *gcov_seq_next(struct seq_file *seq, void *data, loff_t *pos)
108  {
109  	struct gcov_iterator *iter = data;
110  
111  	if (gcov_iter_next(iter))
112  		return NULL;
113  	(*pos)++;
114  
115  	return iter;
116  }
117  
118  /* seq_file.show() implementation for gcov data files. */
119  static int gcov_seq_show(struct seq_file *seq, void *data)
120  {
121  	struct gcov_iterator *iter = data;
122  
123  	if (gcov_iter_write(iter, seq))
124  		return -EINVAL;
125  	return 0;
126  }
127  
128  static void gcov_seq_stop(struct seq_file *seq, void *data)
129  {
130  	/* Unused. */
131  }
132  
133  static const struct seq_operations gcov_seq_ops = {
134  	.start	= gcov_seq_start,
135  	.next	= gcov_seq_next,
136  	.show	= gcov_seq_show,
137  	.stop	= gcov_seq_stop,
138  };
139  
140  /*
141   * Return a profiling data set associated with the given node. This is
142   * either a data set for a loaded object file or a data set copy in case
143   * all associated object files have been unloaded.
144   */
145  static struct gcov_info *get_node_info(struct gcov_node *node)
146  {
147  	if (node->num_loaded > 0)
148  		return node->loaded_info[0];
149  
150  	return node->unloaded_info;
151  }
152  
153  /*
154   * Return a newly allocated profiling data set which contains the sum of
155   * all profiling data associated with the given node.
156   */
157  static struct gcov_info *get_accumulated_info(struct gcov_node *node)
158  {
159  	struct gcov_info *info;
160  	int i = 0;
161  
162  	if (node->unloaded_info)
163  		info = gcov_info_dup(node->unloaded_info);
164  	else
165  		info = gcov_info_dup(node->loaded_info[i++]);
166  	if (!info)
167  		return NULL;
168  	for (; i < node->num_loaded; i++)
169  		gcov_info_add(info, node->loaded_info[i]);
170  
171  	return info;
172  }
173  
174  /*
175   * open() implementation for gcov data files. Create a copy of the profiling
176   * data set and initialize the iterator and seq_file interface.
177   */
178  static int gcov_seq_open(struct inode *inode, struct file *file)
179  {
180  	struct gcov_node *node = inode->i_private;
181  	struct gcov_iterator *iter;
182  	struct seq_file *seq;
183  	struct gcov_info *info;
184  	int rc = -ENOMEM;
185  
186  	mutex_lock(&node_lock);
187  	/*
188  	 * Read from a profiling data copy to minimize reference tracking
189  	 * complexity and concurrent access and to keep accumulating multiple
190  	 * profiling data sets associated with one node simple.
191  	 */
192  	info = get_accumulated_info(node);
193  	if (!info)
194  		goto out_unlock;
195  	iter = gcov_iter_new(info);
196  	if (!iter)
197  		goto err_free_info;
198  	rc = seq_open(file, &gcov_seq_ops);
199  	if (rc)
200  		goto err_free_iter_info;
201  	seq = file->private_data;
202  	seq->private = iter;
203  out_unlock:
204  	mutex_unlock(&node_lock);
205  	return rc;
206  
207  err_free_iter_info:
208  	gcov_iter_free(iter);
209  err_free_info:
210  	gcov_info_free(info);
211  	goto out_unlock;
212  }
213  
214  /*
215   * release() implementation for gcov data files. Release resources allocated
216   * by open().
217   */
218  static int gcov_seq_release(struct inode *inode, struct file *file)
219  {
220  	struct gcov_iterator *iter;
221  	struct gcov_info *info;
222  	struct seq_file *seq;
223  
224  	seq = file->private_data;
225  	iter = seq->private;
226  	info = gcov_iter_get_info(iter);
227  	gcov_iter_free(iter);
228  	gcov_info_free(info);
229  	seq_release(inode, file);
230  
231  	return 0;
232  }
233  
234  /*
235   * Find a node by the associated data file name. Needs to be called with
236   * node_lock held.
237   */
238  static struct gcov_node *get_node_by_name(const char *name)
239  {
240  	struct gcov_node *node;
241  	struct gcov_info *info;
242  
243  	list_for_each_entry(node, &all_head, all) {
244  		info = get_node_info(node);
245  		if (info && (strcmp(gcov_info_filename(info), name) == 0))
246  			return node;
247  	}
248  
249  	return NULL;
250  }
251  
252  /*
253   * Reset all profiling data associated with the specified node.
254   */
255  static void reset_node(struct gcov_node *node)
256  {
257  	int i;
258  
259  	if (node->unloaded_info)
260  		gcov_info_reset(node->unloaded_info);
261  	for (i = 0; i < node->num_loaded; i++)
262  		gcov_info_reset(node->loaded_info[i]);
263  }
264  
265  static void remove_node(struct gcov_node *node);
266  
267  /*
268   * write() implementation for gcov data files. Reset profiling data for the
269   * corresponding file. If all associated object files have been unloaded,
270   * remove the debug fs node as well.
271   */
272  static ssize_t gcov_seq_write(struct file *file, const char __user *addr,
273  			      size_t len, loff_t *pos)
274  {
275  	struct seq_file *seq;
276  	struct gcov_info *info;
277  	struct gcov_node *node;
278  
279  	seq = file->private_data;
280  	info = gcov_iter_get_info(seq->private);
281  	mutex_lock(&node_lock);
282  	node = get_node_by_name(gcov_info_filename(info));
283  	if (node) {
284  		/* Reset counts or remove node for unloaded modules. */
285  		if (node->num_loaded == 0)
286  			remove_node(node);
287  		else
288  			reset_node(node);
289  	}
290  	/* Reset counts for open file. */
291  	gcov_info_reset(info);
292  	mutex_unlock(&node_lock);
293  
294  	return len;
295  }
296  
297  /*
298   * Given a string <path> representing a file path of format:
299   *   path/to/file.gcda
300   * construct and return a new string:
301   *   <dir/>path/to/file.<ext>
302   */
303  static char *link_target(const char *dir, const char *path, const char *ext)
304  {
305  	char *target;
306  	char *old_ext;
307  	char *copy;
308  
309  	copy = kstrdup(path, GFP_KERNEL);
310  	if (!copy)
311  		return NULL;
312  	old_ext = strrchr(copy, '.');
313  	if (old_ext)
314  		*old_ext = '\0';
315  	if (dir)
316  		target = kasprintf(GFP_KERNEL, "%s/%s.%s", dir, copy, ext);
317  	else
318  		target = kasprintf(GFP_KERNEL, "%s.%s", copy, ext);
319  	kfree(copy);
320  
321  	return target;
322  }
323  
324  /*
325   * Construct a string representing the symbolic link target for the given
326   * gcov data file name and link type. Depending on the link type and the
327   * location of the data file, the link target can either point to a
328   * subdirectory of srctree, objtree or in an external location.
329   */
330  static char *get_link_target(const char *filename, const struct gcov_link *ext)
331  {
332  	const char *rel;
333  	char *result;
334  
335  	if (strncmp(filename, objtree, strlen(objtree)) == 0) {
336  		rel = filename + strlen(objtree) + 1;
337  		if (ext->dir == SRC_TREE)
338  			result = link_target(srctree, rel, ext->ext);
339  		else
340  			result = link_target(objtree, rel, ext->ext);
341  	} else {
342  		/* External compilation. */
343  		result = link_target(NULL, filename, ext->ext);
344  	}
345  
346  	return result;
347  }
348  
349  #define SKEW_PREFIX	".tmp_"
350  
351  /*
352   * For a filename .tmp_filename.ext return filename.ext. Needed to compensate
353   * for filename skewing caused by the mod-versioning mechanism.
354   */
355  static const char *deskew(const char *basename)
356  {
357  	if (strncmp(basename, SKEW_PREFIX, sizeof(SKEW_PREFIX) - 1) == 0)
358  		return basename + sizeof(SKEW_PREFIX) - 1;
359  	return basename;
360  }
361  
362  /*
363   * Create links to additional files (usually .c and .gcno files) which the
364   * gcov tool expects to find in the same directory as the gcov data file.
365   */
366  static void add_links(struct gcov_node *node, struct dentry *parent)
367  {
368  	const char *basename;
369  	char *target;
370  	int num;
371  	int i;
372  
373  	for (num = 0; gcov_link[num].ext; num++)
374  		/* Nothing. */;
375  	node->links = kcalloc(num, sizeof(struct dentry *), GFP_KERNEL);
376  	if (!node->links)
377  		return;
378  	for (i = 0; i < num; i++) {
379  		target = get_link_target(
380  				gcov_info_filename(get_node_info(node)),
381  				&gcov_link[i]);
382  		if (!target)
383  			goto out_err;
384  		basename = kbasename(target);
385  		if (basename == target)
386  			goto out_err;
387  		node->links[i] = debugfs_create_symlink(deskew(basename),
388  							parent,	target);
389  		kfree(target);
390  	}
391  
392  	return;
393  out_err:
394  	kfree(target);
395  	while (i-- > 0)
396  		debugfs_remove(node->links[i]);
397  	kfree(node->links);
398  	node->links = NULL;
399  }
400  
401  static const struct file_operations gcov_data_fops = {
402  	.open		= gcov_seq_open,
403  	.release	= gcov_seq_release,
404  	.read		= seq_read,
405  	.llseek		= seq_lseek,
406  	.write		= gcov_seq_write,
407  };
408  
409  /* Basic initialization of a new node. */
410  static void init_node(struct gcov_node *node, struct gcov_info *info,
411  		      const char *name, struct gcov_node *parent)
412  {
413  	INIT_LIST_HEAD(&node->list);
414  	INIT_LIST_HEAD(&node->children);
415  	INIT_LIST_HEAD(&node->all);
416  	if (node->loaded_info) {
417  		node->loaded_info[0] = info;
418  		node->num_loaded = 1;
419  	}
420  	node->parent = parent;
421  	if (name)
422  		strcpy(node->name, name);
423  }
424  
425  /*
426   * Create a new node and associated debugfs entry. Needs to be called with
427   * node_lock held.
428   */
429  static struct gcov_node *new_node(struct gcov_node *parent,
430  				  struct gcov_info *info, const char *name)
431  {
432  	struct gcov_node *node;
433  
434  	node = kzalloc(sizeof(struct gcov_node) + strlen(name) + 1, GFP_KERNEL);
435  	if (!node)
436  		goto err_nomem;
437  	if (info) {
438  		node->loaded_info = kcalloc(1, sizeof(struct gcov_info *),
439  					   GFP_KERNEL);
440  		if (!node->loaded_info)
441  			goto err_nomem;
442  	}
443  	init_node(node, info, name, parent);
444  	/* Differentiate between gcov data file nodes and directory nodes. */
445  	if (info) {
446  		node->dentry = debugfs_create_file(deskew(node->name), 0600,
447  					parent->dentry, node, &gcov_data_fops);
448  	} else
449  		node->dentry = debugfs_create_dir(node->name, parent->dentry);
450  	if (info)
451  		add_links(node, parent->dentry);
452  	list_add(&node->list, &parent->children);
453  	list_add(&node->all, &all_head);
454  
455  	return node;
456  
457  err_nomem:
458  	kfree(node);
459  	pr_warn("out of memory\n");
460  	return NULL;
461  }
462  
463  /* Remove symbolic links associated with node. */
464  static void remove_links(struct gcov_node *node)
465  {
466  	int i;
467  
468  	if (!node->links)
469  		return;
470  	for (i = 0; gcov_link[i].ext; i++)
471  		debugfs_remove(node->links[i]);
472  	kfree(node->links);
473  	node->links = NULL;
474  }
475  
476  /*
477   * Remove node from all lists and debugfs and release associated resources.
478   * Needs to be called with node_lock held.
479   */
480  static void release_node(struct gcov_node *node)
481  {
482  	list_del(&node->list);
483  	list_del(&node->all);
484  	debugfs_remove(node->dentry);
485  	remove_links(node);
486  	kfree(node->loaded_info);
487  	if (node->unloaded_info)
488  		gcov_info_free(node->unloaded_info);
489  	kfree(node);
490  }
491  
492  /* Release node and empty parents. Needs to be called with node_lock held. */
493  static void remove_node(struct gcov_node *node)
494  {
495  	struct gcov_node *parent;
496  
497  	while ((node != &root_node) && list_empty(&node->children)) {
498  		parent = node->parent;
499  		release_node(node);
500  		node = parent;
501  	}
502  }
503  
504  /*
505   * Find child node with given basename. Needs to be called with node_lock
506   * held.
507   */
508  static struct gcov_node *get_child_by_name(struct gcov_node *parent,
509  					   const char *name)
510  {
511  	struct gcov_node *node;
512  
513  	list_for_each_entry(node, &parent->children, list) {
514  		if (strcmp(node->name, name) == 0)
515  			return node;
516  	}
517  
518  	return NULL;
519  }
520  
521  /*
522   * write() implementation for reset file. Reset all profiling data to zero
523   * and remove nodes for which all associated object files are unloaded.
524   */
525  static ssize_t reset_write(struct file *file, const char __user *addr,
526  			   size_t len, loff_t *pos)
527  {
528  	struct gcov_node *node;
529  
530  	mutex_lock(&node_lock);
531  restart:
532  	list_for_each_entry(node, &all_head, all) {
533  		if (node->num_loaded > 0)
534  			reset_node(node);
535  		else if (list_empty(&node->children)) {
536  			remove_node(node);
537  			/* Several nodes may have gone - restart loop. */
538  			goto restart;
539  		}
540  	}
541  	mutex_unlock(&node_lock);
542  
543  	return len;
544  }
545  
546  /* read() implementation for reset file. Unused. */
547  static ssize_t reset_read(struct file *file, char __user *addr, size_t len,
548  			  loff_t *pos)
549  {
550  	/* Allow read operation so that a recursive copy won't fail. */
551  	return 0;
552  }
553  
554  static const struct file_operations gcov_reset_fops = {
555  	.write	= reset_write,
556  	.read	= reset_read,
557  	.llseek = noop_llseek,
558  };
559  
560  /*
561   * Create a node for a given profiling data set and add it to all lists and
562   * debugfs. Needs to be called with node_lock held.
563   */
564  static void add_node(struct gcov_info *info)
565  {
566  	char *filename;
567  	char *curr;
568  	char *next;
569  	struct gcov_node *parent;
570  	struct gcov_node *node;
571  
572  	filename = kstrdup(gcov_info_filename(info), GFP_KERNEL);
573  	if (!filename)
574  		return;
575  	parent = &root_node;
576  	/* Create directory nodes along the path. */
577  	for (curr = filename; (next = strchr(curr, '/')); curr = next + 1) {
578  		if (curr == next)
579  			continue;
580  		*next = 0;
581  		if (strcmp(curr, ".") == 0)
582  			continue;
583  		if (strcmp(curr, "..") == 0) {
584  			if (!parent->parent)
585  				goto err_remove;
586  			parent = parent->parent;
587  			continue;
588  		}
589  		node = get_child_by_name(parent, curr);
590  		if (!node) {
591  			node = new_node(parent, NULL, curr);
592  			if (!node)
593  				goto err_remove;
594  		}
595  		parent = node;
596  	}
597  	/* Create file node. */
598  	node = new_node(parent, info, curr);
599  	if (!node)
600  		goto err_remove;
601  out:
602  	kfree(filename);
603  	return;
604  
605  err_remove:
606  	remove_node(parent);
607  	goto out;
608  }
609  
610  /*
611   * Associate a profiling data set with an existing node. Needs to be called
612   * with node_lock held.
613   */
614  static void add_info(struct gcov_node *node, struct gcov_info *info)
615  {
616  	struct gcov_info **loaded_info;
617  	int num = node->num_loaded;
618  
619  	/*
620  	 * Prepare new array. This is done first to simplify cleanup in
621  	 * case the new data set is incompatible, the node only contains
622  	 * unloaded data sets and there's not enough memory for the array.
623  	 */
624  	loaded_info = kcalloc(num + 1, sizeof(struct gcov_info *), GFP_KERNEL);
625  	if (!loaded_info) {
626  		pr_warn("could not add '%s' (out of memory)\n",
627  			gcov_info_filename(info));
628  		return;
629  	}
630  	memcpy(loaded_info, node->loaded_info,
631  	       num * sizeof(struct gcov_info *));
632  	loaded_info[num] = info;
633  	/* Check if the new data set is compatible. */
634  	if (num == 0) {
635  		/*
636  		 * A module was unloaded, modified and reloaded. The new
637  		 * data set replaces the copy of the last one.
638  		 */
639  		if (!gcov_info_is_compatible(node->unloaded_info, info)) {
640  			pr_warn("discarding saved data for %s "
641  				"(incompatible version)\n",
642  				gcov_info_filename(info));
643  			gcov_info_free(node->unloaded_info);
644  			node->unloaded_info = NULL;
645  		}
646  	} else {
647  		/*
648  		 * Two different versions of the same object file are loaded.
649  		 * The initial one takes precedence.
650  		 */
651  		if (!gcov_info_is_compatible(node->loaded_info[0], info)) {
652  			pr_warn("could not add '%s' (incompatible "
653  				"version)\n", gcov_info_filename(info));
654  			kfree(loaded_info);
655  			return;
656  		}
657  	}
658  	/* Overwrite previous array. */
659  	kfree(node->loaded_info);
660  	node->loaded_info = loaded_info;
661  	node->num_loaded = num + 1;
662  }
663  
664  /*
665   * Return the index of a profiling data set associated with a node.
666   */
667  static int get_info_index(struct gcov_node *node, struct gcov_info *info)
668  {
669  	int i;
670  
671  	for (i = 0; i < node->num_loaded; i++) {
672  		if (node->loaded_info[i] == info)
673  			return i;
674  	}
675  	return -ENOENT;
676  }
677  
678  /*
679   * Save the data of a profiling data set which is being unloaded.
680   */
681  static void save_info(struct gcov_node *node, struct gcov_info *info)
682  {
683  	if (node->unloaded_info)
684  		gcov_info_add(node->unloaded_info, info);
685  	else {
686  		node->unloaded_info = gcov_info_dup(info);
687  		if (!node->unloaded_info) {
688  			pr_warn("could not save data for '%s' "
689  				"(out of memory)\n",
690  				gcov_info_filename(info));
691  		}
692  	}
693  }
694  
695  /*
696   * Disassociate a profiling data set from a node. Needs to be called with
697   * node_lock held.
698   */
699  static void remove_info(struct gcov_node *node, struct gcov_info *info)
700  {
701  	int i;
702  
703  	i = get_info_index(node, info);
704  	if (i < 0) {
705  		pr_warn("could not remove '%s' (not found)\n",
706  			gcov_info_filename(info));
707  		return;
708  	}
709  	if (gcov_persist)
710  		save_info(node, info);
711  	/* Shrink array. */
712  	node->loaded_info[i] = node->loaded_info[node->num_loaded - 1];
713  	node->num_loaded--;
714  	if (node->num_loaded > 0)
715  		return;
716  	/* Last loaded data set was removed. */
717  	kfree(node->loaded_info);
718  	node->loaded_info = NULL;
719  	node->num_loaded = 0;
720  	if (!node->unloaded_info)
721  		remove_node(node);
722  }
723  
724  /*
725   * Callback to create/remove profiling files when code compiled with
726   * -fprofile-arcs is loaded/unloaded.
727   */
728  void gcov_event(enum gcov_action action, struct gcov_info *info)
729  {
730  	struct gcov_node *node;
731  
732  	mutex_lock(&node_lock);
733  	node = get_node_by_name(gcov_info_filename(info));
734  	switch (action) {
735  	case GCOV_ADD:
736  		if (node)
737  			add_info(node, info);
738  		else
739  			add_node(info);
740  		break;
741  	case GCOV_REMOVE:
742  		if (node)
743  			remove_info(node, info);
744  		else {
745  			pr_warn("could not remove '%s' (not found)\n",
746  				gcov_info_filename(info));
747  		}
748  		break;
749  	}
750  	mutex_unlock(&node_lock);
751  }
752  
753  /* Create debugfs entries. */
754  static __init int gcov_fs_init(void)
755  {
756  	init_node(&root_node, NULL, NULL, NULL);
757  	/*
758  	 * /sys/kernel/debug/gcov will be parent for the reset control file
759  	 * and all profiling files.
760  	 */
761  	root_node.dentry = debugfs_create_dir("gcov", NULL);
762  	/*
763  	 * Create reset file which resets all profiling counts when written
764  	 * to.
765  	 */
766  	debugfs_create_file("reset", 0600, root_node.dentry, NULL,
767  			    &gcov_reset_fops);
768  	/* Replay previous events to get our fs hierarchy up-to-date. */
769  	gcov_enable_events();
770  	return 0;
771  }
772  device_initcall(gcov_fs_init);
773