root/kernel/gcov/fs.c

DEFINITIONS

1. gcov_persist_setup
2. gcov_seq_start
3. gcov_seq_next
4. gcov_seq_show
5. gcov_seq_stop
6. get_node_info
7. get_accumulated_info
8. gcov_seq_open
9. gcov_seq_release
10. get_node_by_name
11. reset_node
12. gcov_seq_write
13. link_target
14. get_link_target
15. deskew
16. add_links
17. init_node
18. new_node
19. remove_links
20. release_node
21. remove_node
22. get_child_by_name
23. reset_write
24. reset_read
25. add_node
26. add_info
27. get_info_index
28. save_info
29. remove_info
30. gcov_event
31. gcov_fs_init

   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         (*pos)++;
 112         if (gcov_iter_next(iter))
 113                 return NULL;
 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);