~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/fs/tracefs/inode.c

Version: ~ [ linux-5.12-rc7 ] ~ [ linux-5.11.13 ] ~ [ linux-5.10.29 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.111 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.186 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.230 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.266 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.266 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *  inode.c - part of tracefs, a pseudo file system for activating tracing
  4  *
  5  * Based on debugfs by: Greg Kroah-Hartman <greg@kroah.com>
  6  *
  7  *  Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com>
  8  *
  9  * tracefs is the file system that is used by the tracing infrastructure.
 10  */
 11 
 12 #include <linux/module.h>
 13 #include <linux/fs.h>
 14 #include <linux/mount.h>
 15 #include <linux/kobject.h>
 16 #include <linux/namei.h>
 17 #include <linux/tracefs.h>
 18 #include <linux/fsnotify.h>
 19 #include <linux/seq_file.h>
 20 #include <linux/parser.h>
 21 #include <linux/magic.h>
 22 #include <linux/slab.h>
 23 
 24 #define TRACEFS_DEFAULT_MODE    0700
 25 
 26 static struct vfsmount *tracefs_mount;
 27 static int tracefs_mount_count;
 28 static bool tracefs_registered;
 29 
 30 static ssize_t default_read_file(struct file *file, char __user *buf,
 31                                  size_t count, loff_t *ppos)
 32 {
 33         return 0;
 34 }
 35 
 36 static ssize_t default_write_file(struct file *file, const char __user *buf,
 37                                    size_t count, loff_t *ppos)
 38 {
 39         return count;
 40 }
 41 
 42 static const struct file_operations tracefs_file_operations = {
 43         .read =         default_read_file,
 44         .write =        default_write_file,
 45         .open =         simple_open,
 46         .llseek =       noop_llseek,
 47 };
 48 
 49 static struct tracefs_dir_ops {
 50         int (*mkdir)(const char *name);
 51         int (*rmdir)(const char *name);
 52 } tracefs_ops __ro_after_init;
 53 
 54 static char *get_dname(struct dentry *dentry)
 55 {
 56         const char *dname;
 57         char *name;
 58         int len = dentry->d_name.len;
 59 
 60         dname = dentry->d_name.name;
 61         name = kmalloc(len + 1, GFP_KERNEL);
 62         if (!name)
 63                 return NULL;
 64         memcpy(name, dname, len);
 65         name[len] = 0;
 66         return name;
 67 }
 68 
 69 static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode)
 70 {
 71         char *name;
 72         int ret;
 73 
 74         name = get_dname(dentry);
 75         if (!name)
 76                 return -ENOMEM;
 77 
 78         /*
 79          * The mkdir call can call the generic functions that create
 80          * the files within the tracefs system. It is up to the individual
 81          * mkdir routine to handle races.
 82          */
 83         inode_unlock(inode);
 84         ret = tracefs_ops.mkdir(name);
 85         inode_lock(inode);
 86 
 87         kfree(name);
 88 
 89         return ret;
 90 }
 91 
 92 static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
 93 {
 94         char *name;
 95         int ret;
 96 
 97         name = get_dname(dentry);
 98         if (!name)
 99                 return -ENOMEM;
100 
101         /*
102          * The rmdir call can call the generic functions that create
103          * the files within the tracefs system. It is up to the individual
104          * rmdir routine to handle races.
105          * This time we need to unlock not only the parent (inode) but
106          * also the directory that is being deleted.
107          */
108         inode_unlock(inode);
109         inode_unlock(dentry->d_inode);
110 
111         ret = tracefs_ops.rmdir(name);
112 
113         inode_lock_nested(inode, I_MUTEX_PARENT);
114         inode_lock(dentry->d_inode);
115 
116         kfree(name);
117 
118         return ret;
119 }
120 
121 static const struct inode_operations tracefs_dir_inode_operations = {
122         .lookup         = simple_lookup,
123         .mkdir          = tracefs_syscall_mkdir,
124         .rmdir          = tracefs_syscall_rmdir,
125 };
126 
127 static struct inode *tracefs_get_inode(struct super_block *sb)
128 {
129         struct inode *inode = new_inode(sb);
130         if (inode) {
131                 inode->i_ino = get_next_ino();
132                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
133         }
134         return inode;
135 }
136 
137 struct tracefs_mount_opts {
138         kuid_t uid;
139         kgid_t gid;
140         umode_t mode;
141 };
142 
143 enum {
144         Opt_uid,
145         Opt_gid,
146         Opt_mode,
147         Opt_err
148 };
149 
150 static const match_table_t tokens = {
151         {Opt_uid, "uid=%u"},
152         {Opt_gid, "gid=%u"},
153         {Opt_mode, "mode=%o"},
154         {Opt_err, NULL}
155 };
156 
157 struct tracefs_fs_info {
158         struct tracefs_mount_opts mount_opts;
159 };
160 
161 static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
162 {
163         substring_t args[MAX_OPT_ARGS];
164         int option;
165         int token;
166         kuid_t uid;
167         kgid_t gid;
168         char *p;
169 
170         opts->mode = TRACEFS_DEFAULT_MODE;
171 
172         while ((p = strsep(&data, ",")) != NULL) {
173                 if (!*p)
174                         continue;
175 
176                 token = match_token(p, tokens, args);
177                 switch (token) {
178                 case Opt_uid:
179                         if (match_int(&args[0], &option))
180                                 return -EINVAL;
181                         uid = make_kuid(current_user_ns(), option);
182                         if (!uid_valid(uid))
183                                 return -EINVAL;
184                         opts->uid = uid;
185                         break;
186                 case Opt_gid:
187                         if (match_int(&args[0], &option))
188                                 return -EINVAL;
189                         gid = make_kgid(current_user_ns(), option);
190                         if (!gid_valid(gid))
191                                 return -EINVAL;
192                         opts->gid = gid;
193                         break;
194                 case Opt_mode:
195                         if (match_octal(&args[0], &option))
196                                 return -EINVAL;
197                         opts->mode = option & S_IALLUGO;
198                         break;
199                 /*
200                  * We might like to report bad mount options here;
201                  * but traditionally tracefs has ignored all mount options
202                  */
203                 }
204         }
205 
206         return 0;
207 }
208 
209 static int tracefs_apply_options(struct super_block *sb)
210 {
211         struct tracefs_fs_info *fsi = sb->s_fs_info;
212         struct inode *inode = sb->s_root->d_inode;
213         struct tracefs_mount_opts *opts = &fsi->mount_opts;
214 
215         inode->i_mode &= ~S_IALLUGO;
216         inode->i_mode |= opts->mode;
217 
218         inode->i_uid = opts->uid;
219         inode->i_gid = opts->gid;
220 
221         return 0;
222 }
223 
224 static int tracefs_remount(struct super_block *sb, int *flags, char *data)
225 {
226         int err;
227         struct tracefs_fs_info *fsi = sb->s_fs_info;
228 
229         sync_filesystem(sb);
230         err = tracefs_parse_options(data, &fsi->mount_opts);
231         if (err)
232                 goto fail;
233 
234         tracefs_apply_options(sb);
235 
236 fail:
237         return err;
238 }
239 
240 static int tracefs_show_options(struct seq_file *m, struct dentry *root)
241 {
242         struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
243         struct tracefs_mount_opts *opts = &fsi->mount_opts;
244 
245         if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
246                 seq_printf(m, ",uid=%u",
247                            from_kuid_munged(&init_user_ns, opts->uid));
248         if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
249                 seq_printf(m, ",gid=%u",
250                            from_kgid_munged(&init_user_ns, opts->gid));
251         if (opts->mode != TRACEFS_DEFAULT_MODE)
252                 seq_printf(m, ",mode=%o", opts->mode);
253 
254         return 0;
255 }
256 
257 static const struct super_operations tracefs_super_operations = {
258         .statfs         = simple_statfs,
259         .remount_fs     = tracefs_remount,
260         .show_options   = tracefs_show_options,
261 };
262 
263 static int trace_fill_super(struct super_block *sb, void *data, int silent)
264 {
265         static const struct tree_descr trace_files[] = {{""}};
266         struct tracefs_fs_info *fsi;
267         int err;
268 
269         fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
270         sb->s_fs_info = fsi;
271         if (!fsi) {
272                 err = -ENOMEM;
273                 goto fail;
274         }
275 
276         err = tracefs_parse_options(data, &fsi->mount_opts);
277         if (err)
278                 goto fail;
279 
280         err  =  simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
281         if (err)
282                 goto fail;
283 
284         sb->s_op = &tracefs_super_operations;
285 
286         tracefs_apply_options(sb);
287 
288         return 0;
289 
290 fail:
291         kfree(fsi);
292         sb->s_fs_info = NULL;
293         return err;
294 }
295 
296 static struct dentry *trace_mount(struct file_system_type *fs_type,
297                         int flags, const char *dev_name,
298                         void *data)
299 {
300         return mount_single(fs_type, flags, data, trace_fill_super);
301 }
302 
303 static struct file_system_type trace_fs_type = {
304         .owner =        THIS_MODULE,
305         .name =         "tracefs",
306         .mount =        trace_mount,
307         .kill_sb =      kill_litter_super,
308 };
309 MODULE_ALIAS_FS("tracefs");
310 
311 static struct dentry *start_creating(const char *name, struct dentry *parent)
312 {
313         struct dentry *dentry;
314         int error;
315 
316         pr_debug("tracefs: creating file '%s'\n",name);
317 
318         error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
319                               &tracefs_mount_count);
320         if (error)
321                 return ERR_PTR(error);
322 
323         /* If the parent is not specified, we create it in the root.
324          * We need the root dentry to do this, which is in the super
325          * block. A pointer to that is in the struct vfsmount that we
326          * have around.
327          */
328         if (!parent)
329                 parent = tracefs_mount->mnt_root;
330 
331         inode_lock(parent->d_inode);
332         dentry = lookup_one_len(name, parent, strlen(name));
333         if (!IS_ERR(dentry) && dentry->d_inode) {
334                 dput(dentry);
335                 dentry = ERR_PTR(-EEXIST);
336         }
337 
338         if (IS_ERR(dentry)) {
339                 inode_unlock(parent->d_inode);
340                 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
341         }
342 
343         return dentry;
344 }
345 
346 static struct dentry *failed_creating(struct dentry *dentry)
347 {
348         inode_unlock(dentry->d_parent->d_inode);
349         dput(dentry);
350         simple_release_fs(&tracefs_mount, &tracefs_mount_count);
351         return NULL;
352 }
353 
354 static struct dentry *end_creating(struct dentry *dentry)
355 {
356         inode_unlock(dentry->d_parent->d_inode);
357         return dentry;
358 }
359 
360 /**
361  * tracefs_create_file - create a file in the tracefs filesystem
362  * @name: a pointer to a string containing the name of the file to create.
363  * @mode: the permission that the file should have.
364  * @parent: a pointer to the parent dentry for this file.  This should be a
365  *          directory dentry if set.  If this parameter is NULL, then the
366  *          file will be created in the root of the tracefs filesystem.
367  * @data: a pointer to something that the caller will want to get to later
368  *        on.  The inode.i_private pointer will point to this value on
369  *        the open() call.
370  * @fops: a pointer to a struct file_operations that should be used for
371  *        this file.
372  *
373  * This is the basic "create a file" function for tracefs.  It allows for a
374  * wide range of flexibility in creating a file, or a directory (if you want
375  * to create a directory, the tracefs_create_dir() function is
376  * recommended to be used instead.)
377  *
378  * This function will return a pointer to a dentry if it succeeds.  This
379  * pointer must be passed to the tracefs_remove() function when the file is
380  * to be removed (no automatic cleanup happens if your module is unloaded,
381  * you are responsible here.)  If an error occurs, %NULL will be returned.
382  *
383  * If tracefs is not enabled in the kernel, the value -%ENODEV will be
384  * returned.
385  */
386 struct dentry *tracefs_create_file(const char *name, umode_t mode,
387                                    struct dentry *parent, void *data,
388                                    const struct file_operations *fops)
389 {
390         struct dentry *dentry;
391         struct inode *inode;
392 
393         if (!(mode & S_IFMT))
394                 mode |= S_IFREG;
395         BUG_ON(!S_ISREG(mode));
396         dentry = start_creating(name, parent);
397 
398         if (IS_ERR(dentry))
399                 return NULL;
400 
401         inode = tracefs_get_inode(dentry->d_sb);
402         if (unlikely(!inode))
403                 return failed_creating(dentry);
404 
405         inode->i_mode = mode;
406         inode->i_fop = fops ? fops : &tracefs_file_operations;
407         inode->i_private = data;
408         d_instantiate(dentry, inode);
409         fsnotify_create(dentry->d_parent->d_inode, dentry);
410         return end_creating(dentry);
411 }
412 
413 static struct dentry *__create_dir(const char *name, struct dentry *parent,
414                                    const struct inode_operations *ops)
415 {
416         struct dentry *dentry = start_creating(name, parent);
417         struct inode *inode;
418 
419         if (IS_ERR(dentry))
420                 return NULL;
421 
422         inode = tracefs_get_inode(dentry->d_sb);
423         if (unlikely(!inode))
424                 return failed_creating(dentry);
425 
426         inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
427         inode->i_op = ops;
428         inode->i_fop = &simple_dir_operations;
429 
430         /* directory inodes start off with i_nlink == 2 (for "." entry) */
431         inc_nlink(inode);
432         d_instantiate(dentry, inode);
433         inc_nlink(dentry->d_parent->d_inode);
434         fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
435         return end_creating(dentry);
436 }
437 
438 /**
439  * tracefs_create_dir - create a directory in the tracefs filesystem
440  * @name: a pointer to a string containing the name of the directory to
441  *        create.
442  * @parent: a pointer to the parent dentry for this file.  This should be a
443  *          directory dentry if set.  If this parameter is NULL, then the
444  *          directory will be created in the root of the tracefs filesystem.
445  *
446  * This function creates a directory in tracefs with the given name.
447  *
448  * This function will return a pointer to a dentry if it succeeds.  This
449  * pointer must be passed to the tracefs_remove() function when the file is
450  * to be removed. If an error occurs, %NULL will be returned.
451  *
452  * If tracing is not enabled in the kernel, the value -%ENODEV will be
453  * returned.
454  */
455 struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
456 {
457         return __create_dir(name, parent, &simple_dir_inode_operations);
458 }
459 
460 /**
461  * tracefs_create_instance_dir - create the tracing instances directory
462  * @name: The name of the instances directory to create
463  * @parent: The parent directory that the instances directory will exist
464  * @mkdir: The function to call when a mkdir is performed.
465  * @rmdir: The function to call when a rmdir is performed.
466  *
467  * Only one instances directory is allowed.
468  *
469  * The instances directory is special as it allows for mkdir and rmdir to
470  * to be done by userspace. When a mkdir or rmdir is performed, the inode
471  * locks are released and the methhods passed in (@mkdir and @rmdir) are
472  * called without locks and with the name of the directory being created
473  * within the instances directory.
474  *
475  * Returns the dentry of the instances directory.
476  */
477 __init struct dentry *tracefs_create_instance_dir(const char *name,
478                                           struct dentry *parent,
479                                           int (*mkdir)(const char *name),
480                                           int (*rmdir)(const char *name))
481 {
482         struct dentry *dentry;
483 
484         /* Only allow one instance of the instances directory. */
485         if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
486                 return NULL;
487 
488         dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
489         if (!dentry)
490                 return NULL;
491 
492         tracefs_ops.mkdir = mkdir;
493         tracefs_ops.rmdir = rmdir;
494 
495         return dentry;
496 }
497 
498 static int __tracefs_remove(struct dentry *dentry, struct dentry *parent)
499 {
500         int ret = 0;
501 
502         if (simple_positive(dentry)) {
503                 if (dentry->d_inode) {
504                         dget(dentry);
505                         switch (dentry->d_inode->i_mode & S_IFMT) {
506                         case S_IFDIR:
507                                 ret = simple_rmdir(parent->d_inode, dentry);
508                                 if (!ret)
509                                         fsnotify_rmdir(parent->d_inode, dentry);
510                                 break;
511                         default:
512                                 simple_unlink(parent->d_inode, dentry);
513                                 fsnotify_unlink(parent->d_inode, dentry);
514                                 break;
515                         }
516                         if (!ret)
517                                 d_delete(dentry);
518                         dput(dentry);
519                 }
520         }
521         return ret;
522 }
523 
524 /**
525  * tracefs_remove - removes a file or directory from the tracefs filesystem
526  * @dentry: a pointer to a the dentry of the file or directory to be
527  *          removed.
528  *
529  * This function removes a file or directory in tracefs that was previously
530  * created with a call to another tracefs function (like
531  * tracefs_create_file() or variants thereof.)
532  */
533 void tracefs_remove(struct dentry *dentry)
534 {
535         struct dentry *parent;
536         int ret;
537 
538         if (IS_ERR_OR_NULL(dentry))
539                 return;
540 
541         parent = dentry->d_parent;
542         inode_lock(parent->d_inode);
543         ret = __tracefs_remove(dentry, parent);
544         inode_unlock(parent->d_inode);
545         if (!ret)
546                 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
547 }
548 
549 /**
550  * tracefs_remove_recursive - recursively removes a directory
551  * @dentry: a pointer to a the dentry of the directory to be removed.
552  *
553  * This function recursively removes a directory tree in tracefs that
554  * was previously created with a call to another tracefs function
555  * (like tracefs_create_file() or variants thereof.)
556  */
557 void tracefs_remove_recursive(struct dentry *dentry)
558 {
559         struct dentry *child, *parent;
560 
561         if (IS_ERR_OR_NULL(dentry))
562                 return;
563 
564         parent = dentry;
565  down:
566         inode_lock(parent->d_inode);
567  loop:
568         /*
569          * The parent->d_subdirs is protected by the d_lock. Outside that
570          * lock, the child can be unlinked and set to be freed which can
571          * use the d_u.d_child as the rcu head and corrupt this list.
572          */
573         spin_lock(&parent->d_lock);
574         list_for_each_entry(child, &parent->d_subdirs, d_child) {
575                 if (!simple_positive(child))
576                         continue;
577 
578                 /* perhaps simple_empty(child) makes more sense */
579                 if (!list_empty(&child->d_subdirs)) {
580                         spin_unlock(&parent->d_lock);
581                         inode_unlock(parent->d_inode);
582                         parent = child;
583                         goto down;
584                 }
585 
586                 spin_unlock(&parent->d_lock);
587 
588                 if (!__tracefs_remove(child, parent))
589                         simple_release_fs(&tracefs_mount, &tracefs_mount_count);
590 
591                 /*
592                  * The parent->d_lock protects agaist child from unlinking
593                  * from d_subdirs. When releasing the parent->d_lock we can
594                  * no longer trust that the next pointer is valid.
595                  * Restart the loop. We'll skip this one with the
596                  * simple_positive() check.
597                  */
598                 goto loop;
599         }
600         spin_unlock(&parent->d_lock);
601 
602         inode_unlock(parent->d_inode);
603         child = parent;
604         parent = parent->d_parent;
605         inode_lock(parent->d_inode);
606 
607         if (child != dentry)
608                 /* go up */
609                 goto loop;
610 
611         if (!__tracefs_remove(child, parent))
612                 simple_release_fs(&tracefs_mount, &tracefs_mount_count);
613         inode_unlock(parent->d_inode);
614 }
615 
616 /**
617  * tracefs_initialized - Tells whether tracefs has been registered
618  */
619 bool tracefs_initialized(void)
620 {
621         return tracefs_registered;
622 }
623 
624 static int __init tracefs_init(void)
625 {
626         int retval;
627 
628         retval = sysfs_create_mount_point(kernel_kobj, "tracing");
629         if (retval)
630                 return -EINVAL;
631 
632         retval = register_filesystem(&trace_fs_type);
633         if (!retval)
634                 tracefs_registered = true;
635 
636         return retval;
637 }
638 core_initcall(tracefs_init);
639 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp