fs/debugfs/inode.c

   1 /*
   2  *  file.c - part of debugfs, a tiny little debug file system
   3  *
   4  *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   5  *  Copyright (C) 2004 IBM Inc.
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License version
   9  *      2 as published by the Free Software Foundation.
  10  *
  11  *  debugfs is for people to use instead of /proc or /sys.
  12  *  See Documentation/DocBook/kernel-api for more details.
  13  *
  14  */
  15
  16 /* uncomment to get debug messages from the debug filesystem, ah the irony. */
  17 /* #define DEBUG */
  18
  19 #include <linux/module.h>
  20 #include <linux/fs.h>
  21 #include <linux/mount.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/init.h>
  24 #include <linux/kobject.h>
  25 #include <linux/namei.h>
  26 #include <linux/debugfs.h>
  27 #include <linux/fsnotify.h>
  28 #include <linux/string.h>
  29
  30 #define DEBUGFS_MAGIC   0x64626720
  31
  32 /* declared over in file.c */
  33 extern struct file_operations debugfs_file_operations;
  34 extern struct inode_operations debugfs_link_operations;
  35
  36 static struct vfsmount *debugfs_mount;
  37 static int debugfs_mount_count;
  38
  39 static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev)
  40 {
  41         struct inode *inode = new_inode(sb);
  42
  43         if (inode) {
  44                 inode->i_mode = mode;
  45                 inode->i_uid = 0;
  46                 inode->i_gid = 0;
  47                 inode->i_blocks = 0;
  48                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  49                 switch (mode & S_IFMT) {
  50                 default:
  51                         init_special_inode(inode, mode, dev);
  52                         break;
  53                 case S_IFREG:
  54                         inode->i_fop = &debugfs_file_operations;
  55                         break;
  56                 case S_IFLNK:
  57                         inode->i_op = &debugfs_link_operations;
  58                         break;
  59                 case S_IFDIR:
  60                         inode->i_op = &simple_dir_inode_operations;
  61                         inode->i_fop = &simple_dir_operations;
  62
  63                         /* directory inodes start off with i_nlink == 2
  64                          * (for "." entry) */
  65                         inc_nlink(inode);
  66                         break;
  67                 }
  68         }
  69         return inode;
  70 }
  71
  72 /* SMP-safe */
  73 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
  74                          int mode, dev_t dev)
  75 {
  76         struct inode *inode;
  77         int error = -EPERM;
  78
  79         if (dentry->d_inode)
  80                 return -EEXIST;
  81
  82         inode = debugfs_get_inode(dir->i_sb, mode, dev);
  83         if (inode) {
  84                 d_instantiate(dentry, inode);
  85                 dget(dentry);
  86                 error = 0;
  87         }
  88         return error;
  89 }
  90
  91 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
  92 {
  93         int res;
  94
  95         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  96         res = debugfs_mknod(dir, dentry, mode, 0);
  97         if (!res) {
  98                 inc_nlink(dir);
  99                 fsnotify_mkdir(dir, dentry);
 100         }
 101         return res;
 102 }
 103
 104 static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode)
 105 {
 106         mode = (mode & S_IALLUGO) | S_IFLNK;
 107         return debugfs_mknod(dir, dentry, mode, 0);
 108 }
 109
 110 static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode)
 111 {
 112         int res;
 113
 114         mode = (mode & S_IALLUGO) | S_IFREG;
 115         res = debugfs_mknod(dir, dentry, mode, 0);
 116         if (!res)
 117                 fsnotify_create(dir, dentry);
 118         return res;
 119 }
 120
 121 static inline int debugfs_positive(struct dentry *dentry)
 122 {
 123         return dentry->d_inode && !d_unhashed(dentry);
 124 }
 125
 126 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 127 {
 128         static struct tree_descr debug_files[] = {{""}};
 129
 130         return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 131 }
 132
 133 static int debug_get_sb(struct file_system_type *fs_type,
 134                         int flags, const char *dev_name,
 135                         void *data, struct vfsmount *mnt)
 136 {
 137         return get_sb_single(fs_type, flags, data, debug_fill_super, mnt);
 138 }
 139
 140 static struct file_system_type debug_fs_type = {
 141         .owner =        THIS_MODULE,
 142         .name =         "debugfs",
 143         .get_sb =       debug_get_sb,
 144         .kill_sb =      kill_litter_super,
 145 };
 146
 147 static int debugfs_create_by_name(const char *name, mode_t mode,
 148                                   struct dentry *parent,
 149                                   struct dentry **dentry)
 150 {
 151         int error = 0;
 152
 153         /* If the parent is not specified, we create it in the root.
 154          * We need the root dentry to do this, which is in the super
 155          * block. A pointer to that is in the struct vfsmount that we
 156          * have around.
 157          */
 158         if (!parent) {
 159                 if (debugfs_mount && debugfs_mount->mnt_sb) {
 160                         parent = debugfs_mount->mnt_sb->s_root;
 161                 }
 162         }
 163         if (!parent) {
 164                 pr_debug("debugfs: Ah! can not find a parent!\n");
 165                 return -EFAULT;
 166         }
 167
 168         *dentry = NULL;
 169         mutex_lock(&parent->d_inode->i_mutex);
 170         *dentry = lookup_one_len(name, parent, strlen(name));
 171         if (!IS_ERR(*dentry)) {
 172                 switch (mode & S_IFMT) {
 173                 case S_IFDIR:
 174                         error = debugfs_mkdir(parent->d_inode, *dentry, mode);
 175                         break;
 176                 case S_IFLNK:
 177                         error = debugfs_link(parent->d_inode, *dentry, mode);
 178                         break;
 179                 default:
 180                         error = debugfs_create(parent->d_inode, *dentry, mode);
 181                         break;
 182                 }
 183                 dput(*dentry);
 184         } else
 185                 error = PTR_ERR(*dentry);
 186         mutex_unlock(&parent->d_inode->i_mutex);
 187
 188         return error;
 189 }
 190
 191 /**
 192  * debugfs_create_file - create a file in the debugfs filesystem
 193  * @name: a pointer to a string containing the name of the file to create.
 194  * @mode: the permission that the file should have
 195  * @parent: a pointer to the parent dentry for this file.  This should be a
 196  *          directory dentry if set.  If this paramater is NULL, then the
 197  *          file will be created in the root of the debugfs filesystem.
 198  * @data: a pointer to something that the caller will want to get to later
 199  *        on.  The inode.i_private pointer will point to this value on
 200  *        the open() call.
 201  * @fops: a pointer to a struct file_operations that should be used for
 202  *        this file.
 203  *
 204  * This is the basic "create a file" function for debugfs.  It allows for a
 205  * wide range of flexibility in createing a file, or a directory (if you
 206  * want to create a directory, the debugfs_create_dir() function is
 207  * recommended to be used instead.)
 208  *
 209  * This function will return a pointer to a dentry if it succeeds.  This
 210  * pointer must be passed to the debugfs_remove() function when the file is
 211  * to be removed (no automatic cleanup happens if your module is unloaded,
 212  * you are responsible here.)  If an error occurs, %NULL will be returned.
 213  *
 214  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 215  * returned.
 216  */
 217 struct dentry *debugfs_create_file(const char *name, mode_t mode,
 218                                    struct dentry *parent, void *data,
 219                                    const struct file_operations *fops)
 220 {
 221         struct dentry *dentry = NULL;
 222         int error;
 223
 224         pr_debug("debugfs: creating file '%s'\n",name);
 225
 226         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 227                               &debugfs_mount_count);
 228         if (error)
 229                 goto exit;
 230
 231         error = debugfs_create_by_name(name, mode, parent, &dentry);
 232         if (error) {
 233                 dentry = NULL;
 234                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 235                 goto exit;
 236         }
 237
 238         if (dentry->d_inode) {
 239                 if (data)
 240                         dentry->d_inode->i_private = data;
 241                 if (fops)
 242                         dentry->d_inode->i_fop = fops;
 243         }
 244 exit:
 245         return dentry;
 246 }
 247 EXPORT_SYMBOL_GPL(debugfs_create_file);
 248
 249 /**
 250  * debugfs_create_dir - create a directory in the debugfs filesystem
 251  * @name: a pointer to a string containing the name of the directory to
 252  *        create.
 253  * @parent: a pointer to the parent dentry for this file.  This should be a
 254  *          directory dentry if set.  If this paramater is NULL, then the
 255  *          directory will be created in the root of the debugfs filesystem.
 256  *
 257  * This function creates a directory in debugfs with the given name.
 258  *
 259  * This function will return a pointer to a dentry if it succeeds.  This
 260  * pointer must be passed to the debugfs_remove() function when the file is
 261  * to be removed (no automatic cleanup happens if your module is unloaded,
 262  * you are responsible here.)  If an error occurs, %NULL will be returned.
 263  *
 264  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 265  * returned.
 266  */
 267 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 268 {
 269         return debugfs_create_file(name,
 270                                    S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 271                                    parent, NULL, NULL);
 272 }
 273 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 274
 275 /**
 276  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 277  * @name: a pointer to a string containing the name of the symbolic link to
 278  *        create.
 279  * @parent: a pointer to the parent dentry for this symbolic link.  This
 280  *          should be a directory dentry if set.  If this paramater is NULL,
 281  *          then the symbolic link will be created in the root of the debugfs
 282  *          filesystem.
 283  * @target: a pointer to a string containing the path to the target of the
 284  *          symbolic link.
 285  *
 286  * This function creates a symbolic link with the given name in debugfs that
 287  * links to the given target path.
 288  *
 289  * This function will return a pointer to a dentry if it succeeds.  This
 290  * pointer must be passed to the debugfs_remove() function when the symbolic
 291  * link is to be removed (no automatic cleanup happens if your module is
 292  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 293  * returned.
 294  *
 295  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 296  * returned.
 297  */
 298 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 299                                       const char *target)
 300 {
 301         struct dentry *result;
 302         char *link;
 303
 304         link = kstrdup(target, GFP_KERNEL);
 305         if (!link)
 306                 return NULL;
 307
 308         result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
 309                                      NULL);
 310         if (!result)
 311                 kfree(link);
 312         return result;
 313 }
 314 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 315
 316 /**
 317  * debugfs_remove - removes a file or directory from the debugfs filesystem
 318  * @dentry: a pointer to a the dentry of the file or directory to be
 319  *          removed.
 320  *
 321  * This function removes a file or directory in debugfs that was previously
 322  * created with a call to another debugfs function (like
 323  * debugfs_create_file() or variants thereof.)
 324  *
 325  * This function is required to be called in order for the file to be
 326  * removed, no automatic cleanup of files will happen when a module is
 327  * removed, you are responsible here.
 328  */
 329 void debugfs_remove(struct dentry *dentry)
 330 {
 331         struct dentry *parent;
 332         int ret = 0;
 333
 334         if (!dentry)
 335                 return;
 336
 337         parent = dentry->d_parent;
 338         if (!parent || !parent->d_inode)
 339                 return;
 340
 341         mutex_lock(&parent->d_inode->i_mutex);
 342         if (debugfs_positive(dentry)) {
 343                 if (dentry->d_inode) {
 344                         dget(dentry);
 345                         switch (dentry->d_inode->i_mode & S_IFMT) {
 346                         case S_IFDIR:
 347                                 ret = simple_rmdir(parent->d_inode, dentry);
 348                                 if (ret)
 349                                         printk(KERN_ERR
 350                                                 "DebugFS rmdir on %s failed : "
 351                                                 "directory not empty.\n",
 352                                                 dentry->d_name.name);
 353                                 break;
 354                         case S_IFLNK:
 355                                 kfree(dentry->d_inode->i_private);
 356                                 /* fall through */
 357                         default:
 358                                 simple_unlink(parent->d_inode, dentry);
 359                                 break;
 360                         }
 361                         if (!ret)
 362                                 d_delete(dentry);
 363                         dput(dentry);
 364                 }
 365         }
 366         mutex_unlock(&parent->d_inode->i_mutex);
 367         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 368 }
 369 EXPORT_SYMBOL_GPL(debugfs_remove);
 370
 371 static decl_subsys(debug, NULL, NULL);
 372
 373 static int __init debugfs_init(void)
 374 {
 375         int retval;
 376
 377         kobj_set_kset_s(&debug_subsys, kernel_subsys);
 378         retval = subsystem_register(&debug_subsys);
 379         if (retval)
 380                 return retval;
 381
 382         retval = register_filesystem(&debug_fs_type);
 383         if (retval)
 384                 subsystem_unregister(&debug_subsys);
 385         return retval;
 386 }
 387
 388 static void __exit debugfs_exit(void)
 389 {
 390         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 391         unregister_filesystem(&debug_fs_type);
 392         subsystem_unregister(&debug_subsys);
 393 }
 394
 395 core_initcall(debugfs_init);
 396 module_exit(debugfs_exit);
 397 MODULE_LICENSE("GPL");
 398