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
  29 #define DEBUGFS_MAGIC   0x64626720
  30
  31 /* declared over in file.c */
  32 extern struct file_operations debugfs_file_operations;
  33
  34 static struct vfsmount *debugfs_mount;
  35 static int debugfs_mount_count;
  36
  37 static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev)
  38 {
  39         struct inode *inode = new_inode(sb);
  40
  41         if (inode) {
  42                 inode->i_mode = mode;
  43                 inode->i_uid = 0;
  44                 inode->i_gid = 0;
  45                 inode->i_blocks = 0;
  46                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  47                 switch (mode & S_IFMT) {
  48                 default:
  49                         init_special_inode(inode, mode, dev);
  50                         break;
  51                 case S_IFREG:
  52                         inode->i_fop = &debugfs_file_operations;
  53                         break;
  54                 case S_IFDIR:
  55                         inode->i_op = &simple_dir_inode_operations;
  56                         inode->i_fop = &simple_dir_operations;
  57
  58                         /* directory inodes start off with i_nlink == 2
  59                          * (for "." entry) */
  60                         inc_nlink(inode);
  61                         break;
  62                 }
  63         }
  64         return inode;
  65 }
  66
  67 /* SMP-safe */
  68 static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
  69                          int mode, dev_t dev)
  70 {
  71         struct inode *inode;
  72         int error = -EPERM;
  73
  74         if (dentry->d_inode)
  75                 return -EEXIST;
  76
  77         inode = debugfs_get_inode(dir->i_sb, mode, dev);
  78         if (inode) {
  79                 d_instantiate(dentry, inode);
  80                 dget(dentry);
  81                 error = 0;
  82         }
  83         return error;
  84 }
  85
  86 static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
  87 {
  88         int res;
  89
  90         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
  91         res = debugfs_mknod(dir, dentry, mode, 0);
  92         if (!res) {
  93                 inc_nlink(dir);
  94                 fsnotify_mkdir(dir, dentry);
  95         }
  96         return res;
  97 }
  98
  99 static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode)
 100 {
 101         int res;
 102
 103         mode = (mode & S_IALLUGO) | S_IFREG;
 104         res = debugfs_mknod(dir, dentry, mode, 0);
 105         if (!res)
 106                 fsnotify_create(dir, dentry);
 107         return res;
 108 }
 109
 110 static inline int debugfs_positive(struct dentry *dentry)
 111 {
 112         return dentry->d_inode && !d_unhashed(dentry);
 113 }
 114
 115 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 116 {
 117         static struct tree_descr debug_files[] = {{""}};
 118
 119         return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 120 }
 121
 122 static int debug_get_sb(struct file_system_type *fs_type,
 123                         int flags, const char *dev_name,
 124                         void *data, struct vfsmount *mnt)
 125 {
 126         return get_sb_single(fs_type, flags, data, debug_fill_super, mnt);
 127 }
 128
 129 static struct file_system_type debug_fs_type = {
 130         .owner =        THIS_MODULE,
 131         .name =         "debugfs",
 132         .get_sb =       debug_get_sb,
 133         .kill_sb =      kill_litter_super,
 134 };
 135
 136 static int debugfs_create_by_name(const char *name, mode_t mode,
 137                                   struct dentry *parent,
 138                                   struct dentry **dentry)
 139 {
 140         int error = 0;
 141
 142         /* If the parent is not specified, we create it in the root.
 143          * We need the root dentry to do this, which is in the super
 144          * block. A pointer to that is in the struct vfsmount that we
 145          * have around.
 146          */
 147         if (!parent) {
 148                 if (debugfs_mount && debugfs_mount->mnt_sb) {
 149                         parent = debugfs_mount->mnt_sb->s_root;
 150                 }
 151         }
 152         if (!parent) {
 153                 pr_debug("debugfs: Ah! can not find a parent!\n");
 154                 return -EFAULT;
 155         }
 156
 157         *dentry = NULL;
 158         mutex_lock(&parent->d_inode->i_mutex);
 159         *dentry = lookup_one_len(name, parent, strlen(name));
 160         if (!IS_ERR(*dentry)) {
 161                 if ((mode & S_IFMT) == S_IFDIR)
 162                         error = debugfs_mkdir(parent->d_inode, *dentry, mode);
 163                 else
 164                         error = debugfs_create(parent->d_inode, *dentry, mode);
 165                 dput(*dentry);
 166         } else
 167                 error = PTR_ERR(*dentry);
 168         mutex_unlock(&parent->d_inode->i_mutex);
 169
 170         return error;
 171 }
 172
 173 /**
 174  * debugfs_create_file - create a file in the debugfs filesystem
 175  * @name: a pointer to a string containing the name of the file to create.
 176  * @mode: the permission that the file should have
 177  * @parent: a pointer to the parent dentry for this file.  This should be a
 178  *          directory dentry if set.  If this paramater is NULL, then the
 179  *          file will be created in the root of the debugfs filesystem.
 180  * @data: a pointer to something that the caller will want to get to later
 181  *        on.  The inode.i_private pointer will point to this value on
 182  *        the open() call.
 183  * @fops: a pointer to a struct file_operations that should be used for
 184  *        this file.
 185  *
 186  * This is the basic "create a file" function for debugfs.  It allows for a
 187  * wide range of flexibility in createing a file, or a directory (if you
 188  * want to create a directory, the debugfs_create_dir() function is
 189  * recommended to be used instead.)
 190  *
 191  * This function will return a pointer to a dentry if it succeeds.  This
 192  * pointer must be passed to the debugfs_remove() function when the file is
 193  * to be removed (no automatic cleanup happens if your module is unloaded,
 194  * you are responsible here.)  If an error occurs, %NULL will be returned.
 195  *
 196  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 197  * returned.  It is not wise to check for this value, but rather, check for
 198  * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 199  * code.
 200  */
 201 struct dentry *debugfs_create_file(const char *name, mode_t mode,
 202                                    struct dentry *parent, void *data,
 203                                    const struct file_operations *fops)
 204 {
 205         struct dentry *dentry = NULL;
 206         int error;
 207
 208         pr_debug("debugfs: creating file '%s'\n",name);
 209
 210         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 211                               &debugfs_mount_count);
 212         if (error)
 213                 goto exit;
 214
 215         error = debugfs_create_by_name(name, mode, parent, &dentry);
 216         if (error) {
 217                 dentry = NULL;
 218                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 219                 goto exit;
 220         }
 221
 222         if (dentry->d_inode) {
 223                 if (data)
 224                         dentry->d_inode->i_private = data;
 225                 if (fops)
 226                         dentry->d_inode->i_fop = fops;
 227         }
 228 exit:
 229         return dentry;
 230 }
 231 EXPORT_SYMBOL_GPL(debugfs_create_file);
 232
 233 /**
 234  * debugfs_create_dir - create a directory in the debugfs filesystem
 235  * @name: a pointer to a string containing the name of the directory to
 236  *        create.
 237  * @parent: a pointer to the parent dentry for this file.  This should be a
 238  *          directory dentry if set.  If this paramater is NULL, then the
 239  *          directory will be created in the root of the debugfs filesystem.
 240  *
 241  * This function creates a directory in debugfs with the given name.
 242  *
 243  * This function will return a pointer to a dentry if it succeeds.  This
 244  * pointer must be passed to the debugfs_remove() function when the file is
 245  * to be removed (no automatic cleanup happens if your module is unloaded,
 246  * you are responsible here.)  If an error occurs, %NULL will be returned.
 247  *
 248  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 249  * returned.  It is not wise to check for this value, but rather, check for
 250  * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 251  * code.
 252  */
 253 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 254 {
 255         return debugfs_create_file(name,
 256                                    S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 257                                    parent, NULL, NULL);
 258 }
 259 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 260
 261 /**
 262  * debugfs_remove - removes a file or directory from the debugfs filesystem
 263  * @dentry: a pointer to a the dentry of the file or directory to be
 264  *          removed.
 265  *
 266  * This function removes a file or directory in debugfs that was previously
 267  * created with a call to another debugfs function (like
 268  * debugfs_create_file() or variants thereof.)
 269  *
 270  * This function is required to be called in order for the file to be
 271  * removed, no automatic cleanup of files will happen when a module is
 272  * removed, you are responsible here.
 273  */
 274 void debugfs_remove(struct dentry *dentry)
 275 {
 276         struct dentry *parent;
 277         int ret = 0;
 278
 279         if (!dentry)
 280                 return;
 281
 282         parent = dentry->d_parent;
 283         if (!parent || !parent->d_inode)
 284                 return;
 285
 286         mutex_lock(&parent->d_inode->i_mutex);
 287         if (debugfs_positive(dentry)) {
 288                 if (dentry->d_inode) {
 289                         dget(dentry);
 290                         if (S_ISDIR(dentry->d_inode->i_mode)) {
 291                                 ret = simple_rmdir(parent->d_inode, dentry);
 292                                 if (ret)
 293                                         printk(KERN_ERR
 294                                                 "DebugFS rmdir on %s failed : "
 295                                                 "directory not empty.\n",
 296                                                 dentry->d_name.name);
 297                         } else
 298                                 simple_unlink(parent->d_inode, dentry);
 299                         if (!ret)
 300                                 d_delete(dentry);
 301                         dput(dentry);
 302                 }
 303         }
 304         mutex_unlock(&parent->d_inode->i_mutex);
 305         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 306 }
 307 EXPORT_SYMBOL_GPL(debugfs_remove);
 308
 309 static decl_subsys(debug, NULL, NULL);
 310
 311 static int __init debugfs_init(void)
 312 {
 313         int retval;
 314
 315         kset_set_kset_s(&debug_subsys, kernel_subsys);
 316         retval = subsystem_register(&debug_subsys);
 317         if (retval)
 318                 return retval;
 319
 320         retval = register_filesystem(&debug_fs_type);
 321         if (retval)
 322                 subsystem_unregister(&debug_subsys);
 323         return retval;
 324 }
 325
 326 static void __exit debugfs_exit(void)
 327 {
 328         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 329         unregister_filesystem(&debug_fs_type);
 330         subsystem_unregister(&debug_subsys);
 331 }
 332
 333 core_initcall(debugfs_init);
 334 module_exit(debugfs_exit);
 335 MODULE_LICENSE("GPL");
 336