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