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