release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/base/devtmpfs.c

   1 /* Modified by Broadcom Corp. Portions Copyright (c) Broadcom Corp, 2012. */
   2 /*
   3  * devtmpfs - kernel-maintained tmpfs-based /dev
   4  *
   5  * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org>
   6  *
   7  * During bootup, before any driver core device is registered,
   8  * devtmpfs, a tmpfs-based filesystem is created. Every driver-core
   9  * device which requests a device node, will add a node in this
  10  * filesystem.
  11  * By default, all devices are named after the the name of the
  12  * device, owned by root and have a default mode of 0600. Subsystems
  13  * can overwrite the default setting if needed.
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/syscalls.h>
  18 #include <linux/mount.h>
  19 #include <linux/device.h>
  20 #include <linux/genhd.h>
  21 #include <linux/namei.h>
  22 #include <linux/fs.h>
  23 #include <linux/shmem_fs.h>
  24 #include <linux/ramfs.h>
  25 #include <linux/cred.h>
  26 #include <linux/sched.h>
  27 #include <linux/init_task.h>
  28 #include <linux/slab.h>
  29
  30 static struct vfsmount *dev_mnt;
  31
  32 #if defined CONFIG_DEVTMPFS_MOUNT
  33 static int dev_mount = 1;
  34 #else
  35 static int dev_mount;
  36 #endif
  37
  38 static DEFINE_MUTEX(dirlock);
  39
  40 static int __init mount_param(char *str)
  41 {
  42         dev_mount = simple_strtoul(str, NULL, 0);
  43         return 1;
  44 }
  45 __setup("devtmpfs.mount=", mount_param);
  46
  47 static int dev_get_sb(struct file_system_type *fs_type, int flags,
  48                       const char *dev_name, void *data, struct vfsmount *mnt)
  49 {
  50 #ifdef CONFIG_TMPFS
  51         return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt);
  52 #else
  53         return get_sb_single(fs_type, flags, data, ramfs_fill_super, mnt);
  54 #endif
  55 }
  56
  57 static struct file_system_type dev_fs_type = {
  58         .name = "devtmpfs",
  59         .get_sb = dev_get_sb,
  60         .kill_sb = kill_litter_super,
  61 };
  62
  63 #ifdef CONFIG_BLOCK
  64 static inline int is_blockdev(struct device *dev)
  65 {
  66         return dev->class == &block_class;
  67 }
  68 #else
  69 static inline int is_blockdev(struct device *dev) { return 0; }
  70 #endif
  71
  72 static int dev_mkdir(const char *name, mode_t mode)
  73 {
  74         struct nameidata nd;
  75         struct dentry *dentry;
  76         int err;
  77
  78         err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
  79                               name, LOOKUP_PARENT, &nd);
  80         if (err)
  81                 return err;
  82
  83         dentry = lookup_create(&nd, 1);
  84         if (!IS_ERR(dentry)) {
  85                 err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
  86                 if (!err)
  87                         /* mark as kernel-created inode */
  88                         dentry->d_inode->i_private = &dev_mnt;
  89                 dput(dentry);
  90         } else {
  91                 err = PTR_ERR(dentry);
  92         }
  93
  94         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
  95         path_put(&nd.path);
  96         return err;
  97 }
  98
  99 static int create_path(const char *nodepath)
 100 {
 101         int err;
 102
 103         mutex_lock(&dirlock);
 104         err = dev_mkdir(nodepath, 0755);
 105         if (err == -ENOENT) {
 106                 char *path;
 107                 char *s;
 108
 109                 /* parent directories do not exist, create them */
 110                 path = kstrdup(nodepath, GFP_KERNEL);
 111                 if (!path) {
 112                         err = -ENOMEM;
 113                         goto out;
 114                 }
 115                 s = path;
 116                 for (;;) {
 117                         s = strchr(s, '/');
 118                         if (!s)
 119                                 break;
 120                         s[0] = '\0';
 121                         err = dev_mkdir(path, 0755);
 122                         if (err && err != -EEXIST)
 123                                 break;
 124                         s[0] = '/';
 125                         s++;
 126                 }
 127                 kfree(path);
 128         }
 129 out:
 130         mutex_unlock(&dirlock);
 131         return err;
 132 }
 133
 134 int devtmpfs_create_node(struct device *dev)
 135 {
 136         const char *tmp = NULL;
 137         const char *nodename;
 138         const struct cred *curr_cred;
 139         mode_t mode = 0;
 140         struct nameidata nd;
 141         struct dentry *dentry;
 142         int err;
 143
 144         if (!dev_mnt)
 145                 return 0;
 146
 147         nodename = device_get_devnode(dev, &mode, &tmp);
 148         if (!nodename)
 149                 return -ENOMEM;
 150
 151         if (mode == 0)
 152                 mode = 0600;
 153         if (is_blockdev(dev))
 154                 mode |= S_IFBLK;
 155         else
 156                 mode |= S_IFCHR;
 157
 158         curr_cred = override_creds(&init_cred);
 159
 160         err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
 161                               nodename, LOOKUP_PARENT, &nd);
 162         if (err == -ENOENT) {
 163                 create_path(nodename);
 164                 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
 165                                       nodename, LOOKUP_PARENT, &nd);
 166         }
 167         if (err)
 168                 goto out;
 169
 170         dentry = lookup_create(&nd, 0);
 171         if (!IS_ERR(dentry)) {
 172                 err = vfs_mknod(nd.path.dentry->d_inode,
 173                                 dentry, mode, dev->devt);
 174                 if (!err) {
 175                         struct iattr newattrs;
 176
 177                         /* fixup possibly umasked mode */
 178                         newattrs.ia_mode = mode;
 179                         newattrs.ia_valid = ATTR_MODE;
 180                         mutex_lock(&dentry->d_inode->i_mutex);
 181                         notify_change(dentry, &newattrs);
 182                         mutex_unlock(&dentry->d_inode->i_mutex);
 183
 184                         /* mark as kernel-created inode */
 185                         dentry->d_inode->i_private = &dev_mnt;
 186                 }
 187                 dput(dentry);
 188         } else {
 189                 err = PTR_ERR(dentry);
 190         }
 191
 192         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
 193         path_put(&nd.path);
 194 out:
 195         kfree(tmp);
 196         revert_creds(curr_cred);
 197         return err;
 198 }
 199
 200 static int dev_rmdir(const char *name)
 201 {
 202         struct nameidata nd;
 203         struct dentry *dentry;
 204         int err;
 205
 206         err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
 207                               name, LOOKUP_PARENT, &nd);
 208         if (err)
 209                 return err;
 210
 211         mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
 212         dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
 213         if (!IS_ERR(dentry)) {
 214                 if (dentry->d_inode) {
 215                         if (dentry->d_inode->i_private == &dev_mnt)
 216                                 err = vfs_rmdir(nd.path.dentry->d_inode,
 217                                                 dentry);
 218                         else
 219                                 err = -EPERM;
 220                 } else {
 221                         err = -ENOENT;
 222                 }
 223                 dput(dentry);
 224         } else {
 225                 err = PTR_ERR(dentry);
 226         }
 227
 228         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
 229         path_put(&nd.path);
 230         return err;
 231 }
 232
 233 static int delete_path(const char *nodepath)
 234 {
 235         const char *path;
 236         int err = 0;
 237
 238         path = kstrdup(nodepath, GFP_KERNEL);
 239         if (!path)
 240                 return -ENOMEM;
 241
 242         mutex_lock(&dirlock);
 243         for (;;) {
 244                 char *base;
 245
 246                 base = strrchr(path, '/');
 247                 if (!base)
 248                         break;
 249                 base[0] = '\0';
 250                 err = dev_rmdir(path);
 251                 if (err)
 252                         break;
 253         }
 254         mutex_unlock(&dirlock);
 255
 256         kfree(path);
 257         return err;
 258 }
 259
 260 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
 261 {
 262         /* did we create it */
 263         if (inode->i_private != &dev_mnt)
 264                 return 0;
 265
 266         /* does the dev_t match */
 267         if (is_blockdev(dev)) {
 268                 if (!S_ISBLK(stat->mode))
 269                         return 0;
 270         } else {
 271                 if (!S_ISCHR(stat->mode))
 272                         return 0;
 273         }
 274         if (stat->rdev != dev->devt)
 275                 return 0;
 276
 277         /* ours */
 278         return 1;
 279 }
 280
 281 int devtmpfs_delete_node(struct device *dev)
 282 {
 283         const char *tmp = NULL;
 284         const char *nodename;
 285         const struct cred *curr_cred;
 286         struct nameidata nd;
 287         struct dentry *dentry;
 288         struct kstat stat;
 289         int deleted = 1;
 290         int err;
 291
 292         if (!dev_mnt)
 293                 return 0;
 294
 295         nodename = device_get_devnode(dev, NULL, &tmp);
 296         if (!nodename)
 297                 return -ENOMEM;
 298
 299         curr_cred = override_creds(&init_cred);
 300         err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
 301                               nodename, LOOKUP_PARENT, &nd);
 302         if (err)
 303                 goto out;
 304
 305         mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
 306         dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
 307         if (!IS_ERR(dentry)) {
 308                 if (dentry->d_inode) {
 309                         err = vfs_getattr(nd.path.mnt, dentry, &stat);
 310                         if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
 311                                 struct iattr newattrs;
 312                                 /*
 313                                  * before unlinking this node, reset permissions
 314                                  * of possible references like hardlinks
 315                                  */
 316                                 newattrs.ia_uid = 0;
 317                                 newattrs.ia_gid = 0;
 318                                 newattrs.ia_mode = stat.mode & ~0777;
 319                                 newattrs.ia_valid =
 320                                         ATTR_UID|ATTR_GID|ATTR_MODE;
 321                                 mutex_lock(&dentry->d_inode->i_mutex);
 322                                 notify_change(dentry, &newattrs);
 323                                 mutex_unlock(&dentry->d_inode->i_mutex);
 324                                 err = vfs_unlink(nd.path.dentry->d_inode,
 325                                                  dentry);
 326                                 if (!err || err == -ENOENT)
 327                                         deleted = 1;
 328                         }
 329                 } else {
 330                         err = -ENOENT;
 331                 }
 332                 dput(dentry);
 333         } else {
 334                 err = PTR_ERR(dentry);
 335         }
 336         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
 337
 338         path_put(&nd.path);
 339         if (deleted && strchr(nodename, '/'))
 340                 delete_path(nodename);
 341 out:
 342         kfree(tmp);
 343         revert_creds(curr_cred);
 344         return err;
 345 }
 346
 347 /*
 348  * If configured, or requested by the commandline, devtmpfs will be
 349  * auto-mounted after the kernel mounted the root filesystem.
 350  */
 351 int devtmpfs_mount(const char *mntdir)
 352 {
 353         int err;
 354
 355         if (!dev_mount)
 356                 return 0;
 357
 358         if (!dev_mnt)
 359                 return 0;
 360
 361         err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
 362         if (err)
 363                 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
 364         else
 365                 printk(KERN_INFO "devtmpfs: mounted\n");
 366         return err;
 367 }
 368
 369 /*
 370  * Create devtmpfs instance, driver-core devices will add their device
 371  * nodes here.
 372  */
 373 int __init devtmpfs_init(void)
 374 {
 375         int err;
 376         struct vfsmount *mnt;
 377         char *options = "mode=0755";
 378         /* LR: char options[] = "..."; caused misaligned access, gcc issue */
 379
 380         err = register_filesystem(&dev_fs_type);
 381         if (err) {
 382                 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
 383                        "type %i\n", err);
 384                 return err;
 385         }
 386
 387         mnt = kern_mount_data(&dev_fs_type, options);
 388         if (IS_ERR(mnt)) {
 389                 err = PTR_ERR(mnt);
 390                 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
 391                 unregister_filesystem(&dev_fs_type);
 392                 return err;
 393         }
 394         dev_mnt = mnt;
 395
 396         printk(KERN_INFO "devtmpfs: initialized\n");
 397         return 0;
 398 }