fs/devpts/inode.c

   1 /* -*- linux-c -*- --------------------------------------------------------- *
   2  *
   3  * linux/fs/devpts/inode.c
   4  *
   5  *  Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
   6  *
   7  * This file is part of the Linux kernel and is made available under
   8  * the terms of the GNU General Public License, version 2, or at your
   9  * option, any later version, incorporated herein by reference.
  10  *
  11  * ------------------------------------------------------------------------- */
  12
  13 #include <linux/module.h>
  14 #include <linux/init.h>
  15 #include <linux/fs.h>
  16 #include <linux/sched.h>
  17 #include <linux/namei.h>
  18 #include <linux/mount.h>
  19 #include <linux/tty.h>
  20 #include <linux/mutex.h>
  21 #include <linux/idr.h>
  22 #include <linux/devpts_fs.h>
  23 #include <linux/parser.h>
  24 #include <linux/fsnotify.h>
  25 #include <linux/seq_file.h>
  26
  27 #define DEVPTS_SUPER_MAGIC 0x1cd1
  28
  29 #define DEVPTS_DEFAULT_MODE 0600
  30 #define PTMX_MINOR      2
  31
  32 extern int pty_limit;                   /* Config limit on Unix98 ptys */
  33 static DEFINE_MUTEX(allocated_ptys_lock);
  34
  35 static struct vfsmount *devpts_mnt;
  36
  37 struct pts_mount_opts {
  38         int setuid;
  39         int setgid;
  40         uid_t   uid;
  41         gid_t   gid;
  42         umode_t mode;
  43 };
  44
  45 enum {
  46         Opt_uid, Opt_gid, Opt_mode,
  47         Opt_err
  48 };
  49
  50 static const match_table_t tokens = {
  51         {Opt_uid, "uid=%u"},
  52         {Opt_gid, "gid=%u"},
  53         {Opt_mode, "mode=%o"},
  54         {Opt_err, NULL}
  55 };
  56
  57 struct pts_fs_info {
  58         struct ida allocated_ptys;
  59         struct pts_mount_opts mount_opts;
  60 };
  61
  62 static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
  63 {
  64         return sb->s_fs_info;
  65 }
  66
  67 static inline struct super_block *pts_sb_from_inode(struct inode *inode)
  68 {
  69         if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
  70                 return inode->i_sb;
  71
  72         return devpts_mnt->mnt_sb;
  73 }
  74
  75 static int devpts_remount(struct super_block *sb, int *flags, char *data)
  76 {
  77         char *p;
  78         struct pts_fs_info *fsi = DEVPTS_SB(sb);
  79         struct pts_mount_opts *opts = &fsi->mount_opts;
  80
  81         opts->setuid  = 0;
  82         opts->setgid  = 0;
  83         opts->uid     = 0;
  84         opts->gid     = 0;
  85         opts->mode    = DEVPTS_DEFAULT_MODE;
  86
  87         while ((p = strsep(&data, ",")) != NULL) {
  88                 substring_t args[MAX_OPT_ARGS];
  89                 int token;
  90                 int option;
  91
  92                 if (!*p)
  93                         continue;
  94
  95                 token = match_token(p, tokens, args);
  96                 switch (token) {
  97                 case Opt_uid:
  98                         if (match_int(&args[0], &option))
  99                                 return -EINVAL;
 100                         opts->uid = option;
 101                         opts->setuid = 1;
 102                         break;
 103                 case Opt_gid:
 104                         if (match_int(&args[0], &option))
 105                                 return -EINVAL;
 106                         opts->gid = option;
 107                         opts->setgid = 1;
 108                         break;
 109                 case Opt_mode:
 110                         if (match_octal(&args[0], &option))
 111                                 return -EINVAL;
 112                         opts->mode = option & S_IALLUGO;
 113                         break;
 114                 default:
 115                         printk(KERN_ERR "devpts: called with bogus options\n");
 116                         return -EINVAL;
 117                 }
 118         }
 119
 120         return 0;
 121 }
 122
 123 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
 124 {
 125         struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
 126         struct pts_mount_opts *opts = &fsi->mount_opts;
 127
 128         if (opts->setuid)
 129                 seq_printf(seq, ",uid=%u", opts->uid);
 130         if (opts->setgid)
 131                 seq_printf(seq, ",gid=%u", opts->gid);
 132         seq_printf(seq, ",mode=%03o", opts->mode);
 133
 134         return 0;
 135 }
 136
 137 static const struct super_operations devpts_sops = {
 138         .statfs         = simple_statfs,
 139         .remount_fs     = devpts_remount,
 140         .show_options   = devpts_show_options,
 141 };
 142
 143 static void *new_pts_fs_info(void)
 144 {
 145         struct pts_fs_info *fsi;
 146
 147         fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
 148         if (!fsi)
 149                 return NULL;
 150
 151         ida_init(&fsi->allocated_ptys);
 152         fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
 153
 154         return fsi;
 155 }
 156
 157 static int
 158 devpts_fill_super(struct super_block *s, void *data, int silent)
 159 {
 160         struct inode * inode;
 161
 162         s->s_blocksize = 1024;
 163         s->s_blocksize_bits = 10;
 164         s->s_magic = DEVPTS_SUPER_MAGIC;
 165         s->s_op = &devpts_sops;
 166         s->s_time_gran = 1;
 167
 168         s->s_fs_info = new_pts_fs_info();
 169         if (!s->s_fs_info)
 170                 goto fail;
 171
 172         inode = new_inode(s);
 173         if (!inode)
 174                 goto free_fsi;
 175         inode->i_ino = 1;
 176         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 177         inode->i_blocks = 0;
 178         inode->i_uid = inode->i_gid = 0;
 179         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 180         inode->i_op = &simple_dir_inode_operations;
 181         inode->i_fop = &simple_dir_operations;
 182         inode->i_nlink = 2;
 183
 184         s->s_root = d_alloc_root(inode);
 185         if (s->s_root)
 186                 return 0;
 187
 188         printk("devpts: get root dentry failed\n");
 189         iput(inode);
 190
 191 free_fsi:
 192         kfree(s->s_fs_info);
 193 fail:
 194         return -ENOMEM;
 195 }
 196
 197 static int devpts_get_sb(struct file_system_type *fs_type,
 198         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 199 {
 200         return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
 201 }
 202
 203 static void devpts_kill_sb(struct super_block *sb)
 204 {
 205         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 206
 207         kfree(fsi);
 208         kill_anon_super(sb);
 209 }
 210
 211 static struct file_system_type devpts_fs_type = {
 212         .owner          = THIS_MODULE,
 213         .name           = "devpts",
 214         .get_sb         = devpts_get_sb,
 215         .kill_sb        = devpts_kill_sb,
 216 };
 217
 218 /*
 219  * The normal naming convention is simply /dev/pts/<number>; this conforms
 220  * to the System V naming convention
 221  */
 222
 223 int devpts_new_index(struct inode *ptmx_inode)
 224 {
 225         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
 226         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 227         int index;
 228         int ida_ret;
 229
 230 retry:
 231         if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
 232                 return -ENOMEM;
 233         }
 234
 235         mutex_lock(&allocated_ptys_lock);
 236         ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
 237         if (ida_ret < 0) {
 238                 mutex_unlock(&allocated_ptys_lock);
 239                 if (ida_ret == -EAGAIN)
 240                         goto retry;
 241                 return -EIO;
 242         }
 243
 244         if (index >= pty_limit) {
 245                 ida_remove(&fsi->allocated_ptys, index);
 246                 mutex_unlock(&allocated_ptys_lock);
 247                 return -EIO;
 248         }
 249         mutex_unlock(&allocated_ptys_lock);
 250         return index;
 251 }
 252
 253 void devpts_kill_index(struct inode *ptmx_inode, int idx)
 254 {
 255         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
 256         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 257
 258         mutex_lock(&allocated_ptys_lock);
 259         ida_remove(&fsi->allocated_ptys, idx);
 260         mutex_unlock(&allocated_ptys_lock);
 261 }
 262
 263 int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
 264 {
 265         int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
 266         struct tty_driver *driver = tty->driver;
 267         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 268         struct dentry *dentry;
 269         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
 270         struct inode *inode = new_inode(sb);
 271         struct dentry *root = sb->s_root;
 272         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 273         struct pts_mount_opts *opts = &fsi->mount_opts;
 274         char s[12];
 275
 276         /* We're supposed to be given the slave end of a pty */
 277         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 278         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 279
 280         if (!inode)
 281                 return -ENOMEM;
 282
 283         inode->i_ino = number+2;
 284         inode->i_uid = config.setuid ? config.uid : current_fsuid();
 285         inode->i_gid = config.setgid ? config.gid : current_fsgid();
 286         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 287         init_special_inode(inode, S_IFCHR|opts->mode, device);
 288         inode->i_private = tty;
 289         tty->driver_data = inode;
 290
 291         sprintf(s, "%d", number);
 292
 293         mutex_lock(&root->d_inode->i_mutex);
 294
 295         dentry = d_alloc_name(root, s);
 296         if (!IS_ERR(dentry)) {
 297                 d_add(dentry, inode);
 298                 fsnotify_create(root->d_inode, dentry);
 299         }
 300
 301         mutex_unlock(&root->d_inode->i_mutex);
 302
 303         return 0;
 304 }
 305
 306 struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
 307 {
 308         BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
 309
 310         if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
 311                 return (struct tty_struct *)pts_inode->i_private;
 312         return NULL;
 313 }
 314
 315 void devpts_pty_kill(struct tty_struct *tty)
 316 {
 317         struct inode *inode = tty->driver_data;
 318         struct super_block *sb = pts_sb_from_inode(inode);
 319         struct dentry *root = sb->s_root;
 320         struct dentry *dentry;
 321
 322         BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
 323
 324         mutex_lock(&root->d_inode->i_mutex);
 325
 326         dentry = d_find_alias(inode);
 327         if (dentry && !IS_ERR(dentry)) {
 328                 inode->i_nlink--;
 329                 d_delete(dentry);
 330                 dput(dentry);
 331         }
 332
 333         mutex_unlock(&root->d_inode->i_mutex);
 334 }
 335
 336 static int __init init_devpts_fs(void)
 337 {
 338         int err = register_filesystem(&devpts_fs_type);
 339         if (!err) {
 340                 devpts_mnt = kern_mount(&devpts_fs_type);
 341                 if (IS_ERR(devpts_mnt))
 342                         err = PTR_ERR(devpts_mnt);
 343         }
 344         return err;
 345 }
 346
 347 static void __exit exit_devpts_fs(void)
 348 {
 349         unregister_filesystem(&devpts_fs_type);
 350         mntput(devpts_mnt);
 351 }
 352
 353 module_init(init_devpts_fs)
 354 module_exit(exit_devpts_fs)
 355 MODULE_LICENSE("GPL");