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   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 parse_mount_options(char *data, struct pts_mount_opts *opts)
  76 {
  77         char *p;
  78
  79         opts->setuid  = 0;
  80         opts->setgid  = 0;
  81         opts->uid     = 0;
  82         opts->gid     = 0;
  83         opts->mode    = DEVPTS_DEFAULT_MODE;
  84
  85         while ((p = strsep(&data, ",")) != NULL) {
  86                 substring_t args[MAX_OPT_ARGS];
  87                 int token;
  88                 int option;
  89
  90                 if (!*p)
  91                         continue;
  92
  93                 token = match_token(p, tokens, args);
  94                 switch (token) {
  95                 case Opt_uid:
  96                         if (match_int(&args[0], &option))
  97                                 return -EINVAL;
  98                         opts->uid = option;
  99                         opts->setuid = 1;
 100                         break;
 101                 case Opt_gid:
 102                         if (match_int(&args[0], &option))
 103                                 return -EINVAL;
 104                         opts->gid = option;
 105                         opts->setgid = 1;
 106                         break;
 107                 case Opt_mode:
 108                         if (match_octal(&args[0], &option))
 109                                 return -EINVAL;
 110                         opts->mode = option & S_IALLUGO;
 111                         break;
 112                 default:
 113                         printk(KERN_ERR "devpts: called with bogus options\n");
 114                         return -EINVAL;
 115                 }
 116         }
 117
 118         return 0;
 119 }
 120
 121 static int devpts_remount(struct super_block *sb, int *flags, char *data)
 122 {
 123         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 124         struct pts_mount_opts *opts = &fsi->mount_opts;
 125
 126         return parse_mount_options(data, opts);
 127 }
 128
 129 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
 130 {
 131         struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
 132         struct pts_mount_opts *opts = &fsi->mount_opts;
 133
 134         if (opts->setuid)
 135                 seq_printf(seq, ",uid=%u", opts->uid);
 136         if (opts->setgid)
 137                 seq_printf(seq, ",gid=%u", opts->gid);
 138         seq_printf(seq, ",mode=%03o", opts->mode);
 139
 140         return 0;
 141 }
 142
 143 static const struct super_operations devpts_sops = {
 144         .statfs         = simple_statfs,
 145         .remount_fs     = devpts_remount,
 146         .show_options   = devpts_show_options,
 147 };
 148
 149 static void *new_pts_fs_info(void)
 150 {
 151         struct pts_fs_info *fsi;
 152
 153         fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
 154         if (!fsi)
 155                 return NULL;
 156
 157         ida_init(&fsi->allocated_ptys);
 158         fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
 159
 160         return fsi;
 161 }
 162
 163 static int
 164 devpts_fill_super(struct super_block *s, void *data, int silent)
 165 {
 166         struct inode * inode;
 167
 168         s->s_blocksize = 1024;
 169         s->s_blocksize_bits = 10;
 170         s->s_magic = DEVPTS_SUPER_MAGIC;
 171         s->s_op = &devpts_sops;
 172         s->s_time_gran = 1;
 173
 174         s->s_fs_info = new_pts_fs_info();
 175         if (!s->s_fs_info)
 176                 goto fail;
 177
 178         inode = new_inode(s);
 179         if (!inode)
 180                 goto free_fsi;
 181         inode->i_ino = 1;
 182         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 183         inode->i_blocks = 0;
 184         inode->i_uid = inode->i_gid = 0;
 185         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 186         inode->i_op = &simple_dir_inode_operations;
 187         inode->i_fop = &simple_dir_operations;
 188         inode->i_nlink = 2;
 189
 190         s->s_root = d_alloc_root(inode);
 191         if (s->s_root)
 192                 return 0;
 193
 194         printk("devpts: get root dentry failed\n");
 195         iput(inode);
 196
 197 free_fsi:
 198         kfree(s->s_fs_info);
 199 fail:
 200         return -ENOMEM;
 201 }
 202
 203 static int devpts_get_sb(struct file_system_type *fs_type,
 204         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 205 {
 206         return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
 207 }
 208
 209 static void devpts_kill_sb(struct super_block *sb)
 210 {
 211         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 212
 213         kfree(fsi);
 214         kill_anon_super(sb);
 215 }
 216
 217 static struct file_system_type devpts_fs_type = {
 218         .owner          = THIS_MODULE,
 219         .name           = "devpts",
 220         .get_sb         = devpts_get_sb,
 221         .kill_sb        = devpts_kill_sb,
 222 };
 223
 224 /*
 225  * The normal naming convention is simply /dev/pts/<number>; this conforms
 226  * to the System V naming convention
 227  */
 228
 229 int devpts_new_index(struct inode *ptmx_inode)
 230 {
 231         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
 232         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 233         int index;
 234         int ida_ret;
 235
 236 retry:
 237         if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
 238                 return -ENOMEM;
 239         }
 240
 241         mutex_lock(&allocated_ptys_lock);
 242         ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
 243         if (ida_ret < 0) {
 244                 mutex_unlock(&allocated_ptys_lock);
 245                 if (ida_ret == -EAGAIN)
 246                         goto retry;
 247                 return -EIO;
 248         }
 249
 250         if (index >= pty_limit) {
 251                 ida_remove(&fsi->allocated_ptys, index);
 252                 mutex_unlock(&allocated_ptys_lock);
 253                 return -EIO;
 254         }
 255         mutex_unlock(&allocated_ptys_lock);
 256         return index;
 257 }
 258
 259 void devpts_kill_index(struct inode *ptmx_inode, int idx)
 260 {
 261         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
 262         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 263
 264         mutex_lock(&allocated_ptys_lock);
 265         ida_remove(&fsi->allocated_ptys, idx);
 266         mutex_unlock(&allocated_ptys_lock);
 267 }
 268
 269 int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
 270 {
 271         int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
 272         struct tty_driver *driver = tty->driver;
 273         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 274         struct dentry *dentry;
 275         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
 276         struct inode *inode = new_inode(sb);
 277         struct dentry *root = sb->s_root;
 278         struct pts_fs_info *fsi = DEVPTS_SB(sb);
 279         struct pts_mount_opts *opts = &fsi->mount_opts;
 280         char s[12];
 281
 282         /* We're supposed to be given the slave end of a pty */
 283         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 284         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 285
 286         if (!inode)
 287                 return -ENOMEM;
 288
 289         inode->i_ino = number+2;
 290         inode->i_uid = config.setuid ? config.uid : current_fsuid();
 291         inode->i_gid = config.setgid ? config.gid : current_fsgid();
 292         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 293         init_special_inode(inode, S_IFCHR|opts->mode, device);
 294         inode->i_private = tty;
 295         tty->driver_data = inode;
 296
 297         sprintf(s, "%d", number);
 298
 299         mutex_lock(&root->d_inode->i_mutex);
 300
 301         dentry = d_alloc_name(root, s);
 302         if (!IS_ERR(dentry)) {
 303                 d_add(dentry, inode);
 304                 fsnotify_create(root->d_inode, dentry);
 305         }
 306
 307         mutex_unlock(&root->d_inode->i_mutex);
 308
 309         return 0;
 310 }
 311
 312 struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
 313 {
 314         BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
 315
 316         if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
 317                 return (struct tty_struct *)pts_inode->i_private;
 318         return NULL;
 319 }
 320
 321 void devpts_pty_kill(struct tty_struct *tty)
 322 {
 323         struct inode *inode = tty->driver_data;
 324         struct super_block *sb = pts_sb_from_inode(inode);
 325         struct dentry *root = sb->s_root;
 326         struct dentry *dentry;
 327
 328         BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
 329
 330         mutex_lock(&root->d_inode->i_mutex);
 331
 332         dentry = d_find_alias(inode);
 333         if (dentry && !IS_ERR(dentry)) {
 334                 inode->i_nlink--;
 335                 d_delete(dentry);
 336                 dput(dentry);
 337         }
 338
 339         mutex_unlock(&root->d_inode->i_mutex);
 340 }
 341
 342 static int __init init_devpts_fs(void)
 343 {
 344         int err = register_filesystem(&devpts_fs_type);
 345         if (!err) {
 346                 devpts_mnt = kern_mount(&devpts_fs_type);
 347                 if (IS_ERR(devpts_mnt))
 348                         err = PTR_ERR(devpts_mnt);
 349         }
 350         return err;
 351 }
 352
 353 static void __exit exit_devpts_fs(void)
 354 {
 355         unregister_filesystem(&devpts_fs_type);
 356         mntput(devpts_mnt);
 357 }
 358
 359 module_init(init_devpts_fs)
 360 module_exit(exit_devpts_fs)
 361 MODULE_LICENSE("GPL");