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