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
  31 extern int pty_limit;                   /* Config limit on Unix98 ptys */
  32 static DEFINE_IDA(allocated_ptys);
  33 static DEFINE_MUTEX(allocated_ptys_lock);
  34
  35 static struct vfsmount *devpts_mnt;
  36 static struct dentry *devpts_root;
  37
  38 static struct {
  39         int setuid;
  40         int setgid;
  41         uid_t   uid;
  42         gid_t   gid;
  43         umode_t mode;
  44 } config = {.mode = DEVPTS_DEFAULT_MODE};
  45
  46 enum {
  47         Opt_uid, Opt_gid, Opt_mode,
  48         Opt_err
  49 };
  50
  51 static match_table_t tokens = {
  52         {Opt_uid, "uid=%u"},
  53         {Opt_gid, "gid=%u"},
  54         {Opt_mode, "mode=%o"},
  55         {Opt_err, NULL}
  56 };
  57
  58 static int devpts_remount(struct super_block *sb, int *flags, char *data)
  59 {
  60         char *p;
  61
  62         config.setuid  = 0;
  63         config.setgid  = 0;
  64         config.uid     = 0;
  65         config.gid     = 0;
  66         config.mode    = DEVPTS_DEFAULT_MODE;
  67
  68         while ((p = strsep(&data, ",")) != NULL) {
  69                 substring_t args[MAX_OPT_ARGS];
  70                 int token;
  71                 int option;
  72
  73                 if (!*p)
  74                         continue;
  75
  76                 token = match_token(p, tokens, args);
  77                 switch (token) {
  78                 case Opt_uid:
  79                         if (match_int(&args[0], &option))
  80                                 return -EINVAL;
  81                         config.uid = option;
  82                         config.setuid = 1;
  83                         break;
  84                 case Opt_gid:
  85                         if (match_int(&args[0], &option))
  86                                 return -EINVAL;
  87                         config.gid = option;
  88                         config.setgid = 1;
  89                         break;
  90                 case Opt_mode:
  91                         if (match_octal(&args[0], &option))
  92                                 return -EINVAL;
  93                         config.mode = option & S_IALLUGO;
  94                         break;
  95                 default:
  96                         printk(KERN_ERR "devpts: called with bogus options\n");
  97                         return -EINVAL;
  98                 }
  99         }
 100
 101         return 0;
 102 }
 103
 104 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
 105 {
 106         if (config.setuid)
 107                 seq_printf(seq, ",uid=%u", config.uid);
 108         if (config.setgid)
 109                 seq_printf(seq, ",gid=%u", config.gid);
 110         seq_printf(seq, ",mode=%03o", config.mode);
 111
 112         return 0;
 113 }
 114
 115 static const struct super_operations devpts_sops = {
 116         .statfs         = simple_statfs,
 117         .remount_fs     = devpts_remount,
 118         .show_options   = devpts_show_options,
 119 };
 120
 121 static int
 122 devpts_fill_super(struct super_block *s, void *data, int silent)
 123 {
 124         struct inode * inode;
 125
 126         s->s_blocksize = 1024;
 127         s->s_blocksize_bits = 10;
 128         s->s_magic = DEVPTS_SUPER_MAGIC;
 129         s->s_op = &devpts_sops;
 130         s->s_time_gran = 1;
 131
 132         inode = new_inode(s);
 133         if (!inode)
 134                 goto fail;
 135         inode->i_ino = 1;
 136         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 137         inode->i_blocks = 0;
 138         inode->i_uid = inode->i_gid = 0;
 139         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 140         inode->i_op = &simple_dir_inode_operations;
 141         inode->i_fop = &simple_dir_operations;
 142         inode->i_nlink = 2;
 143
 144         devpts_root = s->s_root = d_alloc_root(inode);
 145         if (s->s_root)
 146                 return 0;
 147
 148         printk("devpts: get root dentry failed\n");
 149         iput(inode);
 150 fail:
 151         return -ENOMEM;
 152 }
 153
 154 static int devpts_get_sb(struct file_system_type *fs_type,
 155         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 156 {
 157         return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
 158 }
 159
 160 static struct file_system_type devpts_fs_type = {
 161         .owner          = THIS_MODULE,
 162         .name           = "devpts",
 163         .get_sb         = devpts_get_sb,
 164         .kill_sb        = kill_anon_super,
 165 };
 166
 167 /*
 168  * The normal naming convention is simply /dev/pts/<number>; this conforms
 169  * to the System V naming convention
 170  */
 171
 172 static struct dentry *get_node(int num)
 173 {
 174         char s[12];
 175         struct dentry *root = devpts_root;
 176         mutex_lock(&root->d_inode->i_mutex);
 177         return lookup_one_len(s, root, sprintf(s, "%d", num));
 178 }
 179
 180 int devpts_new_index(void)
 181 {
 182         int index;
 183         int ida_ret;
 184
 185 retry:
 186         if (!ida_pre_get(&allocated_ptys, GFP_KERNEL)) {
 187                 return -ENOMEM;
 188         }
 189
 190         mutex_lock(&allocated_ptys_lock);
 191         ida_ret = ida_get_new(&allocated_ptys, &index);
 192         if (ida_ret < 0) {
 193                 mutex_unlock(&allocated_ptys_lock);
 194                 if (ida_ret == -EAGAIN)
 195                         goto retry;
 196                 return -EIO;
 197         }
 198
 199         if (index >= pty_limit) {
 200                 ida_remove(&allocated_ptys, index);
 201                 mutex_unlock(&allocated_ptys_lock);
 202                 return -EIO;
 203         }
 204         mutex_unlock(&allocated_ptys_lock);
 205         return index;
 206 }
 207
 208 void devpts_kill_index(int idx)
 209 {
 210         mutex_lock(&allocated_ptys_lock);
 211         ida_remove(&allocated_ptys, idx);
 212         mutex_unlock(&allocated_ptys_lock);
 213 }
 214
 215 int devpts_pty_new(struct tty_struct *tty)
 216 {
 217         int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
 218         struct tty_driver *driver = tty->driver;
 219         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 220         struct dentry *dentry;
 221         struct inode *inode = new_inode(devpts_mnt->mnt_sb);
 222
 223         /* We're supposed to be given the slave end of a pty */
 224         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 225         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 226
 227         if (!inode)
 228                 return -ENOMEM;
 229
 230         inode->i_ino = number+2;
 231         inode->i_uid = config.setuid ? config.uid : current->fsuid;
 232         inode->i_gid = config.setgid ? config.gid : current->fsgid;
 233         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 234         init_special_inode(inode, S_IFCHR|config.mode, device);
 235         inode->i_private = tty;
 236
 237         dentry = get_node(number);
 238         if (!IS_ERR(dentry) && !dentry->d_inode) {
 239                 d_instantiate(dentry, inode);
 240                 fsnotify_create(devpts_root->d_inode, dentry);
 241         }
 242
 243         mutex_unlock(&devpts_root->d_inode->i_mutex);
 244
 245         return 0;
 246 }
 247
 248 struct tty_struct *devpts_get_tty(int number)
 249 {
 250         struct dentry *dentry = get_node(number);
 251         struct tty_struct *tty;
 252
 253         tty = NULL;
 254         if (!IS_ERR(dentry)) {
 255                 if (dentry->d_inode)
 256                         tty = dentry->d_inode->i_private;
 257                 dput(dentry);
 258         }
 259
 260         mutex_unlock(&devpts_root->d_inode->i_mutex);
 261
 262         return tty;
 263 }
 264
 265 void devpts_pty_kill(int number)
 266 {
 267         struct dentry *dentry = get_node(number);
 268
 269         if (!IS_ERR(dentry)) {
 270                 struct inode *inode = dentry->d_inode;
 271                 if (inode) {
 272                         inode->i_nlink--;
 273                         d_delete(dentry);
 274                         dput(dentry);
 275                 }
 276                 dput(dentry);
 277         }
 278         mutex_unlock(&devpts_root->d_inode->i_mutex);
 279 }
 280
 281 static int __init init_devpts_fs(void)
 282 {
 283         int err = register_filesystem(&devpts_fs_type);
 284         if (!err) {
 285                 devpts_mnt = kern_mount(&devpts_fs_type);
 286                 if (IS_ERR(devpts_mnt))
 287                         err = PTR_ERR(devpts_mnt);
 288         }
 289         return err;
 290 }
 291
 292 static void __exit exit_devpts_fs(void)
 293 {
 294         unregister_filesystem(&devpts_fs_type);
 295         mntput(devpts_mnt);
 296 }
 297
 298 module_init(init_devpts_fs)
 299 module_exit(exit_devpts_fs)
 300 MODULE_LICENSE("GPL");