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