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/devpts_fs.h>
  21 #include <linux/parser.h>
  22 #include <linux/fsnotify.h>
  23
  24 #define DEVPTS_SUPER_MAGIC 0x1cd1
  25
  26 static struct vfsmount *devpts_mnt;
  27 static struct dentry *devpts_root;
  28
  29 static struct {
  30         int setuid;
  31         int setgid;
  32         uid_t   uid;
  33         gid_t   gid;
  34         umode_t mode;
  35 } config = {.mode = 0600};
  36
  37 enum {
  38         Opt_uid, Opt_gid, Opt_mode,
  39         Opt_err
  40 };
  41
  42 static match_table_t tokens = {
  43         {Opt_uid, "uid=%u"},
  44         {Opt_gid, "gid=%u"},
  45         {Opt_mode, "mode=%o"},
  46         {Opt_err, NULL}
  47 };
  48
  49 static int devpts_remount(struct super_block *sb, int *flags, char *data)
  50 {
  51         char *p;
  52
  53         config.setuid  = 0;
  54         config.setgid  = 0;
  55         config.uid     = 0;
  56         config.gid     = 0;
  57         config.mode    = 0600;
  58
  59         while ((p = strsep(&data, ",")) != NULL) {
  60                 substring_t args[MAX_OPT_ARGS];
  61                 int token;
  62                 int option;
  63
  64                 if (!*p)
  65                         continue;
  66
  67                 token = match_token(p, tokens, args);
  68                 switch (token) {
  69                 case Opt_uid:
  70                         if (match_int(&args[0], &option))
  71                                 return -EINVAL;
  72                         config.uid = option;
  73                         config.setuid = 1;
  74                         break;
  75                 case Opt_gid:
  76                         if (match_int(&args[0], &option))
  77                                 return -EINVAL;
  78                         config.gid = option;
  79                         config.setgid = 1;
  80                         break;
  81                 case Opt_mode:
  82                         if (match_octal(&args[0], &option))
  83                                 return -EINVAL;
  84                         config.mode = option & ~S_IFMT;
  85                         break;
  86                 default:
  87                         printk(KERN_ERR "devpts: called with bogus options\n");
  88                         return -EINVAL;
  89                 }
  90         }
  91
  92         return 0;
  93 }
  94
  95 static const struct super_operations devpts_sops = {
  96         .statfs         = simple_statfs,
  97         .remount_fs     = devpts_remount,
  98 };
  99
 100 static int
 101 devpts_fill_super(struct super_block *s, void *data, int silent)
 102 {
 103         struct inode * inode;
 104
 105         s->s_blocksize = 1024;
 106         s->s_blocksize_bits = 10;
 107         s->s_magic = DEVPTS_SUPER_MAGIC;
 108         s->s_op = &devpts_sops;
 109         s->s_time_gran = 1;
 110
 111         inode = new_inode(s);
 112         if (!inode)
 113                 goto fail;
 114         inode->i_ino = 1;
 115         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 116         inode->i_blocks = 0;
 117         inode->i_uid = inode->i_gid = 0;
 118         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 119         inode->i_op = &simple_dir_inode_operations;
 120         inode->i_fop = &simple_dir_operations;
 121         inode->i_nlink = 2;
 122
 123         devpts_root = s->s_root = d_alloc_root(inode);
 124         if (s->s_root)
 125                 return 0;
 126
 127         printk("devpts: get root dentry failed\n");
 128         iput(inode);
 129 fail:
 130         return -ENOMEM;
 131 }
 132
 133 static int devpts_get_sb(struct file_system_type *fs_type,
 134         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 135 {
 136         return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
 137 }
 138
 139 static struct file_system_type devpts_fs_type = {
 140         .owner          = THIS_MODULE,
 141         .name           = "devpts",
 142         .get_sb         = devpts_get_sb,
 143         .kill_sb        = kill_anon_super,
 144 };
 145
 146 /*
 147  * The normal naming convention is simply /dev/pts/<number>; this conforms
 148  * to the System V naming convention
 149  */
 150
 151 static struct dentry *get_node(int num)
 152 {
 153         char s[12];
 154         struct dentry *root = devpts_root;
 155         mutex_lock(&root->d_inode->i_mutex);
 156         return lookup_one_len(s, root, sprintf(s, "%d", num));
 157 }
 158
 159 int devpts_pty_new(struct tty_struct *tty)
 160 {
 161         int number = tty->index;
 162         struct tty_driver *driver = tty->driver;
 163         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 164         struct dentry *dentry;
 165         struct inode *inode = new_inode(devpts_mnt->mnt_sb);
 166
 167         /* We're supposed to be given the slave end of a pty */
 168         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 169         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 170
 171         if (!inode)
 172                 return -ENOMEM;
 173
 174         inode->i_ino = number+2;
 175         inode->i_uid = config.setuid ? config.uid : current->fsuid;
 176         inode->i_gid = config.setgid ? config.gid : current->fsgid;
 177         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 178         init_special_inode(inode, S_IFCHR|config.mode, device);
 179         inode->i_private = tty;
 180
 181         dentry = get_node(number);
 182         if (!IS_ERR(dentry) && !dentry->d_inode) {
 183                 d_instantiate(dentry, inode);
 184                 fsnotify_create(devpts_root->d_inode, dentry);
 185         }
 186
 187         mutex_unlock(&devpts_root->d_inode->i_mutex);
 188
 189         return 0;
 190 }
 191
 192 struct tty_struct *devpts_get_tty(int number)
 193 {
 194         struct dentry *dentry = get_node(number);
 195         struct tty_struct *tty;
 196
 197         tty = NULL;
 198         if (!IS_ERR(dentry)) {
 199                 if (dentry->d_inode)
 200                         tty = dentry->d_inode->i_private;
 201                 dput(dentry);
 202         }
 203
 204         mutex_unlock(&devpts_root->d_inode->i_mutex);
 205
 206         return tty;
 207 }
 208
 209 void devpts_pty_kill(int number)
 210 {
 211         struct dentry *dentry = get_node(number);
 212
 213         if (!IS_ERR(dentry)) {
 214                 struct inode *inode = dentry->d_inode;
 215                 if (inode) {
 216                         inode->i_nlink--;
 217                         d_delete(dentry);
 218                         dput(dentry);
 219                 }
 220                 dput(dentry);
 221         }
 222         mutex_unlock(&devpts_root->d_inode->i_mutex);
 223 }
 224
 225 static int __init init_devpts_fs(void)
 226 {
 227         int err = register_filesystem(&devpts_fs_type);
 228         if (!err) {
 229                 devpts_mnt = kern_mount(&devpts_fs_type);
 230                 if (IS_ERR(devpts_mnt))
 231                         err = PTR_ERR(devpts_mnt);
 232         }
 233         return err;
 234 }
 235
 236 static void __exit exit_devpts_fs(void)
 237 {
 238         unregister_filesystem(&devpts_fs_type);
 239         mntput(devpts_mnt);
 240 }
 241
 242 module_init(init_devpts_fs)
 243 module_exit(exit_devpts_fs)
 244 MODULE_LICENSE("GPL");