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 #include <linux/seq_file.h>
  24
  25 #define DEVPTS_SUPER_MAGIC 0x1cd1
  26
  27 #define DEVPTS_DEFAULT_MODE 0600
  28
  29 static struct vfsmount *devpts_mnt;
  30 static struct dentry *devpts_root;
  31
  32 static struct {
  33         int setuid;
  34         int setgid;
  35         uid_t   uid;
  36         gid_t   gid;
  37         umode_t mode;
  38 } config = {.mode = DEVPTS_DEFAULT_MODE};
  39
  40 enum {
  41         Opt_uid, Opt_gid, Opt_mode,
  42         Opt_err
  43 };
  44
  45 static match_table_t tokens = {
  46         {Opt_uid, "uid=%u"},
  47         {Opt_gid, "gid=%u"},
  48         {Opt_mode, "mode=%o"},
  49         {Opt_err, NULL}
  50 };
  51
  52 static int devpts_remount(struct super_block *sb, int *flags, char *data)
  53 {
  54         char *p;
  55
  56         config.setuid  = 0;
  57         config.setgid  = 0;
  58         config.uid     = 0;
  59         config.gid     = 0;
  60         config.mode    = DEVPTS_DEFAULT_MODE;
  61
  62         while ((p = strsep(&data, ",")) != NULL) {
  63                 substring_t args[MAX_OPT_ARGS];
  64                 int token;
  65                 int option;
  66
  67                 if (!*p)
  68                         continue;
  69
  70                 token = match_token(p, tokens, args);
  71                 switch (token) {
  72                 case Opt_uid:
  73                         if (match_int(&args[0], &option))
  74                                 return -EINVAL;
  75                         config.uid = option;
  76                         config.setuid = 1;
  77                         break;
  78                 case Opt_gid:
  79                         if (match_int(&args[0], &option))
  80                                 return -EINVAL;
  81                         config.gid = option;
  82                         config.setgid = 1;
  83                         break;
  84                 case Opt_mode:
  85                         if (match_octal(&args[0], &option))
  86                                 return -EINVAL;
  87                         config.mode = option & S_IALLUGO;
  88                         break;
  89                 default:
  90                         printk(KERN_ERR "devpts: called with bogus options\n");
  91                         return -EINVAL;
  92                 }
  93         }
  94
  95         return 0;
  96 }
  97
  98 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
  99 {
 100         if (config.setuid)
 101                 seq_printf(seq, ",uid=%u", config.uid);
 102         if (config.setgid)
 103                 seq_printf(seq, ",gid=%u", config.gid);
 104         seq_printf(seq, ",mode=%03o", config.mode);
 105
 106         return 0;
 107 }
 108
 109 static const struct super_operations devpts_sops = {
 110         .statfs         = simple_statfs,
 111         .remount_fs     = devpts_remount,
 112         .show_options   = devpts_show_options,
 113 };
 114
 115 static int
 116 devpts_fill_super(struct super_block *s, void *data, int silent)
 117 {
 118         struct inode * inode;
 119
 120         s->s_blocksize = 1024;
 121         s->s_blocksize_bits = 10;
 122         s->s_magic = DEVPTS_SUPER_MAGIC;
 123         s->s_op = &devpts_sops;
 124         s->s_time_gran = 1;
 125
 126         inode = new_inode(s);
 127         if (!inode)
 128                 goto fail;
 129         inode->i_ino = 1;
 130         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 131         inode->i_blocks = 0;
 132         inode->i_uid = inode->i_gid = 0;
 133         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 134         inode->i_op = &simple_dir_inode_operations;
 135         inode->i_fop = &simple_dir_operations;
 136         inode->i_nlink = 2;
 137
 138         devpts_root = s->s_root = d_alloc_root(inode);
 139         if (s->s_root)
 140                 return 0;
 141
 142         printk("devpts: get root dentry failed\n");
 143         iput(inode);
 144 fail:
 145         return -ENOMEM;
 146 }
 147
 148 static int devpts_get_sb(struct file_system_type *fs_type,
 149         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 150 {
 151         return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
 152 }
 153
 154 static struct file_system_type devpts_fs_type = {
 155         .owner          = THIS_MODULE,
 156         .name           = "devpts",
 157         .get_sb         = devpts_get_sb,
 158         .kill_sb        = kill_anon_super,
 159 };
 160
 161 /*
 162  * The normal naming convention is simply /dev/pts/<number>; this conforms
 163  * to the System V naming convention
 164  */
 165
 166 static struct dentry *get_node(int num)
 167 {
 168         char s[12];
 169         struct dentry *root = devpts_root;
 170         mutex_lock(&root->d_inode->i_mutex);
 171         return lookup_one_len(s, root, sprintf(s, "%d", num));
 172 }
 173
 174 int devpts_pty_new(struct tty_struct *tty)
 175 {
 176         int number = tty->index;
 177         struct tty_driver *driver = tty->driver;
 178         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 179         struct dentry *dentry;
 180         struct inode *inode = new_inode(devpts_mnt->mnt_sb);
 181
 182         /* We're supposed to be given the slave end of a pty */
 183         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 184         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 185
 186         if (!inode)
 187                 return -ENOMEM;
 188
 189         inode->i_ino = number+2;
 190         inode->i_uid = config.setuid ? config.uid : current->fsuid;
 191         inode->i_gid = config.setgid ? config.gid : current->fsgid;
 192         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 193         init_special_inode(inode, S_IFCHR|config.mode, device);
 194         inode->i_private = tty;
 195
 196         dentry = get_node(number);
 197         if (!IS_ERR(dentry) && !dentry->d_inode) {
 198                 d_instantiate(dentry, inode);
 199                 fsnotify_create(devpts_root->d_inode, dentry);
 200         }
 201
 202         mutex_unlock(&devpts_root->d_inode->i_mutex);
 203
 204         return 0;
 205 }
 206
 207 struct tty_struct *devpts_get_tty(int number)
 208 {
 209         struct dentry *dentry = get_node(number);
 210         struct tty_struct *tty;
 211
 212         tty = NULL;
 213         if (!IS_ERR(dentry)) {
 214                 if (dentry->d_inode)
 215                         tty = dentry->d_inode->i_private;
 216                 dput(dentry);
 217         }
 218
 219         mutex_unlock(&devpts_root->d_inode->i_mutex);
 220
 221         return tty;
 222 }
 223
 224 void devpts_pty_kill(int number)
 225 {
 226         struct dentry *dentry = get_node(number);
 227
 228         if (!IS_ERR(dentry)) {
 229                 struct inode *inode = dentry->d_inode;
 230                 if (inode) {
 231                         inode->i_nlink--;
 232                         d_delete(dentry);
 233                         dput(dentry);
 234                 }
 235                 dput(dentry);
 236         }
 237         mutex_unlock(&devpts_root->d_inode->i_mutex);
 238 }
 239
 240 static int __init init_devpts_fs(void)
 241 {
 242         int err = register_filesystem(&devpts_fs_type);
 243         if (!err) {
 244                 devpts_mnt = kern_mount(&devpts_fs_type);
 245                 if (IS_ERR(devpts_mnt))
 246                         err = PTR_ERR(devpts_mnt);
 247         }
 248         return err;
 249 }
 250
 251 static void __exit exit_devpts_fs(void)
 252 {
 253         unregister_filesystem(&devpts_fs_type);
 254         mntput(devpts_mnt);
 255 }
 256
 257 module_init(init_devpts_fs)
 258 module_exit(exit_devpts_fs)
 259 MODULE_LICENSE("GPL");