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