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/xattr.h>
  22
  23 #define DEVPTS_SUPER_MAGIC 0x1cd1
  24
  25 extern struct xattr_handler devpts_xattr_security_handler;
  26
  27 static struct xattr_handler *devpts_xattr_handlers[] = {
  28 #ifdef CONFIG_DEVPTS_FS_SECURITY
  29         &devpts_xattr_security_handler,
  30 #endif
  31         NULL
  32 };
  33
  34 struct inode_operations devpts_file_inode_operations = {
  35 #ifdef CONFIG_DEVPTS_FS_XATTR
  36         .setxattr       = generic_setxattr,
  37         .getxattr       = generic_getxattr,
  38         .listxattr      = generic_listxattr,
  39         .removexattr    = generic_removexattr,
  40 #endif
  41 };
  42
  43 static struct vfsmount *devpts_mnt;
  44 static struct dentry *devpts_root;
  45
  46 static struct {
  47         int setuid;
  48         int setgid;
  49         uid_t   uid;
  50         gid_t   gid;
  51         umode_t mode;
  52 } config = {.mode = 0600};
  53
  54 static int devpts_remount(struct super_block *sb, int *flags, char *data)
  55 {
  56         int setuid = 0;
  57         int setgid = 0;
  58         uid_t uid = 0;
  59         gid_t gid = 0;
  60         umode_t mode = 0600;
  61         char *this_char;
  62
  63         this_char = NULL;
  64         while ((this_char = strsep(&data, ",")) != NULL) {
  65                 int n;
  66                 char dummy;
  67                 if (!*this_char)
  68                         continue;
  69                 if (sscanf(this_char, "uid=%i%c", &n, &dummy) == 1) {
  70                         setuid = 1;
  71                         uid = n;
  72                 } else if (sscanf(this_char, "gid=%i%c", &n, &dummy) == 1) {
  73                         setgid = 1;
  74                         gid = n;
  75                 } else if (sscanf(this_char, "mode=%o%c", &n, &dummy) == 1)
  76                         mode = n & ~S_IFMT;
  77                 else {
  78                         printk("devpts: called with bogus options\n");
  79                         return -EINVAL;
  80                 }
  81         }
  82         config.setuid  = setuid;
  83         config.setgid  = setgid;
  84         config.uid     = uid;
  85         config.gid     = gid;
  86         config.mode    = mode;
  87
  88         return 0;
  89 }
  90
  91 static struct super_operations devpts_sops = {
  92         .statfs         = simple_statfs,
  93         .remount_fs     = devpts_remount,
  94 };
  95
  96 static int
  97 devpts_fill_super(struct super_block *s, void *data, int silent)
  98 {
  99         struct inode * inode;
 100
 101         s->s_blocksize = 1024;
 102         s->s_blocksize_bits = 10;
 103         s->s_magic = DEVPTS_SUPER_MAGIC;
 104         s->s_op = &devpts_sops;
 105         s->s_xattr = devpts_xattr_handlers;
 106
 107         inode = new_inode(s);
 108         if (!inode)
 109                 goto fail;
 110         inode->i_ino = 1;
 111         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 112         inode->i_blocks = 0;
 113         inode->i_blksize = 1024;
 114         inode->i_uid = inode->i_gid = 0;
 115         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 116         inode->i_op = &simple_dir_inode_operations;
 117         inode->i_fop = &simple_dir_operations;
 118         inode->i_nlink = 2;
 119
 120         devpts_root = s->s_root = d_alloc_root(inode);
 121         if (s->s_root)
 122                 return 0;
 123
 124         printk("devpts: get root dentry failed\n");
 125         iput(inode);
 126 fail:
 127         return -ENOMEM;
 128 }
 129
 130 static struct super_block *devpts_get_sb(struct file_system_type *fs_type,
 131         int flags, const char *dev_name, void *data)
 132 {
 133         return get_sb_single(fs_type, flags, data, devpts_fill_super);
 134 }
 135
 136 static struct file_system_type devpts_fs_type = {
 137         .owner          = THIS_MODULE,
 138         .name           = "devpts",
 139         .get_sb         = devpts_get_sb,
 140         .kill_sb        = kill_anon_super,
 141 };
 142
 143 /*
 144  * The normal naming convention is simply /dev/pts/<number>; this conforms
 145  * to the System V naming convention
 146  */
 147
 148 static struct dentry *get_node(int num)
 149 {
 150         char s[12];
 151         struct dentry *root = devpts_root;
 152         down(&root->d_inode->i_sem);
 153         return lookup_one_len(s, root, sprintf(s, "%d", num));
 154 }
 155
 156 int devpts_pty_new(struct tty_struct *tty)
 157 {
 158         int number = tty->index;
 159         struct tty_driver *driver = tty->driver;
 160         dev_t device = MKDEV(driver->major, driver->minor_start+number);
 161         struct dentry *dentry;
 162         struct inode *inode = new_inode(devpts_mnt->mnt_sb);
 163
 164         /* We're supposed to be given the slave end of a pty */
 165         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
 166         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
 167
 168         if (!inode)
 169                 return -ENOMEM;
 170
 171         inode->i_ino = number+2;
 172         inode->i_blksize = 1024;
 173         inode->i_uid = config.setuid ? config.uid : current->fsuid;
 174         inode->i_gid = config.setgid ? config.gid : current->fsgid;
 175         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 176         init_special_inode(inode, S_IFCHR|config.mode, device);
 177         inode->i_op = &devpts_file_inode_operations;
 178         inode->u.generic_ip = tty;
 179
 180         dentry = get_node(number);
 181         if (!IS_ERR(dentry) && !dentry->d_inode)
 182                 d_instantiate(dentry, inode);
 183
 184         up(&devpts_root->d_inode->i_sem);
 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->u.generic_ip;
 198                 dput(dentry);
 199         }
 200
 201         up(&devpts_root->d_inode->i_sem);
 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         up(&devpts_root->d_inode->i_sem);
 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");