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