| 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/mutex.h> |
| 21 | #include <linux/idr.h> |
| 22 | #include <linux/devpts_fs.h> |
| 23 | #include <linux/parser.h> |
| 24 | #include <linux/fsnotify.h> |
| 25 | #include <linux/seq_file.h> |
| 26 | |
| 27 | #define DEVPTS_SUPER_MAGIC 0x1cd1 |
| 28 | |
| 29 | #define DEVPTS_DEFAULT_MODE 0600 |
| 30 | #define PTMX_MINOR 2 |
| 31 | |
| 32 | extern int pty_limit; /* Config limit on Unix98 ptys */ |
| 33 | static DEFINE_MUTEX(allocated_ptys_lock); |
| 34 | |
| 35 | static struct vfsmount *devpts_mnt; |
| 36 | |
| 37 | struct pts_mount_opts { |
| 38 | int setuid; |
| 39 | int setgid; |
| 40 | uid_t uid; |
| 41 | gid_t gid; |
| 42 | umode_t mode; |
| 43 | }; |
| 44 | |
| 45 | enum { |
| 46 | Opt_uid, Opt_gid, Opt_mode, |
| 47 | Opt_err |
| 48 | }; |
| 49 | |
| 50 | static const match_table_t tokens = { |
| 51 | {Opt_uid, "uid=%u"}, |
| 52 | {Opt_gid, "gid=%u"}, |
| 53 | {Opt_mode, "mode=%o"}, |
| 54 | {Opt_err, NULL} |
| 55 | }; |
| 56 | |
| 57 | struct pts_fs_info { |
| 58 | struct ida allocated_ptys; |
| 59 | struct pts_mount_opts mount_opts; |
| 60 | }; |
| 61 | |
| 62 | static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb) |
| 63 | { |
| 64 | return sb->s_fs_info; |
| 65 | } |
| 66 | |
| 67 | static inline struct super_block *pts_sb_from_inode(struct inode *inode) |
| 68 | { |
| 69 | if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) |
| 70 | return inode->i_sb; |
| 71 | |
| 72 | return devpts_mnt->mnt_sb; |
| 73 | } |
| 74 | |
| 75 | static int devpts_remount(struct super_block *sb, int *flags, char *data) |
| 76 | { |
| 77 | char *p; |
| 78 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 79 | struct pts_mount_opts *opts = &fsi->mount_opts; |
| 80 | |
| 81 | opts->setuid = 0; |
| 82 | opts->setgid = 0; |
| 83 | opts->uid = 0; |
| 84 | opts->gid = 0; |
| 85 | opts->mode = DEVPTS_DEFAULT_MODE; |
| 86 | |
| 87 | while ((p = strsep(&data, ",")) != NULL) { |
| 88 | substring_t args[MAX_OPT_ARGS]; |
| 89 | int token; |
| 90 | int option; |
| 91 | |
| 92 | if (!*p) |
| 93 | continue; |
| 94 | |
| 95 | token = match_token(p, tokens, args); |
| 96 | switch (token) { |
| 97 | case Opt_uid: |
| 98 | if (match_int(&args[0], &option)) |
| 99 | return -EINVAL; |
| 100 | opts->uid = option; |
| 101 | opts->setuid = 1; |
| 102 | break; |
| 103 | case Opt_gid: |
| 104 | if (match_int(&args[0], &option)) |
| 105 | return -EINVAL; |
| 106 | opts->gid = option; |
| 107 | opts->setgid = 1; |
| 108 | break; |
| 109 | case Opt_mode: |
| 110 | if (match_octal(&args[0], &option)) |
| 111 | return -EINVAL; |
| 112 | opts->mode = option & S_IALLUGO; |
| 113 | break; |
| 114 | default: |
| 115 | printk(KERN_ERR "devpts: called with bogus options\n"); |
| 116 | return -EINVAL; |
| 117 | } |
| 118 | } |
| 119 | |
| 120 | return 0; |
| 121 | } |
| 122 | |
| 123 | static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs) |
| 124 | { |
| 125 | struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb); |
| 126 | struct pts_mount_opts *opts = &fsi->mount_opts; |
| 127 | |
| 128 | if (opts->setuid) |
| 129 | seq_printf(seq, ",uid=%u", opts->uid); |
| 130 | if (opts->setgid) |
| 131 | seq_printf(seq, ",gid=%u", opts->gid); |
| 132 | seq_printf(seq, ",mode=%03o", opts->mode); |
| 133 | |
| 134 | return 0; |
| 135 | } |
| 136 | |
| 137 | static const struct super_operations devpts_sops = { |
| 138 | .statfs = simple_statfs, |
| 139 | .remount_fs = devpts_remount, |
| 140 | .show_options = devpts_show_options, |
| 141 | }; |
| 142 | |
| 143 | static void *new_pts_fs_info(void) |
| 144 | { |
| 145 | struct pts_fs_info *fsi; |
| 146 | |
| 147 | fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL); |
| 148 | if (!fsi) |
| 149 | return NULL; |
| 150 | |
| 151 | ida_init(&fsi->allocated_ptys); |
| 152 | fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; |
| 153 | |
| 154 | return fsi; |
| 155 | } |
| 156 | |
| 157 | static int |
| 158 | devpts_fill_super(struct super_block *s, void *data, int silent) |
| 159 | { |
| 160 | struct inode * inode; |
| 161 | |
| 162 | s->s_blocksize = 1024; |
| 163 | s->s_blocksize_bits = 10; |
| 164 | s->s_magic = DEVPTS_SUPER_MAGIC; |
| 165 | s->s_op = &devpts_sops; |
| 166 | s->s_time_gran = 1; |
| 167 | |
| 168 | s->s_fs_info = new_pts_fs_info(); |
| 169 | if (!s->s_fs_info) |
| 170 | goto fail; |
| 171 | |
| 172 | inode = new_inode(s); |
| 173 | if (!inode) |
| 174 | goto free_fsi; |
| 175 | inode->i_ino = 1; |
| 176 | inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; |
| 177 | inode->i_blocks = 0; |
| 178 | inode->i_uid = inode->i_gid = 0; |
| 179 | inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR; |
| 180 | inode->i_op = &simple_dir_inode_operations; |
| 181 | inode->i_fop = &simple_dir_operations; |
| 182 | inode->i_nlink = 2; |
| 183 | |
| 184 | s->s_root = d_alloc_root(inode); |
| 185 | if (s->s_root) |
| 186 | return 0; |
| 187 | |
| 188 | printk("devpts: get root dentry failed\n"); |
| 189 | iput(inode); |
| 190 | |
| 191 | free_fsi: |
| 192 | kfree(s->s_fs_info); |
| 193 | fail: |
| 194 | return -ENOMEM; |
| 195 | } |
| 196 | |
| 197 | static int devpts_get_sb(struct file_system_type *fs_type, |
| 198 | int flags, const char *dev_name, void *data, struct vfsmount *mnt) |
| 199 | { |
| 200 | return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt); |
| 201 | } |
| 202 | |
| 203 | static void devpts_kill_sb(struct super_block *sb) |
| 204 | { |
| 205 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 206 | |
| 207 | kfree(fsi); |
| 208 | kill_anon_super(sb); |
| 209 | } |
| 210 | |
| 211 | static struct file_system_type devpts_fs_type = { |
| 212 | .owner = THIS_MODULE, |
| 213 | .name = "devpts", |
| 214 | .get_sb = devpts_get_sb, |
| 215 | .kill_sb = devpts_kill_sb, |
| 216 | }; |
| 217 | |
| 218 | /* |
| 219 | * The normal naming convention is simply /dev/pts/<number>; this conforms |
| 220 | * to the System V naming convention |
| 221 | */ |
| 222 | |
| 223 | int devpts_new_index(struct inode *ptmx_inode) |
| 224 | { |
| 225 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
| 226 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 227 | int index; |
| 228 | int ida_ret; |
| 229 | |
| 230 | retry: |
| 231 | if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) { |
| 232 | return -ENOMEM; |
| 233 | } |
| 234 | |
| 235 | mutex_lock(&allocated_ptys_lock); |
| 236 | ida_ret = ida_get_new(&fsi->allocated_ptys, &index); |
| 237 | if (ida_ret < 0) { |
| 238 | mutex_unlock(&allocated_ptys_lock); |
| 239 | if (ida_ret == -EAGAIN) |
| 240 | goto retry; |
| 241 | return -EIO; |
| 242 | } |
| 243 | |
| 244 | if (index >= pty_limit) { |
| 245 | ida_remove(&fsi->allocated_ptys, index); |
| 246 | mutex_unlock(&allocated_ptys_lock); |
| 247 | return -EIO; |
| 248 | } |
| 249 | mutex_unlock(&allocated_ptys_lock); |
| 250 | return index; |
| 251 | } |
| 252 | |
| 253 | void devpts_kill_index(struct inode *ptmx_inode, int idx) |
| 254 | { |
| 255 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
| 256 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 257 | |
| 258 | mutex_lock(&allocated_ptys_lock); |
| 259 | ida_remove(&fsi->allocated_ptys, idx); |
| 260 | mutex_unlock(&allocated_ptys_lock); |
| 261 | } |
| 262 | |
| 263 | int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty) |
| 264 | { |
| 265 | int number = tty->index; /* tty layer puts index from devpts_new_index() in here */ |
| 266 | struct tty_driver *driver = tty->driver; |
| 267 | dev_t device = MKDEV(driver->major, driver->minor_start+number); |
| 268 | struct dentry *dentry; |
| 269 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
| 270 | struct inode *inode = new_inode(sb); |
| 271 | struct dentry *root = sb->s_root; |
| 272 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 273 | struct pts_mount_opts *opts = &fsi->mount_opts; |
| 274 | char s[12]; |
| 275 | |
| 276 | /* We're supposed to be given the slave end of a pty */ |
| 277 | BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY); |
| 278 | BUG_ON(driver->subtype != PTY_TYPE_SLAVE); |
| 279 | |
| 280 | if (!inode) |
| 281 | return -ENOMEM; |
| 282 | |
| 283 | inode->i_ino = number+2; |
| 284 | inode->i_uid = config.setuid ? config.uid : current_fsuid(); |
| 285 | inode->i_gid = config.setgid ? config.gid : current_fsgid(); |
| 286 | inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; |
| 287 | init_special_inode(inode, S_IFCHR|opts->mode, device); |
| 288 | inode->i_private = tty; |
| 289 | tty->driver_data = inode; |
| 290 | |
| 291 | sprintf(s, "%d", number); |
| 292 | |
| 293 | mutex_lock(&root->d_inode->i_mutex); |
| 294 | |
| 295 | dentry = d_alloc_name(root, s); |
| 296 | if (!IS_ERR(dentry)) { |
| 297 | d_add(dentry, inode); |
| 298 | fsnotify_create(root->d_inode, dentry); |
| 299 | } |
| 300 | |
| 301 | mutex_unlock(&root->d_inode->i_mutex); |
| 302 | |
| 303 | return 0; |
| 304 | } |
| 305 | |
| 306 | struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number) |
| 307 | { |
| 308 | BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); |
| 309 | |
| 310 | if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) |
| 311 | return (struct tty_struct *)pts_inode->i_private; |
| 312 | return NULL; |
| 313 | } |
| 314 | |
| 315 | void devpts_pty_kill(struct tty_struct *tty) |
| 316 | { |
| 317 | struct inode *inode = tty->driver_data; |
| 318 | struct super_block *sb = pts_sb_from_inode(inode); |
| 319 | struct dentry *root = sb->s_root; |
| 320 | struct dentry *dentry; |
| 321 | |
| 322 | BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); |
| 323 | |
| 324 | mutex_lock(&root->d_inode->i_mutex); |
| 325 | |
| 326 | dentry = d_find_alias(inode); |
| 327 | if (dentry && !IS_ERR(dentry)) { |
| 328 | inode->i_nlink--; |
| 329 | d_delete(dentry); |
| 330 | dput(dentry); |
| 331 | } |
| 332 | |
| 333 | mutex_unlock(&root->d_inode->i_mutex); |
| 334 | } |
| 335 | |
| 336 | static int __init init_devpts_fs(void) |
| 337 | { |
| 338 | int err = register_filesystem(&devpts_fs_type); |
| 339 | if (!err) { |
| 340 | devpts_mnt = kern_mount(&devpts_fs_type); |
| 341 | if (IS_ERR(devpts_mnt)) |
| 342 | err = PTR_ERR(devpts_mnt); |
| 343 | } |
| 344 | return err; |
| 345 | } |
| 346 | |
| 347 | static void __exit exit_devpts_fs(void) |
| 348 | { |
| 349 | unregister_filesystem(&devpts_fs_type); |
| 350 | mntput(devpts_mnt); |
| 351 | } |
| 352 | |
| 353 | module_init(init_devpts_fs) |
| 354 | module_exit(exit_devpts_fs) |
| 355 | MODULE_LICENSE("GPL"); |