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