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