drivers/isdn/capi/capifs.c

   1 /* $Id: capifs.c,v 1.1.2.3 2004/01/16 21:09:26 keil Exp $
   2  *
   3  * Copyright 2000 by Carsten Paeth <calle@calle.de>
   4  *
   5  * Heavily based on devpts filesystem from H. Peter Anvin
   6  *
   7  * This software may be used and distributed according to the terms
   8  * of the GNU General Public License, incorporated herein by reference.
   9  *
  10  */
  11
  12 #include <linux/fs.h>
  13 #include <linux/mount.h>
  14 #include <linux/slab.h>
  15 #include <linux/namei.h>
  16 #include <linux/module.h>
  17 #include <linux/init.h>
  18 #include <linux/ctype.h>
  19 #include <linux/sched.h>        /* current */
  20
  21 #include "capifs.h"
  22
  23 MODULE_DESCRIPTION("CAPI4Linux: /dev/capi/ filesystem");
  24 MODULE_AUTHOR("Carsten Paeth");
  25 MODULE_LICENSE("GPL");
  26
  27 /* ------------------------------------------------------------------ */
  28
  29 #define CAPIFS_SUPER_MAGIC (('C'<<8)|'N')
  30
  31 static struct vfsmount *capifs_mnt;
  32 static int capifs_mnt_count;
  33
  34 static struct {
  35         int setuid;
  36         int setgid;
  37         uid_t   uid;
  38         gid_t   gid;
  39         umode_t mode;
  40 } config = {.mode = 0600};
  41
  42 /* ------------------------------------------------------------------ */
  43
  44 static int capifs_remount(struct super_block *s, int *flags, char *data)
  45 {
  46         int setuid = 0;
  47         int setgid = 0;
  48         uid_t uid = 0;
  49         gid_t gid = 0;
  50         umode_t mode = 0600;
  51         char *this_char;
  52         char *new_opt = kstrdup(data, GFP_KERNEL);
  53
  54         this_char = NULL;
  55         while ((this_char = strsep(&data, ",")) != NULL) {
  56                 int n;
  57                 char dummy;
  58                 if (!*this_char)
  59                         continue;
  60                 if (sscanf(this_char, "uid=%i%c", &n, &dummy) == 1) {
  61                         setuid = 1;
  62                         uid = n;
  63                 } else if (sscanf(this_char, "gid=%i%c", &n, &dummy) == 1) {
  64                         setgid = 1;
  65                         gid = n;
  66                 } else if (sscanf(this_char, "mode=%o%c", &n, &dummy) == 1)
  67                         mode = n & ~S_IFMT;
  68                 else {
  69                         kfree(new_opt);
  70                         printk("capifs: called with bogus options\n");
  71                         return -EINVAL;
  72                 }
  73         }
  74
  75         mutex_lock(&s->s_root->d_inode->i_mutex);
  76
  77         replace_mount_options(s, new_opt);
  78         config.setuid  = setuid;
  79         config.setgid  = setgid;
  80         config.uid     = uid;
  81         config.gid     = gid;
  82         config.mode    = mode;
  83
  84         mutex_unlock(&s->s_root->d_inode->i_mutex);
  85
  86         return 0;
  87 }
  88
  89 static const struct super_operations capifs_sops =
  90 {
  91         .statfs         = simple_statfs,
  92         .remount_fs     = capifs_remount,
  93         .show_options   = generic_show_options,
  94 };
  95
  96
  97 static int
  98 capifs_fill_super(struct super_block *s, void *data, int silent)
  99 {
 100         struct inode * inode;
 101
 102         s->s_blocksize = 1024;
 103         s->s_blocksize_bits = 10;
 104         s->s_magic = CAPIFS_SUPER_MAGIC;
 105         s->s_op = &capifs_sops;
 106         s->s_time_gran = 1;
 107
 108         inode = new_inode(s);
 109         if (!inode)
 110                 goto fail;
 111         inode->i_ino = 1;
 112         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 113         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
 114         inode->i_op = &simple_dir_inode_operations;
 115         inode->i_fop = &simple_dir_operations;
 116         inode->i_nlink = 2;
 117
 118         s->s_root = d_alloc_root(inode);
 119         if (s->s_root)
 120                 return 0;
 121
 122         printk("capifs: get root dentry failed\n");
 123         iput(inode);
 124 fail:
 125         return -ENOMEM;
 126 }
 127
 128 static struct dentry *capifs_mount(struct file_system_type *fs_type,
 129         int flags, const char *dev_name, void *data)
 130 {
 131         return mount_single(fs_type, flags, data, capifs_fill_super);
 132 }
 133
 134 static struct file_system_type capifs_fs_type = {
 135         .owner          = THIS_MODULE,
 136         .name           = "capifs",
 137         .mount          = capifs_mount,
 138         .kill_sb        = kill_anon_super,
 139 };
 140
 141 static struct dentry *new_ncci(unsigned int number, dev_t device)
 142 {
 143         struct super_block *s = capifs_mnt->mnt_sb;
 144         struct dentry *root = s->s_root;
 145         struct dentry *dentry;
 146         struct inode *inode;
 147         char name[10];
 148         int namelen;
 149
 150         mutex_lock(&root->d_inode->i_mutex);
 151
 152         namelen = sprintf(name, "%d", number);
 153         dentry = lookup_one_len(name, root, namelen);
 154         if (IS_ERR(dentry)) {
 155                 dentry = NULL;
 156                 goto unlock_out;
 157         }
 158
 159         if (dentry->d_inode) {
 160                 dput(dentry);
 161                 dentry = NULL;
 162                 goto unlock_out;
 163         }
 164
 165         inode = new_inode(s);
 166         if (!inode) {
 167                 dput(dentry);
 168                 dentry = NULL;
 169                 goto unlock_out;
 170         }
 171
 172         /* config contents is protected by root's i_mutex */
 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         inode->i_ino = number + 2;
 177         init_special_inode(inode, S_IFCHR|config.mode, device);
 178
 179         d_instantiate(dentry, inode);
 180         dget(dentry);
 181
 182 unlock_out:
 183         mutex_unlock(&root->d_inode->i_mutex);
 184
 185         return dentry;
 186 }
 187
 188 struct dentry *capifs_new_ncci(unsigned int number, dev_t device)
 189 {
 190         struct dentry *dentry;
 191
 192         if (simple_pin_fs(&capifs_fs_type, &capifs_mnt, &capifs_mnt_count) < 0)
 193                 return NULL;
 194
 195         dentry = new_ncci(number, device);
 196         if (!dentry)
 197                 simple_release_fs(&capifs_mnt, &capifs_mnt_count);
 198
 199         return dentry;
 200 }
 201
 202 void capifs_free_ncci(struct dentry *dentry)
 203 {
 204         struct dentry *root = capifs_mnt->mnt_sb->s_root;
 205         struct inode *inode;
 206
 207         if (!dentry)
 208                 return;
 209
 210         mutex_lock(&root->d_inode->i_mutex);
 211
 212         inode = dentry->d_inode;
 213         if (inode) {
 214                 drop_nlink(inode);
 215                 d_delete(dentry);
 216                 dput(dentry);
 217         }
 218         dput(dentry);
 219
 220         mutex_unlock(&root->d_inode->i_mutex);
 221
 222         simple_release_fs(&capifs_mnt, &capifs_mnt_count);
 223 }
 224
 225 static int __init capifs_init(void)
 226 {
 227         return register_filesystem(&capifs_fs_type);
 228 }
 229
 230 static void __exit capifs_exit(void)
 231 {
 232         unregister_filesystem(&capifs_fs_type);
 233 }
 234
 235 EXPORT_SYMBOL(capifs_new_ncci);
 236 EXPORT_SYMBOL(capifs_free_ncci);
 237
 238 module_init(capifs_init);
 239 module_exit(capifs_exit);