fs/efivarfs/super.c

   1 /*
   2  * Copyright (C) 2012 Red Hat, Inc.
   3  * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/ctype.h>
  11 #include <linux/efi.h>
  12 #include <linux/fs.h>
  13 #include <linux/module.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/ucs2_string.h>
  16 #include <linux/slab.h>
  17 #include <linux/magic.h>
  18
  19 #include "internal.h"
  20
  21 LIST_HEAD(efivarfs_list);
  22
  23 static void efivarfs_evict_inode(struct inode *inode)
  24 {
  25         clear_inode(inode);
  26 }
  27
  28 static const struct super_operations efivarfs_ops = {
  29         .statfs = simple_statfs,
  30         .drop_inode = generic_delete_inode,
  31         .evict_inode = efivarfs_evict_inode,
  32         .show_options = generic_show_options,
  33 };
  34
  35 static struct super_block *efivarfs_sb;
  36
  37 /*
  38  * Compare two efivarfs file names.
  39  *
  40  * An efivarfs filename is composed of two parts,
  41  *
  42  *      1. A case-sensitive variable name
  43  *      2. A case-insensitive GUID
  44  *
  45  * So we need to perform a case-sensitive match on part 1 and a
  46  * case-insensitive match on part 2.
  47  */
  48 static int efivarfs_d_compare(const struct dentry *dentry,
  49                               unsigned int len, const char *str,
  50                               const struct qstr *name)
  51 {
  52         int guid = len - EFI_VARIABLE_GUID_LEN;
  53
  54         if (name->len != len)
  55                 return 1;
  56
  57         /* Case-sensitive compare for the variable name */
  58         if (memcmp(str, name->name, guid))
  59                 return 1;
  60
  61         /* Case-insensitive compare for the GUID */
  62         return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
  63 }
  64
  65 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
  66 {
  67         unsigned long hash = init_name_hash(dentry);
  68         const unsigned char *s = qstr->name;
  69         unsigned int len = qstr->len;
  70
  71         if (!efivarfs_valid_name(s, len))
  72                 return -EINVAL;
  73
  74         while (len-- > EFI_VARIABLE_GUID_LEN)
  75                 hash = partial_name_hash(*s++, hash);
  76
  77         /* GUID is case-insensitive. */
  78         while (len--)
  79                 hash = partial_name_hash(tolower(*s++), hash);
  80
  81         qstr->hash = end_name_hash(hash);
  82         return 0;
  83 }
  84
  85 static const struct dentry_operations efivarfs_d_ops = {
  86         .d_compare = efivarfs_d_compare,
  87         .d_hash = efivarfs_d_hash,
  88         .d_delete = always_delete_dentry,
  89 };
  90
  91 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
  92 {
  93         struct dentry *d;
  94         struct qstr q;
  95         int err;
  96
  97         q.name = name;
  98         q.len = strlen(name);
  99
 100         err = efivarfs_d_hash(parent, &q);
 101         if (err)
 102                 return ERR_PTR(err);
 103
 104         d = d_alloc(parent, &q);
 105         if (d)
 106                 return d;
 107
 108         return ERR_PTR(-ENOMEM);
 109 }
 110
 111 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 112                              unsigned long name_size, void *data)
 113 {
 114         struct super_block *sb = (struct super_block *)data;
 115         struct efivar_entry *entry;
 116         struct inode *inode = NULL;
 117         struct dentry *dentry, *root = sb->s_root;
 118         unsigned long size = 0;
 119         char *name;
 120         int len;
 121         int err = -ENOMEM;
 122         bool is_removable = false;
 123
 124         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 125         if (!entry)
 126                 return err;
 127
 128         memcpy(entry->var.VariableName, name16, name_size);
 129         memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
 130
 131         len = ucs2_utf8size(entry->var.VariableName);
 132
 133         /* name, plus '-', plus GUID, plus NUL*/
 134         name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
 135         if (!name)
 136                 goto fail;
 137
 138         ucs2_as_utf8(name, entry->var.VariableName, len);
 139
 140         if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
 141                 is_removable = true;
 142
 143         name[len] = '-';
 144
 145         efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
 146
 147         name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
 148
 149         inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
 150                                    is_removable);
 151         if (!inode)
 152                 goto fail_name;
 153
 154         dentry = efivarfs_alloc_dentry(root, name);
 155         if (IS_ERR(dentry)) {
 156                 err = PTR_ERR(dentry);
 157                 goto fail_inode;
 158         }
 159
 160         /* copied by the above to local storage in the dentry. */
 161         kfree(name);
 162
 163         efivar_entry_size(entry, &size);
 164         efivar_entry_add(entry, &efivarfs_list);
 165
 166         inode_lock(inode);
 167         inode->i_private = entry;
 168         i_size_write(inode, size + sizeof(entry->var.Attributes));
 169         inode_unlock(inode);
 170         d_add(dentry, inode);
 171
 172         return 0;
 173
 174 fail_inode:
 175         iput(inode);
 176 fail_name:
 177         kfree(name);
 178 fail:
 179         kfree(entry);
 180         return err;
 181 }
 182
 183 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 184 {
 185         efivar_entry_remove(entry);
 186         kfree(entry);
 187         return 0;
 188 }
 189
 190 static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 191 {
 192         struct inode *inode = NULL;
 193         struct dentry *root;
 194         int err;
 195
 196         efivarfs_sb = sb;
 197
 198         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 199         sb->s_blocksize         = PAGE_SIZE;
 200         sb->s_blocksize_bits    = PAGE_SHIFT;
 201         sb->s_magic             = EFIVARFS_MAGIC;
 202         sb->s_op                = &efivarfs_ops;
 203         sb->s_d_op              = &efivarfs_d_ops;
 204         sb->s_time_gran         = 1;
 205
 206         inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
 207         if (!inode)
 208                 return -ENOMEM;
 209         inode->i_op = &efivarfs_dir_inode_operations;
 210
 211         root = d_make_root(inode);
 212         sb->s_root = root;
 213         if (!root)
 214                 return -ENOMEM;
 215
 216         INIT_LIST_HEAD(&efivarfs_list);
 217
 218         err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
 219         if (err)
 220                 __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 221
 222         return err;
 223 }
 224
 225 static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
 226                                     int flags, const char *dev_name, void *data)
 227 {
 228         return mount_single(fs_type, flags, data, efivarfs_fill_super);
 229 }
 230
 231 static void efivarfs_kill_sb(struct super_block *sb)
 232 {
 233         kill_litter_super(sb);
 234         efivarfs_sb = NULL;
 235
 236         /* Remove all entries and destroy */
 237         __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 238 }
 239
 240 static struct file_system_type efivarfs_type = {
 241         .owner   = THIS_MODULE,
 242         .name    = "efivarfs",
 243         .mount   = efivarfs_mount,
 244         .kill_sb = efivarfs_kill_sb,
 245 };
 246
 247 static __init int efivarfs_init(void)
 248 {
 249         if (!efi_enabled(EFI_RUNTIME_SERVICES))
 250                 return -ENODEV;
 251
 252         if (!efivars_kobject())
 253                 return -ENODEV;
 254
 255         return register_filesystem(&efivarfs_type);
 256 }
 257
 258 static __exit void efivarfs_exit(void)
 259 {
 260         unregister_filesystem(&efivarfs_type);
 261 }
 262
 263 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 264 MODULE_DESCRIPTION("EFI Variable Filesystem");
 265 MODULE_LICENSE("GPL");
 266 MODULE_ALIAS_FS("efivarfs");
 267
 268 module_init(efivarfs_init);
 269 module_exit(efivarfs_exit);