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 *parent,
  49                               const struct dentry *dentry,
  50                               unsigned int len, const char *str,
  51                               const struct qstr *name)
  52 {
  53         int guid = len - EFI_VARIABLE_GUID_LEN;
  54
  55         if (name->len != len)
  56                 return 1;
  57
  58         /* Case-sensitive compare for the variable name */
  59         if (memcmp(str, name->name, guid))
  60                 return 1;
  61
  62         /* Case-insensitive compare for the GUID */
  63         return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
  64 }
  65
  66 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
  67 {
  68         unsigned long hash = init_name_hash();
  69         const unsigned char *s = qstr->name;
  70         unsigned int len = qstr->len;
  71
  72         if (!efivarfs_valid_name(s, len))
  73                 return -EINVAL;
  74
  75         while (len-- > EFI_VARIABLE_GUID_LEN)
  76                 hash = partial_name_hash(*s++, hash);
  77
  78         /* GUID is case-insensitive. */
  79         while (len--)
  80                 hash = partial_name_hash(tolower(*s++), hash);
  81
  82         qstr->hash = end_name_hash(hash);
  83         return 0;
  84 }
  85
  86 static const struct dentry_operations efivarfs_d_ops = {
  87         .d_compare = efivarfs_d_compare,
  88         .d_hash = efivarfs_d_hash,
  89         .d_delete = always_delete_dentry,
  90 };
  91
  92 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
  93 {
  94         struct dentry *d;
  95         struct qstr q;
  96         int err;
  97
  98         q.name = name;
  99         q.len = strlen(name);
 100
 101         err = efivarfs_d_hash(NULL, &q);
 102         if (err)
 103                 return ERR_PTR(err);
 104
 105         d = d_alloc(parent, &q);
 106         if (d)
 107                 return d;
 108
 109         return ERR_PTR(-ENOMEM);
 110 }
 111
 112 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 113                              unsigned long name_size, void *data)
 114 {
 115         struct super_block *sb = (struct super_block *)data;
 116         struct efivar_entry *entry;
 117         struct inode *inode = NULL;
 118         struct dentry *dentry, *root = sb->s_root;
 119         unsigned long size = 0;
 120         char *name;
 121         int len;
 122         int err = -ENOMEM;
 123         bool is_removable = false;
 124
 125         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 126         if (!entry)
 127                 return err;
 128
 129         memcpy(entry->var.VariableName, name16, name_size);
 130         memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
 131
 132         len = ucs2_utf8size(entry->var.VariableName);
 133
 134         /* name, plus '-', plus GUID, plus NUL*/
 135         name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
 136         if (!name)
 137                 goto fail;
 138
 139         ucs2_as_utf8(name, entry->var.VariableName, len);
 140
 141         if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
 142                 is_removable = true;
 143
 144         name[len] = '-';
 145
 146         efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
 147
 148         name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
 149
 150         inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
 151                                    is_removable);
 152         if (!inode)
 153                 goto fail_name;
 154
 155         dentry = efivarfs_alloc_dentry(root, name);
 156         if (IS_ERR(dentry)) {
 157                 err = PTR_ERR(dentry);
 158                 goto fail_inode;
 159         }
 160
 161         /* copied by the above to local storage in the dentry. */
 162         kfree(name);
 163
 164         efivar_entry_size(entry, &size);
 165         efivar_entry_add(entry, &efivarfs_list);
 166
 167         mutex_lock(&inode->i_mutex);
 168         inode->i_private = entry;
 169         i_size_write(inode, size + sizeof(entry->var.Attributes));
 170         mutex_unlock(&inode->i_mutex);
 171         d_add(dentry, inode);
 172
 173         return 0;
 174
 175 fail_inode:
 176         iput(inode);
 177 fail_name:
 178         kfree(name);
 179 fail:
 180         kfree(entry);
 181         return err;
 182 }
 183
 184 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 185 {
 186         efivar_entry_remove(entry);
 187         kfree(entry);
 188         return 0;
 189 }
 190
 191 static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 192 {
 193         struct inode *inode = NULL;
 194         struct dentry *root;
 195         int err;
 196
 197         efivarfs_sb = sb;
 198
 199         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 200         sb->s_blocksize         = PAGE_CACHE_SIZE;
 201         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 202         sb->s_magic             = EFIVARFS_MAGIC;
 203         sb->s_op                = &efivarfs_ops;
 204         sb->s_d_op              = &efivarfs_d_ops;
 205         sb->s_time_gran         = 1;
 206
 207         inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
 208         if (!inode)
 209                 return -ENOMEM;
 210         inode->i_op = &efivarfs_dir_inode_operations;
 211
 212         root = d_make_root(inode);
 213         sb->s_root = root;
 214         if (!root)
 215                 return -ENOMEM;
 216
 217         INIT_LIST_HEAD(&efivarfs_list);
 218
 219         err = efivar_init(efivarfs_callback, (void *)sb, false,
 220                           true, &efivarfs_list);
 221         if (err)
 222                 __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 223
 224         return err;
 225 }
 226
 227 static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
 228                                     int flags, const char *dev_name, void *data)
 229 {
 230         return mount_single(fs_type, flags, data, efivarfs_fill_super);
 231 }
 232
 233 static void efivarfs_kill_sb(struct super_block *sb)
 234 {
 235         kill_litter_super(sb);
 236         efivarfs_sb = NULL;
 237
 238         /* Remove all entries and destroy */
 239         __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 240 }
 241
 242 static struct file_system_type efivarfs_type = {
 243         .owner   = THIS_MODULE,
 244         .name    = "efivarfs",
 245         .mount   = efivarfs_mount,
 246         .kill_sb = efivarfs_kill_sb,
 247 };
 248
 249 static __init int efivarfs_init(void)
 250 {
 251         if (!efi_enabled(EFI_RUNTIME_SERVICES))
 252                 return -ENODEV;
 253
 254         if (!efivars_kobject())
 255                 return -ENODEV;
 256
 257         return register_filesystem(&efivarfs_type);
 258 }
 259
 260 static __exit void efivarfs_exit(void)
 261 {
 262         unregister_filesystem(&efivarfs_type);
 263 }
 264
 265 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 266 MODULE_DESCRIPTION("EFI Variable Filesystem");
 267 MODULE_LICENSE("GPL");
 268 MODULE_ALIAS_FS("efivarfs");
 269
 270 module_init(efivarfs_init);
 271 module_exit(efivarfs_exit);