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 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, i;
 122         int err = -ENOMEM;
 123
 124         entry = kmalloc(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_strlen(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         for (i = 0; i < len; i++)
 139                 name[i] = entry->var.VariableName[i] & 0xFF;
 140
 141         name[len] = '-';
 142
 143         efi_guid_unparse(&entry->var.VendorGuid, name + len + 1);
 144
 145         name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
 146
 147         inode = efivarfs_get_inode(sb, root->d_inode, S_IFREG | 0644, 0);
 148         if (!inode)
 149                 goto fail_name;
 150
 151         dentry = efivarfs_alloc_dentry(root, name);
 152         if (IS_ERR(dentry)) {
 153                 err = PTR_ERR(dentry);
 154                 goto fail_inode;
 155         }
 156
 157         /* copied by the above to local storage in the dentry. */
 158         kfree(name);
 159
 160         efivar_entry_size(entry, &size);
 161         efivar_entry_add(entry, &efivarfs_list);
 162
 163         mutex_lock(&inode->i_mutex);
 164         inode->i_private = entry;
 165         i_size_write(inode, size + sizeof(entry->var.Attributes));
 166         mutex_unlock(&inode->i_mutex);
 167         d_add(dentry, inode);
 168
 169         return 0;
 170
 171 fail_inode:
 172         iput(inode);
 173 fail_name:
 174         kfree(name);
 175 fail:
 176         kfree(entry);
 177         return err;
 178 }
 179
 180 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 181 {
 182         efivar_entry_remove(entry);
 183         kfree(entry);
 184         return 0;
 185 }
 186
 187 static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 188 {
 189         struct inode *inode = NULL;
 190         struct dentry *root;
 191         int err;
 192
 193         efivarfs_sb = sb;
 194
 195         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 196         sb->s_blocksize         = PAGE_CACHE_SIZE;
 197         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 198         sb->s_magic             = EFIVARFS_MAGIC;
 199         sb->s_op                = &efivarfs_ops;
 200         sb->s_d_op              = &efivarfs_d_ops;
 201         sb->s_time_gran         = 1;
 202
 203         inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0);
 204         if (!inode)
 205                 return -ENOMEM;
 206         inode->i_op = &efivarfs_dir_inode_operations;
 207
 208         root = d_make_root(inode);
 209         sb->s_root = root;
 210         if (!root)
 211                 return -ENOMEM;
 212
 213         INIT_LIST_HEAD(&efivarfs_list);
 214
 215         err = efivar_init(efivarfs_callback, (void *)sb, false,
 216                           true, &efivarfs_list);
 217         if (err)
 218                 __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 219
 220         return err;
 221 }
 222
 223 static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
 224                                     int flags, const char *dev_name, void *data)
 225 {
 226         return mount_single(fs_type, flags, data, efivarfs_fill_super);
 227 }
 228
 229 static void efivarfs_kill_sb(struct super_block *sb)
 230 {
 231         kill_litter_super(sb);
 232         efivarfs_sb = NULL;
 233
 234         /* Remove all entries and destroy */
 235         __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 236 }
 237
 238 static struct file_system_type efivarfs_type = {
 239         .name    = "efivarfs",
 240         .mount   = efivarfs_mount,
 241         .kill_sb = efivarfs_kill_sb,
 242 };
 243
 244 static __init int efivarfs_init(void)
 245 {
 246         if (!efi_enabled(EFI_RUNTIME_SERVICES))
 247                 return 0;
 248
 249         if (!efivars_kobject())
 250                 return 0;
 251
 252         return register_filesystem(&efivarfs_type);
 253 }
 254
 255 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 256 MODULE_DESCRIPTION("EFI Variable Filesystem");
 257 MODULE_LICENSE("GPL");
 258 MODULE_ALIAS_FS("efivarfs");
 259
 260 module_init(efivarfs_init);