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 };
  33
  34 static struct super_block *efivarfs_sb;
  35
  36 /*
  37  * Compare two efivarfs file names.
  38  *
  39  * An efivarfs filename is composed of two parts,
  40  *
  41  *      1. A case-sensitive variable name
  42  *      2. A case-insensitive GUID
  43  *
  44  * So we need to perform a case-sensitive match on part 1 and a
  45  * case-insensitive match on part 2.
  46  */
  47 static int efivarfs_d_compare(const struct dentry *dentry,
  48                               unsigned int len, const char *str,
  49                               const struct qstr *name)
  50 {
  51         int guid = len - EFI_VARIABLE_GUID_LEN;
  52
  53         if (name->len != len)
  54                 return 1;
  55
  56         /* Case-sensitive compare for the variable name */
  57         if (memcmp(str, name->name, guid))
  58                 return 1;
  59
  60         /* Case-insensitive compare for the GUID */
  61         return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
  62 }
  63
  64 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
  65 {
  66         unsigned long hash = init_name_hash(dentry);
  67         const unsigned char *s = qstr->name;
  68         unsigned int len = qstr->len;
  69
  70         if (!efivarfs_valid_name(s, len))
  71                 return -EINVAL;
  72
  73         while (len-- > EFI_VARIABLE_GUID_LEN)
  74                 hash = partial_name_hash(*s++, hash);
  75
  76         /* GUID is case-insensitive. */
  77         while (len--)
  78                 hash = partial_name_hash(tolower(*s++), hash);
  79
  80         qstr->hash = end_name_hash(hash);
  81         return 0;
  82 }
  83
  84 static const struct dentry_operations efivarfs_d_ops = {
  85         .d_compare = efivarfs_d_compare,
  86         .d_hash = efivarfs_d_hash,
  87         .d_delete = always_delete_dentry,
  88 };
  89
  90 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
  91 {
  92         struct dentry *d;
  93         struct qstr q;
  94         int err;
  95
  96         q.name = name;
  97         q.len = strlen(name);
  98
  99         err = efivarfs_d_hash(parent, &q);
 100         if (err)
 101                 return ERR_PTR(err);
 102
 103         d = d_alloc(parent, &q);
 104         if (d)
 105                 return d;
 106
 107         return ERR_PTR(-ENOMEM);
 108 }
 109
 110 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 111                              unsigned long name_size, void *data)
 112 {
 113         struct super_block *sb = (struct super_block *)data;
 114         struct efivar_entry *entry;
 115         struct inode *inode = NULL;
 116         struct dentry *dentry, *root = sb->s_root;
 117         unsigned long size = 0;
 118         char *name;
 119         int len;
 120         int err = -ENOMEM;
 121         bool is_removable = false;
 122
 123         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 124         if (!entry)
 125                 return err;
 126
 127         memcpy(entry->var.VariableName, name16, name_size);
 128         memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
 129
 130         len = ucs2_utf8size(entry->var.VariableName);
 131
 132         /* name, plus '-', plus GUID, plus NUL*/
 133         name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
 134         if (!name)
 135                 goto fail;
 136
 137         ucs2_as_utf8(name, entry->var.VariableName, len);
 138
 139         if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
 140                 is_removable = true;
 141
 142         name[len] = '-';
 143
 144         efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
 145
 146         name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
 147
 148         inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
 149                                    is_removable);
 150         if (!inode)
 151                 goto fail_name;
 152
 153         dentry = efivarfs_alloc_dentry(root, name);
 154         if (IS_ERR(dentry)) {
 155                 err = PTR_ERR(dentry);
 156                 goto fail_inode;
 157         }
 158
 159         efivar_entry_size(entry, &size);
 160         err = efivar_entry_add(entry, &efivarfs_list);
 161         if (err)
 162                 goto fail_inode;
 163
 164         /* copied by the above to local storage in the dentry. */
 165         kfree(name);
 166
 167         inode_lock(inode);
 168         inode->i_private = entry;
 169         i_size_write(inode, size + sizeof(entry->var.Attributes));
 170         inode_unlock(inode);
 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         int err = efivar_entry_remove(entry);
 187
 188         if (err)
 189                 return err;
 190         kfree(entry);
 191         return 0;
 192 }
 193
 194 static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 195 {
 196         struct inode *inode = NULL;
 197         struct dentry *root;
 198         int err;
 199
 200         efivarfs_sb = sb;
 201
 202         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 203         sb->s_blocksize         = PAGE_SIZE;
 204         sb->s_blocksize_bits    = PAGE_SHIFT;
 205         sb->s_magic             = EFIVARFS_MAGIC;
 206         sb->s_op                = &efivarfs_ops;
 207         sb->s_d_op              = &efivarfs_d_ops;
 208         sb->s_time_gran         = 1;
 209
 210         inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
 211         if (!inode)
 212                 return -ENOMEM;
 213         inode->i_op = &efivarfs_dir_inode_operations;
 214
 215         root = d_make_root(inode);
 216         sb->s_root = root;
 217         if (!root)
 218                 return -ENOMEM;
 219
 220         INIT_LIST_HEAD(&efivarfs_list);
 221
 222         err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
 223         if (err)
 224                 __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 225
 226         return err;
 227 }
 228
 229 static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
 230                                     int flags, const char *dev_name, void *data)
 231 {
 232         return mount_single(fs_type, flags, data, efivarfs_fill_super);
 233 }
 234
 235 static void efivarfs_kill_sb(struct super_block *sb)
 236 {
 237         kill_litter_super(sb);
 238         efivarfs_sb = NULL;
 239
 240         /* Remove all entries and destroy */
 241         __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 242 }
 243
 244 static struct file_system_type efivarfs_type = {
 245         .owner   = THIS_MODULE,
 246         .name    = "efivarfs",
 247         .mount   = efivarfs_mount,
 248         .kill_sb = efivarfs_kill_sb,
 249 };
 250
 251 static __init int efivarfs_init(void)
 252 {
 253         if (!efi_enabled(EFI_RUNTIME_SERVICES))
 254                 return -ENODEV;
 255
 256         if (!efivars_kobject())
 257                 return -ENODEV;
 258
 259         return register_filesystem(&efivarfs_type);
 260 }
 261
 262 static __exit void efivarfs_exit(void)
 263 {
 264         unregister_filesystem(&efivarfs_type);
 265 }
 266
 267 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 268 MODULE_DESCRIPTION("EFI Variable Filesystem");
 269 MODULE_LICENSE("GPL");
 270 MODULE_ALIAS_FS("efivarfs");
 271
 272 module_init(efivarfs_init);
 273 module_exit(efivarfs_exit);