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
  16 #include "internal.h"
  17
  18 LIST_HEAD(efivarfs_list);
  19
  20 static void efivarfs_evict_inode(struct inode *inode)
  21 {
  22         clear_inode(inode);
  23 }
  24
  25 static const struct super_operations efivarfs_ops = {
  26         .statfs = simple_statfs,
  27         .drop_inode = generic_delete_inode,
  28         .evict_inode = efivarfs_evict_inode,
  29         .show_options = generic_show_options,
  30 };
  31
  32 static struct super_block *efivarfs_sb;
  33
  34 /*
  35  * Compare two efivarfs file names.
  36  *
  37  * An efivarfs filename is composed of two parts,
  38  *
  39  *      1. A case-sensitive variable name
  40  *      2. A case-insensitive GUID
  41  *
  42  * So we need to perform a case-sensitive match on part 1 and a
  43  * case-insensitive match on part 2.
  44  */
  45 static int efivarfs_d_compare(const struct dentry *parent, const struct inode *pinode,
  46                               const struct dentry *dentry, const struct inode *inode,
  47                               unsigned int len, const char *str,
  48                               const struct qstr *name)
  49 {
  50         int guid = len - EFI_VARIABLE_GUID_LEN;
  51
  52         if (name->len != len)
  53                 return 1;
  54
  55         /* Case-sensitive compare for the variable name */
  56         if (memcmp(str, name->name, guid))
  57                 return 1;
  58
  59         /* Case-insensitive compare for the GUID */
  60         return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
  61 }
  62
  63 static int efivarfs_d_hash(const struct dentry *dentry,
  64                            const struct inode *inode, struct qstr *qstr)
  65 {
  66         unsigned long hash = init_name_hash();
  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 /*
  85  * Retaining negative dentries for an in-memory filesystem just wastes
  86  * memory and lookup time: arrange for them to be deleted immediately.
  87  */
  88 static int efivarfs_delete_dentry(const struct dentry *dentry)
  89 {
  90         return 1;
  91 }
  92
  93 static struct dentry_operations efivarfs_d_ops = {
  94         .d_compare = efivarfs_d_compare,
  95         .d_hash = efivarfs_d_hash,
  96         .d_delete = efivarfs_delete_dentry,
  97 };
  98
  99 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
 100 {
 101         struct dentry *d;
 102         struct qstr q;
 103         int err;
 104
 105         q.name = name;
 106         q.len = strlen(name);
 107
 108         err = efivarfs_d_hash(NULL, NULL, &q);
 109         if (err)
 110                 return ERR_PTR(err);
 111
 112         d = d_alloc(parent, &q);
 113         if (d)
 114                 return d;
 115
 116         return ERR_PTR(-ENOMEM);
 117 }
 118
 119 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 120                              unsigned long name_size, void *data)
 121 {
 122         struct super_block *sb = (struct super_block *)data;
 123         struct efivar_entry *entry;
 124         struct inode *inode = NULL;
 125         struct dentry *dentry, *root = sb->s_root;
 126         unsigned long size = 0;
 127         char *name;
 128         int len, i;
 129         int err = -ENOMEM;
 130
 131         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 132         if (!entry)
 133                 return err;
 134
 135         memcpy(entry->var.VariableName, name16, name_size);
 136         memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
 137
 138         len = utf16_strlen(entry->var.VariableName);
 139
 140         /* name, plus '-', plus GUID, plus NUL*/
 141         name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
 142         if (!name)
 143                 goto fail;
 144
 145         for (i = 0; i < len; i++)
 146                 name[i] = entry->var.VariableName[i] & 0xFF;
 147
 148         name[len] = '-';
 149
 150         efi_guid_unparse(&entry->var.VendorGuid, name + len + 1);
 151
 152         name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
 153
 154         inode = efivarfs_get_inode(sb, root->d_inode, S_IFREG | 0644, 0);
 155         if (!inode)
 156                 goto fail_name;
 157
 158         dentry = efivarfs_alloc_dentry(root, name);
 159         if (IS_ERR(dentry)) {
 160                 err = PTR_ERR(dentry);
 161                 goto fail_inode;
 162         }
 163
 164         /* copied by the above to local storage in the dentry. */
 165         kfree(name);
 166
 167         efivar_entry_size(entry, &size);
 168         efivar_entry_add(entry, &efivarfs_list);
 169
 170         mutex_lock(&inode->i_mutex);
 171         inode->i_private = entry;
 172         i_size_write(inode, size + sizeof(entry->var.Attributes));
 173         mutex_unlock(&inode->i_mutex);
 174         d_add(dentry, inode);
 175
 176         return 0;
 177
 178 fail_inode:
 179         iput(inode);
 180 fail_name:
 181         kfree(name);
 182 fail:
 183         kfree(entry);
 184         return err;
 185 }
 186
 187 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 188 {
 189         efivar_entry_remove(entry);
 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_CACHE_SIZE;
 204         sb->s_blocksize_bits    = PAGE_CACHE_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);
 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, false,
 223                           true, &efivarfs_list);
 224         if (err)
 225                 __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 226
 227         return err;
 228 }
 229
 230 static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
 231                                     int flags, const char *dev_name, void *data)
 232 {
 233         return mount_single(fs_type, flags, data, efivarfs_fill_super);
 234 }
 235
 236 static void efivarfs_kill_sb(struct super_block *sb)
 237 {
 238         kill_litter_super(sb);
 239         efivarfs_sb = NULL;
 240
 241         /* Remove all entries and destroy */
 242         __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 243 }
 244
 245 static struct file_system_type efivarfs_type = {
 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 0;
 255
 256         if (!efivars_kobject())
 257                 return 0;
 258
 259         return register_filesystem(&efivarfs_type);
 260 }
 261
 262 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 263 MODULE_DESCRIPTION("EFI Variable Filesystem");
 264 MODULE_LICENSE("GPL");
 265 MODULE_ALIAS_FS("efivarfs");
 266
 267 module_init(efivarfs_init);