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 /*
  87  * Retaining negative dentries for an in-memory filesystem just wastes
  88  * memory and lookup time: arrange for them to be deleted immediately.
  89  */
  90 static int efivarfs_delete_dentry(const struct dentry *dentry)
  91 {
  92         return 1;
  93 }
  94
  95 static struct dentry_operations efivarfs_d_ops = {
  96         .d_compare = efivarfs_d_compare,
  97         .d_hash = efivarfs_d_hash,
  98         .d_delete = efivarfs_delete_dentry,
  99 };
 100
 101 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
 102 {
 103         struct dentry *d;
 104         struct qstr q;
 105         int err;
 106
 107         q.name = name;
 108         q.len = strlen(name);
 109
 110         err = efivarfs_d_hash(NULL, &q);
 111         if (err)
 112                 return ERR_PTR(err);
 113
 114         d = d_alloc(parent, &q);
 115         if (d)
 116                 return d;
 117
 118         return ERR_PTR(-ENOMEM);
 119 }
 120
 121 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 122                              unsigned long name_size, void *data)
 123 {
 124         struct super_block *sb = (struct super_block *)data;
 125         struct efivar_entry *entry;
 126         struct inode *inode = NULL;
 127         struct dentry *dentry, *root = sb->s_root;
 128         unsigned long size = 0;
 129         char *name;
 130         int len, i;
 131         int err = -ENOMEM;
 132
 133         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 134         if (!entry)
 135                 return err;
 136
 137         memcpy(entry->var.VariableName, name16, name_size);
 138         memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
 139
 140         len = ucs2_strlen(entry->var.VariableName);
 141
 142         /* name, plus '-', plus GUID, plus NUL*/
 143         name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
 144         if (!name)
 145                 goto fail;
 146
 147         for (i = 0; i < len; i++)
 148                 name[i] = entry->var.VariableName[i] & 0xFF;
 149
 150         name[len] = '-';
 151
 152         efi_guid_unparse(&entry->var.VendorGuid, name + len + 1);
 153
 154         name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
 155
 156         inode = efivarfs_get_inode(sb, root->d_inode, S_IFREG | 0644, 0);
 157         if (!inode)
 158                 goto fail_name;
 159
 160         dentry = efivarfs_alloc_dentry(root, name);
 161         if (IS_ERR(dentry)) {
 162                 err = PTR_ERR(dentry);
 163                 goto fail_inode;
 164         }
 165
 166         /* copied by the above to local storage in the dentry. */
 167         kfree(name);
 168
 169         efivar_entry_size(entry, &size);
 170         efivar_entry_add(entry, &efivarfs_list);
 171
 172         mutex_lock(&inode->i_mutex);
 173         inode->i_private = entry;
 174         i_size_write(inode, size + sizeof(entry->var.Attributes));
 175         mutex_unlock(&inode->i_mutex);
 176         d_add(dentry, inode);
 177
 178         return 0;
 179
 180 fail_inode:
 181         iput(inode);
 182 fail_name:
 183         kfree(name);
 184 fail:
 185         kfree(entry);
 186         return err;
 187 }
 188
 189 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 190 {
 191         efivar_entry_remove(entry);
 192         kfree(entry);
 193         return 0;
 194 }
 195
 196 static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 197 {
 198         struct inode *inode = NULL;
 199         struct dentry *root;
 200         int err;
 201
 202         efivarfs_sb = sb;
 203
 204         sb->s_maxbytes          = MAX_LFS_FILESIZE;
 205         sb->s_blocksize         = PAGE_CACHE_SIZE;
 206         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
 207         sb->s_magic             = EFIVARFS_MAGIC;
 208         sb->s_op                = &efivarfs_ops;
 209         sb->s_d_op              = &efivarfs_d_ops;
 210         sb->s_time_gran         = 1;
 211
 212         inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0);
 213         if (!inode)
 214                 return -ENOMEM;
 215         inode->i_op = &efivarfs_dir_inode_operations;
 216
 217         root = d_make_root(inode);
 218         sb->s_root = root;
 219         if (!root)
 220                 return -ENOMEM;
 221
 222         INIT_LIST_HEAD(&efivarfs_list);
 223
 224         err = efivar_init(efivarfs_callback, (void *)sb, false,
 225                           true, &efivarfs_list);
 226         if (err)
 227                 __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 228
 229         return err;
 230 }
 231
 232 static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
 233                                     int flags, const char *dev_name, void *data)
 234 {
 235         return mount_single(fs_type, flags, data, efivarfs_fill_super);
 236 }
 237
 238 static void efivarfs_kill_sb(struct super_block *sb)
 239 {
 240         kill_litter_super(sb);
 241         efivarfs_sb = NULL;
 242
 243         /* Remove all entries and destroy */
 244         __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
 245 }
 246
 247 static struct file_system_type efivarfs_type = {
 248         .name    = "efivarfs",
 249         .mount   = efivarfs_mount,
 250         .kill_sb = efivarfs_kill_sb,
 251 };
 252
 253 static __init int efivarfs_init(void)
 254 {
 255         if (!efi_enabled(EFI_RUNTIME_SERVICES))
 256                 return 0;
 257
 258         if (!efivars_kobject())
 259                 return 0;
 260
 261         return register_filesystem(&efivarfs_type);
 262 }
 263
 264 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 265 MODULE_DESCRIPTION("EFI Variable Filesystem");
 266 MODULE_LICENSE("GPL");
 267 MODULE_ALIAS_FS("efivarfs");
 268
 269 module_init(efivarfs_init);