linux/fs/efivarfs/super.c
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   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
  21LIST_HEAD(efivarfs_list);
  22
  23static void efivarfs_evict_inode(struct inode *inode)
  24{
  25        clear_inode(inode);
  26}
  27
  28static 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
  35static 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 */
  48static 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
  66static 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 */
  90static int efivarfs_delete_dentry(const struct dentry *dentry)
  91{
  92        return 1;
  93}
  94
  95static 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
 101static 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
 121static 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
 180fail_inode:
 181        iput(inode);
 182fail_name:
 183        kfree(name);
 184fail:
 185        kfree(entry);
 186        return err;
 187}
 188
 189static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 190{
 191        efivar_entry_remove(entry);
 192        kfree(entry);
 193        return 0;
 194}
 195
 196static 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
 232static 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
 238static 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
 247static struct file_system_type efivarfs_type = {
 248        .name    = "efivarfs",
 249        .mount   = efivarfs_mount,
 250        .kill_sb = efivarfs_kill_sb,
 251};
 252
 253static __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
 264MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
 265MODULE_DESCRIPTION("EFI Variable Filesystem");
 266MODULE_LICENSE("GPL");
 267MODULE_ALIAS_FS("efivarfs");
 268
 269module_init(efivarfs_init);
 270
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