1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2012 Red Hat, Inc.
4 * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
5 */
6
7 #include <linux/ctype.h>
8 #include <linux/efi.h>
9 #include <linux/fs.h>
10 #include <linux/fs_context.h>
11 #include <linux/module.h>
12 #include <linux/pagemap.h>
13 #include <linux/ucs2_string.h>
14 #include <linux/slab.h>
15 #include <linux/magic.h>
16 #include <linux/printk.h>
17
18 #include "internal.h"
19
20 LIST_HEAD(efivarfs_list);
21
efivarfs_evict_inode(struct inode * inode)22 static void efivarfs_evict_inode(struct inode *inode)
23 {
24 clear_inode(inode);
25 }
26
27 static const struct super_operations efivarfs_ops = {
28 .statfs = simple_statfs,
29 .drop_inode = generic_delete_inode,
30 .evict_inode = efivarfs_evict_inode,
31 };
32
33 /*
34 * Compare two efivarfs file names.
35 *
36 * An efivarfs filename is composed of two parts,
37 *
38 * 1. A case-sensitive variable name
39 * 2. A case-insensitive GUID
40 *
41 * So we need to perform a case-sensitive match on part 1 and a
42 * case-insensitive match on part 2.
43 */
efivarfs_d_compare(const struct dentry * dentry,unsigned int len,const char * str,const struct qstr * name)44 static int efivarfs_d_compare(const struct dentry *dentry,
45 unsigned int len, const char *str,
46 const struct qstr *name)
47 {
48 int guid = len - EFI_VARIABLE_GUID_LEN;
49
50 if (name->len != len)
51 return 1;
52
53 /* Case-sensitive compare for the variable name */
54 if (memcmp(str, name->name, guid))
55 return 1;
56
57 /* Case-insensitive compare for the GUID */
58 return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
59 }
60
efivarfs_d_hash(const struct dentry * dentry,struct qstr * qstr)61 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
62 {
63 unsigned long hash = init_name_hash(dentry);
64 const unsigned char *s = qstr->name;
65 unsigned int len = qstr->len;
66
67 if (!efivarfs_valid_name(s, len))
68 return -EINVAL;
69
70 while (len-- > EFI_VARIABLE_GUID_LEN)
71 hash = partial_name_hash(*s++, hash);
72
73 /* GUID is case-insensitive. */
74 while (len--)
75 hash = partial_name_hash(tolower(*s++), hash);
76
77 qstr->hash = end_name_hash(hash);
78 return 0;
79 }
80
81 static const struct dentry_operations efivarfs_d_ops = {
82 .d_compare = efivarfs_d_compare,
83 .d_hash = efivarfs_d_hash,
84 .d_delete = always_delete_dentry,
85 };
86
efivarfs_alloc_dentry(struct dentry * parent,char * name)87 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
88 {
89 struct dentry *d;
90 struct qstr q;
91 int err;
92
93 q.name = name;
94 q.len = strlen(name);
95
96 err = efivarfs_d_hash(parent, &q);
97 if (err)
98 return ERR_PTR(err);
99
100 d = d_alloc(parent, &q);
101 if (d)
102 return d;
103
104 return ERR_PTR(-ENOMEM);
105 }
106
efivarfs_callback(efi_char16_t * name16,efi_guid_t vendor,unsigned long name_size,void * data)107 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
108 unsigned long name_size, void *data)
109 {
110 struct super_block *sb = (struct super_block *)data;
111 struct efivar_entry *entry;
112 struct inode *inode = NULL;
113 struct dentry *dentry, *root = sb->s_root;
114 unsigned long size = 0;
115 char *name;
116 int len;
117 int err = -ENOMEM;
118 bool is_removable = false;
119
120 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
121 if (!entry)
122 return err;
123
124 memcpy(entry->var.VariableName, name16, name_size);
125 memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
126
127 len = ucs2_utf8size(entry->var.VariableName);
128
129 /* name, plus '-', plus GUID, plus NUL*/
130 name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
131 if (!name)
132 goto fail;
133
134 ucs2_as_utf8(name, entry->var.VariableName, len);
135
136 if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
137 is_removable = true;
138
139 name[len] = '-';
140
141 efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
142
143 name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
144
145 /* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
146 strreplace(name, '/', '!');
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
efivarfs_destroy(struct efivar_entry * entry,void * data)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
efivarfs_fill_super(struct super_block * sb,struct fs_context * fc)194 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
195 {
196 struct inode *inode = NULL;
197 struct dentry *root;
198 int err;
199
200 sb->s_maxbytes = MAX_LFS_FILESIZE;
201 sb->s_blocksize = PAGE_SIZE;
202 sb->s_blocksize_bits = PAGE_SHIFT;
203 sb->s_magic = EFIVARFS_MAGIC;
204 sb->s_op = &efivarfs_ops;
205 sb->s_d_op = &efivarfs_d_ops;
206 sb->s_time_gran = 1;
207
208 if (!efivar_supports_writes())
209 sb->s_flags |= SB_RDONLY;
210
211 inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
212 if (!inode)
213 return -ENOMEM;
214 inode->i_op = &efivarfs_dir_inode_operations;
215
216 root = d_make_root(inode);
217 sb->s_root = root;
218 if (!root)
219 return -ENOMEM;
220
221 INIT_LIST_HEAD(&efivarfs_list);
222
223 err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
224 if (err)
225 __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
226
227 return err;
228 }
229
efivarfs_get_tree(struct fs_context * fc)230 static int efivarfs_get_tree(struct fs_context *fc)
231 {
232 return get_tree_single(fc, efivarfs_fill_super);
233 }
234
efivarfs_reconfigure(struct fs_context * fc)235 static int efivarfs_reconfigure(struct fs_context *fc)
236 {
237 if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
238 pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
239 return -EINVAL;
240 }
241
242 return 0;
243 }
244
245 static const struct fs_context_operations efivarfs_context_ops = {
246 .get_tree = efivarfs_get_tree,
247 .reconfigure = efivarfs_reconfigure,
248 };
249
efivarfs_init_fs_context(struct fs_context * fc)250 static int efivarfs_init_fs_context(struct fs_context *fc)
251 {
252 fc->ops = &efivarfs_context_ops;
253 return 0;
254 }
255
efivarfs_kill_sb(struct super_block * sb)256 static void efivarfs_kill_sb(struct super_block *sb)
257 {
258 kill_litter_super(sb);
259
260 /* Remove all entries and destroy */
261 __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
262 }
263
264 static struct file_system_type efivarfs_type = {
265 .owner = THIS_MODULE,
266 .name = "efivarfs",
267 .init_fs_context = efivarfs_init_fs_context,
268 .kill_sb = efivarfs_kill_sb,
269 };
270
efivarfs_init(void)271 static __init int efivarfs_init(void)
272 {
273 if (!efivars_kobject())
274 return -ENODEV;
275
276 return register_filesystem(&efivarfs_type);
277 }
278
efivarfs_exit(void)279 static __exit void efivarfs_exit(void)
280 {
281 unregister_filesystem(&efivarfs_type);
282 }
283
284 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
285 MODULE_DESCRIPTION("EFI Variable Filesystem");
286 MODULE_LICENSE("GPL");
287 MODULE_IMPORT_NS(ANDROID_GKI_VFS_EXPORT_ONLY);
288 MODULE_ALIAS_FS("efivarfs");
289
290 module_init(efivarfs_init);
291 module_exit(efivarfs_exit);
292