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/statfs.h>
17 #include <linux/printk.h>
18
19 #include "internal.h"
20
21 LIST_HEAD(efivarfs_list);
22
efivarfs_evict_inode(struct inode * inode)23 static void efivarfs_evict_inode(struct inode *inode)
24 {
25 clear_inode(inode);
26 }
27
efivarfs_statfs(struct dentry * dentry,struct kstatfs * buf)28 static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
29 {
30 const u32 attr = EFI_VARIABLE_NON_VOLATILE |
31 EFI_VARIABLE_BOOTSERVICE_ACCESS |
32 EFI_VARIABLE_RUNTIME_ACCESS;
33 u64 storage_space, remaining_space, max_variable_size;
34 efi_status_t status;
35
36 /* Some UEFI firmware does not implement QueryVariableInfo() */
37 storage_space = remaining_space = 0;
38 if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
39 status = efivar_query_variable_info(attr, &storage_space,
40 &remaining_space,
41 &max_variable_size);
42 if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
43 pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
44 status);
45 }
46
47 /*
48 * This is not a normal filesystem, so no point in pretending it has a block
49 * size; we declare f_bsize to 1, so that we can then report the exact value
50 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
51 */
52 buf->f_bsize = 1;
53 buf->f_namelen = NAME_MAX;
54 buf->f_blocks = storage_space;
55 buf->f_bfree = remaining_space;
56 buf->f_type = dentry->d_sb->s_magic;
57
58 /*
59 * In f_bavail we declare the free space that the kernel will allow writing
60 * when the storage_paranoia x86 quirk is active. To use more, users
61 * should boot the kernel with efi_no_storage_paranoia.
62 */
63 if (remaining_space > efivar_reserved_space())
64 buf->f_bavail = remaining_space - efivar_reserved_space();
65 else
66 buf->f_bavail = 0;
67
68 return 0;
69 }
70 static const struct super_operations efivarfs_ops = {
71 .statfs = efivarfs_statfs,
72 .drop_inode = generic_delete_inode,
73 .evict_inode = efivarfs_evict_inode,
74 };
75
76 /*
77 * Compare two efivarfs file names.
78 *
79 * An efivarfs filename is composed of two parts,
80 *
81 * 1. A case-sensitive variable name
82 * 2. A case-insensitive GUID
83 *
84 * So we need to perform a case-sensitive match on part 1 and a
85 * case-insensitive match on part 2.
86 */
efivarfs_d_compare(const struct dentry * dentry,unsigned int len,const char * str,const struct qstr * name)87 static int efivarfs_d_compare(const struct dentry *dentry,
88 unsigned int len, const char *str,
89 const struct qstr *name)
90 {
91 int guid = len - EFI_VARIABLE_GUID_LEN;
92
93 if (name->len != len)
94 return 1;
95
96 /* Case-sensitive compare for the variable name */
97 if (memcmp(str, name->name, guid))
98 return 1;
99
100 /* Case-insensitive compare for the GUID */
101 return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
102 }
103
efivarfs_d_hash(const struct dentry * dentry,struct qstr * qstr)104 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
105 {
106 unsigned long hash = init_name_hash(dentry);
107 const unsigned char *s = qstr->name;
108 unsigned int len = qstr->len;
109
110 if (!efivarfs_valid_name(s, len))
111 return -EINVAL;
112
113 while (len-- > EFI_VARIABLE_GUID_LEN)
114 hash = partial_name_hash(*s++, hash);
115
116 /* GUID is case-insensitive. */
117 while (len--)
118 hash = partial_name_hash(tolower(*s++), hash);
119
120 qstr->hash = end_name_hash(hash);
121 return 0;
122 }
123
124 static const struct dentry_operations efivarfs_d_ops = {
125 .d_compare = efivarfs_d_compare,
126 .d_hash = efivarfs_d_hash,
127 .d_delete = always_delete_dentry,
128 };
129
efivarfs_alloc_dentry(struct dentry * parent,char * name)130 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
131 {
132 struct dentry *d;
133 struct qstr q;
134 int err;
135
136 q.name = name;
137 q.len = strlen(name);
138
139 err = efivarfs_d_hash(parent, &q);
140 if (err)
141 return ERR_PTR(err);
142
143 d = d_alloc(parent, &q);
144 if (d)
145 return d;
146
147 return ERR_PTR(-ENOMEM);
148 }
149
efivarfs_callback(efi_char16_t * name16,efi_guid_t vendor,unsigned long name_size,void * data)150 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
151 unsigned long name_size, void *data)
152 {
153 struct super_block *sb = (struct super_block *)data;
154 struct efivar_entry *entry;
155 struct inode *inode = NULL;
156 struct dentry *dentry, *root = sb->s_root;
157 unsigned long size = 0;
158 char *name;
159 int len;
160 int err = -ENOMEM;
161 bool is_removable = false;
162
163 if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
164 return 0;
165
166 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
167 if (!entry)
168 return err;
169
170 memcpy(entry->var.VariableName, name16, name_size);
171 memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
172
173 len = ucs2_utf8size(entry->var.VariableName);
174
175 /* name, plus '-', plus GUID, plus NUL*/
176 name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
177 if (!name)
178 goto fail;
179
180 ucs2_as_utf8(name, entry->var.VariableName, len);
181
182 if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
183 is_removable = true;
184
185 name[len] = '-';
186
187 efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
188
189 name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
190
191 /* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
192 strreplace(name, '/', '!');
193
194 inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
195 is_removable);
196 if (!inode)
197 goto fail_name;
198
199 dentry = efivarfs_alloc_dentry(root, name);
200 if (IS_ERR(dentry)) {
201 err = PTR_ERR(dentry);
202 goto fail_inode;
203 }
204
205 __efivar_entry_get(entry, NULL, &size, NULL);
206 __efivar_entry_add(entry, &efivarfs_list);
207
208 /* copied by the above to local storage in the dentry. */
209 kfree(name);
210
211 inode_lock(inode);
212 inode->i_private = entry;
213 i_size_write(inode, size + sizeof(entry->var.Attributes));
214 inode_unlock(inode);
215 d_add(dentry, inode);
216
217 return 0;
218
219 fail_inode:
220 iput(inode);
221 fail_name:
222 kfree(name);
223 fail:
224 kfree(entry);
225 return err;
226 }
227
efivarfs_destroy(struct efivar_entry * entry,void * data)228 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
229 {
230 efivar_entry_remove(entry);
231 kfree(entry);
232 return 0;
233 }
234
efivarfs_fill_super(struct super_block * sb,struct fs_context * fc)235 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
236 {
237 struct inode *inode = NULL;
238 struct dentry *root;
239 int err;
240
241 if (!efivar_is_available())
242 return -EOPNOTSUPP;
243
244 sb->s_maxbytes = MAX_LFS_FILESIZE;
245 sb->s_blocksize = PAGE_SIZE;
246 sb->s_blocksize_bits = PAGE_SHIFT;
247 sb->s_magic = EFIVARFS_MAGIC;
248 sb->s_op = &efivarfs_ops;
249 sb->s_d_op = &efivarfs_d_ops;
250 sb->s_time_gran = 1;
251
252 if (!efivar_supports_writes())
253 sb->s_flags |= SB_RDONLY;
254
255 inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
256 if (!inode)
257 return -ENOMEM;
258 inode->i_op = &efivarfs_dir_inode_operations;
259
260 root = d_make_root(inode);
261 sb->s_root = root;
262 if (!root)
263 return -ENOMEM;
264
265 INIT_LIST_HEAD(&efivarfs_list);
266
267 err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
268 if (err)
269 efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
270
271 return err;
272 }
273
efivarfs_get_tree(struct fs_context * fc)274 static int efivarfs_get_tree(struct fs_context *fc)
275 {
276 return get_tree_single(fc, efivarfs_fill_super);
277 }
278
efivarfs_reconfigure(struct fs_context * fc)279 static int efivarfs_reconfigure(struct fs_context *fc)
280 {
281 if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
282 pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
283 return -EINVAL;
284 }
285
286 return 0;
287 }
288
289 static const struct fs_context_operations efivarfs_context_ops = {
290 .get_tree = efivarfs_get_tree,
291 .reconfigure = efivarfs_reconfigure,
292 };
293
efivarfs_init_fs_context(struct fs_context * fc)294 static int efivarfs_init_fs_context(struct fs_context *fc)
295 {
296 fc->ops = &efivarfs_context_ops;
297 return 0;
298 }
299
efivarfs_kill_sb(struct super_block * sb)300 static void efivarfs_kill_sb(struct super_block *sb)
301 {
302 struct efivarfs_fs_info *sfi = sb->s_fs_info;
303
304 kill_litter_super(sb);
305
306 if (!efivar_is_available())
307 return;
308
309 /* Remove all entries and destroy */
310 efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
311 kfree(sfi);
312 }
313
314 static struct file_system_type efivarfs_type = {
315 .owner = THIS_MODULE,
316 .name = "efivarfs",
317 .init_fs_context = efivarfs_init_fs_context,
318 .kill_sb = efivarfs_kill_sb,
319 };
320
efivarfs_init(void)321 static __init int efivarfs_init(void)
322 {
323 return register_filesystem(&efivarfs_type);
324 }
325
efivarfs_exit(void)326 static __exit void efivarfs_exit(void)
327 {
328 unregister_filesystem(&efivarfs_type);
329 }
330
331 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
332 MODULE_DESCRIPTION("EFI Variable Filesystem");
333 MODULE_LICENSE("GPL");
334 MODULE_ALIAS_FS("efivarfs");
335
336 module_init(efivarfs_init);
337 module_exit(efivarfs_exit);
338