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 while (len-- > EFI_VARIABLE_GUID_LEN)
111 hash = partial_name_hash(*s++, hash);
112
113 /* GUID is case-insensitive. */
114 while (len--)
115 hash = partial_name_hash(tolower(*s++), hash);
116
117 qstr->hash = end_name_hash(hash);
118 return 0;
119 }
120
121 static const struct dentry_operations efivarfs_d_ops = {
122 .d_compare = efivarfs_d_compare,
123 .d_hash = efivarfs_d_hash,
124 .d_delete = always_delete_dentry,
125 };
126
efivarfs_alloc_dentry(struct dentry * parent,char * name)127 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
128 {
129 struct dentry *d;
130 struct qstr q;
131 int err;
132
133 q.name = name;
134 q.len = strlen(name);
135
136 err = efivarfs_d_hash(parent, &q);
137 if (err)
138 return ERR_PTR(err);
139
140 d = d_alloc(parent, &q);
141 if (d)
142 return d;
143
144 return ERR_PTR(-ENOMEM);
145 }
146
efivarfs_callback(efi_char16_t * name16,efi_guid_t vendor,unsigned long name_size,void * data)147 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
148 unsigned long name_size, void *data)
149 {
150 struct super_block *sb = (struct super_block *)data;
151 struct efivar_entry *entry;
152 struct inode *inode = NULL;
153 struct dentry *dentry, *root = sb->s_root;
154 unsigned long size = 0;
155 char *name;
156 int len;
157 int err = -ENOMEM;
158 bool is_removable = false;
159
160 if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
161 return 0;
162
163 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
164 if (!entry)
165 return err;
166
167 memcpy(entry->var.VariableName, name16, name_size);
168 memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
169
170 len = ucs2_utf8size(entry->var.VariableName);
171
172 /* name, plus '-', plus GUID, plus NUL*/
173 name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
174 if (!name)
175 goto fail;
176
177 ucs2_as_utf8(name, entry->var.VariableName, len);
178
179 if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
180 is_removable = true;
181
182 name[len] = '-';
183
184 efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
185
186 name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
187
188 /* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
189 strreplace(name, '/', '!');
190
191 inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
192 is_removable);
193 if (!inode)
194 goto fail_name;
195
196 dentry = efivarfs_alloc_dentry(root, name);
197 if (IS_ERR(dentry)) {
198 err = PTR_ERR(dentry);
199 goto fail_inode;
200 }
201
202 __efivar_entry_get(entry, NULL, &size, NULL);
203 __efivar_entry_add(entry, &efivarfs_list);
204
205 /* copied by the above to local storage in the dentry. */
206 kfree(name);
207
208 inode_lock(inode);
209 inode->i_private = entry;
210 i_size_write(inode, size + sizeof(entry->var.Attributes));
211 inode_unlock(inode);
212 d_add(dentry, inode);
213
214 return 0;
215
216 fail_inode:
217 iput(inode);
218 fail_name:
219 kfree(name);
220 fail:
221 kfree(entry);
222 return err;
223 }
224
efivarfs_destroy(struct efivar_entry * entry,void * data)225 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
226 {
227 efivar_entry_remove(entry);
228 kfree(entry);
229 return 0;
230 }
231
efivarfs_fill_super(struct super_block * sb,struct fs_context * fc)232 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
233 {
234 struct inode *inode = NULL;
235 struct dentry *root;
236 int err;
237
238 if (!efivar_is_available())
239 return -EOPNOTSUPP;
240
241 sb->s_maxbytes = MAX_LFS_FILESIZE;
242 sb->s_blocksize = PAGE_SIZE;
243 sb->s_blocksize_bits = PAGE_SHIFT;
244 sb->s_magic = EFIVARFS_MAGIC;
245 sb->s_op = &efivarfs_ops;
246 sb->s_d_op = &efivarfs_d_ops;
247 sb->s_time_gran = 1;
248
249 if (!efivar_supports_writes())
250 sb->s_flags |= SB_RDONLY;
251
252 inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
253 if (!inode)
254 return -ENOMEM;
255 inode->i_op = &efivarfs_dir_inode_operations;
256
257 root = d_make_root(inode);
258 sb->s_root = root;
259 if (!root)
260 return -ENOMEM;
261
262 INIT_LIST_HEAD(&efivarfs_list);
263
264 err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
265 if (err)
266 efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
267
268 return err;
269 }
270
efivarfs_get_tree(struct fs_context * fc)271 static int efivarfs_get_tree(struct fs_context *fc)
272 {
273 return get_tree_single(fc, efivarfs_fill_super);
274 }
275
efivarfs_reconfigure(struct fs_context * fc)276 static int efivarfs_reconfigure(struct fs_context *fc)
277 {
278 if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
279 pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
280 return -EINVAL;
281 }
282
283 return 0;
284 }
285
286 static const struct fs_context_operations efivarfs_context_ops = {
287 .get_tree = efivarfs_get_tree,
288 .reconfigure = efivarfs_reconfigure,
289 };
290
efivarfs_init_fs_context(struct fs_context * fc)291 static int efivarfs_init_fs_context(struct fs_context *fc)
292 {
293 fc->ops = &efivarfs_context_ops;
294 return 0;
295 }
296
efivarfs_kill_sb(struct super_block * sb)297 static void efivarfs_kill_sb(struct super_block *sb)
298 {
299 struct efivarfs_fs_info *sfi = sb->s_fs_info;
300
301 kill_litter_super(sb);
302
303 if (!efivar_is_available())
304 return;
305
306 /* Remove all entries and destroy */
307 efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
308 kfree(sfi);
309 }
310
311 static struct file_system_type efivarfs_type = {
312 .owner = THIS_MODULE,
313 .name = "efivarfs",
314 .init_fs_context = efivarfs_init_fs_context,
315 .kill_sb = efivarfs_kill_sb,
316 };
317
efivarfs_init(void)318 static __init int efivarfs_init(void)
319 {
320 return register_filesystem(&efivarfs_type);
321 }
322
efivarfs_exit(void)323 static __exit void efivarfs_exit(void)
324 {
325 unregister_filesystem(&efivarfs_type);
326 }
327
328 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
329 MODULE_DESCRIPTION("EFI Variable Filesystem");
330 MODULE_LICENSE("GPL");
331 MODULE_ALIAS_FS("efivarfs");
332
333 module_init(efivarfs_init);
334 module_exit(efivarfs_exit);
335