xref: /openbmc/linux/fs/efivarfs/super.c (revision 2984f26a) 
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 
23 static void efivarfs_evict_inode(struct inode *inode)
24 {
25 	clear_inode(inode);
26 }
27 
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  */
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 
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 
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 
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 
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 
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 
274 static int efivarfs_get_tree(struct fs_context *fc)
275 {
276 	return get_tree_single(fc, efivarfs_fill_super);
277 }
278 
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 
294 static int efivarfs_init_fs_context(struct fs_context *fc)
295 {
296 	fc->ops = &efivarfs_context_ops;
297 	return 0;
298 }
299 
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 
321 static __init int efivarfs_init(void)
322 {
323 	return register_filesystem(&efivarfs_type);
324 }
325 
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