xref: /openbmc/linux/fs/efivarfs/super.c (revision c4c3c32d) 
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 
18 #include "internal.h"
19 
20 LIST_HEAD(efivarfs_list);
21 
22 static void efivarfs_evict_inode(struct inode *inode)
23 {
24 	clear_inode(inode);
25 }
26 
27 static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
28 {
29 	const u32 attr = EFI_VARIABLE_NON_VOLATILE |
30 			 EFI_VARIABLE_BOOTSERVICE_ACCESS |
31 			 EFI_VARIABLE_RUNTIME_ACCESS;
32 	u64 storage_space, remaining_space, max_variable_size;
33 	efi_status_t status;
34 
35 	status = efivar_query_variable_info(attr, &storage_space, &remaining_space,
36 					    &max_variable_size);
37 	if (status != EFI_SUCCESS)
38 		return efi_status_to_err(status);
39 
40 	/*
41 	 * This is not a normal filesystem, so no point in pretending it has a block
42 	 * size; we declare f_bsize to 1, so that we can then report the exact value
43 	 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
44 	 */
45 	buf->f_bsize	= 1;
46 	buf->f_namelen	= NAME_MAX;
47 	buf->f_blocks	= storage_space;
48 	buf->f_bfree	= remaining_space;
49 	buf->f_type	= dentry->d_sb->s_magic;
50 
51 	/*
52 	 * In f_bavail we declare the free space that the kernel will allow writing
53 	 * when the storage_paranoia x86 quirk is active. To use more, users
54 	 * should boot the kernel with efi_no_storage_paranoia.
55 	 */
56 	if (remaining_space > efivar_reserved_space())
57 		buf->f_bavail = remaining_space - efivar_reserved_space();
58 	else
59 		buf->f_bavail = 0;
60 
61 	return 0;
62 }
63 static const struct super_operations efivarfs_ops = {
64 	.statfs = efivarfs_statfs,
65 	.drop_inode = generic_delete_inode,
66 	.evict_inode = efivarfs_evict_inode,
67 };
68 
69 /*
70  * Compare two efivarfs file names.
71  *
72  * An efivarfs filename is composed of two parts,
73  *
74  *	1. A case-sensitive variable name
75  *	2. A case-insensitive GUID
76  *
77  * So we need to perform a case-sensitive match on part 1 and a
78  * case-insensitive match on part 2.
79  */
80 static int efivarfs_d_compare(const struct dentry *dentry,
81 			      unsigned int len, const char *str,
82 			      const struct qstr *name)
83 {
84 	int guid = len - EFI_VARIABLE_GUID_LEN;
85 
86 	if (name->len != len)
87 		return 1;
88 
89 	/* Case-sensitive compare for the variable name */
90 	if (memcmp(str, name->name, guid))
91 		return 1;
92 
93 	/* Case-insensitive compare for the GUID */
94 	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
95 }
96 
97 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
98 {
99 	unsigned long hash = init_name_hash(dentry);
100 	const unsigned char *s = qstr->name;
101 	unsigned int len = qstr->len;
102 
103 	if (!efivarfs_valid_name(s, len))
104 		return -EINVAL;
105 
106 	while (len-- > EFI_VARIABLE_GUID_LEN)
107 		hash = partial_name_hash(*s++, hash);
108 
109 	/* GUID is case-insensitive. */
110 	while (len--)
111 		hash = partial_name_hash(tolower(*s++), hash);
112 
113 	qstr->hash = end_name_hash(hash);
114 	return 0;
115 }
116 
117 static const struct dentry_operations efivarfs_d_ops = {
118 	.d_compare = efivarfs_d_compare,
119 	.d_hash = efivarfs_d_hash,
120 	.d_delete = always_delete_dentry,
121 };
122 
123 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
124 {
125 	struct dentry *d;
126 	struct qstr q;
127 	int err;
128 
129 	q.name = name;
130 	q.len = strlen(name);
131 
132 	err = efivarfs_d_hash(parent, &q);
133 	if (err)
134 		return ERR_PTR(err);
135 
136 	d = d_alloc(parent, &q);
137 	if (d)
138 		return d;
139 
140 	return ERR_PTR(-ENOMEM);
141 }
142 
143 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
144 			     unsigned long name_size, void *data)
145 {
146 	struct super_block *sb = (struct super_block *)data;
147 	struct efivar_entry *entry;
148 	struct inode *inode = NULL;
149 	struct dentry *dentry, *root = sb->s_root;
150 	unsigned long size = 0;
151 	char *name;
152 	int len;
153 	int err = -ENOMEM;
154 	bool is_removable = false;
155 
156 	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
157 		return 0;
158 
159 	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
160 	if (!entry)
161 		return err;
162 
163 	memcpy(entry->var.VariableName, name16, name_size);
164 	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
165 
166 	len = ucs2_utf8size(entry->var.VariableName);
167 
168 	/* name, plus '-', plus GUID, plus NUL*/
169 	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
170 	if (!name)
171 		goto fail;
172 
173 	ucs2_as_utf8(name, entry->var.VariableName, len);
174 
175 	if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
176 		is_removable = true;
177 
178 	name[len] = '-';
179 
180 	efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
181 
182 	name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
183 
184 	/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
185 	strreplace(name, '/', '!');
186 
187 	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
188 				   is_removable);
189 	if (!inode)
190 		goto fail_name;
191 
192 	dentry = efivarfs_alloc_dentry(root, name);
193 	if (IS_ERR(dentry)) {
194 		err = PTR_ERR(dentry);
195 		goto fail_inode;
196 	}
197 
198 	__efivar_entry_get(entry, NULL, &size, NULL);
199 	__efivar_entry_add(entry, &efivarfs_list);
200 
201 	/* copied by the above to local storage in the dentry. */
202 	kfree(name);
203 
204 	inode_lock(inode);
205 	inode->i_private = entry;
206 	i_size_write(inode, size + sizeof(entry->var.Attributes));
207 	inode_unlock(inode);
208 	d_add(dentry, inode);
209 
210 	return 0;
211 
212 fail_inode:
213 	iput(inode);
214 fail_name:
215 	kfree(name);
216 fail:
217 	kfree(entry);
218 	return err;
219 }
220 
221 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
222 {
223 	efivar_entry_remove(entry);
224 	kfree(entry);
225 	return 0;
226 }
227 
228 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
229 {
230 	struct inode *inode = NULL;
231 	struct dentry *root;
232 	int err;
233 
234 	if (!efivar_is_available())
235 		return -EOPNOTSUPP;
236 
237 	sb->s_maxbytes          = MAX_LFS_FILESIZE;
238 	sb->s_blocksize         = PAGE_SIZE;
239 	sb->s_blocksize_bits    = PAGE_SHIFT;
240 	sb->s_magic             = EFIVARFS_MAGIC;
241 	sb->s_op                = &efivarfs_ops;
242 	sb->s_d_op		= &efivarfs_d_ops;
243 	sb->s_time_gran         = 1;
244 
245 	if (!efivar_supports_writes())
246 		sb->s_flags |= SB_RDONLY;
247 
248 	inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
249 	if (!inode)
250 		return -ENOMEM;
251 	inode->i_op = &efivarfs_dir_inode_operations;
252 
253 	root = d_make_root(inode);
254 	sb->s_root = root;
255 	if (!root)
256 		return -ENOMEM;
257 
258 	INIT_LIST_HEAD(&efivarfs_list);
259 
260 	err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
261 	if (err)
262 		efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
263 
264 	return err;
265 }
266 
267 static int efivarfs_get_tree(struct fs_context *fc)
268 {
269 	return get_tree_single(fc, efivarfs_fill_super);
270 }
271 
272 static const struct fs_context_operations efivarfs_context_ops = {
273 	.get_tree	= efivarfs_get_tree,
274 };
275 
276 static int efivarfs_init_fs_context(struct fs_context *fc)
277 {
278 	fc->ops = &efivarfs_context_ops;
279 	return 0;
280 }
281 
282 static void efivarfs_kill_sb(struct super_block *sb)
283 {
284 	kill_litter_super(sb);
285 
286 	if (!efivar_is_available())
287 		return;
288 
289 	/* Remove all entries and destroy */
290 	efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
291 }
292 
293 static struct file_system_type efivarfs_type = {
294 	.owner   = THIS_MODULE,
295 	.name    = "efivarfs",
296 	.init_fs_context = efivarfs_init_fs_context,
297 	.kill_sb = efivarfs_kill_sb,
298 };
299 
300 static __init int efivarfs_init(void)
301 {
302 	return register_filesystem(&efivarfs_type);
303 }
304 
305 static __exit void efivarfs_exit(void)
306 {
307 	unregister_filesystem(&efivarfs_type);
308 }
309 
310 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
311 MODULE_DESCRIPTION("EFI Variable Filesystem");
312 MODULE_LICENSE("GPL");
313 MODULE_ALIAS_FS("efivarfs");
314 
315 module_init(efivarfs_init);
316 module_exit(efivarfs_exit);
317