xref: /openbmc/linux/fs/efivarfs/super.c (revision 7ca4282ade77de53b6e9ffa2695566e5d35dab1e) 
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 
17 #include "internal.h"
18 
19 LIST_HEAD(efivarfs_list);
20 
21 static void efivarfs_evict_inode(struct inode *inode)
22 {
23 	clear_inode(inode);
24 	kfree(inode->i_private);
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  */
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 
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 
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 
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 
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 
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 
230 static int efivarfs_get_tree(struct fs_context *fc)
231 {
232 	return get_tree_single(fc, efivarfs_fill_super);
233 }
234 
235 static const struct fs_context_operations efivarfs_context_ops = {
236 	.get_tree	= efivarfs_get_tree,
237 };
238 
239 static int efivarfs_init_fs_context(struct fs_context *fc)
240 {
241 	fc->ops = &efivarfs_context_ops;
242 	return 0;
243 }
244 
245 static void efivarfs_kill_sb(struct super_block *sb)
246 {
247 	kill_litter_super(sb);
248 
249 	/* Remove all entries and destroy */
250 	__efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
251 }
252 
253 static struct file_system_type efivarfs_type = {
254 	.owner   = THIS_MODULE,
255 	.name    = "efivarfs",
256 	.init_fs_context = efivarfs_init_fs_context,
257 	.kill_sb = efivarfs_kill_sb,
258 };
259 
260 static __init int efivarfs_init(void)
261 {
262 	if (!efivars_kobject())
263 		return -ENODEV;
264 
265 	return register_filesystem(&efivarfs_type);
266 }
267 
268 static __exit void efivarfs_exit(void)
269 {
270 	unregister_filesystem(&efivarfs_type);
271 }
272 
273 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
274 MODULE_DESCRIPTION("EFI Variable Filesystem");
275 MODULE_LICENSE("GPL");
276 MODULE_ALIAS_FS("efivarfs");
277 
278 module_init(efivarfs_init);
279 module_exit(efivarfs_exit);
280