xref: /openbmc/linux/fs/efivarfs/super.c (revision b868a02e)
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 }
25 
26 static const struct super_operations efivarfs_ops = {
27 	.statfs = simple_statfs,
28 	.drop_inode = generic_delete_inode,
29 	.evict_inode = efivarfs_evict_inode,
30 };
31 
32 /*
33  * Compare two efivarfs file names.
34  *
35  * An efivarfs filename is composed of two parts,
36  *
37  *	1. A case-sensitive variable name
38  *	2. A case-insensitive GUID
39  *
40  * So we need to perform a case-sensitive match on part 1 and a
41  * case-insensitive match on part 2.
42  */
43 static int efivarfs_d_compare(const struct dentry *dentry,
44 			      unsigned int len, const char *str,
45 			      const struct qstr *name)
46 {
47 	int guid = len - EFI_VARIABLE_GUID_LEN;
48 
49 	if (name->len != len)
50 		return 1;
51 
52 	/* Case-sensitive compare for the variable name */
53 	if (memcmp(str, name->name, guid))
54 		return 1;
55 
56 	/* Case-insensitive compare for the GUID */
57 	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
58 }
59 
60 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
61 {
62 	unsigned long hash = init_name_hash(dentry);
63 	const unsigned char *s = qstr->name;
64 	unsigned int len = qstr->len;
65 
66 	if (!efivarfs_valid_name(s, len))
67 		return -EINVAL;
68 
69 	while (len-- > EFI_VARIABLE_GUID_LEN)
70 		hash = partial_name_hash(*s++, hash);
71 
72 	/* GUID is case-insensitive. */
73 	while (len--)
74 		hash = partial_name_hash(tolower(*s++), hash);
75 
76 	qstr->hash = end_name_hash(hash);
77 	return 0;
78 }
79 
80 static const struct dentry_operations efivarfs_d_ops = {
81 	.d_compare = efivarfs_d_compare,
82 	.d_hash = efivarfs_d_hash,
83 	.d_delete = always_delete_dentry,
84 };
85 
86 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
87 {
88 	struct dentry *d;
89 	struct qstr q;
90 	int err;
91 
92 	q.name = name;
93 	q.len = strlen(name);
94 
95 	err = efivarfs_d_hash(parent, &q);
96 	if (err)
97 		return ERR_PTR(err);
98 
99 	d = d_alloc(parent, &q);
100 	if (d)
101 		return d;
102 
103 	return ERR_PTR(-ENOMEM);
104 }
105 
106 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
107 			     unsigned long name_size, void *data)
108 {
109 	struct super_block *sb = (struct super_block *)data;
110 	struct efivar_entry *entry;
111 	struct inode *inode = NULL;
112 	struct dentry *dentry, *root = sb->s_root;
113 	unsigned long size = 0;
114 	char *name;
115 	int len;
116 	int err = -ENOMEM;
117 	bool is_removable = false;
118 
119 	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
120 	if (!entry)
121 		return err;
122 
123 	memcpy(entry->var.VariableName, name16, name_size);
124 	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
125 
126 	len = ucs2_utf8size(entry->var.VariableName);
127 
128 	/* name, plus '-', plus GUID, plus NUL*/
129 	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
130 	if (!name)
131 		goto fail;
132 
133 	ucs2_as_utf8(name, entry->var.VariableName, len);
134 
135 	if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
136 		is_removable = true;
137 
138 	name[len] = '-';
139 
140 	efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
141 
142 	name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
143 
144 	/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
145 	strreplace(name, '/', '!');
146 
147 	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
148 				   is_removable);
149 	if (!inode)
150 		goto fail_name;
151 
152 	dentry = efivarfs_alloc_dentry(root, name);
153 	if (IS_ERR(dentry)) {
154 		err = PTR_ERR(dentry);
155 		goto fail_inode;
156 	}
157 
158 	__efivar_entry_get(entry, NULL, &size, NULL);
159 	__efivar_entry_add(entry, &efivarfs_list);
160 
161 	/* copied by the above to local storage in the dentry. */
162 	kfree(name);
163 
164 	inode_lock(inode);
165 	inode->i_private = entry;
166 	i_size_write(inode, size + sizeof(entry->var.Attributes));
167 	inode_unlock(inode);
168 	d_add(dentry, inode);
169 
170 	return 0;
171 
172 fail_inode:
173 	iput(inode);
174 fail_name:
175 	kfree(name);
176 fail:
177 	kfree(entry);
178 	return err;
179 }
180 
181 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
182 {
183 	efivar_entry_remove(entry);
184 	kfree(entry);
185 	return 0;
186 }
187 
188 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
189 {
190 	struct inode *inode = NULL;
191 	struct dentry *root;
192 	int err;
193 
194 	sb->s_maxbytes          = MAX_LFS_FILESIZE;
195 	sb->s_blocksize         = PAGE_SIZE;
196 	sb->s_blocksize_bits    = PAGE_SHIFT;
197 	sb->s_magic             = EFIVARFS_MAGIC;
198 	sb->s_op                = &efivarfs_ops;
199 	sb->s_d_op		= &efivarfs_d_ops;
200 	sb->s_time_gran         = 1;
201 
202 	if (!efivar_supports_writes())
203 		sb->s_flags |= SB_RDONLY;
204 
205 	inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
206 	if (!inode)
207 		return -ENOMEM;
208 	inode->i_op = &efivarfs_dir_inode_operations;
209 
210 	root = d_make_root(inode);
211 	sb->s_root = root;
212 	if (!root)
213 		return -ENOMEM;
214 
215 	INIT_LIST_HEAD(&efivarfs_list);
216 
217 	err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
218 	if (err)
219 		efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
220 
221 	return err;
222 }
223 
224 static int efivarfs_get_tree(struct fs_context *fc)
225 {
226 	return get_tree_single(fc, efivarfs_fill_super);
227 }
228 
229 static const struct fs_context_operations efivarfs_context_ops = {
230 	.get_tree	= efivarfs_get_tree,
231 };
232 
233 static int efivarfs_init_fs_context(struct fs_context *fc)
234 {
235 	fc->ops = &efivarfs_context_ops;
236 	return 0;
237 }
238 
239 static void efivarfs_kill_sb(struct super_block *sb)
240 {
241 	kill_litter_super(sb);
242 
243 	/* Remove all entries and destroy */
244 	efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
245 }
246 
247 static struct file_system_type efivarfs_type = {
248 	.owner   = THIS_MODULE,
249 	.name    = "efivarfs",
250 	.init_fs_context = efivarfs_init_fs_context,
251 	.kill_sb = efivarfs_kill_sb,
252 };
253 
254 static __init int efivarfs_init(void)
255 {
256 	if (!efivars_kobject())
257 		return -ENODEV;
258 
259 	return register_filesystem(&efivarfs_type);
260 }
261 
262 static __exit void efivarfs_exit(void)
263 {
264 	unregister_filesystem(&efivarfs_type);
265 }
266 
267 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
268 MODULE_DESCRIPTION("EFI Variable Filesystem");
269 MODULE_LICENSE("GPL");
270 MODULE_ALIAS_FS("efivarfs");
271 
272 module_init(efivarfs_init);
273 module_exit(efivarfs_exit);
274