1/*
2 * Copyright (C) 2012 Red Hat, Inc.
3 * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 */
9
10#include <linux/efi.h>
11#include <linux/fs.h>
12#include <linux/ctype.h>
13#include <linux/slab.h>
14
15#include "internal.h"
16
17struct inode *efivarfs_get_inode(struct super_block *sb,
18				const struct inode *dir, int mode,
19				dev_t dev, bool is_removable)
20{
21	struct inode *inode = new_inode(sb);
22
23	if (inode) {
24		inode->i_ino = get_next_ino();
25		inode->i_mode = mode;
26		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
27		inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
28		switch (mode & S_IFMT) {
29		case S_IFREG:
30			inode->i_fop = &efivarfs_file_operations;
31			break;
32		case S_IFDIR:
33			inode->i_op = &efivarfs_dir_inode_operations;
34			inode->i_fop = &simple_dir_operations;
35			inc_nlink(inode);
36			break;
37		}
38	}
39	return inode;
40}
41
42/*
43 * Return true if 'str' is a valid efivarfs filename of the form,
44 *
45 *	VariableName-12345678-1234-1234-1234-1234567891bc
46 */
47bool efivarfs_valid_name(const char *str, int len)
48{
49	static const char dashes[EFI_VARIABLE_GUID_LEN] = {
50		[8] = 1, [13] = 1, [18] = 1, [23] = 1
51	};
52	const char *s = str + len - EFI_VARIABLE_GUID_LEN;
53	int i;
54
55	/*
56	 * We need a GUID, plus at least one letter for the variable name,
57	 * plus the '-' separator
58	 */
59	if (len < EFI_VARIABLE_GUID_LEN + 2)
60		return false;
61
62	/* GUID must be preceded by a '-' */
63	if (*(s - 1) != '-')
64		return false;
65
66	/*
67	 * Validate that 's' is of the correct format, e.g.
68	 *
69	 *	12345678-1234-1234-1234-123456789abc
70	 */
71	for (i = 0; i < EFI_VARIABLE_GUID_LEN; i++) {
72		if (dashes[i]) {
73			if (*s++ != '-')
74				return false;
75		} else {
76			if (!isxdigit(*s++))
77				return false;
78		}
79	}
80
81	return true;
82}
83
84static void efivarfs_hex_to_guid(const char *str, efi_guid_t *guid)
85{
86	guid->b[0] = hex_to_bin(str[6]) << 4 | hex_to_bin(str[7]);
87	guid->b[1] = hex_to_bin(str[4]) << 4 | hex_to_bin(str[5]);
88	guid->b[2] = hex_to_bin(str[2]) << 4 | hex_to_bin(str[3]);
89	guid->b[3] = hex_to_bin(str[0]) << 4 | hex_to_bin(str[1]);
90	guid->b[4] = hex_to_bin(str[11]) << 4 | hex_to_bin(str[12]);
91	guid->b[5] = hex_to_bin(str[9]) << 4 | hex_to_bin(str[10]);
92	guid->b[6] = hex_to_bin(str[16]) << 4 | hex_to_bin(str[17]);
93	guid->b[7] = hex_to_bin(str[14]) << 4 | hex_to_bin(str[15]);
94	guid->b[8] = hex_to_bin(str[19]) << 4 | hex_to_bin(str[20]);
95	guid->b[9] = hex_to_bin(str[21]) << 4 | hex_to_bin(str[22]);
96	guid->b[10] = hex_to_bin(str[24]) << 4 | hex_to_bin(str[25]);
97	guid->b[11] = hex_to_bin(str[26]) << 4 | hex_to_bin(str[27]);
98	guid->b[12] = hex_to_bin(str[28]) << 4 | hex_to_bin(str[29]);
99	guid->b[13] = hex_to_bin(str[30]) << 4 | hex_to_bin(str[31]);
100	guid->b[14] = hex_to_bin(str[32]) << 4 | hex_to_bin(str[33]);
101	guid->b[15] = hex_to_bin(str[34]) << 4 | hex_to_bin(str[35]);
102}
103
104static int efivarfs_create(struct inode *dir, struct dentry *dentry,
105			  umode_t mode, bool excl)
106{
107	struct inode *inode = NULL;
108	struct efivar_entry *var;
109	int namelen, i = 0, err = 0;
110	bool is_removable = false;
111
112	if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
113		return -EINVAL;
114
115	var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
116	if (!var)
117		return -ENOMEM;
118
119	/* length of the variable name itself: remove GUID and separator */
120	namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
121
122	efivarfs_hex_to_guid(dentry->d_name.name + namelen + 1,
123			&var->var.VendorGuid);
124
125	if (efivar_variable_is_removable(var->var.VendorGuid,
126					 dentry->d_name.name, namelen))
127		is_removable = true;
128
129	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
130	if (!inode) {
131		err = -ENOMEM;
132		goto out;
133	}
134
135	for (i = 0; i < namelen; i++)
136		var->var.VariableName[i] = dentry->d_name.name[i];
137
138	var->var.VariableName[i] = '\0';
139
140	inode->i_private = var;
141
142	efivar_entry_add(var, &efivarfs_list);
143	d_instantiate(dentry, inode);
144	dget(dentry);
145out:
146	if (err) {
147		kfree(var);
148		if (inode)
149			iput(inode);
150	}
151	return err;
152}
153
154static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
155{
156	struct efivar_entry *var = d_inode(dentry)->i_private;
157
158	if (efivar_entry_delete(var))
159		return -EINVAL;
160
161	drop_nlink(d_inode(dentry));
162	dput(dentry);
163	return 0;
164};
165
166const struct inode_operations efivarfs_dir_inode_operations = {
167	.lookup = simple_lookup,
168	.unlink = efivarfs_unlink,
169	.create = efivarfs_create,
170};
171