1/*
 2 * coreboot_table.c
 3 *
 4 * Module providing coreboot table access.
 5 *
 6 * Copyright 2017 Google Inc.
 7 *
 8 * This program is free software; you can redistribute it and/or modify
 9 * it under the terms of the GNU General Public License v2.0 as published by
10 * the Free Software Foundation.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 */
17
18#include <linux/err.h>
19#include <linux/init.h>
20#include <linux/io.h>
21#include <linux/kernel.h>
22#include <linux/module.h>
23
24#include "coreboot_table.h"
25
26struct coreboot_table_entry {
27	u32 tag;
28	u32 size;
29};
30
31static struct coreboot_table_header __iomem *ptr_header;
32
33/*
34 * This function parses the coreboot table for an entry that contains the base
35 * address of the given entry tag. The coreboot table consists of a header
36 * directly followed by a number of small, variable-sized entries, which each
37 * contain an identifying tag and their length as the first two fields.
38 */
39int coreboot_table_find(int tag, void *data, size_t data_size)
40{
41	struct coreboot_table_header header;
42	struct coreboot_table_entry entry;
43	void *ptr_entry;
44	int i;
45
46	if (!ptr_header)
47		return -EPROBE_DEFER;
48
49	memcpy_fromio(&header, ptr_header, sizeof(header));
50
51	if (strncmp(header.signature, "LBIO", sizeof(header.signature))) {
52		pr_warn("coreboot_table: coreboot table missing or corrupt!\n");
53		return -ENODEV;
54	}
55
56	ptr_entry = (void *)ptr_header + header.header_bytes;
57
58	for (i = 0; i < header.table_entries; i++) {
59		memcpy_fromio(&entry, ptr_entry, sizeof(entry));
60		if (entry.tag == tag) {
61			if (data_size < entry.size)
62				return -EINVAL;
63
64			memcpy_fromio(data, ptr_entry, entry.size);
65
66			return 0;
67		}
68
69		ptr_entry += entry.size;
70	}
71
72	return -ENOENT;
73}
74EXPORT_SYMBOL(coreboot_table_find);
75
76int coreboot_table_init(void __iomem *ptr)
77{
78	ptr_header = ptr;
79
80	return 0;
81}
82EXPORT_SYMBOL(coreboot_table_init);
83
84int coreboot_table_exit(void)
85{
86	if (ptr_header)
87		iounmap(ptr_header);
88
89	return 0;
90}
91EXPORT_SYMBOL(coreboot_table_exit);
92
93MODULE_AUTHOR("Google, Inc.");
94MODULE_LICENSE("GPL");