1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Support for extracting embedded firmware for peripherals from EFI code,
4 *
5 * Copyright (c) 2018 Hans de Goede <hdegoede@redhat.com>
6 */
7
8#include <linux/dmi.h>
9#include <linux/efi.h>
10#include <linux/efi_embedded_fw.h>
11#include <linux/io.h>
12#include <linux/slab.h>
13#include <linux/types.h>
14#include <linux/vmalloc.h>
15#include <crypto/sha2.h>
16
17/* Exported for use by lib/test_firmware.c only */
18LIST_HEAD(efi_embedded_fw_list);
19EXPORT_SYMBOL_NS_GPL(efi_embedded_fw_list, TEST_FIRMWARE);
20bool efi_embedded_fw_checked;
21EXPORT_SYMBOL_NS_GPL(efi_embedded_fw_checked, TEST_FIRMWARE);
22
23static const struct dmi_system_id * const embedded_fw_table[] = {
24#ifdef CONFIG_TOUCHSCREEN_DMI
25	touchscreen_dmi_table,
26#endif
27	NULL
28};
29
30/*
31 * Note the efi_check_for_embedded_firmwares() code currently makes the
32 * following 2 assumptions. This may needs to be revisited if embedded firmware
33 * is found where this is not true:
34 * 1) The firmware is only found in EFI_BOOT_SERVICES_CODE memory segments
35 * 2) The firmware always starts at an offset which is a multiple of 8 bytes
36 */
37static int __init efi_check_md_for_embedded_firmware(
38	efi_memory_desc_t *md, const struct efi_embedded_fw_desc *desc)
39{
40	struct efi_embedded_fw *fw;
41	u8 hash[32];
42	u64 i, size;
43	u8 *map;
44
45	size = md->num_pages << EFI_PAGE_SHIFT;
46	map = memremap(md->phys_addr, size, MEMREMAP_WB);
47	if (!map) {
48		pr_err("Error mapping EFI mem at %#llx\n", md->phys_addr);
49		return -ENOMEM;
50	}
51
52	for (i = 0; (i + desc->length) <= size; i += 8) {
53		if (memcmp(map + i, desc->prefix, EFI_EMBEDDED_FW_PREFIX_LEN))
54			continue;
55
56		sha256(map + i, desc->length, hash);
57		if (memcmp(hash, desc->sha256, 32) == 0)
58			break;
59	}
60	if ((i + desc->length) > size) {
61		memunmap(map);
62		return -ENOENT;
63	}
64
65	pr_info("Found EFI embedded fw '%s'\n", desc->name);
66
67	fw = kmalloc(sizeof(*fw), GFP_KERNEL);
68	if (!fw) {
69		memunmap(map);
70		return -ENOMEM;
71	}
72
73	fw->data = kmemdup(map + i, desc->length, GFP_KERNEL);
74	memunmap(map);
75	if (!fw->data) {
76		kfree(fw);
77		return -ENOMEM;
78	}
79
80	fw->name = desc->name;
81	fw->length = desc->length;
82	list_add(&fw->list, &efi_embedded_fw_list);
83
84	return 0;
85}
86
87void __init efi_check_for_embedded_firmwares(void)
88{
89	const struct efi_embedded_fw_desc *fw_desc;
90	const struct dmi_system_id *dmi_id;
91	efi_memory_desc_t *md;
92	int i, r;
93
94	for (i = 0; embedded_fw_table[i]; i++) {
95		dmi_id = dmi_first_match(embedded_fw_table[i]);
96		if (!dmi_id)
97			continue;
98
99		fw_desc = dmi_id->driver_data;
100
101		/*
102		 * In some drivers the struct driver_data contains may contain
103		 * other driver specific data after the fw_desc struct; and
104		 * the fw_desc struct itself may be empty, skip these.
105		 */
106		if (!fw_desc->name)
107			continue;
108
109		for_each_efi_memory_desc(md) {
110			if (md->type != EFI_BOOT_SERVICES_CODE)
111				continue;
112
113			r = efi_check_md_for_embedded_firmware(md, fw_desc);
114			if (r == 0)
115				break;
116		}
117	}
118
119	efi_embedded_fw_checked = true;
120}
121
122int efi_get_embedded_fw(const char *name, const u8 **data, size_t *size)
123{
124	struct efi_embedded_fw *iter, *fw = NULL;
125
126	if (!efi_embedded_fw_checked) {
127		pr_warn("Warning %s called while we did not check for embedded fw\n",
128			__func__);
129		return -ENOENT;
130	}
131
132	list_for_each_entry(iter, &efi_embedded_fw_list, list) {
133		if (strcmp(name, iter->name) == 0) {
134			fw = iter;
135			break;
136		}
137	}
138
139	if (!fw)
140		return -ENOENT;
141
142	*data = fw->data;
143	*size = fw->length;
144
145	return 0;
146}
147EXPORT_SYMBOL_GPL(efi_get_embedded_fw);
148