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 */
18 LIST_HEAD(efi_embedded_fw_list);
19 EXPORT_SYMBOL_NS_GPL(efi_embedded_fw_list, TEST_FIRMWARE);
20 bool efi_embedded_fw_checked;
21 EXPORT_SYMBOL_NS_GPL(efi_embedded_fw_checked, TEST_FIRMWARE);
22 
23 static 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  */
37 static 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 
87 void __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 
122 int 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 }
147 EXPORT_SYMBOL_GPL(efi_get_embedded_fw);
148