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/sha.h>
16 
17 /* Exported for use by lib/test_firmware.c only */
18 LIST_HEAD(efi_embedded_fw_list);
19 EXPORT_SYMBOL_GPL(efi_embedded_fw_list);
20 
21 static bool checked_for_fw;
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 sha256_state sctx;
41 	struct efi_embedded_fw *fw;
42 	u8 sha256[32];
43 	u64 i, size;
44 	u8 *map;
45 
46 	size = md->num_pages << EFI_PAGE_SHIFT;
47 	map = memremap(md->phys_addr, size, MEMREMAP_WB);
48 	if (!map) {
49 		pr_err("Error mapping EFI mem at %#llx\n", md->phys_addr);
50 		return -ENOMEM;
51 	}
52 
53 	for (i = 0; (i + desc->length) <= size; i += 8) {
54 		if (memcmp(map + i, desc->prefix, EFI_EMBEDDED_FW_PREFIX_LEN))
55 			continue;
56 
57 		sha256_init(&sctx);
58 		sha256_update(&sctx, map + i, desc->length);
59 		sha256_final(&sctx, sha256);
60 		if (memcmp(sha256, desc->sha256, 32) == 0)
61 			break;
62 	}
63 	if ((i + desc->length) > size) {
64 		memunmap(map);
65 		return -ENOENT;
66 	}
67 
68 	pr_info("Found EFI embedded fw '%s'\n", desc->name);
69 
70 	fw = kmalloc(sizeof(*fw), GFP_KERNEL);
71 	if (!fw) {
72 		memunmap(map);
73 		return -ENOMEM;
74 	}
75 
76 	fw->data = kmemdup(map + i, desc->length, GFP_KERNEL);
77 	memunmap(map);
78 	if (!fw->data) {
79 		kfree(fw);
80 		return -ENOMEM;
81 	}
82 
83 	fw->name = desc->name;
84 	fw->length = desc->length;
85 	list_add(&fw->list, &efi_embedded_fw_list);
86 
87 	return 0;
88 }
89 
90 void __init efi_check_for_embedded_firmwares(void)
91 {
92 	const struct efi_embedded_fw_desc *fw_desc;
93 	const struct dmi_system_id *dmi_id;
94 	efi_memory_desc_t *md;
95 	int i, r;
96 
97 	for (i = 0; embedded_fw_table[i]; i++) {
98 		dmi_id = dmi_first_match(embedded_fw_table[i]);
99 		if (!dmi_id)
100 			continue;
101 
102 		fw_desc = dmi_id->driver_data;
103 
104 		/*
105 		 * In some drivers the struct driver_data contains may contain
106 		 * other driver specific data after the fw_desc struct; and
107 		 * the fw_desc struct itself may be empty, skip these.
108 		 */
109 		if (!fw_desc->name)
110 			continue;
111 
112 		for_each_efi_memory_desc(md) {
113 			if (md->type != EFI_BOOT_SERVICES_CODE)
114 				continue;
115 
116 			r = efi_check_md_for_embedded_firmware(md, fw_desc);
117 			if (r == 0)
118 				break;
119 		}
120 	}
121 
122 	checked_for_fw = true;
123 }
124 
125 int efi_get_embedded_fw(const char *name, const u8 **data, size_t *size)
126 {
127 	struct efi_embedded_fw *iter, *fw = NULL;
128 
129 	if (!checked_for_fw) {
130 		pr_warn("Warning %s called while we did not check for embedded fw\n",
131 			__func__);
132 		return -ENOENT;
133 	}
134 
135 	list_for_each_entry(iter, &efi_embedded_fw_list, list) {
136 		if (strcmp(name, iter->name) == 0) {
137 			fw = iter;
138 			break;
139 		}
140 	}
141 
142 	if (!fw)
143 		return -ENOENT;
144 
145 	*data = fw->data;
146 	*size = fw->length;
147 
148 	return 0;
149 }
150 EXPORT_SYMBOL_GPL(efi_get_embedded_fw);
151