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 */
efi_check_md_for_embedded_firmware(efi_memory_desc_t * md,const struct efi_embedded_fw_desc * desc)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
efi_check_for_embedded_firmwares(void)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
efi_get_embedded_fw(const char * name,const u8 ** data,size_t * size)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