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Rob Clark9975fe92017-09-13 18:05:38 -04001/*
2 * EFI utils
3 *
4 * Copyright (c) 2017 Rob Clark
5 *
6 * SPDX-License-Identifier: GPL-2.0+
7 */
8
9#include <common.h>
10#include <charset.h>
11#include <malloc.h>
12#include <efi_loader.h>
13
14static const struct efi_boot_services *bs;
15static const struct efi_runtime_services *rs;
16
17#define LOAD_OPTION_ACTIVE 0x00000001
18#define LOAD_OPTION_FORCE_RECONNECT 0x00000002
19#define LOAD_OPTION_HIDDEN 0x00000008
20
21/*
22 * bootmgr implements the logic of trying to find a payload to boot
23 * based on the BootOrder + BootXXXX variables, and then loading it.
24 *
25 * TODO detecting a special key held (f9?) and displaying a boot menu
26 * like you would get on a PC would be clever.
27 *
28 * TODO if we had a way to write and persist variables after the OS
29 * has started, we'd also want to check OsIndications to see if we
30 * should do normal or recovery boot.
31 */
32
33
34/*
35 * See section 3.1.3 in the v2.7 UEFI spec for more details on
36 * the layout of EFI_LOAD_OPTION. In short it is:
37 *
38 * typedef struct _EFI_LOAD_OPTION {
39 * UINT32 Attributes;
40 * UINT16 FilePathListLength;
41 * // CHAR16 Description[]; <-- variable length, NULL terminated
42 * // EFI_DEVICE_PATH_PROTOCOL FilePathList[]; <-- FilePathListLength bytes
43 * // UINT8 OptionalData[];
44 * } EFI_LOAD_OPTION;
45 */
46struct load_option {
47 u32 attributes;
48 u16 file_path_length;
49 u16 *label;
50 struct efi_device_path *file_path;
51 u8 *optional_data;
52};
53
54/* parse an EFI_LOAD_OPTION, as described above */
55static void parse_load_option(struct load_option *lo, void *ptr)
56{
57 lo->attributes = *(u32 *)ptr;
58 ptr += sizeof(u32);
59
60 lo->file_path_length = *(u16 *)ptr;
61 ptr += sizeof(u16);
62
63 lo->label = ptr;
64 ptr += (utf16_strlen(lo->label) + 1) * 2;
65
66 lo->file_path = ptr;
67 ptr += lo->file_path_length;
68
69 lo->optional_data = ptr;
70}
71
72/* free() the result */
73static void *get_var(u16 *name, const efi_guid_t *vendor,
74 unsigned long *size)
75{
76 efi_guid_t *v = (efi_guid_t *)vendor;
77 efi_status_t ret;
78 void *buf = NULL;
79
80 *size = 0;
81 EFI_CALL(ret = rs->get_variable((s16 *)name, v, NULL, size, buf));
82 if (ret == EFI_BUFFER_TOO_SMALL) {
83 buf = malloc(*size);
84 EFI_CALL(ret = rs->get_variable((s16 *)name, v, NULL, size, buf));
85 }
86
87 if (ret != EFI_SUCCESS) {
88 free(buf);
89 *size = 0;
90 return NULL;
91 }
92
93 return buf;
94}
95
96/*
97 * Attempt to load load-option number 'n', returning device_path and file_path
98 * if successful. This checks that the EFI_LOAD_OPTION is active (enabled)
99 * and that the specified file to boot exists.
100 */
101static void *try_load_entry(uint16_t n, struct efi_device_path **device_path,
102 struct efi_device_path **file_path)
103{
104 struct load_option lo;
105 u16 varname[] = L"Boot0000";
106 u16 hexmap[] = L"0123456789ABCDEF";
107 void *load_option, *image = NULL;
108 unsigned long size;
109
110 varname[4] = hexmap[(n & 0xf000) >> 12];
111 varname[5] = hexmap[(n & 0x0f00) >> 8];
112 varname[6] = hexmap[(n & 0x00f0) >> 4];
113 varname[7] = hexmap[(n & 0x000f) >> 0];
114
115 load_option = get_var(varname, &efi_global_variable_guid, &size);
116 if (!load_option)
117 return NULL;
118
119 parse_load_option(&lo, load_option);
120
121 if (lo.attributes & LOAD_OPTION_ACTIVE) {
122 efi_status_t ret;
Rob Clark9975fe92017-09-13 18:05:38 -0400123
Heinrich Schuchardt4a8b5e72018-01-26 07:20:54 +0100124 debug("%s: trying to load \"%ls\" from %pD\n",
125 __func__, lo.label, lo.file_path);
Rob Clark9975fe92017-09-13 18:05:38 -0400126
127 ret = efi_load_image_from_path(lo.file_path, &image);
128
129 if (ret != EFI_SUCCESS)
130 goto error;
131
132 printf("Booting: %ls\n", lo.label);
133 efi_dp_split_file_path(lo.file_path, device_path, file_path);
134 }
135
136error:
137 free(load_option);
138
139 return image;
140}
141
142/*
143 * Attempt to load, in the order specified by BootOrder EFI variable, the
144 * available load-options, finding and returning the first one that can
145 * be loaded successfully.
146 */
147void *efi_bootmgr_load(struct efi_device_path **device_path,
148 struct efi_device_path **file_path)
149{
150 uint16_t *bootorder;
151 unsigned long size;
152 void *image = NULL;
153 int i, num;
154
155 __efi_entry_check();
156
157 bs = systab.boottime;
158 rs = systab.runtime;
159
160 bootorder = get_var(L"BootOrder", &efi_global_variable_guid, &size);
161 if (!bootorder)
162 goto error;
163
164 num = size / sizeof(uint16_t);
165 for (i = 0; i < num; i++) {
166 debug("%s: trying to load Boot%04X\n", __func__, bootorder[i]);
167 image = try_load_entry(bootorder[i], device_path, file_path);
168 if (image)
169 break;
170 }
171
172 free(bootorder);
173
174error:
175 __efi_exit_check();
176
177 return image;
178}