1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * EFI utils 4 * 5 * Copyright (c) 2017 Rob Clark 6 */ 7 8 #include <common.h> 9 #include <charset.h> 10 #include <malloc.h> 11 #include <efi_loader.h> 12 13 static const struct efi_boot_services *bs; 14 static const struct efi_runtime_services *rs; 15 16 #define LOAD_OPTION_ACTIVE 0x00000001 17 #define LOAD_OPTION_FORCE_RECONNECT 0x00000002 18 #define LOAD_OPTION_HIDDEN 0x00000008 19 20 /* 21 * bootmgr implements the logic of trying to find a payload to boot 22 * based on the BootOrder + BootXXXX variables, and then loading it. 23 * 24 * TODO detecting a special key held (f9?) and displaying a boot menu 25 * like you would get on a PC would be clever. 26 * 27 * TODO if we had a way to write and persist variables after the OS 28 * has started, we'd also want to check OsIndications to see if we 29 * should do normal or recovery boot. 30 */ 31 32 33 /* 34 * See section 3.1.3 in the v2.7 UEFI spec for more details on 35 * the layout of EFI_LOAD_OPTION. In short it is: 36 * 37 * typedef struct _EFI_LOAD_OPTION { 38 * UINT32 Attributes; 39 * UINT16 FilePathListLength; 40 * // CHAR16 Description[]; <-- variable length, NULL terminated 41 * // EFI_DEVICE_PATH_PROTOCOL FilePathList[]; <-- FilePathListLength bytes 42 * // UINT8 OptionalData[]; 43 * } EFI_LOAD_OPTION; 44 */ 45 struct load_option { 46 u32 attributes; 47 u16 file_path_length; 48 u16 *label; 49 struct efi_device_path *file_path; 50 u8 *optional_data; 51 }; 52 53 /* parse an EFI_LOAD_OPTION, as described above */ 54 static void parse_load_option(struct load_option *lo, void *ptr) 55 { 56 lo->attributes = *(u32 *)ptr; 57 ptr += sizeof(u32); 58 59 lo->file_path_length = *(u16 *)ptr; 60 ptr += sizeof(u16); 61 62 lo->label = ptr; 63 ptr += (u16_strlen(lo->label) + 1) * 2; 64 65 lo->file_path = ptr; 66 ptr += lo->file_path_length; 67 68 lo->optional_data = ptr; 69 } 70 71 /* free() the result */ 72 static void *get_var(u16 *name, const efi_guid_t *vendor, 73 efi_uintn_t *size) 74 { 75 efi_guid_t *v = (efi_guid_t *)vendor; 76 efi_status_t ret; 77 void *buf = NULL; 78 79 *size = 0; 80 EFI_CALL(ret = rs->get_variable(name, v, NULL, size, buf)); 81 if (ret == EFI_BUFFER_TOO_SMALL) { 82 buf = malloc(*size); 83 EFI_CALL(ret = rs->get_variable(name, v, NULL, size, buf)); 84 } 85 86 if (ret != EFI_SUCCESS) { 87 free(buf); 88 *size = 0; 89 return NULL; 90 } 91 92 return buf; 93 } 94 95 /* 96 * Attempt to load load-option number 'n', returning device_path and file_path 97 * if successful. This checks that the EFI_LOAD_OPTION is active (enabled) 98 * and that the specified file to boot exists. 99 */ 100 static void *try_load_entry(uint16_t n, struct efi_device_path **device_path, 101 struct efi_device_path **file_path) 102 { 103 struct load_option lo; 104 u16 varname[] = L"Boot0000"; 105 u16 hexmap[] = L"0123456789ABCDEF"; 106 void *load_option, *image = NULL; 107 efi_uintn_t size; 108 109 varname[4] = hexmap[(n & 0xf000) >> 12]; 110 varname[5] = hexmap[(n & 0x0f00) >> 8]; 111 varname[6] = hexmap[(n & 0x00f0) >> 4]; 112 varname[7] = hexmap[(n & 0x000f) >> 0]; 113 114 load_option = get_var(varname, &efi_global_variable_guid, &size); 115 if (!load_option) 116 return NULL; 117 118 parse_load_option(&lo, load_option); 119 120 if (lo.attributes & LOAD_OPTION_ACTIVE) { 121 efi_status_t ret; 122 123 debug("%s: trying to load \"%ls\" from %pD\n", 124 __func__, lo.label, lo.file_path); 125 126 ret = efi_load_image_from_path(lo.file_path, &image); 127 128 if (ret != EFI_SUCCESS) 129 goto error; 130 131 printf("Booting: %ls\n", lo.label); 132 efi_dp_split_file_path(lo.file_path, device_path, file_path); 133 } 134 135 error: 136 free(load_option); 137 138 return image; 139 } 140 141 /* 142 * Attempt to load, in the order specified by BootOrder EFI variable, the 143 * available load-options, finding and returning the first one that can 144 * be loaded successfully. 145 */ 146 void *efi_bootmgr_load(struct efi_device_path **device_path, 147 struct efi_device_path **file_path) 148 { 149 uint16_t *bootorder; 150 efi_uintn_t size; 151 void *image = NULL; 152 int i, num; 153 154 __efi_entry_check(); 155 156 bs = systab.boottime; 157 rs = systab.runtime; 158 159 bootorder = get_var(L"BootOrder", &efi_global_variable_guid, &size); 160 if (!bootorder) 161 goto error; 162 163 num = size / sizeof(uint16_t); 164 for (i = 0; i < num; i++) { 165 debug("%s: trying to load Boot%04X\n", __func__, bootorder[i]); 166 image = try_load_entry(bootorder[i], device_path, file_path); 167 if (image) 168 break; 169 } 170 171 free(bootorder); 172 173 error: 174 __efi_exit_check(); 175 176 return image; 177 } 178