lib/efi_loader/efi_bootmgr.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  *  EFI boot manager
   4  *
   5  *  Copyright (c) 2017 Rob Clark
   6  */
   7
   8 #define LOG_CATEGORY LOGC_EFI
   9
  10 #include <common.h>
  11 #include <charset.h>
  12 #include <log.h>
  13 #include <malloc.h>
  14 #include <efi_loader.h>
  15 #include <efi_variable.h>
  16 #include <asm/unaligned.h>
  17
  18 static const struct efi_boot_services *bs;
  19 static const struct efi_runtime_services *rs;
  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  * get_var() - get UEFI variable
  35  *
  36  * It is the caller's duty to free the returned buffer.
  37  *
  38  * @name:       name of variable
  39  * @vendor:     vendor GUID of variable
  40  * @size:       size of allocated buffer
  41  * Return:      buffer with variable data or NULL
  42  */
  43 static void *get_var(u16 *name, const efi_guid_t *vendor,
  44                      efi_uintn_t *size)
  45 {
  46         efi_status_t ret;
  47         void *buf = NULL;
  48
  49         *size = 0;
  50         ret = efi_get_variable_int(name, vendor, NULL, size, buf, NULL);
  51         if (ret == EFI_BUFFER_TOO_SMALL) {
  52                 buf = malloc(*size);
  53                 ret = efi_get_variable_int(name, vendor, NULL, size, buf, NULL);
  54         }
  55
  56         if (ret != EFI_SUCCESS) {
  57                 free(buf);
  58                 *size = 0;
  59                 return NULL;
  60         }
  61
  62         return buf;
  63 }
  64
  65 /**
  66  * try_load_entry() - try to load image for boot option
  67  *
  68  * Attempt to load load-option number 'n', returning device_path and file_path
  69  * if successful. This checks that the EFI_LOAD_OPTION is active (enabled)
  70  * and that the specified file to boot exists.
  71  *
  72  * @n:                  number of the boot option, e.g. 0x0a13 for Boot0A13
  73  * @handle:             on return handle for the newly installed image
  74  * @load_options:       load options set on the loaded image protocol
  75  * Return:              status code
  76  */
  77 static efi_status_t try_load_entry(u16 n, efi_handle_t *handle,
  78                                    void **load_options)
  79 {
  80         struct efi_load_option lo;
  81         u16 varname[] = L"Boot0000";
  82         u16 hexmap[] = L"0123456789ABCDEF";
  83         void *load_option;
  84         efi_uintn_t size;
  85         efi_status_t ret;
  86
  87         varname[4] = hexmap[(n & 0xf000) >> 12];
  88         varname[5] = hexmap[(n & 0x0f00) >> 8];
  89         varname[6] = hexmap[(n & 0x00f0) >> 4];
  90         varname[7] = hexmap[(n & 0x000f) >> 0];
  91
  92         load_option = get_var(varname, &efi_global_variable_guid, &size);
  93         if (!load_option)
  94                 return EFI_LOAD_ERROR;
  95
  96         ret = efi_deserialize_load_option(&lo, load_option, &size);
  97         if (ret != EFI_SUCCESS) {
  98                 log_warning("Invalid load option for %ls\n", varname);
  99                 goto error;
 100         }
 101
 102         if (lo.attributes & LOAD_OPTION_ACTIVE) {
 103                 u32 attributes;
 104
 105                 log_debug("%s: trying to load \"%ls\" from %pD\n",
 106                           __func__, lo.label, lo.file_path);
 107
 108                 ret = EFI_CALL(efi_load_image(true, efi_root, lo.file_path,
 109                                               NULL, 0, handle));
 110                 if (ret != EFI_SUCCESS) {
 111                         log_warning("Loading %ls '%ls' failed\n",
 112                                     varname, lo.label);
 113                         goto error;
 114                 }
 115
 116                 attributes = EFI_VARIABLE_BOOTSERVICE_ACCESS |
 117                              EFI_VARIABLE_RUNTIME_ACCESS;
 118                 ret = efi_set_variable_int(L"BootCurrent",
 119                                            &efi_global_variable_guid,
 120                                            attributes, sizeof(n), &n, false);
 121                 if (ret != EFI_SUCCESS)
 122                         goto unload;
 123                 /* try to register load file2 for initrd's */
 124                 if (IS_ENABLED(CONFIG_EFI_LOAD_FILE2_INITRD)) {
 125                         ret = efi_initrd_register();
 126                         if (ret != EFI_SUCCESS)
 127                                 goto unload;
 128                 }
 129
 130                 log_info("Booting: %ls\n", lo.label);
 131         } else {
 132                 ret = EFI_LOAD_ERROR;
 133         }
 134
 135         /* Set load options */
 136         if (size) {
 137                 *load_options = malloc(size);
 138                 if (!*load_options) {
 139                         ret = EFI_OUT_OF_RESOURCES;
 140                         goto error;
 141                 }
 142                 memcpy(*load_options, lo.optional_data, size);
 143                 ret = efi_set_load_options(*handle, size, *load_options);
 144         } else {
 145                 *load_options = NULL;
 146         }
 147
 148 error:
 149         free(load_option);
 150
 151         return ret;
 152
 153 unload:
 154         if (EFI_CALL(efi_unload_image(*handle)) != EFI_SUCCESS)
 155                 log_err("Unloading image failed\n");
 156         free(load_option);
 157
 158         return ret;
 159 }
 160
 161 /**
 162  * efi_bootmgr_load() - try to load from BootNext or BootOrder
 163  *
 164  * Attempt to load from BootNext or in the order specified by BootOrder
 165  * EFI variable, the available load-options, finding and returning
 166  * the first one that can be loaded successfully.
 167  *
 168  * @handle:             on return handle for the newly installed image
 169  * @load_options:       load options set on the loaded image protocol
 170  * Return:              status code
 171  */
 172 efi_status_t efi_bootmgr_load(efi_handle_t *handle, void **load_options)
 173 {
 174         u16 bootnext, *bootorder;
 175         efi_uintn_t size;
 176         int i, num;
 177         efi_status_t ret;
 178
 179         bs = systab.boottime;
 180         rs = systab.runtime;
 181
 182         /* BootNext */
 183         size = sizeof(bootnext);
 184         ret = efi_get_variable_int(L"BootNext",
 185                                    &efi_global_variable_guid,
 186                                    NULL, &size, &bootnext, NULL);
 187         if (ret == EFI_SUCCESS || ret == EFI_BUFFER_TOO_SMALL) {
 188                 /* BootNext does exist here */
 189                 if (ret == EFI_BUFFER_TOO_SMALL || size != sizeof(u16))
 190                         log_err("BootNext must be 16-bit integer\n");
 191
 192                 /* delete BootNext */
 193                 ret = efi_set_variable_int(L"BootNext",
 194                                            &efi_global_variable_guid,
 195                                            0, 0, NULL, false);
 196
 197                 /* load BootNext */
 198                 if (ret == EFI_SUCCESS) {
 199                         if (size == sizeof(u16)) {
 200                                 ret = try_load_entry(bootnext, handle,
 201                                                      load_options);
 202                                 if (ret == EFI_SUCCESS)
 203                                         return ret;
 204                                 log_warning(
 205                                         "Loading from BootNext failed, falling back to BootOrder\n");
 206                         }
 207                 } else {
 208                         log_err("Deleting BootNext failed\n");
 209                 }
 210         }
 211
 212         /* BootOrder */
 213         bootorder = get_var(L"BootOrder", &efi_global_variable_guid, &size);
 214         if (!bootorder) {
 215                 log_info("BootOrder not defined\n");
 216                 ret = EFI_NOT_FOUND;
 217                 goto error;
 218         }
 219
 220         num = size / sizeof(uint16_t);
 221         for (i = 0; i < num; i++) {
 222                 log_debug("%s trying to load Boot%04X\n", __func__,
 223                           bootorder[i]);
 224                 ret = try_load_entry(bootorder[i], handle, load_options);
 225                 if (ret == EFI_SUCCESS)
 226                         break;
 227         }
 228
 229         free(bootorder);
 230
 231 error:
 232         return ret;
 233 }