LXR uboot/lib/efi_loader/efi

   1/*
   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;
 123                u16 *str = NULL;
 124
 125                debug("%s: trying to load \"%ls\" from: %ls\n", __func__,
 126                      lo.label, (str = efi_dp_str(lo.file_path)));
 127                efi_free_pool(str);
 128
 129                ret = efi_load_image_from_path(lo.file_path, &image);
 130
 131                if (ret != EFI_SUCCESS)
 132                        goto error;
 133
 134                printf("Booting: %ls\n", lo.label);
 135                efi_dp_split_file_path(lo.file_path, device_path, file_path);
 136        }
 137
 138error:
 139        free(load_option);
 140
 141        return image;
 142}
 143
 144/*
 145 * Attempt to load, in the order specified by BootOrder EFI variable, the
 146 * available load-options, finding and returning the first one that can
 147 * be loaded successfully.
 148 */
 149void *efi_bootmgr_load(struct efi_device_path **device_path,
 150                       struct efi_device_path **file_path)
 151{
 152        uint16_t *bootorder;
 153        unsigned long size;
 154        void *image = NULL;
 155        int i, num;
 156
 157        __efi_entry_check();
 158
 159        bs = systab.boottime;
 160        rs = systab.runtime;
 161
 162        bootorder = get_var(L"BootOrder", &efi_global_variable_guid, &size);
 163        if (!bootorder)
 164                goto error;
 165
 166        num = size / sizeof(uint16_t);
 167        for (i = 0; i < num; i++) {
 168                debug("%s: trying to load Boot%04X\n", __func__, bootorder[i]);
 169                image = try_load_entry(bootorder[i], device_path, file_path);
 170                if (image)
 171                        break;
 172        }
 173
 174        free(bootorder);
 175
 176error:
 177        __efi_exit_check();
 178
 179        return image;
 180}
 181