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 #include <common.h>
   9 #include <charset.h>
  10 #include <malloc.h>
  11 #include <efi_loader.h>
  12 #include <asm/unaligned.h>
  13
  14 static const struct efi_boot_services *bs;
  15 static const struct efi_runtime_services *rs;
  16
  17 /*
  18  * bootmgr implements the logic of trying to find a payload to boot
  19  * based on the BootOrder + BootXXXX variables, and then loading it.
  20  *
  21  * TODO detecting a special key held (f9?) and displaying a boot menu
  22  * like you would get on a PC would be clever.
  23  *
  24  * TODO if we had a way to write and persist variables after the OS
  25  * has started, we'd also want to check OsIndications to see if we
  26  * should do normal or recovery boot.
  27  */
  28
  29
  30 /* Parse serialized data and transform it into efi_load_option structure */
  31 void efi_deserialize_load_option(struct efi_load_option *lo, u8 *data)
  32 {
  33         lo->attributes = get_unaligned_le32(data);
  34         data += sizeof(u32);
  35
  36         lo->file_path_length = get_unaligned_le16(data);
  37         data += sizeof(u16);
  38
  39         /* FIXME */
  40         lo->label = (u16 *)data;
  41         data += (u16_strlen(lo->label) + 1) * sizeof(u16);
  42
  43         /* FIXME */
  44         lo->file_path = (struct efi_device_path *)data;
  45         data += lo->file_path_length;
  46
  47         lo->optional_data = data;
  48 }
  49
  50 /*
  51  * Serialize efi_load_option structure into byte stream for BootXXXX.
  52  * Return a size of allocated data.
  53  */
  54 unsigned long efi_serialize_load_option(struct efi_load_option *lo, u8 **data)
  55 {
  56         unsigned long label_len, option_len;
  57         unsigned long size;
  58         u8 *p;
  59
  60         label_len = (u16_strlen(lo->label) + 1) * sizeof(u16);
  61         option_len = strlen((char *)lo->optional_data);
  62
  63         /* total size */
  64         size = sizeof(lo->attributes);
  65         size += sizeof(lo->file_path_length);
  66         size += label_len;
  67         size += lo->file_path_length;
  68         size += option_len + 1;
  69         p = malloc(size);
  70         if (!p)
  71                 return 0;
  72
  73         /* copy data */
  74         *data = p;
  75         memcpy(p, &lo->attributes, sizeof(lo->attributes));
  76         p += sizeof(lo->attributes);
  77
  78         memcpy(p, &lo->file_path_length, sizeof(lo->file_path_length));
  79         p += sizeof(lo->file_path_length);
  80
  81         memcpy(p, lo->label, label_len);
  82         p += label_len;
  83
  84         memcpy(p, lo->file_path, lo->file_path_length);
  85         p += lo->file_path_length;
  86
  87         memcpy(p, lo->optional_data, option_len);
  88         p += option_len;
  89         *(char *)p = '\0';
  90
  91         return size;
  92 }
  93
  94 /* free() the result */
  95 static void *get_var(u16 *name, const efi_guid_t *vendor,
  96                      efi_uintn_t *size)
  97 {
  98         efi_guid_t *v = (efi_guid_t *)vendor;
  99         efi_status_t ret;
 100         void *buf = NULL;
 101
 102         *size = 0;
 103         EFI_CALL(ret = rs->get_variable(name, v, NULL, size, buf));
 104         if (ret == EFI_BUFFER_TOO_SMALL) {
 105                 buf = malloc(*size);
 106                 EFI_CALL(ret = rs->get_variable(name, v, NULL, size, buf));
 107         }
 108
 109         if (ret != EFI_SUCCESS) {
 110                 free(buf);
 111                 *size = 0;
 112                 return NULL;
 113         }
 114
 115         return buf;
 116 }
 117
 118 /*
 119  * Attempt to load load-option number 'n', returning device_path and file_path
 120  * if successful.  This checks that the EFI_LOAD_OPTION is active (enabled)
 121  * and that the specified file to boot exists.
 122  */
 123 static void *try_load_entry(uint16_t n, struct efi_device_path **device_path,
 124                             struct efi_device_path **file_path)
 125 {
 126         struct efi_load_option lo;
 127         u16 varname[] = L"Boot0000";
 128         u16 hexmap[] = L"0123456789ABCDEF";
 129         void *load_option, *image = NULL;
 130         efi_uintn_t size;
 131
 132         varname[4] = hexmap[(n & 0xf000) >> 12];
 133         varname[5] = hexmap[(n & 0x0f00) >> 8];
 134         varname[6] = hexmap[(n & 0x00f0) >> 4];
 135         varname[7] = hexmap[(n & 0x000f) >> 0];
 136
 137         load_option = get_var(varname, &efi_global_variable_guid, &size);
 138         if (!load_option)
 139                 return NULL;
 140
 141         efi_deserialize_load_option(&lo, load_option);
 142
 143         if (lo.attributes & LOAD_OPTION_ACTIVE) {
 144                 u32 attributes;
 145                 efi_status_t ret;
 146
 147                 debug("%s: trying to load \"%ls\" from %pD\n",
 148                       __func__, lo.label, lo.file_path);
 149
 150                 ret = efi_load_image_from_path(lo.file_path, &image, &size);
 151
 152                 if (ret != EFI_SUCCESS)
 153                         goto error;
 154
 155                 attributes = EFI_VARIABLE_BOOTSERVICE_ACCESS |
 156                              EFI_VARIABLE_RUNTIME_ACCESS;
 157                 size = sizeof(n);
 158                 ret = EFI_CALL(efi_set_variable(
 159                                 L"BootCurrent",
 160                                 (efi_guid_t *)&efi_global_variable_guid,
 161                                 attributes, size, &n));
 162                 if (ret != EFI_SUCCESS)
 163                         goto error;
 164
 165                 printf("Booting: %ls\n", lo.label);
 166                 efi_dp_split_file_path(lo.file_path, device_path, file_path);
 167         }
 168
 169 error:
 170         free(load_option);
 171
 172         return image;
 173 }
 174
 175 /*
 176  * Attempt to load from BootNext or in the order specified by BootOrder
 177  * EFI variable, the available load-options, finding and returning
 178  * the first one that can be loaded successfully.
 179  */
 180 void *efi_bootmgr_load(struct efi_device_path **device_path,
 181                        struct efi_device_path **file_path)
 182 {
 183         u16 bootnext, *bootorder;
 184         efi_uintn_t size;
 185         void *image = NULL;
 186         int i, num;
 187         efi_status_t ret;
 188
 189         bs = systab.boottime;
 190         rs = systab.runtime;
 191
 192         /* BootNext */
 193         bootnext = 0;
 194         size = sizeof(bootnext);
 195         ret = EFI_CALL(efi_get_variable(L"BootNext",
 196                                         (efi_guid_t *)&efi_global_variable_guid,
 197                                         NULL, &size, &bootnext));
 198         if (ret == EFI_SUCCESS || ret == EFI_BUFFER_TOO_SMALL) {
 199                 /* BootNext does exist here */
 200                 if (ret == EFI_BUFFER_TOO_SMALL || size != sizeof(u16))
 201                         printf("BootNext must be 16-bit integer\n");
 202
 203                 /* delete BootNext */
 204                 ret = EFI_CALL(efi_set_variable(
 205                                         L"BootNext",
 206                                         (efi_guid_t *)&efi_global_variable_guid,
 207                                         0, 0, &bootnext));
 208
 209                 /* load BootNext */
 210                 if (ret == EFI_SUCCESS) {
 211                         if (size == sizeof(u16)) {
 212                                 image = try_load_entry(bootnext, device_path,
 213                                                        file_path);
 214                                 if (image)
 215                                         return image;
 216                         }
 217                 } else {
 218                         printf("Deleting BootNext failed\n");
 219                 }
 220         }
 221
 222         /* BootOrder */
 223         bootorder = get_var(L"BootOrder", &efi_global_variable_guid, &size);
 224         if (!bootorder) {
 225                 printf("BootOrder not defined\n");
 226                 goto error;
 227         }
 228
 229         num = size / sizeof(uint16_t);
 230         for (i = 0; i < num; i++) {
 231                 debug("%s: trying to load Boot%04X\n", __func__, bootorder[i]);
 232                 image = try_load_entry(bootorder[i], device_path, file_path);
 233                 if (image)
 234                         break;
 235         }
 236
 237         free(bootorder);
 238
 239 error:
 240         return image;
 241 }