lib/efi_loader/efi_file.c

   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 <efi_loader.h>
  11 #include <malloc.h>
  12 #include <mapmem.h>
  13 #include <fs.h>
  14
  15 /* GUID for file system information */
  16 const efi_guid_t efi_file_system_info_guid = EFI_FILE_SYSTEM_INFO_GUID;
  17
  18 struct file_system {
  19         struct efi_simple_file_system_protocol base;
  20         struct efi_device_path *dp;
  21         struct blk_desc *desc;
  22         int part;
  23 };
  24 #define to_fs(x) container_of(x, struct file_system, base)
  25
  26 struct file_handle {
  27         struct efi_file_handle base;
  28         struct file_system *fs;
  29         loff_t offset;       /* current file position/cursor */
  30         int isdir;
  31
  32         /* for reading a directory: */
  33         struct fs_dir_stream *dirs;
  34         struct fs_dirent *dent;
  35
  36         char path[0];
  37 };
  38 #define to_fh(x) container_of(x, struct file_handle, base)
  39
  40 static const struct efi_file_handle efi_file_handle_protocol;
  41
  42 static char *basename(struct file_handle *fh)
  43 {
  44         char *s = strrchr(fh->path, '/');
  45         if (s)
  46                 return s + 1;
  47         return fh->path;
  48 }
  49
  50 static int set_blk_dev(struct file_handle *fh)
  51 {
  52         return fs_set_blk_dev_with_part(fh->fs->desc, fh->fs->part);
  53 }
  54
  55 /**
  56  * is_dir() - check if file handle points to directory
  57  *
  58  * We assume that set_blk_dev(fh) has been called already.
  59  *
  60  * @fh:         file handle
  61  * Return:      true if file handle points to a directory
  62  */
  63 static int is_dir(struct file_handle *fh)
  64 {
  65         struct fs_dir_stream *dirs;
  66
  67         dirs = fs_opendir(fh->path);
  68         if (!dirs)
  69                 return 0;
  70
  71         fs_closedir(dirs);
  72
  73         return 1;
  74 }
  75
  76 /*
  77  * Normalize a path which may include either back or fwd slashes,
  78  * double slashes, . or .. entries in the path, etc.
  79  */
  80 static int sanitize_path(char *path)
  81 {
  82         char *p;
  83
  84         /* backslash to slash: */
  85         p = path;
  86         while ((p = strchr(p, '\\')))
  87                 *p++ = '/';
  88
  89         /* handle double-slashes: */
  90         p = path;
  91         while ((p = strstr(p, "//"))) {
  92                 char *src = p + 1;
  93                 memmove(p, src, strlen(src) + 1);
  94         }
  95
  96         /* handle extra /.'s */
  97         p = path;
  98         while ((p = strstr(p, "/."))) {
  99                 /*
 100                  * You'd be tempted to do this *after* handling ".."s
 101                  * below to avoid having to check if "/." is start of
 102                  * a "/..", but that won't have the correct results..
 103                  * for example, "/foo/./../bar" would get resolved to
 104                  * "/foo/bar" if you did these two passes in the other
 105                  * order
 106                  */
 107                 if (p[2] == '.') {
 108                         p += 2;
 109                         continue;
 110                 }
 111                 char *src = p + 2;
 112                 memmove(p, src, strlen(src) + 1);
 113         }
 114
 115         /* handle extra /..'s: */
 116         p = path;
 117         while ((p = strstr(p, "/.."))) {
 118                 char *src = p + 3;
 119
 120                 p--;
 121
 122                 /* find beginning of previous path entry: */
 123                 while (true) {
 124                         if (p < path)
 125                                 return -1;
 126                         if (*p == '/')
 127                                 break;
 128                         p--;
 129                 }
 130
 131                 memmove(p, src, strlen(src) + 1);
 132         }
 133
 134         return 0;
 135 }
 136
 137 /**
 138  * efi_create_file() - create file or directory
 139  *
 140  * @fh:                 file handle
 141  * @attributes:         attributes for newly created file
 142  * Returns:             0 for success
 143  */
 144 static int efi_create_file(struct file_handle *fh, u64 attributes)
 145 {
 146         loff_t actwrite;
 147         void *buffer = &actwrite;
 148
 149         if (attributes & EFI_FILE_DIRECTORY)
 150                 return fs_mkdir(fh->path);
 151         else
 152                 return fs_write(fh->path, map_to_sysmem(buffer), 0, 0,
 153                                 &actwrite);
 154 }
 155
 156 /**
 157  * file_open() - open a file handle
 158  *
 159  * @fs:                 file system
 160  * @parent:             directory relative to which the file is to be opened
 161  * @file_name:          path of the file to be opened. '\', '.', or '..' may
 162  *                      be used as modifiers. A leading backslash indicates an
 163  *                      absolute path.
 164  * @mode:               bit mask indicating the access mode (read, write,
 165  *                      create)
 166  * @attributes:         attributes for newly created file
 167  * Returns:             handle to the opened file or NULL
 168  */
 169 static struct efi_file_handle *file_open(struct file_system *fs,
 170                 struct file_handle *parent, u16 *file_name, u64 mode,
 171                 u64 attributes)
 172 {
 173         struct file_handle *fh;
 174         char f0[MAX_UTF8_PER_UTF16] = {0};
 175         int plen = 0;
 176         int flen = 0;
 177
 178         if (file_name) {
 179                 utf16_to_utf8((u8 *)f0, file_name, 1);
 180                 flen = u16_strlen(file_name);
 181         }
 182
 183         /* we could have a parent, but also an absolute path: */
 184         if (f0[0] == '\\') {
 185                 plen = 0;
 186         } else if (parent) {
 187                 plen = strlen(parent->path) + 1;
 188         }
 189
 190         /* +2 is for null and '/' */
 191         fh = calloc(1, sizeof(*fh) + plen + (flen * MAX_UTF8_PER_UTF16) + 2);
 192
 193         fh->base = efi_file_handle_protocol;
 194         fh->fs = fs;
 195
 196         if (parent) {
 197                 char *p = fh->path;
 198                 int exists;
 199
 200                 if (plen > 0) {
 201                         strcpy(p, parent->path);
 202                         p += plen - 1;
 203                         *p++ = '/';
 204                 }
 205
 206                 utf16_to_utf8((u8 *)p, file_name, flen);
 207
 208                 if (sanitize_path(fh->path))
 209                         goto error;
 210
 211                 /* check if file exists: */
 212                 if (set_blk_dev(fh))
 213                         goto error;
 214
 215                 exists = fs_exists(fh->path);
 216                 /* fs_exists() calls fs_close(), so open file system again */
 217                 if (set_blk_dev(fh))
 218                         goto error;
 219
 220                 if (!exists) {
 221                         if (!(mode & EFI_FILE_MODE_CREATE) ||
 222                             efi_create_file(fh, attributes))
 223                                 goto error;
 224                 }
 225
 226                 /* figure out if file is a directory: */
 227                 fh->isdir = is_dir(fh);
 228         } else {
 229                 fh->isdir = 1;
 230                 strcpy(fh->path, "");
 231         }
 232
 233         return &fh->base;
 234
 235 error:
 236         free(fh);
 237         return NULL;
 238 }
 239
 240 static efi_status_t EFIAPI efi_file_open(struct efi_file_handle *file,
 241                 struct efi_file_handle **new_handle,
 242                 u16 *file_name, u64 open_mode, u64 attributes)
 243 {
 244         struct file_handle *fh = to_fh(file);
 245         efi_status_t ret;
 246
 247         EFI_ENTRY("%p, %p, \"%ls\", %llx, %llu", file, new_handle,
 248                   file_name, open_mode, attributes);
 249
 250         /* Check parameters */
 251         if (!file || !new_handle || !file_name) {
 252                 ret = EFI_INVALID_PARAMETER;
 253                 goto out;
 254         }
 255         if (open_mode != EFI_FILE_MODE_READ &&
 256             open_mode != (EFI_FILE_MODE_READ | EFI_FILE_MODE_WRITE) &&
 257             open_mode != (EFI_FILE_MODE_READ | EFI_FILE_MODE_WRITE |
 258                          EFI_FILE_MODE_CREATE)) {
 259                 ret = EFI_INVALID_PARAMETER;
 260                 goto out;
 261         }
 262         /*
 263          * The UEFI spec requires that attributes are only set in create mode.
 264          * The SCT does not care about this and sets EFI_FILE_DIRECTORY in
 265          * read mode. EDK2 does not check that attributes are zero if not in
 266          * create mode.
 267          *
 268          * So here we only check attributes in create mode and do not check
 269          * that they are zero otherwise.
 270          */
 271         if ((open_mode & EFI_FILE_MODE_CREATE) &&
 272             (attributes & (EFI_FILE_READ_ONLY | ~EFI_FILE_VALID_ATTR))) {
 273                 ret = EFI_INVALID_PARAMETER;
 274                 goto out;
 275         }
 276
 277         /* Open file */
 278         *new_handle = file_open(fh->fs, fh, file_name, open_mode, attributes);
 279         if (*new_handle) {
 280                 EFI_PRINT("file handle %p\n", *new_handle);
 281                 ret = EFI_SUCCESS;
 282         } else {
 283                 ret = EFI_NOT_FOUND;
 284         }
 285 out:
 286         return EFI_EXIT(ret);
 287 }
 288
 289 static efi_status_t file_close(struct file_handle *fh)
 290 {
 291         fs_closedir(fh->dirs);
 292         free(fh);
 293         return EFI_SUCCESS;
 294 }
 295
 296 static efi_status_t EFIAPI efi_file_close(struct efi_file_handle *file)
 297 {
 298         struct file_handle *fh = to_fh(file);
 299         EFI_ENTRY("%p", file);
 300         return EFI_EXIT(file_close(fh));
 301 }
 302
 303 static efi_status_t EFIAPI efi_file_delete(struct efi_file_handle *file)
 304 {
 305         struct file_handle *fh = to_fh(file);
 306         efi_status_t ret = EFI_SUCCESS;
 307
 308         EFI_ENTRY("%p", file);
 309
 310         if (set_blk_dev(fh)) {
 311                 ret = EFI_DEVICE_ERROR;
 312                 goto error;
 313         }
 314
 315         if (fs_unlink(fh->path))
 316                 ret = EFI_DEVICE_ERROR;
 317         file_close(fh);
 318
 319 error:
 320         return EFI_EXIT(ret);
 321 }
 322
 323 static efi_status_t file_read(struct file_handle *fh, u64 *buffer_size,
 324                 void *buffer)
 325 {
 326         loff_t actread;
 327
 328         if (fs_read(fh->path, map_to_sysmem(buffer), fh->offset,
 329                     *buffer_size, &actread))
 330                 return EFI_DEVICE_ERROR;
 331
 332         *buffer_size = actread;
 333         fh->offset += actread;
 334
 335         return EFI_SUCCESS;
 336 }
 337
 338 static efi_status_t dir_read(struct file_handle *fh, u64 *buffer_size,
 339                 void *buffer)
 340 {
 341         struct efi_file_info *info = buffer;
 342         struct fs_dirent *dent;
 343         unsigned int required_size;
 344
 345         if (!fh->dirs) {
 346                 assert(fh->offset == 0);
 347                 fh->dirs = fs_opendir(fh->path);
 348                 if (!fh->dirs)
 349                         return EFI_DEVICE_ERROR;
 350         }
 351
 352         /*
 353          * So this is a bit awkward.  Since fs layer is stateful and we
 354          * can't rewind an entry, in the EFI_BUFFER_TOO_SMALL case below
 355          * we might have to return without consuming the dent.. so we
 356          * have to stash it for next call.
 357          */
 358         if (fh->dent) {
 359                 dent = fh->dent;
 360                 fh->dent = NULL;
 361         } else {
 362                 dent = fs_readdir(fh->dirs);
 363         }
 364
 365
 366         if (!dent) {
 367                 /* no more files in directory: */
 368                 /* workaround shim.efi bug/quirk.. as find_boot_csv()
 369                  * loops through directory contents, it initially calls
 370                  * read w/ zero length buffer to find out how much mem
 371                  * to allocate for the EFI_FILE_INFO, then allocates,
 372                  * and then calls a 2nd time.  If we return size of
 373                  * zero the first time, it happily passes that to
 374                  * AllocateZeroPool(), and when that returns NULL it
 375                  * thinks it is EFI_OUT_OF_RESOURCES.  So on first
 376                  * call return a non-zero size:
 377                  */
 378                 if (*buffer_size == 0)
 379                         *buffer_size = sizeof(*info);
 380                 else
 381                         *buffer_size = 0;
 382                 return EFI_SUCCESS;
 383         }
 384
 385         /* check buffer size: */
 386         required_size = sizeof(*info) + 2 * (strlen(dent->name) + 1);
 387         if (*buffer_size < required_size) {
 388                 *buffer_size = required_size;
 389                 fh->dent = dent;
 390                 return EFI_BUFFER_TOO_SMALL;
 391         }
 392
 393         *buffer_size = required_size;
 394         memset(info, 0, required_size);
 395
 396         info->size = required_size;
 397         info->file_size = dent->size;
 398         info->physical_size = dent->size;
 399
 400         if (dent->type == FS_DT_DIR)
 401                 info->attribute |= EFI_FILE_DIRECTORY;
 402
 403         ascii2unicode(info->file_name, dent->name);
 404
 405         fh->offset++;
 406
 407         return EFI_SUCCESS;
 408 }
 409
 410 static efi_status_t EFIAPI efi_file_read(struct efi_file_handle *file,
 411                                          efi_uintn_t *buffer_size, void *buffer)
 412 {
 413         struct file_handle *fh = to_fh(file);
 414         efi_status_t ret = EFI_SUCCESS;
 415         u64 bs;
 416
 417         EFI_ENTRY("%p, %p, %p", file, buffer_size, buffer);
 418
 419         if (!buffer_size || !buffer) {
 420                 ret = EFI_INVALID_PARAMETER;
 421                 goto error;
 422         }
 423
 424         if (set_blk_dev(fh)) {
 425                 ret = EFI_DEVICE_ERROR;
 426                 goto error;
 427         }
 428
 429         bs = *buffer_size;
 430         if (fh->isdir)
 431                 ret = dir_read(fh, &bs, buffer);
 432         else
 433                 ret = file_read(fh, &bs, buffer);
 434         if (bs <= SIZE_MAX)
 435                 *buffer_size = bs;
 436         else
 437                 *buffer_size = SIZE_MAX;
 438
 439 error:
 440         return EFI_EXIT(ret);
 441 }
 442
 443 static efi_status_t EFIAPI efi_file_write(struct efi_file_handle *file,
 444                                           efi_uintn_t *buffer_size,
 445                                           void *buffer)
 446 {
 447         struct file_handle *fh = to_fh(file);
 448         efi_status_t ret = EFI_SUCCESS;
 449         loff_t actwrite;
 450
 451         EFI_ENTRY("%p, %p, %p", file, buffer_size, buffer);
 452
 453         if (set_blk_dev(fh)) {
 454                 ret = EFI_DEVICE_ERROR;
 455                 goto error;
 456         }
 457
 458         if (fs_write(fh->path, map_to_sysmem(buffer), fh->offset, *buffer_size,
 459                      &actwrite)) {
 460                 ret = EFI_DEVICE_ERROR;
 461                 goto error;
 462         }
 463
 464         *buffer_size = actwrite;
 465         fh->offset += actwrite;
 466
 467 error:
 468         return EFI_EXIT(ret);
 469 }
 470
 471 /**
 472  * efi_file_getpos() - get current position in file
 473  *
 474  * This function implements the GetPosition service of the EFI file protocol.
 475  * See the UEFI spec for details.
 476  *
 477  * @file:       file handle
 478  * @pos:        pointer to file position
 479  * Return:      status code
 480  */
 481 static efi_status_t EFIAPI efi_file_getpos(struct efi_file_handle *file,
 482                                            u64 *pos)
 483 {
 484         efi_status_t ret = EFI_SUCCESS;
 485         struct file_handle *fh = to_fh(file);
 486
 487         EFI_ENTRY("%p, %p", file, pos);
 488
 489         if (fh->isdir) {
 490                 ret = EFI_UNSUPPORTED;
 491                 goto out;
 492         }
 493
 494         *pos = fh->offset;
 495 out:
 496         return EFI_EXIT(ret);
 497 }
 498
 499 /**
 500  * efi_file_setpos() - set current position in file
 501  *
 502  * This function implements the SetPosition service of the EFI file protocol.
 503  * See the UEFI spec for details.
 504  *
 505  * @file:       file handle
 506  * @pos:        new file position
 507  * Return:      status code
 508  */
 509 static efi_status_t EFIAPI efi_file_setpos(struct efi_file_handle *file,
 510                                            u64 pos)
 511 {
 512         struct file_handle *fh = to_fh(file);
 513         efi_status_t ret = EFI_SUCCESS;
 514
 515         EFI_ENTRY("%p, %llu", file, pos);
 516
 517         if (fh->isdir) {
 518                 if (pos != 0) {
 519                         ret = EFI_UNSUPPORTED;
 520                         goto error;
 521                 }
 522                 fs_closedir(fh->dirs);
 523                 fh->dirs = NULL;
 524         }
 525
 526         if (pos == ~0ULL) {
 527                 loff_t file_size;
 528
 529                 if (set_blk_dev(fh)) {
 530                         ret = EFI_DEVICE_ERROR;
 531                         goto error;
 532                 }
 533
 534                 if (fs_size(fh->path, &file_size)) {
 535                         ret = EFI_DEVICE_ERROR;
 536                         goto error;
 537                 }
 538
 539                 pos = file_size;
 540         }
 541
 542         fh->offset = pos;
 543
 544 error:
 545         return EFI_EXIT(ret);
 546 }
 547
 548 static efi_status_t EFIAPI efi_file_getinfo(struct efi_file_handle *file,
 549                                             const efi_guid_t *info_type,
 550                                             efi_uintn_t *buffer_size,
 551                                             void *buffer)
 552 {
 553         struct file_handle *fh = to_fh(file);
 554         efi_status_t ret = EFI_SUCCESS;
 555
 556         EFI_ENTRY("%p, %pUl, %p, %p", file, info_type, buffer_size, buffer);
 557
 558         if (!guidcmp(info_type, &efi_file_info_guid)) {
 559                 struct efi_file_info *info = buffer;
 560                 char *filename = basename(fh);
 561                 unsigned int required_size;
 562                 loff_t file_size;
 563
 564                 /* check buffer size: */
 565                 required_size = sizeof(*info) + 2 * (strlen(filename) + 1);
 566                 if (*buffer_size < required_size) {
 567                         *buffer_size = required_size;
 568                         ret = EFI_BUFFER_TOO_SMALL;
 569                         goto error;
 570                 }
 571
 572                 if (set_blk_dev(fh)) {
 573                         ret = EFI_DEVICE_ERROR;
 574                         goto error;
 575                 }
 576
 577                 if (fs_size(fh->path, &file_size)) {
 578                         ret = EFI_DEVICE_ERROR;
 579                         goto error;
 580                 }
 581
 582                 memset(info, 0, required_size);
 583
 584                 info->size = required_size;
 585                 info->file_size = file_size;
 586                 info->physical_size = file_size;
 587
 588                 if (fh->isdir)
 589                         info->attribute |= EFI_FILE_DIRECTORY;
 590
 591                 ascii2unicode(info->file_name, filename);
 592         } else if (!guidcmp(info_type, &efi_file_system_info_guid)) {
 593                 struct efi_file_system_info *info = buffer;
 594                 disk_partition_t part;
 595                 efi_uintn_t required_size;
 596                 int r;
 597
 598                 if (fh->fs->part >= 1)
 599                         r = part_get_info(fh->fs->desc, fh->fs->part, &part);
 600                 else
 601                         r = part_get_info_whole_disk(fh->fs->desc, &part);
 602                 if (r < 0) {
 603                         ret = EFI_DEVICE_ERROR;
 604                         goto error;
 605                 }
 606                 required_size = sizeof(info) + 2 *
 607                                 (strlen((const char *)part.name) + 1);
 608                 if (*buffer_size < required_size) {
 609                         *buffer_size = required_size;
 610                         ret = EFI_BUFFER_TOO_SMALL;
 611                         goto error;
 612                 }
 613
 614                 memset(info, 0, required_size);
 615
 616                 info->size = required_size;
 617                 info->read_only = true;
 618                 info->volume_size = part.size * part.blksz;
 619                 info->free_space = 0;
 620                 info->block_size = part.blksz;
 621                 /*
 622                  * TODO: The volume label is not available in U-Boot.
 623                  * Use the partition name as substitute.
 624                  */
 625                 ascii2unicode((u16 *)info->volume_label,
 626                               (const char *)part.name);
 627         } else {
 628                 ret = EFI_UNSUPPORTED;
 629         }
 630
 631 error:
 632         return EFI_EXIT(ret);
 633 }
 634
 635 static efi_status_t EFIAPI efi_file_setinfo(struct efi_file_handle *file,
 636                                             const efi_guid_t *info_type,
 637                                             efi_uintn_t buffer_size,
 638                                             void *buffer)
 639 {
 640         struct file_handle *fh = to_fh(file);
 641         efi_status_t ret = EFI_UNSUPPORTED;
 642
 643         EFI_ENTRY("%p, %pUl, %zu, %p", file, info_type, buffer_size, buffer);
 644
 645         if (!guidcmp(info_type, &efi_file_info_guid)) {
 646                 struct efi_file_info *info = (struct efi_file_info *)buffer;
 647                 char *filename = basename(fh);
 648                 char *new_file_name, *pos;
 649                 loff_t file_size;
 650
 651                 if (buffer_size < sizeof(struct efi_file_info)) {
 652                         ret = EFI_BAD_BUFFER_SIZE;
 653                         goto out;
 654                 }
 655                 /* We cannot change the directory attribute */
 656                 if (!fh->isdir != !(info->attribute & EFI_FILE_DIRECTORY)) {
 657                         ret = EFI_ACCESS_DENIED;
 658                         goto out;
 659                 }
 660                 /* Check for renaming */
 661                 new_file_name = malloc(utf16_utf8_strlen(info->file_name));
 662                 if (!new_file_name) {
 663                         ret = EFI_OUT_OF_RESOURCES;
 664                         goto out;
 665                 }
 666                 pos = new_file_name;
 667                 utf16_utf8_strcpy(&pos, info->file_name);
 668                 if (strcmp(new_file_name, filename)) {
 669                         /* TODO: we do not support renaming */
 670                         EFI_PRINT("Renaming not supported\n");
 671                         free(new_file_name);
 672                         ret = EFI_ACCESS_DENIED;
 673                         goto out;
 674                 }
 675                 free(new_file_name);
 676                 /* Check for truncation */
 677                 if (set_blk_dev(fh)) {
 678                         ret = EFI_DEVICE_ERROR;
 679                         goto out;
 680                 }
 681                 if (fs_size(fh->path, &file_size)) {
 682                         ret = EFI_DEVICE_ERROR;
 683                         goto out;
 684                 }
 685                 if (file_size != info->file_size) {
 686                         /* TODO: we do not support truncation */
 687                         EFI_PRINT("Truncation not supported\n");
 688                         ret = EFI_ACCESS_DENIED;
 689                         goto out;
 690                 }
 691                 /*
 692                  * We do not care for the other attributes
 693                  * TODO: Support read only
 694                  */
 695                 ret = EFI_SUCCESS;
 696         } else if (!guidcmp(info_type, &efi_file_system_info_guid)) {
 697                 if (buffer_size < sizeof(struct efi_file_system_info)) {
 698                         ret = EFI_BAD_BUFFER_SIZE;
 699                         goto out;
 700                 }
 701         } else {
 702                 ret = EFI_UNSUPPORTED;
 703         }
 704 out:
 705         return EFI_EXIT(ret);
 706 }
 707
 708 static efi_status_t EFIAPI efi_file_flush(struct efi_file_handle *file)
 709 {
 710         EFI_ENTRY("%p", file);
 711         return EFI_EXIT(EFI_SUCCESS);
 712 }
 713
 714 static const struct efi_file_handle efi_file_handle_protocol = {
 715         /*
 716          * TODO: We currently only support EFI file protocol revision 0x00010000
 717          *       while UEFI specs 2.4 - 2.7 prescribe revision 0x00020000.
 718          */
 719         .rev = EFI_FILE_PROTOCOL_REVISION,
 720         .open = efi_file_open,
 721         .close = efi_file_close,
 722         .delete = efi_file_delete,
 723         .read = efi_file_read,
 724         .write = efi_file_write,
 725         .getpos = efi_file_getpos,
 726         .setpos = efi_file_setpos,
 727         .getinfo = efi_file_getinfo,
 728         .setinfo = efi_file_setinfo,
 729         .flush = efi_file_flush,
 730 };
 731
 732 /**
 733  * efi_file_from_path() - open file via device path
 734  *
 735  * @fp:         device path
 736  * @return:     EFI_FILE_PROTOCOL for the file or NULL
 737  */
 738 struct efi_file_handle *efi_file_from_path(struct efi_device_path *fp)
 739 {
 740         struct efi_simple_file_system_protocol *v;
 741         struct efi_file_handle *f;
 742         efi_status_t ret;
 743
 744         v = efi_fs_from_path(fp);
 745         if (!v)
 746                 return NULL;
 747
 748         EFI_CALL(ret = v->open_volume(v, &f));
 749         if (ret != EFI_SUCCESS)
 750                 return NULL;
 751
 752         /* Skip over device-path nodes before the file path. */
 753         while (fp && !EFI_DP_TYPE(fp, MEDIA_DEVICE, FILE_PATH))
 754                 fp = efi_dp_next(fp);
 755
 756         /*
 757          * Step through the nodes of the directory path until the actual file
 758          * node is reached which is the final node in the device path.
 759          */
 760         while (fp) {
 761                 struct efi_device_path_file_path *fdp =
 762                         container_of(fp, struct efi_device_path_file_path, dp);
 763                 struct efi_file_handle *f2;
 764
 765                 if (!EFI_DP_TYPE(fp, MEDIA_DEVICE, FILE_PATH)) {
 766                         printf("bad file path!\n");
 767                         f->close(f);
 768                         return NULL;
 769                 }
 770
 771                 EFI_CALL(ret = f->open(f, &f2, fdp->str,
 772                                        EFI_FILE_MODE_READ, 0));
 773                 if (ret != EFI_SUCCESS)
 774                         return NULL;
 775
 776                 fp = efi_dp_next(fp);
 777
 778                 EFI_CALL(f->close(f));
 779                 f = f2;
 780         }
 781
 782         return f;
 783 }
 784
 785 static efi_status_t EFIAPI
 786 efi_open_volume(struct efi_simple_file_system_protocol *this,
 787                 struct efi_file_handle **root)
 788 {
 789         struct file_system *fs = to_fs(this);
 790
 791         EFI_ENTRY("%p, %p", this, root);
 792
 793         *root = file_open(fs, NULL, NULL, 0, 0);
 794
 795         return EFI_EXIT(EFI_SUCCESS);
 796 }
 797
 798 struct efi_simple_file_system_protocol *
 799 efi_simple_file_system(struct blk_desc *desc, int part,
 800                        struct efi_device_path *dp)
 801 {
 802         struct file_system *fs;
 803
 804         fs = calloc(1, sizeof(*fs));
 805         fs->base.rev = EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_REVISION;
 806         fs->base.open_volume = efi_open_volume;
 807         fs->desc = desc;
 808         fs->part = part;
 809         fs->dp = dp;
 810
 811         return &fs->base;
 812 }