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sd-boot: Use backup LBA location from first GPT header

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If a disk were dd'd to a lager block device, the last block on it
is not necessarily the backup header.
This commit is contained in:
Jan Janssen
2021-09-27 12:20:15 +02:00
committed by Lennart Poettering
parent 393955fd21
commit d09065f894
1 changed files with 22 additions and 5 deletions
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27
src/boot/efi/xbootldr.c
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@@ -76,6 +76,7 @@ static BOOLEAN verify_gpt(union GptHeaderBuffer *gpt_header_buffer, EFI_LBA lba_
static EFI_STATUS try_gpt(
EFI_BLOCK_IO *block_io,
EFI_LBA lba,
EFI_LBA *ret_backup_lba, /* May be changed even on error! */
UINT32 *ret_part_number,
UINT64 *ret_part_start,
UINT64 *ret_part_size,
@@ -103,6 +104,10 @@ static EFI_STATUS try_gpt(
if (EFI_ERROR(err))
return err;
/* Indicate the location of backup LBA even if the rest of the header is corrupt. */
if (ret_backup_lba)
*ret_backup_lba = gpt.gpt_header.AlternateLBA;
if (!verify_gpt(&gpt, lba))
return EFI_NOT_FOUND;
@@ -210,14 +215,26 @@ static EFI_STATUS find_device(
block_io->Media->LastBlock <= 1)
continue;
/* Try both copies of the GPT header, in case one is corrupted */
for (UINTN nr = 0; nr < 2; nr++) {
/* Read the first copy at LBA 1 and then try backup GPT header at the very last
* LBA of this block device if it was corrupted. */
EFI_LBA lba = nr == 0 ? 1 : block_io->Media->LastBlock;
/* Try several copies of the GPT header, in case one is corrupted */
EFI_LBA backup_lba = 0;
for (UINTN nr = 0; nr < 3; nr++) {
EFI_LBA lba;
/* Read the first copy at LBA 1 and then try the backup GPT header pointed
* to by the first header if that one was corrupted. As a last resort,
* try the very last LBA of this block device. */
if (nr == 0)
lba = 1;
else if (nr == 1 && backup_lba != 0)
lba = backup_lba;
else if (nr == 2 && backup_lba != block_io->Media->LastBlock)
lba = block_io->Media->LastBlock;
else
continue;
err = try_gpt(
block_io, lba,
nr == 0 ? &backup_lba : NULL, /* Only get backup LBA location from first GPT header. */
ret_part_number,
ret_part_start,
ret_part_size,