On 12/3/25 4:19 PM, Sascha Hauer wrote:
> In preparation for writing the inactive GPT first factor out a function
> which either writes the primary or alternate GPT based on a boolean
> argument.
>
> Signed-off-by: Sascha Hauer <[email protected]>
Reviewed-by: Ahmad Fatoum <[email protected]>
> ---
> common/partitions/efi.c | 92
> ++++++++++++++++++++++++++++---------------------
> 1 file changed, 53 insertions(+), 39 deletions(-)
>
> diff --git a/common/partitions/efi.c b/common/partitions/efi.c
> index
> 76c5393dddb04e2966d3a4b4478d5085f008d935..8da62acf36646b62ff2fac25673adbc48650d299
> 100644
> --- a/common/partitions/efi.c
> +++ b/common/partitions/efi.c
> @@ -740,75 +740,89 @@ static int efi_protective_mbr(struct block_device *blk)
> return ret;
> }
>
> -static __maybe_unused int efi_partition_write(struct partition_desc *pd)
> +static int __efi_partition_write(struct efi_partition_desc *epd, bool
> primary)
> {
> - struct block_device *blk = pd->blk;
> - struct efi_partition_desc *epd = container_of(pd, struct
> efi_partition_desc, pd);
> - gpt_header *gpt = epd->gpt, *altgpt;
> + struct block_device *blk = epd->pd.blk;
> + gpt_header *gpt;
> + unsigned int count, size;
> + uint64_t my_lba, partition_entry_lba;
> int ret;
> - uint32_t count;
> - uint64_t from, size;
>
> - if (le32_to_cpu(gpt->num_partition_entries) != 128) {
> - /*
> - * This is not yet properly implemented. At least writing of the
> - * alternative GPT is not correctly implemented for this case as
> - * we can't assume that the partition entries are written at
> - * last_lba() - 32, we would have to calculate that from the
> number
> - * of partition entries.
> - */
> - pr_err("num_partition_entries is != 128. This is not yet
> supported for writing\n");
> - return -EINVAL;
> - }
> + gpt = xmemdup(epd->gpt, SECTOR_SIZE);
>
> count = le32_to_cpu(gpt->num_partition_entries) *
> le32_to_cpu(gpt->sizeof_partition_entry);
>
> - gpt->my_lba = cpu_to_le64(1);
> - gpt->alternate_lba = cpu_to_le64(last_lba(blk));
> + size = count / GPT_BLOCK_SIZE;
> +
> + if (primary) {
> + my_lba = 1;
> + partition_entry_lba = le64_to_cpu(gpt->partition_entry_lba);
> + gpt->alternate_lba = cpu_to_le64(last_lba(blk));
> + } else {
> + my_lba = last_lba(blk);
> + partition_entry_lba = last_lba(blk) - 32;
> + gpt->alternate_lba = cpu_to_le64(1);
> + }
> +
> + gpt->my_lba = cpu_to_le64(my_lba);
> + gpt->partition_entry_lba = cpu_to_le64(partition_entry_lba);
> gpt->partition_entry_array_crc32 = cpu_to_le32(efi_crc32(
> (const unsigned char *)epd->ptes, count));
> gpt->header_crc32 = 0;
> gpt->header_crc32 = cpu_to_le32(efi_crc32((const unsigned char *)gpt,
>
> le32_to_cpu(gpt->header_size)));
>
> - ret = efi_protective_mbr(blk);
> + ret = block_write(blk, gpt, my_lba, 1);
> if (ret)
> - return ret;
> + goto err_block_write;
>
> - ret = block_write(blk, gpt, 1, 1);
> + ret = block_write(blk, epd->ptes, partition_entry_lba, size);
> if (ret)
> goto err_block_write;
>
> - from = le64_to_cpu(gpt->partition_entry_lba);
> - size = count / GPT_BLOCK_SIZE;
> +err_block_write:
> + free(gpt);
>
> - ret = block_write(blk, epd->ptes, from, size);
> - if (ret)
> - goto err_block_write;
> + return ret;
> +}
>
> - altgpt = xmemdup(gpt, SECTOR_SIZE);
> +static __maybe_unused int efi_partition_write(struct partition_desc *pd)
> +{
> + struct block_device *blk = pd->blk;
> + struct efi_partition_desc *epd = container_of(pd, struct
> efi_partition_desc, pd);
> + gpt_header *gpt = epd->gpt;
> + int ret;
>
> - altgpt->alternate_lba = cpu_to_le64(1);
> - altgpt->my_lba = cpu_to_le64(last_lba(blk));
> - altgpt->partition_entry_lba = cpu_to_le64(last_lba(blk) - 32);
> - altgpt->header_crc32 = 0;
> - altgpt->header_crc32 = cpu_to_le32(efi_crc32((const unsigned char
> *)altgpt,
> -
> le32_to_cpu(altgpt->header_size)));
> - ret = block_write(blk, altgpt, last_lba(blk), 1);
> + if (le32_to_cpu(gpt->num_partition_entries) != 128) {
> + /*
> + * This is not yet properly implemented. At least writing of the
> + * alternative GPT is not correctly implemented for this case as
> + * we can't assume that the partition entries are written at
> + * last_lba() - 32, we would have to calculate that from the
> number
> + * of partition entries.
> + */
> + pr_err("num_partition_entries is != 128. This is not yet
> supported for writing\n");
> + return -EINVAL;
> + }
>
> - free(altgpt);
> + ret = efi_protective_mbr(blk);
> + if (ret)
> + return ret;
>
> + ret = __efi_partition_write(epd, true);
> if (ret)
> goto err_block_write;
> - ret = block_write(blk, epd->ptes, last_lba(blk) - 32, size);
> +
> + ret = __efi_partition_write(epd, false);
> if (ret)
> goto err_block_write;
>
> - return 0;
> + ret = 0;
>
> err_block_write:
> - pr_err("Cannot write to block device: %pe\n", ERR_PTR(ret));
> + if (ret)
> + pr_err("Cannot write to block device: %pe\n", ERR_PTR(ret));
>
> return ret;
> }
>
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