[PATCH 4/5] efi_loader: disk: Extend EFI_PARTITION_INFO_PROTOCOL to support MBR
Heinrich Schuchardt
xypron.glpk at gmx.de
Tue Jan 20 15:53:02 CET 2026
On 1/20/26 14:36, Javier Martinez Canillas wrote:
> The EFI_PARTITION_INFO_PROTOCOL provides detailed information about
> partitions. The UEFI specification mentions that both GPT and MBR
> partition schemes are supported, but the U-Boot implementation only
> supports the former.
>
> This can cause compatibility issues for platforms whose boot ROM only
> supports MBR. This change adds support for MBR partition tables to
> the protocol, making U-Boot compatible with systems that require a
> legacy MBR table.
>
> To implement this, the existing part_get_info_extended() function,
> which already traverses DOS partitions, is refactored to optionally
> retrieve the raw MBR partition record. This provides the necessary
> data for the EFI subsystem.
>
> Signed-off-by: Javier Martinez Canillas <javierm at redhat.com>
> ---
>
> disk/part_dos.c | 63 ++++++++++++++++++++++++---------------
> include/part.h | 14 +++++++++
> lib/efi_loader/efi_disk.c | 9 ++++--
> 3 files changed, 59 insertions(+), 27 deletions(-)
>
> diff --git a/disk/part_dos.c b/disk/part_dos.c
> index 60c3d6773696..5b508483bae7 100644
> --- a/disk/part_dos.c
> +++ b/disk/part_dos.c
> @@ -201,7 +201,9 @@ static void print_partition_extended(struct blk_desc *desc,
Please add a Sphinx style function description describing the usage of
the parameters.
> static int part_get_info_extended(struct blk_desc *desc,
> lbaint_t ext_part_sector, lbaint_t relative,
> int part_num, int which_part,
> - struct disk_partition *info, uint disksig)
> + struct disk_partition *info,
> + dos_partition_t *mbr,
> + uint disksig)
> {
> ALLOC_CACHE_ALIGN_BUFFER(unsigned char, buffer, desc->blksz);
> struct disk_partition wdinfo = { 0 };
> @@ -232,9 +234,11 @@ static int part_get_info_extended(struct blk_desc *desc,
> if (CONFIG_IS_ENABLED(PARTITION_UUIDS) && !ext_part_sector)
> disksig = get_unaligned_le32(&buffer[DOS_PART_DISKSIG_OFFSET]);
>
> - ret = part_get_info_whole_disk(desc, &wdinfo);
> - if (ret)
> - return ret;
> + if (info) {
> + ret = part_get_info_whole_disk(desc, &wdinfo);
> + if (ret)
> + return ret;
> + }
>
> /* Print all primary/logical partitions */
> pt = (dos_partition_t *) (buffer + DOS_PART_TBL_OFFSET);
> @@ -247,25 +251,29 @@ static int part_get_info_extended(struct blk_desc *desc,
> (pt->sys_ind != 0) &&
> (part_num == which_part) &&
> (ext_part_sector == 0 || is_extended(pt->sys_ind) == 0)) {
> - if (wdinfo.blksz > DOS_PART_DEFAULT_SECTOR)
> - info->blksz = wdinfo.blksz;
> - else
> - info->blksz = DOS_PART_DEFAULT_SECTOR;
> - info->start = (lbaint_t)(ext_part_sector +
> - get_unaligned_le32(&pt->start_sect));
> - info->size = (lbaint_t)get_unaligned_le32(&pt->nr_sects);
> - part_set_generic_name(desc, part_num,
> - (char *)info->name);
> - /* sprintf(info->type, "%d, pt->sys_ind); */
> - strcpy((char *)info->type, "U-Boot");
> - info->bootable = get_bootable(pt);
> - if (CONFIG_IS_ENABLED(PARTITION_UUIDS)) {
> - char str[12];
> -
> - sprintf(str, "%08x-%02x", disksig, part_num);
> - disk_partition_set_uuid(info, str);
> + if (info) {
> + if (wdinfo.blksz > DOS_PART_DEFAULT_SECTOR)
> + info->blksz = wdinfo.blksz;
> + else
> + info->blksz = DOS_PART_DEFAULT_SECTOR;
> + info->start = (lbaint_t)(ext_part_sector +
> + get_unaligned_le32(&pt->start_sect));
> + info->size = (lbaint_t)get_unaligned_le32(&pt->nr_sects);
> + part_set_generic_name(desc, part_num,
> + (char *)info->name);
> + /* sprintf(info->type, "%d, pt->sys_ind); */
> + strcpy((char *)info->type, "U-Boot");
> + info->bootable = get_bootable(pt);
> + if (CONFIG_IS_ENABLED(PARTITION_UUIDS)) {
> + char str[12];
> +
> + sprintf(str, "%08x-%02x", disksig, part_num);
> + disk_partition_set_uuid(info, str);
> + }
> + info->sys_ind = pt->sys_ind;
> }
> - info->sys_ind = pt->sys_ind;
> + if (mbr)
> + memcpy(mbr, pt, sizeof(*mbr));
> return 0;
> }
>
> @@ -285,7 +293,8 @@ static int part_get_info_extended(struct blk_desc *desc,
>
> return part_get_info_extended(desc, lba_start,
> ext_part_sector == 0 ? lba_start : relative,
> - part_num, which_part, info, disksig);
> + part_num, which_part, info,
> + mbr, disksig);
> }
> }
>
> @@ -317,7 +326,13 @@ static void __maybe_unused part_print_dos(struct blk_desc *desc)
> static int __maybe_unused part_get_info_dos(struct blk_desc *desc, int part,
> struct disk_partition *info)
> {
> - return part_get_info_extended(desc, 0, 0, 1, part, info, 0);
> + return part_get_info_extended(desc, 0, 0, 1, part, info, NULL, 0);
> +}
> +
> +int __maybe_unused part_get_mbr(struct blk_desc *desc, int part,
> + dos_partition_t *mbr)
> +{
> + return part_get_info_extended(desc, 0, 0, 1, part, NULL, mbr, 0);
> }
>
> int is_valid_dos_buf(void *buf)
> diff --git a/include/part.h b/include/part.h
> index daebbbc2e68f..84dbdbbd1494 100644
> --- a/include/part.h
> +++ b/include/part.h
> @@ -704,6 +704,20 @@ int write_mbr_partitions(struct blk_desc *dev,
> int layout_mbr_partitions(struct disk_partition *p, int count,
> lbaint_t total_sectors);
>
> +/**
> + * part_get_mbr() - Get the MBR partition record of a partition
> + *
> + * This function reads the MBR partition record for a given block
> + * device and partition number.
> + *
> + * @desc: block device descriptor
> + * @part: partition number for which to return the partition record
> + * @mbr: MBR partition record
> + *
> + * Return: 0 on success, otherwise error
> + */
> +int part_get_mbr(struct blk_desc *desc, int part, dos_partition_t *mbr);
> +
> #endif
>
Please, put the partition library changes into one patch and the EFI
changes into another.
Best regards
Heinrich
> #if CONFIG_IS_ENABLED(PARTITIONS)
> diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
> index 130c4db9606f..f8a57539ec61 100644
> --- a/lib/efi_loader/efi_disk.c
> +++ b/lib/efi_loader/efi_disk.c
> @@ -475,9 +475,12 @@ static efi_status_t efi_disk_add_dev(
> #if CONFIG_IS_ENABLED(DOS_PARTITION)
> case PART_TYPE_DOS:
> info->type = PARTITION_TYPE_MBR;
> -
> - /* TODO: implement support for MBR partition types */
> - log_debug("EFI_PARTITION_INFO_PROTOCOL doesn't support MBR\n");
> + ret = part_get_mbr(desc, part, &info->info.mbr);
> + if (ret) {
> + log_debug("get MBR for part %d failed %ld\n",
> + part, ret);
> + goto error;
> + }
> break;
> #endif
> default:
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