[PATCH 4/5] efi_loader: disk: Extend EFI_PARTITION_INFO_PROTOCOL to support MBR

[Javier Martinez Canillas <javierm@redhat.com>]

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@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,
 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
 
 #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:
-- 
2.52.0