[U-Boot] [PATCH 2/2] disk: efi: ignore 'IGNOREME' GPT header found on cros eMMCs

[Urja Rannikko <urjaman@gmail.com>]

Some ChromeOS devices (atleast veyron speedy) have the first 8MiB of
the eMMC write protected and equipped with a dummy 'IGNOREME' GPT
header - instead of spewing error messages about it, just silently
try the backup GPT.

Note: this does not touch the gpt cmd writing/verifying functions,
those will still complain.

Signed-off-by: Urja Rannikko <urjaman@gmail.com>
---
 disk/part_efi.c    | 28 +++++++++++++++++++++-------
 include/part_efi.h |  2 ++
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/disk/part_efi.c b/disk/part_efi.c
index 5f935da4c2..83ba7db665 100644
--- a/disk/part_efi.c
+++ b/disk/part_efi.c
@@ -893,7 +893,7 @@ static int is_pmbr_valid(legacy_mbr * mbr)
  * gpt is a GPT header ptr, filled on return.
  * ptes is a PTEs ptr, filled on return.
  *
- * Description: returns 1 if valid,  0 on error.
+ * Description: returns 1 if valid,  0 on error, 2 if ignored header
  * If valid, returns pointers to PTEs.
  */
 static int is_gpt_valid(struct blk_desc *dev_desc, u64 lba,
@@ -919,6 +919,12 @@ static int is_gpt_valid(struct blk_desc *dev_desc, u64 lba,
 		return 0;
 	}
 
+	/* Invalid but nothing to yell about. */
+	if (le64_to_cpu(pgpt_head->signature) == GPT_HEADER_CHROMEOS_IGNORE) {
+		debug("ChromeOS 'IGNOREME' GPT header found and ignored\n");
+		return 2;
+	}
+
 	if (validate_gpt_header(pgpt_head, (lbaint_t)lba, dev_desc->lba))
 		return 0;
 
@@ -962,16 +968,24 @@ static int is_gpt_valid(struct blk_desc *dev_desc, u64 lba,
 static int find_valid_gpt(struct blk_desc *dev_desc, gpt_header *gpt_head,
 			  gpt_entry **pgpt_pte)
 {
-	if (is_gpt_valid(dev_desc, GPT_PRIMARY_PARTITION_TABLE_LBA,
-			 gpt_head, pgpt_pte) != 1) {
-		printf("%s: *** ERROR: Invalid GPT ***\n", __func__);
-		if (is_gpt_valid(dev_desc, (dev_desc->lba - 1),
-				 gpt_head, pgpt_pte) != 1) {
+	int r;
+
+	r = is_gpt_valid(dev_desc, GPT_PRIMARY_PARTITION_TABLE_LBA, gpt_head,
+			 pgpt_pte);
+
+	if (r != 1) {
+		if (r != 2)
+			printf("%s: *** ERROR: Invalid GPT ***\n", __func__);
+
+		if (is_gpt_valid(dev_desc, (dev_desc->lba - 1), gpt_head,
+				 pgpt_pte) != 1) {
 			printf("%s: *** ERROR: Invalid Backup GPT ***\n",
 			       __func__);
 			return 0;
 		}
-		printf("%s: ***        Using Backup GPT ***\n",  __func__);
+		if (r != 2)
+			printf("%s: ***        Using Backup GPT ***\n",
+			       __func__);
 	}
 	return 1;
 }
diff --git a/include/part_efi.h b/include/part_efi.h
index 7170b61c95..eb5797af74 100644
--- a/include/part_efi.h
+++ b/include/part_efi.h
@@ -25,6 +25,8 @@
 #define EFI_PMBR_OSTYPE_EFI_GPT 0xEE
 
 #define GPT_HEADER_SIGNATURE_UBOOT 0x5452415020494645ULL
+#define GPT_HEADER_CHROMEOS_IGNORE 0x454d45524f4e4749ULL // 'IGNOREME'
+
 #define GPT_HEADER_REVISION_V1 0x00010000
 #define GPT_PRIMARY_PARTITION_TABLE_LBA 1ULL
 #define GPT_ENTRY_NUMBERS		CONFIG_EFI_PARTITION_ENTRIES_NUMBERS
-- 
2.21.0