[RFC] CHROMIUM: Two patches for comments: EFI GUID boot for dm-verity

fs/partitions/efi.c

Index: fs/partitions/efi.c
diff --git a/fs/partitions/efi.c b/fs/partitions/efi.c
index 49cfd5f5423894df4c2f52ac48bac1f82a9b43a3..e9e4923707ede7161de16ab502179a8889ce5515 100644
--- a/fs/partitions/efi.c
+++ b/fs/partitions/efi.c
@@ -637,3 +637,62 @@ efi_partition(struct parsed_partitions *state, struct block_device *bdev)
 	printk("\n");
 	return 1;
 }
+
+/**
+ * efi_find_partition(efi_guid_t *guid, struct block_device *bdev)
+ * @guid
+ * @bdev
+ *
+ * Returns:
+ * -1 if an error occurred
+ *  0 if there was no match (or not GPT)
+ *  >=1 is the index of the partition found.
+ *
+ */
+int efi_find_partition(efi_guid_t *guid, struct block_device *bdev) {
+	gpt_header *gpt = NULL;
+	gpt_entry *ptes = NULL;
+	u32 i;
+	struct parsed_partitions *state;
+	int part = 0;
+
+	if (!bdev || !guid)
+		return -1;
+
+	state = kzalloc(sizeof(struct parsed_partitions), GFP_KERNEL);
+	if (!state)
+		return -1;
+
+	state->limit = disk_max_parts(bdev->bd_disk);
+	pr_debug(KERN_WARNING "efi_find_partition looking for gpt\n");
+
+	if (!find_valid_gpt(bdev, &gpt, &ptes) || !gpt || !ptes) {
+		pr_debug(KERN_WARNING "efi_find_partition no GPT\n");
+		kfree(gpt);
+		kfree(ptes);
+		kfree(state);
+		return 0;
+	}
+
+	pr_debug("GUID Partition Table is valid!  Yea!\n");
+
+	pr_debug(KERN_WARNING "efi_find_partition: 0 -> %d (limit:%d)\n",
+		 le32_to_cpu(gpt->num_partition_entries),
+		 state->limit);
+	for (i = 0; i < le32_to_cpu(gpt->num_partition_entries) &&
+		    i < state->limit-1; i++) {
+		if (!is_pte_valid(&ptes[i], last_lba(bdev)))
+			continue;
+
+		/* Bails on first hit so duped "unique" GUIDs will be FCFS. */
+		if (!efi_guidcmp(ptes[i].unique_partition_guid,
+				 *guid)) {
+			part = i + 1;
+			break;
+		}
+	}
+	kfree(ptes);
+	kfree(gpt);
+	kfree(state);
+	return part;
+}