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

fs/partitions/efi.c

 /************************************************************
  * EFI GUID Partition Table handling
  *
  * http://www.uefi.org/specs/
  * http://www.intel.com/technology/efi/
  *
  * efi.[ch] by Matt Domsch <Matt_Domsch@dell.com>
  *   Copyright 2000,2001,2002,2004 Dell Inc.
  *
  *  This program is free software; you can redistribute it and/or modify
@@ skipping 619 matching lines @@
                 /* If this is a RAID volume, tell md */
                 if (!efi_guidcmp(ptes[i].partition_type_guid,
                                  PARTITION_LINUX_RAID_GUID))
                         state->parts[i+1].flags = 1;
         }
         kfree(ptes);
         kfree(gpt);
         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;
+}