Add more test cases for GptInit() and fixed some bugs

src/platform/vboot_reference/cgptlib/cgpt.c

Index: src/platform/vboot_reference/cgptlib/cgpt.c
diff --git a/src/platform/vboot_reference/cgptlib/cgpt.c b/src/platform/vboot_reference/cgptlib/cgpt.c
index 48654731773c42ab2ea9e4dbeedd90ab6c93f948..a8d449d13d55b799b116a7f016c57bb1f4f21ff1 100644
--- a/src/platform/vboot_reference/cgptlib/cgpt.c
+++ b/src/platform/vboot_reference/cgptlib/cgpt.c
@@ -5,31 +5,538 @@
 
 #include "cgpt.h"
 #include <string.h>
+#include "cgpt_internal.h"
+#include "crc32.h"
 #include "gpt.h"
+#include "quick_sort.h"
 #include "utility.h"
 
-/* stub code */
-static int start[] = { 34, 10034 };
+/* Macro to invalidate a GPT header/entries */
+#define INVALIDATE_HEADER(valid_headers, index) \
+  do { \
+    valid_headers &= ~(1<<index); \
+  } while (0)
+#define INVALIDATE_ENTRIES(valid_entries, index) \
+  do { \
+    valid_entries &= ~(1<<index); \
+  } while (0)
+
+/* Checks if sector_bytes and drive_sectors are valid values. */
+int CheckParameters(GptData *gpt) {
+  /* Currently, we only support 512-byte sector. In the future, we may support
+   * larger sector. */
+  if (gpt->sector_bytes != 512)
+    return GPT_ERROR_INVALID_SECTOR_SIZE;
+
+  /* The sector number of a drive should be reasonable. If the given value is
+   * too small to contain basic GPT structure (PMBR + Headers + Entries),
+   * the value is wrong. */
+  if (gpt->drive_sectors < (GPT_PMBR_SECTOR +
+                            GPT_HEADER_SECTOR * 2 +
+                            GPT_ENTRIES_SECTORS * 2))
+    return GPT_ERROR_INVALID_SECTOR_NUMBER;
+
+  return GPT_SUCCESS;
+}
+
+/* Expects header signature should be GPT_HEADER_SIGNATURE. */
+uint32_t CheckHeaderSignature(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  int i;
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    if (Memcmp(headers[i]->signature,
+               GPT_HEADER_SIGNATURE,
+               GPT_HEADER_SIGNATURE_SIZE)) {
+      INVALIDATE_HEADER(valid_headers, i);
+    }
+  }
+  return valid_headers;
+}
+
+/* The header revision should be GPT_HEADER_REVISION. */
+uint32_t CheckRevision(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  int i;
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    if (headers[i]->revision != GPT_HEADER_REVISION)
+      INVALIDATE_HEADER(valid_headers, i);
+  }
+  return valid_headers;
+}
+
+/* A valid header size should be between MIN_SIZE_OF_HEADER and
+ * MAX_SIZE_OF_HEADER. */
+uint32_t CheckSize(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  int i;
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    if ((headers[i]->size < MIN_SIZE_OF_HEADER) ||
+        (headers[i]->size > MAX_SIZE_OF_HEADER))
+      INVALIDATE_HEADER(valid_headers, i);
+  }
+  return valid_headers;
+}
+
+/* Reserved and padding fields should be zero. */
+uint32_t CheckReservedFields(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  int i;
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    if (headers[i]->reserved || headers[i]->padding)
+      INVALIDATE_HEADER(valid_headers, i);
+  }
+  return valid_headers;
+}
+
+/* my_lba field points to the header itself.
+ * So that the my_lba of primary header should be 1 (right after PMBR).
+ * The my_lba of secondary header should be the last secotr on drive. */
+uint32_t CheckMyLba(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *primary_header, *secondary_header;
+
+  primary_header = (GptHeader*)gpt->primary_header;
+  secondary_header = (GptHeader*)gpt->secondary_header;
+
+  if (primary_header->my_lba != GPT_PMBR_SECTOR)  /* 2nd sector on drive */
+    INVALIDATE_HEADER(valid_headers, PRIMARY);
+  if (secondary_header->my_lba != (gpt->drive_sectors - 1))  /* last sector */
+    INVALIDATE_HEADER(valid_headers, SECONDARY);
+  return valid_headers;
+}
+
+/* SizeOfPartitionEntry must be between MIN_SIZE_OF_ENTRY and
+ * MAX_SIZE_OF_ENTRY, and a multiple of SIZE_OF_ENTRY_MULTIPLE. */
+uint32_t CheckSizeOfPartitionEntry(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  int i;
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    uint32_t size_of_entry = headers[i]->size_of_entry;
+    if ((size_of_entry < MIN_SIZE_OF_ENTRY) ||
+        (size_of_entry > MAX_SIZE_OF_ENTRY) ||
+        (size_of_entry & (SIZE_OF_ENTRY_MULTIPLE - 1)))
+      INVALIDATE_HEADER(valid_headers, i);
+  }
+  return valid_headers;
+}
+
+/* number_of_entries must be between MIN_NUMBER_OF_ENTRIES and
+ * MAX_NUMBER_OF_ENTRIES, and size_of_entry * number_of_entries must be
+ * equal to TOTAL_ENTRIES_SIZE. */
+uint32_t CheckNumberOfEntries(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  int i;
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    uint32_t number_of_entries = headers[i]->number_of_entries;
+    if ((number_of_entries < MIN_NUMBER_OF_ENTRIES) ||
+        (number_of_entries > MAX_NUMBER_OF_ENTRIES) ||
+        (number_of_entries * headers[i]->size_of_entry != TOTAL_ENTRIES_SIZE))
+      INVALIDATE_HEADER(valid_headers, i);
+  }
+  return valid_headers;
+}
+
+/* Make sure entries_lba is correct.
+ *   2 for primary entries
+ *   drive_sectors-1-GPT_ENTRIES_SECTORS for secondary entries. */
+uint32_t CheckEntriesLba(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *primary_header, *secondary_header;
+
+  primary_header = (GptHeader*)gpt->primary_header;
+  secondary_header = (GptHeader*)gpt->secondary_header;
+
+  /* We assume the primary partition entry table is located at the sector
+   * right after primary partition header. */
+  if (primary_header->entries_lba != (GPT_PMBR_SECTOR + GPT_HEADER_SECTOR))
+    INVALIDATE_HEADER(valid_headers, PRIMARY);
+  /* We assume the secondary partition entry table is the 32 sectors
+   * right before the secondary partition header. */
+  if (secondary_header->entries_lba !=
+      (gpt->drive_sectors - 1 - GPT_ENTRIES_SECTORS))
+    INVALIDATE_HEADER(valid_headers, SECONDARY);
+  return valid_headers;
+}
+
+/* FirstUsableLBA must be after the end of the primary GPT table array.
+ * LastUsableLBA must be before the start of the secondary GPT table array.
+ * FirstUsableLBA <= LastUsableLBA. */
+uint32_t CheckValidUsableLbas(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  uint64_t end_of_primary_entries;
+  uint64_t start_of_secondary_entries;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  int i;
+
+  end_of_primary_entries = GPT_PMBR_SECTOR + GPT_HEADER_SECTOR +
+                           GPT_ENTRIES_SECTORS;
+  start_of_secondary_entries = (gpt->drive_sectors - 1 - GPT_ENTRIES_SECTORS);
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    if (headers[i]->first_usable_lba < end_of_primary_entries)
+      INVALIDATE_HEADER(valid_headers, i);
+    if (headers[i]->last_usable_lba >= start_of_secondary_entries)
+      INVALIDATE_HEADER(valid_headers, i);
+    if (headers[i]->first_usable_lba > headers[i]->last_usable_lba)
+      INVALIDATE_HEADER(valid_headers, i);
+  }
+
+  if (headers[PRIMARY]->first_usable_lba - headers[PRIMARY]->entries_lba <
+      GPT_ENTRIES_SECTORS)
+    INVALIDATE_HEADER(valid_headers, PRIMARY);
+  if (headers[SECONDARY]->last_usable_lba >= headers[SECONDARY]->entries_lba)
+    INVALIDATE_HEADER(valid_headers, SECONDARY);
+
+  return valid_headers;
+}
+
+/* Checks header CRC */
+uint32_t CheckHeaderCrc(GptData *gpt) {
+  uint32_t crc32, original_crc32;
+  uint32_t valid_headers = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  int i;
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    original_crc32 = headers[i]->header_crc32;
+    headers[i]->header_crc32 = 0;
+    crc32 = Crc32((const uint8_t *)headers[i], headers[i]->size);
+    headers[i]->header_crc32 = original_crc32;
+    if (crc32 != original_crc32)
+      INVALIDATE_HEADER(valid_headers, i);
+  }
+  return valid_headers;
+}
+
+/* Checks entries CRC */
+uint32_t CheckEntriesCrc(GptData *gpt) {
+  uint32_t crc32;
+  uint32_t valid_entries = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  GptEntry *entries[] = {
+    (GptEntry*)gpt->primary_entries,
+    (GptEntry*)gpt->secondary_entries,
+  };
+  int i;
 
-int GptInit(GptData_t *gpt) {
-  int valid_headers[2] = {1, 1};
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    crc32 = Crc32((const uint8_t *)entries[i], TOTAL_ENTRIES_SIZE);
+    if (crc32 != headers[i]->entries_crc32)
+      INVALIDATE_HEADER(valid_entries, i);
+  }
+  return valid_entries;
+}
+
+/* Returns non-zero if the given GUID is non-zero. */
+static int NonZeroGuid(const Guid *guid) {
+  static Guid zero = {{{0, 0, 0, 0, 0, {0, 0, 0, 0, 0, 0}}}};
+  return Memcmp(&zero, guid, sizeof(zero));
+}
+
+/* Checks if entries geometry is valid.
+ * All active (non-zero PartitionTypeGUID) partition entries should have:
+ *   entry.StartingLBA >= header.FirstUsableLBA
+ *   entry.EndingLBA <= header.LastUsableLBA
+ *   entry.StartingLBA <= entry.EndingLBA
+ */
+uint32_t CheckValidEntries(GptData *gpt) {
+  uint32_t valid_entries = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  GptEntry *entries[] = {
+    (GptEntry*)gpt->primary_entries,
+    (GptEntry*)gpt->secondary_entries,
+  };
+  int copy, entry_index;
+  GptEntry *entry;
+
+  for (copy = PRIMARY; copy <= SECONDARY; ++copy) {
+    for (entry_index = 0;
+         entry_index < headers[copy]->number_of_entries;
+         ++entry_index) {
+      entry = (GptEntry*)&(((uint8_t*)entries[copy])
+          [entry_index * headers[copy]->size_of_entry]);
+      if (NonZeroGuid(&entry->type)) {
+        if ((entry->starting_lba < headers[copy]->first_usable_lba) ||
+            (entry->ending_lba > headers[copy]->last_usable_lba) ||
+            (entry->ending_lba < entry->starting_lba))
+          INVALIDATE_HEADER(valid_entries, copy);
+      }
+    }
+  }
+  return valid_entries;
+}
+
+static pair_t pairs[MAX_NUMBER_OF_ENTRIES];
+/* Callback function for QuickSort(). Returns 1 if 'a_' should precede 'b_'. */
+int compare_pair(const void *a_, const void *b_) {
+  const pair_t *a = a_;
+  const pair_t *b = b_;
+  if (a->starting <= b->starting) return 1;
+  return 0;
+}
+
+/* First sorts by starting_lba, and traverse everyone once if its starting_lba
+ * is between previous starting_lba and ending_lba. If yes, overlapped.
+ * Returns 1 if overlap is found. */
+int OverlappedEntries(GptEntry *entries, uint32_t number_of_entries) {
+  int i, num_of_pair = 0;
+  for (i = 0; i < number_of_entries; ++i) {
+    if (NonZeroGuid(&entries[i].type)) {
+      pairs[num_of_pair].starting = entries[i].starting_lba;
+      pairs[num_of_pair].ending = entries[i].ending_lba;
+      ++num_of_pair;
+    }
+  }
+  QuickSort(&pairs, num_of_pair, sizeof(pair_t), compare_pair);
+
+  for (i = 1; i < num_of_pair; ++i) {
+    if ((pairs[i].starting >= pairs[i-1].starting) &&
+        (pairs[i].starting <= pairs[i-1].ending))
+      return 1;
+  }
 
-  /* check header signature */
-  if (Memcmp(gpt->primary_header, GPT_HEADER_SIGNATURE,
-                                  GPT_HEADER_SIGNATURE_SIZE))
-    valid_headers[0] = 0;
-  if (Memcmp(gpt->secondary_header, GPT_HEADER_SIGNATURE,
-                                  GPT_HEADER_SIGNATURE_SIZE))
-    valid_headers[1] = 0;
+  return 0;
+}
+
+/* Checks if any two partitions are overlapped in primary and secondary entries.
+ */
+uint32_t CheckOverlappedPartition(GptData *gpt) {
+  uint32_t valid_entries = MASK_BOTH;
+  GptHeader *headers[] = {
+    (GptHeader*)gpt->primary_header,
+    (GptHeader*)gpt->secondary_header,
+  };
+  GptEntry *entries[] = {
+    (GptEntry*)gpt->primary_entries,
+    (GptEntry*)gpt->secondary_entries,
+  };
+  int i;
+
+  for (i = PRIMARY; i <= SECONDARY; ++i) {
+    if (OverlappedEntries(entries[i], headers[i]->number_of_entries))
+      INVALIDATE_ENTRIES(valid_entries, i);
+  }
+  return valid_entries;
+}
+
+/* Primary entries and secondary entries should be bitwise identical.
+ * If two entries tables are valid, compare them. If not the same,
+ * overwrites secondary with primary (primary always has higher priority),
+ * and marks secondary as modified.
+ * If only one is valid, overwrites invalid one.
+ * If all are invalid, does nothing.
+ * This function returns bit masks for GptData.modified field. */
+uint8_t RepairEntries(GptData *gpt, const uint32_t valid_entries) {
+  if (valid_entries == MASK_BOTH) {
+    if (Memcmp(gpt->primary_entries, gpt->secondary_entries,
+               TOTAL_ENTRIES_SIZE)) {
+      Memcpy(gpt->secondary_entries, gpt->primary_entries, TOTAL_ENTRIES_SIZE);
+      return GPT_MODIFIED_ENTRIES2;
+    }
+  } else if (valid_entries == MASK_PRIMARY) {
+    Memcpy(gpt->secondary_entries, gpt->primary_entries, TOTAL_ENTRIES_SIZE);
+    return GPT_MODIFIED_ENTRIES2;
+  } else if (valid_entries == MASK_SECONDARY) {
+    Memcpy(gpt->primary_entries, gpt->secondary_entries, TOTAL_ENTRIES_SIZE);
+    return GPT_MODIFIED_ENTRIES1;
+  }
 
-  if (!valid_headers[0] && !valid_headers[1])
+  return 0;
+}
+
+/* Two headers are NOT bitwise identical. For example, my_lba pointers to header
+ * itself so that my_lba in primary and secondary is definitely different.
+ * Only the following fields should be identical.
+ *
+ *   first_usable_lba
+ *   last_usable_lba
+ *   number_of_entries
+ *   size_of_entry
+ *   disk_uuid
+ *
+ * If any of above field are not matched, overwrite secondary with primary since
+ * we always trust primary.
+ * If any one of header is invalid, copy from another. */
+int IsSynonymous(const GptHeader* a, const GptHeader* b) {
+  if ((a->first_usable_lba == b->first_usable_lba) &&
+      (a->last_usable_lba == b->last_usable_lba) &&
+      (a->number_of_entries == b->number_of_entries) &&
+      (a->size_of_entry == b->size_of_entry) &&
+      (!Memcmp(&a->disk_uuid, &b->disk_uuid, sizeof(Guid))))
+    return 1;
+  return 0;
+}
+
+/* The above five fields are shared between primary and secondary headers.
+ * We can recover one header from another through copying those fields. */
+void CopySynonymousParts(GptHeader* target, const GptHeader* source) {
+  target->first_usable_lba = source->first_usable_lba;
+  target->last_usable_lba = source->last_usable_lba;
+  target->number_of_entries = source->number_of_entries;
+  target->size_of_entry = source->size_of_entry;
+  Memcpy(&target->disk_uuid, &source->disk_uuid, sizeof(Guid));
+}
+
+/* This function repairs primary and secondary headers if possible.
+ * If both headers are valid (CRC32 is correct) but
+ *   a) indicate inconsistent usable LBA ranges,
+ *   b) inconsistent partition entry size and number,
+ *   c) inconsistent disk_uuid,
+ * we will use the primary header to overwrite secondary header.
+ * If primary is invalid (CRC32 is wrong), then we repair it from secondary.
+ * If secondary is invalid (CRC32 is wrong), then we repair it from primary.
+ * This function returns the bitmasks for modified header.
+ * Note that CRC value is not re-computed in this function. UpdateCrc() will
+ * do it later.
+ */
+uint8_t RepairHeader(GptData *gpt, const uint32_t valid_headers) {
+  GptHeader *primary_header, *secondary_header;
+
+  primary_header = (GptHeader*)gpt->primary_header;
+  secondary_header = (GptHeader*)gpt->secondary_header;
+
+  if (valid_headers == MASK_BOTH) {
+    if (!IsSynonymous(primary_header, secondary_header)) {
+      CopySynonymousParts(secondary_header, primary_header);
+      return GPT_MODIFIED_HEADER2;
+    }
+  } else if (valid_headers == MASK_PRIMARY) {
+    Memcpy(secondary_header, primary_header, primary_header->size);
+    secondary_header->my_lba = gpt->drive_sectors - 1;  /* the last sector */
+    secondary_header->entries_lba = secondary_header->my_lba -
+                                    GPT_ENTRIES_SECTORS;
+    return GPT_MODIFIED_HEADER2;
+  } else if (valid_headers == MASK_SECONDARY) {
+    Memcpy(primary_header, secondary_header, secondary_header->size);
+    primary_header->my_lba = GPT_PMBR_SECTOR;  /* the second sector on drive */
+    primary_header->entries_lba = primary_header->my_lba + GPT_HEADER_SECTOR;
+    return GPT_MODIFIED_HEADER1;
+  }
+
+  return 0;
+}
+
+/*  Update CRC value if necessary.  */
+void UpdateCrc(GptData *gpt) {
+  GptHeader *primary_header, *secondary_header;
+
+  primary_header = (GptHeader*)gpt->primary_header;
+  secondary_header = (GptHeader*)gpt->secondary_header;
+
+  if (gpt->modified & GPT_MODIFIED_HEADER1) {
+    primary_header->header_crc32 = 0;
+    primary_header->header_crc32 = Crc32(
+        (const uint8_t *)primary_header, primary_header->size);
+  }
+  if (gpt->modified & GPT_MODIFIED_HEADER2) {
+    secondary_header->header_crc32 = 0;
+    secondary_header->header_crc32 = Crc32(
+        (const uint8_t *)secondary_header, secondary_header->size);
+  }
+  if (gpt->modified & GPT_MODIFIED_ENTRIES1) {
+    primary_header->entries_crc32 =
+        Crc32(gpt->primary_entries, TOTAL_ENTRIES_SIZE);
+  }
+  if (gpt->modified & GPT_MODIFIED_ENTRIES2) {
+    secondary_header->entries_crc32 =
+        Crc32(gpt->secondary_entries, TOTAL_ENTRIES_SIZE);
+  }
+}
+
+/* Does every sanity check, and returns if any header/entries needs to be
+ * written back. */
+int GptInit(GptData *gpt) {
+  uint32_t valid_headers = MASK_BOTH;
+  uint32_t valid_entries = MASK_BOTH;
+  int retval;
+
+  retval = CheckParameters(gpt);
+  if (retval != GPT_SUCCESS)
+    return retval;
+
+  /* Initialize values */
+  gpt->modified = 0;
+
+  /* Start checking if header parameters are valid. */
+  valid_headers &= CheckHeaderSignature(gpt);
+  valid_headers &= CheckRevision(gpt);
+  valid_headers &= CheckSize(gpt);
+  valid_headers &= CheckReservedFields(gpt);
+  valid_headers &= CheckMyLba(gpt);
+  valid_headers &= CheckSizeOfPartitionEntry(gpt);
+  valid_headers &= CheckNumberOfEntries(gpt);
+  valid_headers &= CheckEntriesLba(gpt);
+  valid_headers &= CheckValidUsableLbas(gpt);
+
+  /* Checks if headers are valid. */
+  valid_headers &= CheckHeaderCrc(gpt);
+  gpt->modified |= RepairHeader(gpt, valid_headers);
+
+  /* Checks if entries are valid. */
+  valid_entries &= CheckEntriesCrc(gpt);
+  valid_entries &= CheckValidEntries(gpt);
+  valid_entries &= CheckOverlappedPartition(gpt);
+  gpt->modified |= RepairEntries(gpt, valid_entries);
+
+  /* Returns error if we don't have any valid header/entries to use. */
+  if (!valid_headers)
     return GPT_ERROR_INVALID_HEADERS;
+  if (!valid_entries)
+    return GPT_ERROR_INVALID_ENTRIES;
+
+  UpdateCrc(gpt);
 
+  /* FIXME: will remove the next line soon. */
   gpt->current_kernel = 1;
   return GPT_SUCCESS;
 }
 
-int GptNextKernelEntry(GptData_t *gpt, uint64_t *start_sector, uint64_t *size) {
+/* stub code */
+static int start[] = { 34, 10034 };
+
+int GptNextKernelEntry(GptData *gpt, uint64_t *start_sector, uint64_t *size) {
   /* FIXME: the following code is not really code, just returns anything */
   gpt->current_kernel ^= 1;
   if (start_sector) *start_sector = start[gpt->current_kernel];
@@ -37,7 +544,7 @@ int GptNextKernelEntry(GptData_t *gpt, uint64_t *start_sector, uint64_t *size) {
   return GPT_SUCCESS;
 }
 
-int GptUpdateKernelEntry(GptData_t *gpt, uint32_t update_type) {
+int GptUpdateKernelEntry(GptData *gpt, uint32_t update_type) {
   /* FIXME: the following code is not really code, just return anything */
   gpt->modified |= (GPT_MODIFIED_HEADER1 | GPT_MODIFIED_ENTRIES1) <<
                    gpt->current_kernel;