firmware/lib/cgptlib/cgptlib_internal.c

/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "cgptlib.h"
#include "cgptlib_internal.h"
#include "crc32.h"
#include "gpt.h"
#include "utility.h"


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 < (1 + 2 * (1 + GPT_ENTRIES_SECTORS)))
    return GPT_ERROR_INVALID_SECTOR_NUMBER;

  return GPT_SUCCESS;
}


uint32_t HeaderCrc(GptHeader* h) {
  uint32_t crc32, original_crc32;

  /* Original CRC is calculated with the CRC field 0. */
  original_crc32 = h->header_crc32;
  h->header_crc32 = 0;
  crc32 = Crc32((const uint8_t *)h, h->size);
  h->header_crc32 = original_crc32;

  return crc32;
}


int CheckHeader(GptHeader *h, int is_secondary, uint64_t drive_sectors) {
  if (!h)
    return 1;

  /* Make sure we're looking at a header of reasonable size before
   * attempting to calculate CRC. */
  if (Memcmp(h->signature, GPT_HEADER_SIGNATURE, GPT_HEADER_SIGNATURE_SIZE))
    return 1;
  if (h->revision != GPT_HEADER_REVISION)
    return 1;
  if (h->size < MIN_SIZE_OF_HEADER || h->size > MAX_SIZE_OF_HEADER)
    return 1;

  /* Check CRC before looking at remaining fields */
  if (HeaderCrc(h) != h->header_crc32)
    return 1;

  /* Reserved fields must be zero. */
  if (h->reserved_zero)
    return 1;

  /* Could check that padding is zero, but that doesn't matter to us. */

  /* If entry size is different than our struct, we won't be able to
   * parse it.  Technically, any size 2^N where N>=7 is valid. */
  if (h->size_of_entry != sizeof(GptEntry))
    return 1;
  if ((h->number_of_entries < MIN_NUMBER_OF_ENTRIES) ||
      (h->number_of_entries > MAX_NUMBER_OF_ENTRIES) ||
      (h->number_of_entries * h->size_of_entry != TOTAL_ENTRIES_SIZE))
    return 1;

  /* Check locations for the header and its entries.  The primary
   * immediately follows the PMBR, and is followed by its entries.
   * The secondary is at the end of the drive, preceded by its
   * entries. */
  if (is_secondary) {
    if (h->my_lba != drive_sectors - 1)
      return 1;
    if (h->entries_lba != h->my_lba - GPT_ENTRIES_SECTORS)
      return 1;
  } else {
    if (h->my_lba != 1)
      return 1;
    if (h->entries_lba != h->my_lba + 1)
      return 1;
  }

  /* 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. */
  if (h->first_usable_lba < 2 + GPT_ENTRIES_SECTORS)
    return 1;
  if (h->last_usable_lba >= drive_sectors - 1 - GPT_ENTRIES_SECTORS)
    return 1;
  if (h->first_usable_lba > h->last_usable_lba)
    return 1;

  /* Success */
  return 0;
}


/* Return non-zero if the entry is unused, 0 if it is used. */
int IsUnusedEntry(const GptEntry* e) {
  static Guid zero = {{{0, 0, 0, 0, 0, {0, 0, 0, 0, 0, 0}}}};
  return !Memcmp(&zero, (const uint8_t*)(&e->type), sizeof(zero));
}

/* Returns non-zero if the entry is a Chrome OS kernel partition, else 0. */
int IsKernelEntry(const GptEntry* e) {
  static Guid chromeos_kernel = GPT_ENT_TYPE_CHROMEOS_KERNEL;
  return !Memcmp(&e->type, &chromeos_kernel, sizeof(Guid));
}


int CheckEntries(GptEntry* entries, GptHeader* h) {

  GptEntry* entry;
  uint32_t crc32;
  uint32_t i;

  /* Check CRC before examining entries. */
  crc32 = Crc32((const uint8_t *)entries,
                h->size_of_entry * h->number_of_entries);
  if (crc32 != h->entries_crc32)
    return 1;

  /* Check all entries. */
  for (i = 0, entry = entries; i < h->number_of_entries; i++, entry++) {
    GptEntry* e2;
    uint32_t i2;

    if (IsUnusedEntry(entry))
      continue;

    /* Entry must be in valid region. */
    if ((entry->starting_lba < h->first_usable_lba) ||
        (entry->ending_lba > h->last_usable_lba) ||
        (entry->ending_lba < entry->starting_lba))
      return 1;

    /* Entry must not overlap other entries. */
    for (i2 = 0, e2 = entries; i2 < h->number_of_entries; i2++, e2++) {
      if (i2 == i || IsUnusedEntry(e2))
        continue;

      if ((entry->starting_lba >= e2->starting_lba) &&
          (entry->starting_lba <= e2->ending_lba))
        return 1;
      if ((entry->ending_lba >= e2->starting_lba) &&
          (entry->ending_lba <= e2->ending_lba))
        return 1;

      /* UniqueGuid field must be unique. */
      if (0 == Memcmp(&entry->unique, &e2->unique, sizeof(Guid)))
        return 1;
    }
  }

  /* Success */
  return 0;
}


/* Returns 0 if the GptHeaders are the same for all fields which don't
 * differ between the primary and secondary headers - that is, all
 * fields other than:
 *
 * my_lba
 * alternate_lba
 * entries_lba */
int HeaderFieldsSame(GptHeader *h1, GptHeader *h2) {
  if (Memcmp(h1->signature, h2->signature, sizeof(h1->signature)))
    return 1;
  if (h1->revision != h2->revision)
    return 1;
  if (h1->size != h2->size)
    return 1;
  if (h1->reserved_zero != h2->reserved_zero)
    return 1;
  if (h1->first_usable_lba != h2->first_usable_lba)
    return 1;
  if (h1->last_usable_lba != h2->last_usable_lba)
    return 1;
  if (Memcmp(&h1->disk_uuid, &h2->disk_uuid, sizeof(Guid)))
    return 1;
  if (h1->number_of_entries != h2->number_of_entries)
    return 1;
  if (h1->size_of_entry != h2->size_of_entry)
    return 1;
  if (h1->entries_crc32 != h2->entries_crc32)
    return 1;

  return 0;
}


int GptSanityCheck(GptData *gpt) {
  int retval;
  GptHeader* header1 = (GptHeader*)(gpt->primary_header);
  GptHeader* header2 = (GptHeader*)(gpt->secondary_header);
  GptEntry* entries1 = (GptEntry*)(gpt->primary_entries);
  GptEntry* entries2 = (GptEntry*)(gpt->secondary_entries);
  GptHeader* goodhdr = NULL;

  gpt->valid_headers = 0;
  gpt->valid_entries = 0;

  retval = CheckParameters(gpt);
  if (retval != GPT_SUCCESS)
    return retval;

  /* Check both headers; we need at least one valid header. */
  if (0 == CheckHeader(header1, 0, gpt->drive_sectors)) {
    gpt->valid_headers |= MASK_PRIMARY;
    goodhdr = header1;
  }
  if (0 == CheckHeader(header2, 1, gpt->drive_sectors)) {
    gpt->valid_headers |= MASK_SECONDARY;
    if (!goodhdr)
      goodhdr = header2;
  }

  if (!gpt->valid_headers)
    return GPT_ERROR_INVALID_HEADERS;

  /* Checks if entries are valid.
   *
   * Note that we use the same header in both checks.  This way we'll
   * catch the case where (header1,entries1) and (header2,entries2)
   * are both valid, but (entries1 != entries2). */
  if (0 == CheckEntries(entries1, goodhdr))
    gpt->valid_entries |= MASK_PRIMARY;
  if (0 == CheckEntries(entries2, goodhdr))
    gpt->valid_entries |= MASK_SECONDARY;

  /* If both headers are good but neither entries were good, check the
   * entries with the secondary header. */
  if (MASK_BOTH == gpt->valid_headers && !gpt->valid_entries) {
    if (0 == CheckEntries(entries1, header2))
      gpt->valid_entries |= MASK_PRIMARY;
    if (0 == CheckEntries(entries2, header2))
      gpt->valid_entries |= MASK_SECONDARY;
    if (gpt->valid_entries) {
      /* Sure enough, header2 had a good CRC for one of the entries.  Mark
       * header1 invalid, so we'll update its entries CRC. */
      gpt->valid_headers &= ~MASK_PRIMARY;
      goodhdr = header2;
    }
  }

  if (!gpt->valid_entries)
    return GPT_ERROR_INVALID_ENTRIES;

  /* Now that we've determined which header contains a good CRC for
   * the entries, make sure the headers are otherwise identical. */
  if (MASK_BOTH == gpt->valid_headers &&
      0 != HeaderFieldsSame(header1, header2))
    gpt->valid_headers &= ~MASK_SECONDARY;

  return GPT_SUCCESS;
}


void GptRepair(GptData *gpt) {
  GptHeader* header1 = (GptHeader*)(gpt->primary_header);
  GptHeader* header2 = (GptHeader*)(gpt->secondary_header);
  GptEntry* entries1 = (GptEntry*)(gpt->primary_entries);
  GptEntry* entries2 = (GptEntry*)(gpt->secondary_entries);
  int entries_size;

  /* Need at least one good header and one good set of entries. */
  if (MASK_NONE == gpt->valid_headers || MASK_NONE == gpt->valid_entries)
    return;

  /* Repair headers if necessary */
  if (MASK_PRIMARY == gpt->valid_headers) {
    /* Primary is good, secondary is bad */
    Memcpy(header2, header1, sizeof(GptHeader));
    header2->my_lba = gpt->drive_sectors - 1;
    header2->alternate_lba = 1;
    header2->entries_lba = header2->my_lba - GPT_ENTRIES_SECTORS;
    header2->header_crc32 = HeaderCrc(header2);
    gpt->modified |= GPT_MODIFIED_HEADER2;
  }
  else if (MASK_SECONDARY == gpt->valid_headers) {
    /* Secondary is good, primary is bad */
    Memcpy(header1, header2, sizeof(GptHeader));
    header1->my_lba = 1;
    header1->alternate_lba = gpt->drive_sectors - 1;
    header1->entries_lba = header1->my_lba + 1;
    header1->header_crc32 = HeaderCrc(header1);
    gpt->modified |= GPT_MODIFIED_HEADER1;
  }
  gpt->valid_headers = MASK_BOTH;

  /* Repair entries if necessary */
  entries_size = header1->size_of_entry * header1->number_of_entries;
  if (MASK_PRIMARY == gpt->valid_entries) {
    /* Primary is good, secondary is bad */
    Memcpy(entries2, entries1, entries_size);
    gpt->modified |= GPT_MODIFIED_ENTRIES2;
  }
  else if (MASK_SECONDARY == gpt->valid_entries) {
    /* Secondary is good, primary is bad */
    Memcpy(entries1, entries2, entries_size);
    gpt->modified |= GPT_MODIFIED_ENTRIES1;
  }
  gpt->valid_entries = MASK_BOTH;
}


int GetEntrySuccessful(const GptEntry* e) {
  return (e->attrs.fields.gpt_att & CGPT_ATTRIBUTE_SUCCESSFUL_MASK) >>
      CGPT_ATTRIBUTE_SUCCESSFUL_OFFSET;
}


int GetEntryPriority(const GptEntry* e) {
  return (e->attrs.fields.gpt_att & CGPT_ATTRIBUTE_PRIORITY_MASK) >>
      CGPT_ATTRIBUTE_PRIORITY_OFFSET;
}


int GetEntryTries(const GptEntry* e) {
  return (e->attrs.fields.gpt_att & CGPT_ATTRIBUTE_TRIES_MASK) >>
      CGPT_ATTRIBUTE_TRIES_OFFSET;
}


void SetEntrySuccessful(GptEntry* e, int successful) {
  if (successful)
    e->attrs.fields.gpt_att |= CGPT_ATTRIBUTE_SUCCESSFUL_MASK;
  else
    e->attrs.fields.gpt_att &= ~CGPT_ATTRIBUTE_SUCCESSFUL_MASK;
}


void SetEntryPriority(GptEntry* e, int priority) {
  e->attrs.fields.gpt_att &= ~CGPT_ATTRIBUTE_PRIORITY_MASK;
  e->attrs.fields.gpt_att |= (priority << CGPT_ATTRIBUTE_PRIORITY_OFFSET) &
      CGPT_ATTRIBUTE_PRIORITY_MASK;
}


void SetEntryTries(GptEntry* e, int tries) {
  e->attrs.fields.gpt_att &= ~CGPT_ATTRIBUTE_TRIES_MASK;
  e->attrs.fields.gpt_att |= (tries << CGPT_ATTRIBUTE_TRIES_OFFSET) &
      CGPT_ATTRIBUTE_TRIES_MASK;
}

void GetCurrentKernelUniqueGuid(GptData *gpt, void *dest) {
  GptEntry* entries = (GptEntry*)gpt->primary_entries;
  GptEntry* e = entries + gpt->current_kernel;
  Memcpy(dest, &e->unique, sizeof(Guid));
}