verity/dm-bht-userspace.cc

/*
 * Copyright (C) 2011 The Chromium OS Authors <chromium-os-dev@chromium.org>
 *
 * Device-Mapper block hash tree interface.
 *
 * This file is released under the GPL.
 */

// NOLINTNEXTLINE(build/include)
#include <errno.h>
#include <string.h>

#include <base/logging.h>

#include "verity/dm-bht.h"

#define DM_MSG_PREFIX "dm bht"

namespace verity {

void dm_bht_set_buffer(struct dm_bht* bht, void* buffer) {
  int depth;
  /* Buffers are externally allocated, so mark them as such. */
  bht->externally_allocated = true;

  auto buffer_p = static_cast<uint8_t*>(buffer);
  for (depth = 0; depth < bht->depth; ++depth) {
    struct dm_bht_level* level = dm_bht_get_level(bht, depth);
    struct dm_bht_entry* entry_end = level->entries + level->count;
    struct dm_bht_entry* entry;

    for (entry = level->entries; entry < entry_end; ++entry) {
      entry->nodes = buffer_p;
      memset(buffer_p, 0, PAGE_SIZE);
      buffer_p += PAGE_SIZE;
    }
  }
}

/**
 * dm_bht_compute - computes and updates all non-block-level hashes in a tree
 * @bht: pointer to a dm_bht_create()d bht
 *
 * Returns 0 on success, >0 when data is pending, and <0 when a IO or other
 * error has occurred.
 *
 * Walks the tree and computes the hashes at each level from the
 * hashes below.
 */
int dm_bht_compute(struct dm_bht* bht) {
  int depth, r = 0;

  for (depth = bht->depth - 2; depth >= 0; depth--) {
    struct dm_bht_level* level = dm_bht_get_level(bht, depth);
    struct dm_bht_level* child_level = level + 1;
    struct dm_bht_entry* entry = level->entries;
    struct dm_bht_entry* child = child_level->entries;
    unsigned int i, j;

    for (i = 0; i < level->count; i++, entry++) {
      unsigned int count = bht->node_count;

      memset(entry->nodes, 0, PAGE_SIZE);
      entry->state = DM_BHT_ENTRY_READY;

      if (i == (level->count - 1))
        count = child_level->count % bht->node_count;
      if (count == 0)
        count = bht->node_count;
      for (j = 0; j < count; j++, child++) {
        uint8_t* digest = dm_bht_node(bht, entry, j);

        r = dm_bht_compute_hash(bht, child->nodes, digest);
        if (r) {
          DLOG(ERROR) << "Failed to update (d=" << depth << ",i=" << i << ")";
          goto out;
        }
      }
    }
  }
  r = dm_bht_compute_hash(bht, bht->levels[0].entries->nodes, bht->root_digest);
  if (r)
    DLOG(ERROR) << "Failed to update root hash";

out:
  return r;
}

/**
 * dm_bht_store_block - sets a given block's hash in the tree
 * @bht: pointer to a dm_bht_create()d bht
 * @block: numeric index of the block in the tree
 * @block_data: array of uint8_ts containing the block of data to hash
 *
 * Returns 0 on success.
 *
 * If the containing entry in the tree is unallocated, it will allocate memory
 * and mark the entry as ready.  All other block entries will be 0s.
 *
 * It is up to the users of the update interface to ensure the entry data is
 * fully populated prior to use. The number of updated entries is NOT tracked.
 */
int dm_bht_store_block(struct dm_bht* bht,
                       unsigned int block,
                       uint8_t* block_data) {
  int depth = bht->depth;
  struct dm_bht_entry* entry = dm_bht_get_entry(bht, depth - 1, block);
  uint8_t* node = dm_bht_get_node(bht, entry, depth, block);

  return dm_bht_compute_hash(bht, block_data, node);
}

}  // namespace verity