src/lib/storage/vfs/cpp/journal/initializer.cc

// Copyright 2019 The Fuchsia 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 "src/lib/storage/vfs/cpp/journal/initializer.h"

#include <lib/cksum.h>
#include <sys/mman.h>
#include <zircon/errors.h>

#include "src/lib/storage/vfs/cpp/journal/format.h"

namespace fs {
namespace {

void InitJournalBlock(cpp20::span<uint8_t> block) {
  memset(block.data(), 0, block.size());
  JournalInfo* info = reinterpret_cast<JournalInfo*>(block.data());
  info->magic = kJournalMagic;

#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
  info->checksum = 0;
#else
  // TODO(fxbug.dev/42698): This checksum should be on entire block and not just JournalInfo.
  info->checksum = crc32(0, block.data(), sizeof(fs::JournalInfo));
#endif
}

}  // namespace

zx_status_t MakeJournal(uint64_t journal_blocks, const WriteBlocksFn& WriteBlocks) {
  uint8_t block[kJournalBlockSize];
  cpp20::span<uint8_t> buffer(block, sizeof(block));
  InitJournalBlock(buffer);

  auto status = WriteBlocks(buffer, 0, 1);
  if (status != ZX_OK) {
    return status;
  }

  // If number of journal metadata blocks change, we need to clear/initialize those blocks. This
  // compile-time assert prevents having uninitialized metadata blocks.
  static_assert(fs::kJournalMetadataBlocks == 1, "Uninitialized blocks in journal");

  // Clear the journal from disk.
  uint64_t block_count = journal_blocks - kJournalMetadataBlocks;
  size_t map_length = kJournalBlockSize * block_count;
  void* blocks = mmap(nullptr, map_length, PROT_READ, MAP_PRIVATE | MAP_ANON, -1, 0);
  if (blocks == MAP_FAILED) {
    return ZX_ERR_NO_MEMORY;
  }

  cpp20::span<const uint8_t> buffers(static_cast<const uint8_t*>(blocks), map_length);
  status = WriteBlocks(buffers, kJournalMetadataBlocks, block_count);

  if (munmap(blocks, map_length) != 0) {
    return ZX_ERR_NO_MEMORY;
  }

  return status;
}

}  // namespace fs