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// 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.
#pragma once
#include <zircon/compiler.h>
#include <zircon/types.h>
namespace abr {
// Magic for the A/B struct when serialized.
constexpr char kMagic[] = "\0AB0";
constexpr size_t kMagicLen = 4;
// Versioning for the on-disk A/B metadata.
constexpr size_t kMajorVersion = 2;
constexpr size_t kMinorVersion = 0;
// Maximum values for slot data.
constexpr uint8_t kMaxPriority = 15;
constexpr uint8_t kMaxTriesRemaining = 7;
// Struct used for recording per-slot metadata.
struct SlotData {
// Slot priority. Valid values range from 0 to kMaxPriority,
// both inclusive with 1 being the lowest and kMaxPriority
// being the highest. The special value 0 is used to indicate the
// slot is unbootable.
uint8_t priority;
// Number of remaining attempts to boot this slot ranging from 0
// to kMaxTriesRemaining.
uint8_t tries_remaining;
// Non-zero if this slot has booted successfully, 0 otherwise.
uint8_t successful_boot;
// Reserved for future use.
uint8_t reserved[1];
// Struct used for recording A/B/R metadata.
// When serialized, data is stored in network byte-order.
struct Data {
// Magic number used for identification - see kMagic.
uint8_t magic[kMagicLen];
// Version of on-disk struct - see k{Major,Minor}Version.
uint8_t version_major;
uint8_t version_minor;
// Padding to ensure |slots| field start eight bytes in.
uint8_t reserved1[2];
// A/B per-slot metadata. Recovery boot does not have its own
// data and will be used if both A/B slots are not bootable
SlotData slots[2];
// Oneshot force recovery boot. Currently unused.
uint8_t oneshot_recovery_boot;
// Reserved for future use.
uint8_t reserved2[11];
// CRC32 of all 28 bytes preceding this field.
uint32_t crc32;
static_assert(sizeof(Data) == 32);
// Interface for interacting with ABR data.
class Client {
virtual ~Client() = default;
// Accessor for underlying Data structure.
virtual const abr::Data& Data() const = 0;
// Persists data to storage. May not do anything if data is unchanged.
virtual zx_status_t Persist(abr::Data data) = 0;
// Validates that the ABR metadata is valid.
bool IsValid() const;
// Updates CRC stored inside of data.
static void UpdateCrc(abr::Data* data);
} // namespace abr