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* Copyright (C) 2008 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <assert.h>
/* Bootloader Message (2-KiB)
* This structure describes the content of a block in flash
* that is used for recovery and the bootloader to talk to
* each other.
* The command field is updated by linux when it wants to
* reboot into recovery or to update radio or bootloader firmware.
* It is also updated by the bootloader when firmware update
* is complete (to boot into recovery for any final cleanup)
* The status field is written by the bootloader after the
* completion of an "update-radio" or "update-hboot" command.
* The recovery field is only written by linux and used
* for the system to send a message to recovery or the
* other way around.
* The stage field is written by packages which restart themselves
* multiple times, so that the UI can reflect which invocation of the
* package it is. If the value is of the format "#/#" (eg, "1/3"),
* the UI will add a simple indicator of that status.
* We used to have slot_suffix field for A/B boot control metadata in
* this struct, which gets unintentionally cleared by recovery or
* uncrypt. Move it into struct bootloader_message_ab to avoid the
* issue.
struct bootloader_message {
char command[32];
char status[32];
char recovery[768];
// The 'recovery' field used to be 1024 bytes. It has only ever
// been used to store the recovery command line, so 768 bytes
// should be plenty. We carve off the last 256 bytes to store the
// stage string (for multistage packages) and possible future
// expansion.
char stage[32];
// The 'reserved' field used to be 224 bytes when it was initially
// carved off from the 1024-byte recovery field. Bump it up to
// 1184-byte so that the entire bootloader_message struct rounds up
// to 2048-byte.
char reserved[1184];
* We must be cautious when changing the bootloader_message struct size,
* because A/B-specific fields may end up with different offsets.
#if (__STDC_VERSION__ >= 201112L) || defined(__cplusplus)
static_assert(sizeof(struct bootloader_message) == 2048,
"struct bootloader_message size changes, which may break A/B devices");
* The A/B-specific bootloader message structure (4-KiB).
* We separate A/B boot control metadata from the regular bootloader
* message struct and keep it here. Everything that's A/B-specific
* stays after struct bootloader_message, which should be managed by
* the A/B-bootloader or boot control HAL.
* The slot_suffix field is used for A/B implementations where the
* bootloader does not set the kernel
* commandline parameter. This is used by fs_mgr to mount /system and
* other partitions with the slotselect flag set in fstab. A/B
* implementations are free to use all 32 bytes and may store private
* data past the first NUL-byte in this field. It is encouraged, but
* not mandatory, to use 'struct bootloader_control' described below.
struct bootloader_message_ab {
struct bootloader_message message;
char slot_suffix[32];
// Round up the entire struct to 4096-byte.
char reserved[2016];
* Be cautious about the struct size change, in case we put anything post
* bootloader_message_ab struct (b/29159185).
#if (__STDC_VERSION__ >= 201112L) || defined(__cplusplus)
static_assert(sizeof(struct bootloader_message_ab) == 4096,
"struct bootloader_message_ab size changes");
#define BOOT_CTRL_MAGIC 0x42414342 /* Bootloader Control AB */
struct slot_metadata {
// Slot priority with 15 meaning highest priority, 1 lowest
// priority and 0 the slot is unbootable.
uint8_t priority : 4;
// Number of times left attempting to boot this slot.
uint8_t tries_remaining : 3;
// 1 if this slot has booted successfully, 0 otherwise.
uint8_t successful_boot : 1;
// 1 if this slot is corrupted from a dm-verity corruption, 0
// otherwise.
uint8_t verity_corrupted : 1;
// Reserved for further use.
uint8_t reserved : 7;
} __attribute__((packed));
/* Bootloader Control AB
* This struct can be used to manage A/B metadata. It is designed to
* be put in the 'slot_suffix' field of the 'bootloader_message'
* structure described above. It is encouraged to use the
* 'bootloader_control' structure to store the A/B metadata, but not
* mandatory.
struct bootloader_control {
// NUL terminated active slot suffix.
char slot_suffix[4];
// Bootloader Control AB magic number (see BOOT_CTRL_MAGIC).
uint32_t magic;
// Version of struct being used (see BOOT_CTRL_VERSION).
uint8_t version;
// Number of slots being managed.
uint8_t nb_slot : 3;
// Number of times left attempting to boot recovery.
uint8_t recovery_tries_remaining : 3;
// Ensure 4-bytes alignment for slot_info field.
uint8_t reserved0[2];
// Per-slot information. Up to 4 slots.
struct slot_metadata slot_info[4];
// Reserved for further use.
uint8_t reserved1[8];
// CRC32 of all 28 bytes preceding this field (little endian
// format).
uint32_t crc32_le;
} __attribute__((packed));
#if (__STDC_VERSION__ >= 201112L) || defined(__cplusplus)
static_assert(sizeof(struct bootloader_control) ==
sizeof(((struct bootloader_message_ab *)0)->slot_suffix),
"struct bootloader_control has wrong size");
/* Read and write the bootloader command from the "misc" partition.
* These return zero on success.
int get_bootloader_message(struct bootloader_message *out);
int set_bootloader_message(const struct bootloader_message *in);