misc_image_layout.md

/misc partition layout

-	-	-	Size	description	Offset
Legacy	bootloader_message		(2K)		--> 0
		command	32	updated by linux/bootloader
		status	32	deprecated
		recovery	768	talking channel between normal/recovery modes
		stage	32	format "#/#", eg, "1/3"
		reserved	1184
-	-	-	-	-
Vendor Area	vendor bootloader msg	N/A	2K	Vendor Area	-->2KB
	vendor bootloader msg	N/A	12K	pure Vendor area	-->4KB
-	-	-	-	-
Wipe	wipe_package info		16K	offset 16KB, Used by uncrypt and recovery to store wipe_package for A/B devices	-->16KB
-	-	-	-	-
System	system_space -> 1 misc_virtual_ab_message		(64)		-->32KB
		version	1
		magic	4
		merge_status	1
		source_slot	1
		reserved	57

vendor area implementation example from Google:

bootctrl.default.so (link libboot_control.a)貌似没人用

使用legacy_boot_control.cpp, 把libboot_control.a的实现的类android::bootable::BootControl包装进去

android.hardware.boot@1.1-impl

使用BootControl.cpp

android::hardware::boot::V1_1::implementation::BootControl

直接使用"android::bootable::BootControl"的实现

libboot_control.a

code location:

hardware/interfaces/boot/1.1/default/boot_control

https://android.googlesource.com/platform/hardware/interfaces/+/refs/heads/master/boot/1.1/default/boot_control/

-	-	-	Offset	Size	description
Vendor Area	bootloader_message_ab		2K	(2K)	Vendor Area
		slot_suffix		32
		update_channel		128
		reserved		1888

32 BYTES "slot_suffix" part details:

-	-	-	Offset	Size	description
	bootloader_control			(32)
		slot_suffix		4
		magic		4
		version		1
		nb_slot		3bits	number slots
		recovery_tries_remaining		3bits
		merge_status		3bits
		reserved0		1
		slot_info		8	slot_metadata * 4
		reverved1		8
		crc32_le		4
	slot_metadata			(2)
		priority		4bits
		tries_remaining		3bits
		successful_boot		1bit
		verity_corrupted		1bit
		reserved		7bits