1. Boot stage

　　BL1,BL2,BL31,BL32,BL33

2. Exception level

　　EL3, EL1S, EL2

3. 那么放在表格里比较一下咯

Boot stage

Exception level

Description

BL1

EL3

Boot ROM firmware (这一段程序由硬件完成，无法修改)

Note: BL1 is embedded in hardware (Boot ROM + PBL commands)

BL2

EL3

Platform initialization firmware(平台初始化固件)

BL31

EL3

Resident runtime firmware

BL32

EL1S

[Optional] Trusted operating system. For example, OP-TEE

BL33

EL2

Normal world bootloader. For example, U-Boot, UEFI