Bl has another meaning, bootloader. Which is what we often call bl lock. In the embedded operating system, the boot loader runs before the operating system kernel runs. You can initialize hardware devices and establish memory space mapping, so that the software and hardware environment of the system can reach a suitable state and prepare the correct environment for eventually calling the operating system kernel.
Detailed introduction:
In mobile phone maintenance, English abbreviations are commonly used, and different meanings need to be translated because of different positions. The English translation of Apple mobile phone is different from that of Android mobile phone. As long as I keep accumulating, it is very important to master English meaning and understand drawings, which is convenient for me to sort out the working principle of unit circuits.
Cell phone Bl lock is the abbreviation of boot program, and its English name is bootloader. If you don't understand bl, you can't brush into the third-party rom. The official purpose is to protect the stability of your mobile phone and break the bl lock, so that you can't resist the virus invasion.
It mainly checks the system label, kernel signature and recovery signature during the boot process. If the signatures are inconsistent, the boot will be terminated, mainly to limit the role of the user to brush the third-party ROM and the third-party recovery.