Android Booting Process

• Reference: Android bootloader/fastboot mode and recovery mode explained/Android boot process
• Reference: Booting Android

One Image Per Day

To add to what Android bootloader/fastboot mode and recovery mode explained/Android boot process has provided, I want to give some more details from Bootloader of normal boot to Kernel.

1. Bootloader of normal boot / PBL (primary bootloader)

   The program is saved inside and run by the CPU and provided by the CPU manufacturer. It cannot be customized by a developer.

2. SBL (Secondary Bootloader)

   Normally it is provided by the device manufacture / OEM. While Primary boot loader doesn't mean the first stage of a boot loader, and secondary boot loader doesn't mean the second stage of a boot loader.

   primary and secondary boot loaders

3. RPM (Resource & Power Manager)

   Normally it is provided by the device manufacture / OEM.

4. TZ (Trust Zone)

   Hardware-backed Keystore
   Trusty

5. LK (Little Kernel)

   • init hardware module
   • update cmdline and distinguish the startup mode
   • select and update device tree
   • setup system status and prepare to init the Kernel
   • fastboot
   • authorization

6. Kernel