U boot secure boot drivers#
U boot secure boot software#
U boot secure boot code#

U-Boot is commonly used as a bootloader in embedded software and it is the one used on STM32MP13. The bootloader stage 2, so called TF-A BL2, is the Trusted Firmware-A (TF-A) binary used as FSBL on STM32MP13.Ģ.2.4 Second stage bootloader ( SSBL) Finally, the FSBL loads the second-stage bootloader ( SSBL) into the DDR external RAM and jumps to it. It supports the FSBL authentication and decryption.Ģ.2.3 First stage bootloader ( FSBL) Īmong other things, this bootloader initializes (part of) the clock tree and the DDR controller.

U boot secure boot code#

The ROM code starts the processor in secure mode.

U boot secure boot drivers#

The Linux kernel is started in the external memory and it initializes all the peripheral drivers that are needed on the platform.įinally, the Linux kernel hands control to the user space starting the init process that runs all initialization actions described in the root file system (rootfs), including the application framework that exposes the user interface ( UI) to the user. U-Boot is commonly used as a Linux bootloader in embedded systems. The second-stage bootloader ( SSBL) runs in a wide RAM so it can implement complex features (such as, USB, Ethernet, display), that are very useful to make Linux kernel loading more flexible (from a storage device on USB or on a network), and user-friendly (by showing a splash screen to the user). The Trusted Firmware-A (TF-A) and U-Boot secondary program loader ( U-Boot SPL) are two possible FSBLs.ġ.1.3 Second-stage bootloader ( SSBL) Finally, the FSBL loads the second-stage bootloader ( SSBL) into the external RAM and jumps to it. In turn, the FSBL and each following component authenticates the next one, up to a level defined by the product manufacturer.ġ.1.2 First stage bootloader ( FSBL) Īmong other things, the first stage bootloader ( FSBL) initializes (part of) the clock tree and the external RAM controller. Most products require to trust the application that is running on the device and the ROM code is the first link in the chain of trust that must be established across all started components: this trust is established by authenticating the FSBL before starting it. It is the first code executed by the processor, and it embeds all the logic needed to select the boot device (serial link or flash) from which the first-stage bootloader ( FSBL) is loaded to the embedded RAM. It fits in a few tens of Kbytes and maps its data in embedded RAM. The ROM code is a piece of software that takes its name from the read only memory ( ROM) where it is stored. These steps areĮxplained in the following paragraphs and illustrated by the diagram on the right, which also gives typical memory sizes for each stage. Starting Linux ® on a processor is done in several steps that progressively initialize the platform peripherals and memories. 1 Generic boot sequence 1.1 Linux start-up