Source Tree Structure
SBL source code is organized into common and platform specific folders:
|<source>/ |-- BuildLoader.py |-- BootloaderCommonPkg/ |-- BootloaderCorePkg/ | |-- Stage1A/ | |-- Stage1B/ | |-- Stage2/ | `-- Tools/ |-- PayloadPkg/ | |-- OsLoader/ | `-- FirmwareUpdate/ |-- Platform/ `-- Silicon/
Here’s a brief description of each of these folders:
Top-level build script. Performs tool chain setup, pre-build, configuration, compilation and post-build steps.
Common libraries for all stages of boot flow
Stage1A code initializes platform from reset vector till Cache-As-RAM (CAR) is setup. It then transfers control to Stage1B.
It invokes FSP-T.
Stage1B code initializes platform from CAR to the point system memory is fully initialized. It then transfers control to Stage2.
It invokes FSP-M.
Stage2 code performs additional platform initialization and transfers control to payload.
It invokes FSP-S.
Contains helper and common scripts for build and configuration during build process
Contains files that implement OS boot logic from boot media.
Contains files that implement platform-independent logic to perform firmware update flow instead of booting OS.
Board specific code for a supported platform.
Silicon specific code for a supported SoC.
SBL source tree contains multiple packages (subdirectories) that are organized in a manner to provide modularity and ease of use when extending new features or porting for a new board. The following rules shall be followed when one makes code changes:
PayloadPkgare mutually exclusive. They should not have code dependency to one or the other.
PayloadPkgshould not have dependency to code under
PayloadPkgshould only depends on libraries in
The source tree is organized as core, silicon and platform. A typical platform porting requires code change only in the platform directories.