![]() Understanding this script is very important to know how boot-loader and kernel are composed and how different sections of boot-loader or kernel are loaded in the memory. This script tells where all the sections are to be loaded in the memory when it runs. All the sections of the object files will be arranged in the executable file based on a script called linker script. Object files and executable files have a file format like elf. An object file or executable file is a collection of sections like. All these object files are linked by linker and an executable file will be created. You can download U-boot from the following site.īased on the configuration of U-boot, all the assembly files (.S) and C files (.c) are compiled using cross compiler which is built for a particular architecture and object files(.o) will be generated. I will explain code from the u-boot-2017.01 source. U-boot is the widely used boot-loader in embedded systems. Some of them are Das U-Boot, Red boot, GRUB (for desktops), LILO, Loadlin,, bootsect-loader, SYSLINUX, EtherBoot, ELILO. ![]() There are a quite few third party boot-loader available and some of them are open source (or free boot-loaders) and some are commercial. Generally boot-loaders provided by board vendors are replaced with these third party boot-loader. You can download these third party boot-loaders into board and can make them default boot-loaders for your board. There are some other third party boot-loaders available which provide rich set of features and easy user interface. In other cases such interfaces could be created by software running in integrated on-chip boot ROM from GPIO pins. In many cases such interfaces are implemented by hardwired logic. After system reset, the micro-controller begins to execute code programmed into its non-volatile memory, just like usual processors are using ROM’s for booting. Then at the manufacturing phase, such interfaces are used to inject boot code (and possibly other code) into non-volatile memory. Some micro-controllers provide special hardware interfaces which can’t be used to take arbitrary control of a system or directly run code, but instead they allow the insertion of boot code into boot-able non-volatile memory (like flash memory) via simple protocols. J TAG is a standard and popular interface provided by many board vendors. Generally done for first time to download the basic boot-loader and for some recovery process. flash) by instructing the processor core to perform the necessary actions to program non-volatile memory. This interface may be used to write the boot loader program into boo-table non-volatile memory (e.g. It is also possible to control the system using a hardware debug interface such as J TAG. Basically it will have some minimal features to load the image and boot it up. Boot-loader will be executed when power is applied to a processor board. Every embedded board comes with a bootstrap to download the kernel image or standalone application into the board and start executing the kernel image or application. Since it should initialize the cpu and should run a program which is located at architecture specific address boot-loaders are highly processor specific and board specific. ![]() ![]() Hardware designers use this information to store the boot-loader code at that address in ROM or flash. Most processors have a default address from which the first bytes of code are fetched upon power is applied or board is reset. ![]() Boot-loader starts before any other software starts and initializes the processor and makes CPU ready to execute a program like an operating system. This is also called bootstrap as it brings(pulls) up system by loading an operating system. Linux boot sequence involves execution of the following components.Ī boot-loader is a small program which will load the kernel image into RAM and boots up the kernel image. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |