Building Embedded Linux

Learn To Be Embedded Linux Training

Embedded Linux TrainingFacebook group: Learn To BeOfficial website: www.L2b-egypt.org

Prepared By: SHATRIX E-Mail: [email protected]

2


Overview•Embedded Linux is the use of Linux in embedded

computer systems such as mobile phones, personal digital assistants, media players, set-top boxes, networking equipment, machine control, industrial automation, navigation equipment and medical instruments.

•Creating an Embedded Linux based system is like a puzzle. Putting the right pieces together will create the final image.

3


Basic embedded Linux arch.•Boot Loader (grub, Lilo, Uboot)•Kernel (Normal or Real-Time)•FileSystem•C Library•User application(s)

4


Host & Target

Croos-PlatformToolchain

GCC

Host

BootLoaderKernel

FilesystemLibraries

Applications

Target

5


To Do List• Cross compilation toolchain▫ Compiler that runs on the development machine, but generates

binary files for the target machine• Bootloader▫ Started by the hardware, responsible for basic initialization, loading

and executing the kernel• Linux Kernel▫ Contains the process and memory management, network stack,

device drivers and provides services to userspace applications• C library▫ The interface between the kernel and the userspace applications

• Filesystem▫ Contains Linux commands, libraries and other needed scripts

• Other libraries and applications

6


What's next?•System integration▫Integrate all the components, bootloader, kernel, third

party libraries and applications and our applications into a working system

•Development of applications▫Normal Linux applications, but using specifically chosen

libraries

7


Root filesystem•The root filesystem, is mounted as /•On embedded systems, this root

filesystem contains all the libraries, applications and data of the system

•Therefore, building the root filesystem is one of the main tasks of integrating embedded Linux components into a device

•The kernel is usually kept separate

BootLoader

Kernel

RootFilesystem

System Contents

8


Cross-compiling Toolchain• The usual development tools available on a GNU/Linux

workstation is a native toolchain• This toolchain runs on your workstation and generates code

for your workstation, usually x86• For embedded system development, it is usually impossible

or not interesting to use a native toolchain▫The target is too restricted in terms of storage and/or memory▫The target is very slow compared to your workstation▫You may not want to install all development tools on your

target.• Therefore, cross compiling toolchains are generally used.

They run on your workstation but generate code for your target.

9


Cross-compiling Toolchain

X86 Binary Target Binary

X86

X86 Target CPU

Source Code

Native Toolchain Cross Toolchain

10


Cross Toolchain components• Binutils is a set of tools to generate and manipulate

binaries for a given CPU architecture▫as, ld, ar, ranlib, strip▫http://www.gnu.org/software/binutils/

• Kernel headers▫Available system calls and their numbers, Constant

definitions, Data structures.• C/C++ libraries▫ Interface between the applications and the kernel▫glibc, uClibc

•GCC compiler•GDB debugger

11


Booting sequence• Bootloader▫ Executed by the hardware at a fixed location in ROM / Flash▫ Initializes support for the device where the kernel image is found

(local storage, network, removable media)▫ Loads the kernel image in RAM▫ Executes the kernel image (with a specified command line)

• Kernel▫ Uncompresses itself▫ Initializes the kernel core and statically compiled drivers (needed to

access the root filesystem)▫Mounts the root filesystem (specified by the root kernel parameter)▫ Executes the first userspace program (specified by the init kernel

parameter)• First userspace program Configures userspace and starts up

system services

12


Linux Kernel

Hardware

Linux Kernel

UserSpaceC Library

app A app B

Calla service

ManageHardware

EventHandler

Eventnotification

13


Linux Kernel•The official version of the Linux kernel, as released by

Linus Torvalds is available at http://www.kernel.org• Incremental patches between versions▫It assumes you already have a base version and you

apply the correct patches in the right order▫Quick to download and apply

•The patch command applies changes to files in the current directory:▫Making changes to existing files▫Creating or deleting files and directories


Thank You

Facebook group: Learn To BeOfficial website: www.L2b-egy.org

Prepared By: SHATRIX E-Mail: [email protected]

Building Embedded Linux

Education