LINUX BOOT PROCEDURE AND BOOTLOADER

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LINUX BOOT PROCEDURE AND BOOTLOADER

• LAB 6

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OUTLINE

• Introduction
• Boot loader
• U-Boot
• Kernel
• INIT
• Lab

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Introduction

• An embedded linux system is typically consist of
  some software below
• Boot loader
• Kernel
• Init program
• Your application

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BOOT LOADER

• Boot loader is a program that
• Execute when board power on
• Detect hareware (if necessary)
• Initialize hardware
• Copy first program, might be
• A simple program
• Bootloader stage N
• OS kernel
• Transfer control to it and go
• Boot loader is varied from different CPU,
  different board.

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BOOT LOADER Execute when board power on

• Any CPU will execute a program at specified
  address when power on
• Boot loader always be placed there

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BOOT LOADER Detect Hardware

• Search for attached device
• Filesystem on storage
• Mouse on USB
• etc
• Use detected device if need
• Read configure file in filesystem

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BOOT LOADER Initialize Hardware

• Some hardware require default value
• Stop interrupt
• Set CPU clock
• Configure RAM or MMU
• Reset other processor such as DSP

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BOOT LOADER Copy First Program

• A simple program
• Non-OS program
• Bootloader stage N
• Boot loader might have multiple stages, multiple
  modes
• OS kernel
• Linux
• WinCE
• etc

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BOOT LOADER Copy First ProgramStage N

• Typical 2 stages in embedded system
• Stage 1
• Write in assembly language to speed up
• Initialize hardware
• Copy Stage 2 to RAM
• Prepare stack for Stage 2
• Jump to Stage 2
• Stage 2
• Write in C for more feature
• Initialize hardware
• Load kernel
• Send parameter to kernel
• Start kernel

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BOOT LOADER Copy First ProgramMultiple modes

• In order to provide more feature, boot loader
  might have multiple modes
• Mode 1 Boot program or kernel
• Copy program only
• Mode 2 Update utility
• Read filesystem or kernel via
• RS232 xmodem protocol (Very Slow)
• Network FTP protocol
• Earse flash and overwrite it with new data

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BOOT LOADER Example
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BOOT LOADER Transfer Control to It and Go

• Copy next program to RAM
• Sometimes might execute on ROM
• Setup stack for it
• Set PC (or jump) to its start address

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U-Boot

• U-Boot Universal Bootloader
• http//u-boot.sourceforge.net/
• Portable and easy to port and to debug
• Support many architectures PPC, ARMs, MIPS, x86,
  m68k, NIOS, Microblaze

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U-BootSupport list
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U-Boot Instructions

• help print online help
• help ltcommandgt show usage
• flinfo print FLASH memory information
• protect enable or disable FLASH write protection
• erase erase FLASH memory
• loadb loadb binary file over serial line (kermit
  mode)
• md memory display
• cp memory copy

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KERNEL

• After kernel is loaded and started, kernel will
  detect and initialize hardware
• After everything is done, find root filesystem
  for VFS (Virtual File System)
• Then, search for init, which is the first program
  in OS
• Init will be the parent of all other process

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INIT

• The first process in OS
• PID 1
• Enter ps aux to show all process
• Typical operation
• Fork shell and execute a script
• Mount all filesystem
• Start all deamon
• Wait for user login
• In embedded system, there are few task to do.

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LAB
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LAB

• LAB 1 Boot loader
• LAB 2 Boot procedure

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LAB 1Boot loader

• Install board
• Install arm tool-train
• Compile U-Boot
• Install JTAG driver
• Install U-Boot

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LAB 1Install board

• Install J-TAG and COM1

1 Pin
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LAB 1 Install arm tool-train Compile U-Boot

• In Linux
• Download cross-3.2.tar.bz2 and
• u-boot-1.1.4.zip
• Install cross-3.2 to /usr/local/arm
• Extract U-Boot and compile it
• After completed, copy u-boot.bin to Windows

make innokom_config make CROSS_COMPILE/usr/local/
arm/bin/arm-linux-
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LAB 1 Install JTAG driver

• In Windows
• Copy GIVEIO.SYS under CgiveIO folder to
  C\WINDOWS\system32\drivers
• Click ???? in ???
• Select ?,??????
• Select ??????
• Select ????
• Select (COM / LPT)
• Click ?????, select giveio.inf

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LAB 1 Install U-Boot

• Place u-boot.bin in the folder where Jen255.exe
  existed
• Execute Jen255.exe and enter
• u-boot.bin
• Open ????? with baud rate 19200 bps, no flow
  control
• Reset board and see if success

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LAB 2

• Re-install origin I-Boot
• Modify boot procedure
• Install kernel and filesystem

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LAB 2 Re-install origin I-Boot

• In Windows
• Execute Jen255.exe again, but enter bootldr
  insteaded

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LAB 2 Modify boot procedure

• Setup kernel and filesystem
• Use compiled kernel
• Modify existed filesystem

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LAB 2 Modify boot procedure(cont)

• In Linux, modify boot procedure

gzip -d ramdisk.gz mount filesystem sudo mount
-o loop ramdisk fs go to init procedure
folder cd fs/etc/init.d/ sudo mv rcS rcS.bak
edit boot procedure sudo vi rcS enter content
as below !/bin/sh while 1 do echo
AHHHHHHHHHHH done mark it as executable sudo
chmod x rcS cd ../../../ sudo umount fs pack
it again gzip -9 ramdisk ramdisk.gz
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LAB 2 Install kernel and filesystem

• In Windows
• Open ????? with baud rate 115200 bps, no flow
  control

setup kernel download xmodem 0xa0020000 flashver
ify 0x040c0000 0xa0020000 0x100000 setup root
filesystem download xmodem 0xa0020000 flashverify
0x041c0000 0xa0020000 0x3D5000
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LAB 2

• Result