/ARMLinux

Primary LanguagePHP

ARMLinux

##Tools

  • cross-compile-toolchain "arm-linux-gnueabi"
  • ccache

##Config Settings

###Kernel

  • used "make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- vexpress_defconfig"

  • Manual set options

  • initramfs source file points to "rootFSconfig"

  • enable loadable module support unchecked

  • remove soundcard support

  • Device Drivers set automatically

  • Generic Driver options -> Select only drivers that don't need compile-time external firmware

  • -> prevent firmware from being built

  • -> include in-kernel firmware blobs in kernel binary

  • Memory Technology Device support

  • Block devices

  • SCSI device support -> SCSI disk support

  • Serial ATA and ...

  • Network device support -> Ethernet driver support

  • HID devices

  • USB support

  • MMC/SD/SDIO card support

  • Realtime Clock

  • IOMMU Hardware support

###Busybox

  • init utilities -> init

  • shells -> ash (associated with "sh")

  • coreutils -> ls, echo

  • editors -> vi

  • Linux System Utilities -> mount, umount, mdev

  • System info -> top, free, ps, rm, uptime, cat, mv, halt, poweroff, reboot, chmod

  • At the moment busybox is statically linked

##How To

###Compile Kernel

  • get latest Linux 3.4.XX Kernel (used 3.4.66)
  • extract kernel
    • command "tar xfvj [ARCHIV].tar.bz2" for .tar.bz2 kernel
  • configure makefile for ccache
    • CC = ccache $(CROSS_COMPILE)gcc
    • HOSTCC = ccache gcc
  • compile kernel
    • command "make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-"
    • use -jN for multithreaded compile
    • "CROSS_COMPILE=arm-linux-gnueabi-" because cross-compiler is "arm-linux-gnueabi-gcc" -> look at CC in makefile

###Compile Busybox

  • get latest stable busybox version (used 1.21.1)
  • extract busybox
    • command "tar xfvj [ARCHIV].tar.bz2" for .tar.bz2 busybox
  • configure makefile for ccache
    • CC = ccache $(CROSS_COMPILE)gcc
    • HOSTCC = ccache gcc
  • compile busybox
    • command "make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-"

###Compile uClibc

  • get latest stable Buildroot
  • extract buildroot
    • command "tar xfvj [ARCHIV].tar.bz2" for .tar.bz2 buildroot
  • compile uClbic
    • command "make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- toolchain"

###Create rootFS with busybox

  • use command "make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- install"
    • in menuconfig BusyBox Settings –> Build Options -> Installation Options (make install behavior) points to output dir of rootFS
  • add other required directories (e.g. "mkdir proc sys var etc dev")
  • add initscript as "/etc/init.d/rcS"
  • use command "find [DIR] | cpio -o -H newc --no-absolute-filenames | gzip -c > rootfs.img.gz"
    • packs [DIR] in cpio and compresses then with gzip

###Run Emulation

  • use "arm-system-qemu" for arm systems
  • use "-M vexpress-a9" to specify Verstaile Express Board with A9 Core
  • QEMU_AUDIO_DRV=none to disable audio
  • -nographic: Redirect output (inclusive serial) to command line

##Questions

Other possibilities to give compile options:

  • Set environment variable with export
  • Set variables in Makefile

enabled device drivers after default config for arm:

  • MTD
  • SATA
  • Ethernet
  • soundcard support
  • HID
  • USB
  • SCSI Disk
  • SD card
  • Realtime Clock
  • IOMMU

It is not required to specify the kernel console= parameter. The kernel uses as default a serial port, and this serial port is redirected to the qemu stdio.

Kernel command line: root=/dev/nfs nfsroot=10.1.69.3:/work/nfsroot ip=dhcp console=ttyAMA0 mem=128M

Serial: AMBA PL011 UART driver mb:uart0: ttyAMA0 at MMIO 0x10009000 (irq = 37) is a PL011 rev1 console [ttyAMA0] enabled

-> The used console is ttyAMA0. Source: https://www.kernel.org/doc/Documentation/arm/Booting

To use a pty terminal -serial pty is needed as qemu parameter. After starting qemu, open the pty used by qemu(for example /dev/pts/25) with screen /dev/pts/25 and enter system_reset in the qemu monitor. Now you can view the kernel messages in the pty.

Informations busybox binary (file):

  • ELF 32-bit
  • ARM-architecture
  • statically linked
  • for Linux 2.6.26
  • BuildID[sha1]=0xc693c46fe189c7ed1dad4a2be2a4865c80b612c3
  • stripped
  • size: 819kB

possibilities to make busybox smaller:

  • link dynamically
  • remove functions
  • use smaller lib than cLibc (e.g. uLibc)

executing "busybox" -> Unable to reserve guest address space

qemu arguments:

  • -rdinit PATH
  • -append "rdinit=/sbin/init ..."

activated network devices:

  • ethernet driver support
    • Broadcom
    • Chelsio
    • Cirrus
    • Faraday
    • Intel
    • Marvell
    • Micrel
    • National semi-conductor
    • SEEQ
    • SMC
    • SMSC
    • STMicroelectronics

supported network devices (qemu):

  • smc91c111

The loopback interface is required to ping the localhost.

##Other useful information

###Explanation of serial and virtual consoles

  • /dev/console:
    Set of devices that can be set with console= parameter at boot time. Can be redirected to virt. console or serial devices, default is /dev/tty0.
  • /dev/tty0
    Current virtual console.
  • /dev/tty[1-x]
    One of the virtual consoles.
  • /dev/tty
    The console used by the process querying it.
  • /dev/ttyS0
    First UART serial port
  • /dev/pty
    Pseudo terminal master side.

How to see the boot messages from the kernel: The kernel has the device /dev/console. This points to the serial terminal by default. So qemu needs to redirect the serial output to its own tty.

Sources:
http://unix.stackexchange.com/questions/60641/linux-difference-between-dev-console-dev-tty-and-dev-tty0 https://www.kernel.org/doc/Documentation/devices.txt

###Qemu Qemu is started with the -nographic option. This means qemu can be used on the command line. The serial ouput is also redirected to the command line. To get help for the qemu monitor, press [Ctrl-a, h].

##Useful Links