= Building Grub =


The following instructions built the image and were run on a Fedora Core 5 Linux host.

Download the latest release of version 2 the [http://www.gnu.org/software/grub/index.html Grub boot loader] from [ftp://ftp.gnu.org/gnu/grub the ftp], [ftp://alpha.gnu.org/gnu/grub/ another ftp] or, you can check out the developer branch using bzr. Remember to run autogen when checking out the development branch... 
 $ sudo apt-get install bzr bison libdevmapper-dev libfreetype6-dev autogen
 $ bzr branch http://bzr.savannah.gnu.org/r/grub/trunk/grub
 $ cd grub
 $ ./autogen.sh

Build the package with the following configure command:

  $ ../grub-1.94/configure --prefix=/tmp/g2/build
  $ make all install

where the prefix can be anything suitable for your machine. If configure fails with a missing LZO library check you have the lzo-devel package installed.

To make the floppy image follow the instructions in the Grub Wiki at http://grub.enbug.org/TestingOnX86. This script is adapted from the instructions:

 #! /bin/sh -x
 grub=/tmp/g2/build
 workspace=/tmp/g2
 mnt=$workspace/mnt/loop
 file=$workspace/rtems-boot.img
 export PATH=$grub/bin:$grub/sbin:$PATH
 mkdir -p $workspace
 cd $workspace
 grub-mkimage -o core.img _chain ls pc multiboot gpt fat boot reboot configfile cat help
 dd if=/dev/zero of=$file bs=512 count=2880
 /sbin/mkdosfs $file
 mkdir -p $mnt
 mount -o loop -t vfat $file $mnt
 mkdir -p $mnt/boot/grub
 cp $grub/lib/grub/i386-pc/boot.img core.img $grub/lib/grub/i386-pc/*.mod $mnt/boot/grub
 echo "configfile (hd0,0)/rtems-grub.cfg" > $mnt/boot/grub/grub.cfg
 echo '(fd0)' $file > tmp_device.map
 grub-setup -d $mnt/boot/grub -r '(fd0)' -m tmp_device.map '(fd0)'
 rm -f tmp_device.map
 umount $mnt
=  Grub2  =

Most of method of the previous is mostly based on grub legacy. And most Linux distributions have updated to Grub2. So in the following, we just introduce how to build a i386 simulation environment based on Grub2 and QEMU.

This is tested on Ubuntu-13.04 and the Grub2 also has been installed.
{{{
#!/bin/bash
set -e

image="rtems-boot.img"
# Hack to make everything owned by the original user.
user=`who am i | awk '{print $1}'`
group=`groups $user | awk '{print $3}'`

# Create the actual disk image - 15MB
dd if=/dev/zero of=${image} bs=512 count=32130 2>/dev/null
chown ${user}:${group} ${image}
# Setup the loopback device, and reture the devie name.
lodev=`losetup -f --show ${image}`
trap 'losetup -d ${lodev}; exit $?' INT TERM EXIT
loname=${lodev##*/}
# Make the partition table, partition and set it bootable.
parted -a minimal --script ${lodev} mklabel msdos mkpart primary ext2 1M 100% \
    set 1 boot on 2>/dev/null

# Get the start sectors.
start=`fdisk -lu ${lodev} | grep "${loname}p1" | awk '{ print $3}'`
# Find the first unused loop device.
lonxt=`losetup -f`
# Create a loop device for this partition, like /dev/sda and /dev/sda0 work.
losetup -o $(expr 512 \* ${start}) ${lonxt} ${lodev}
trap 'losetup -d ${lonxt}; losetup -d ${lodev}; exit $?' INT TERM EXIT

# Make an ext2 filesystem on the first partition.
mkfs.ext2 ${lonxt} &>/dev/null
# Mount the filesystem via loopback.
mount ${lonxt} /mnt
trap 'umount /mnt; losetup -d ${lonxt}; losetup -d ${lodev}; exit $?' INT TERM EXIT
mkdir -p /mnt/boot/grub
echo 'source (hd1,msdos1)/grub.cfg'>/mnt/boot/grub/grub.cfg


mkdir -p /mnt/boot/grub/i386-pc
cp /usr/lib/grub/i386-pc/* /mnt/boot/grub/i386-pc

# Make a bootable image of GRUB.
grub-mkimage -d /usr/lib/grub/i386-pc -O i386-pc --output=core.img \
        --prefix=\(,msdos1\)/boot/grub ext2 part_msdos biosdisk search_fs_uuid
mv core.img /mnt/boot/grub/i386-pc
# Set up a device to boot using GRUB.
grub-bios-setup --allow-floppy  --force --directory=/mnt/boot/grub/i386-pc \
        --device-map= ${lodev}

sync
trap - INT TERM EXIT
umount /mnt
losetup -d ${lonxt}
losetup -d ${lodev}
}}}

We could generate a hard-disk image ''rtems-boot.img''. Before we start qemu, we also should create some other files. The directories and file structure like following.
{{{
$ tree
 |--- rtems-boot.img
 |--- examples
 |    |--- ticker.exe
 |--- grub.cfg
 |--- mkimage.sh
 |--- qemu.sh
}}}
 *  rtems-boot.img: generated by ''mkimage.sh'' shell script.
 *  examples: some RTEMS executable files, such as 'ticker.exe'.
 *  grub.cfg: the Grub2 configration file, you should edit this file when new RTEMS file add.
 *  mkimage.sh: script used to generate hard-disk image, 'sudo ./mkimage.sh'.
 *  qemu.sh: start QEMU, './qemu.sh rtems-boot.img'.

The qemu.sh:
{{{
#!/bin/bash
qemu-system-i386 -m 128 -boot b -hda $1 -hdb fat:. -serial stdio -no-reboot
}}}