Difference between revisions of "QEMU Build Tutorial"

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=== Introduction ===
 
=== Introduction ===
  
If you don't have a mainboard supported by LinuxBIOS don't worry: Qemu can help you to emulate one.
+
If you don't have a mainboard supported by coreboot don't worry: [http://qemu.org/ QEMU] can help you to emulate one. Using coreboot with QEMU may serve the purpose to familiarize you as a developer with coreboot and may be a reference system during development.  
  
This nice tutorial was written by Alan Carvalho de Assis <acassis@gmail.com>, with additions by Ed Swierk <eswierk@arastra.com> (but please use the LinuxBIOS [[Mailinglist]] rather than emailing the authors directly).
+
This nice tutorial was written by [mailto:acassis@gmail.com Alan Carvalho de Assis], with additions by [mailto:eswierk@arastra.com Ed Swierk] (but please use the [[Mailinglist|coreboot mailing list]] rather than emailing the authors directly).
  
While there are many ways to use LinuxBIOS to load and run a Linux kernel, this tutorial covers two of the most common:
+
While there are many ways to use coreboot to load and run a Linux kernel, this tutorial covers two of the most common:
  
* LinuxBIOS with FILO as payload, using FILO to load a Linux kernel (and optional initramfs) from a hard disk image. This approach involves a bit more mechanism (it relies on FILO's built-in disk and filesystem drivers) but it produces a tiny LinuxBIOS image.
+
* coreboot with [[FILO]] as payload, using FILO to load a Linux kernel (and optional initramfs) from a hard disk image. This approach involves a bit more mechanism (it relies on FILO's built-in disk and filesystem drivers) but it produces a tiny coreboot image.
* LinuxBIOS with a Linux kernel (and optional initramfs) as payload. This cuts FILO out of the picture, but the main challenge with is approach is squeezing the resulting LinuxBIOS image into Qemu's BIOS ROM area (currently 2 MB, but easy to extend by patching Qemu).
+
* coreboot with a Linux kernel (and optional initramfs) as payload. This cuts FILO out of the picture, but the main challenge with this approach is squeezing the resulting coreboot image into QEMU's BIOS ROM area (currently 2 MB, but easy to extend by patching QEMU).
  
 
=== Requirements ===   
 
=== Requirements ===   
Line 14: Line 14:
 
You need the following software packages:
 
You need the following software packages:
  
* [http://linuxbios.org/index.php/Download_LinuxBIOS LinuxBIOSv2] r2405 or greater
+
* [[Download_coreboot|coreboot v4]]
* [http://qemu.org/download.html Qemu] 0.9.0 or greater
+
* [http://qemu.org/ Qemu]
* [http://linuxbios.org/index.php/FILO FILO] 0.4.2 or greater (if using FILO)
+
* [[FILO]] 0.6 or greater (if using FILO)
 
* [ftp://ftp.lnxi.com/pub/mkelfImage mkelfImage] 2.7 or greater (if not using FILO)
 
* [ftp://ftp.lnxi.com/pub/mkelfImage mkelfImage] 2.7 or greater (if not using FILO)
  
plus a Linux kernel and root filesystem and a working development environment (make, gcc, etc.).  gcc 4.0.x and 4.1.x are known to work for all packages except Qemu, which requires gcc 3.x.
+
plus a Linux kernel and root filesystem and a working development environment (make, gcc, etc.).
  
 
=== Building or finding a Linux kernel ===
 
=== Building or finding a Linux kernel ===
Line 25: Line 25:
 
If you are using FILO, you can simply grab a Linux kernel and initramfs from your favorite distribution.
 
If you are using FILO, you can simply grab a Linux kernel and initramfs from your favorite distribution.
  
Otherwise, you will probably need to build a kernel and initramfs from scratch, ensuring that the final LinuxBIOS image does not exceed Qemu's BIOS size limit.  Building the kernel and initramfs is beyond the scope of this tutorial; how you configure them depends on your application.
+
Otherwise, you will probably need to build a kernel and initramfs from scratch, ensuring that the final coreboot image does not exceed QEMU's BIOS size limit (2MB if qemu-bios-size patch applied, 256KB otherwise).  Building the kernel and initramfs is beyond the scope of this tutorial; how you configure them depends on your application.
  
 
If you plan to use kexec to chain-boot another Linux kernel, tools from these projects can help automate the process of generating a kernel and initramfs:
 
If you plan to use kexec to chain-boot another Linux kernel, tools from these projects can help automate the process of generating a kernel and initramfs:
Line 33: Line 33:
 
=== Building a FILO payload ===
 
=== Building a FILO payload ===
  
If you plan to build your Linux kernel and root filesystem directly into LinuxBIOS, you can skip this section.
+
If you plan to build your Linux kernel and root filesystem directly into coreboot, you can skip this section.
  
Download FILO (I used filo-0.4.2.tar.bz2), decompress it, and cd to the created directory.
+
Download [[FILO]], and cd to the filo directory
 
    
 
    
First invocation of make creates the default Config file.
+
First invocation of make creates the config file.
  $ make
+
  $ make menuconfig
  
Edit this file as you like. The default configuration worked for me. 
+
Run make again to create build/filo.elf, the ELF FILO image.   
$ vi Config 
+
 
+
Run make again to create filo.elf, the ELF FILO image.   
+
 
  $ make   
 
  $ make   
  
You will use this file (filo.elf) as the LinuxBIOS payload later on.
+
You will use this file (filo.elf) as the coreboot payload later on.
  
 
=== Building a Linux kernel payload ===
 
=== Building a Linux kernel payload ===
Line 55: Line 52:
  
 
Configure and build the mkelfImage binary.
 
Configure and build the mkelfImage binary.
  $ ./configure
+
  $ ./configure && make
$ make
+
  
Now use mkelfImage to convert your Linux kernel image (vmlinuz) and initramfs (initrd) into a usable LinuxBIOS payload (linux.elf):
+
Now use mkelfImage to convert your Linux kernel image (vmlinuz) and initramfs (initrd) into a usable coreboot payload (linux.elf):
 
  $ mkelfImage --append="console=ttyS0" --initrd=initrd vmlinuz linux.elf
 
  $ mkelfImage --append="console=ttyS0" --initrd=initrd vmlinuz linux.elf
  
=== Building LinuxBIOS ===
+
Note: disable CONFIG_WRITE_HIGH_TABLES. Building coreboot with this option enabled crashes during elf image execution.
  
Download the LinuxBIOS source code (I used LinuxBIOSv2-2405) and extract it. 
+
=== Building coreboot ===
 
+
Change to directory targets/emulation/qemu-i386 and modify Config.lb:
+
* change payload to point to your payload (filo.elf or linux.elf)
+
* if you are using a Linux payload, increase the value of option ROM_SIZE to 2048*1024 (2 MB)
+
  
Return to targets directory and execute: 
+
See the [[Build HOWTO]] for information on how to build coreboot for this board.
$ ./buildtarget emulation/qemu-i386 
+
  
Go to targets/emulation/qemu-i386/qemu-i386 and execute: 
+
This creates the coreboot image (build/coreboot.rom).
$ make 
+
 
+
This creates the LinuxBIOS image (qemu-bios.rom).  Copy and rename this file to bios.bin in your home directory.
+
  
 
=== Building Qemu ===
 
=== Building Qemu ===
 +
Qemu used to require patches to work with coreboot, but any current standard build (as packaged by distributions) should be good enough.
  
If you plan to run Qemu version 0.9.0, you will have to build Qemu from source after applying a couple of patches. (Later versions of Qemu might incorporate these patches, allowing you to run them unmodified; hopefully someone will be kind enough to update this tutorial if this happens.)
+
<!--
 +
==== Building Qemu on FreeBSD ====
 +
Qemu can easily be installed using FreeBSD's Ports tree. The Qemu port lives in emulators/qemu. However, as of version 0.9.1 the FreeBSD port can unfortunately no longer be used with coreboot. The latest working version is 0.9.0 which can be retrieved from the FreeBSD CVS repository. For your convenience, an archive of the last working port version has been uploaded to this wiki. You can download the archive from [http://www.coreboot.org/Image:FreeBSD-Qemu-0.9.0.tgz here]. For some reason, the downloaded archive cannot be extracted with tar only, so use these steps to extract the archive:
  
Download the Qemu source code (I used qemu-0.9.0.tar.gz) and extract it.
+
$ gunzip FreeBSD-Qemu-0.9.0.tgz
 +
$ tar -xvf FreeBSD-Qemu.0.9.0.tar
  
Download the two patches and save them to the Qemu source directory:
+
To build and install the port, do this:
* [http://xenon.stanford.edu/~eswierk/misc/qemu-linuxbios/qemu-isa-bios-ram.patch qemu-isa-bios-ram.patch]
+
* [http://xenon.stanford.edu/~eswierk/misc/qemu-linuxbios/qemu-piix-ram-size.patch qemu-piix-ram-size.patch]
+
  
Enter the Qemu source directory and apply the patches:
+
  $ cd qemu
  $ patch -p1 <qemu-isa-bios-ram.patch
+
  $ make clean install
  $ patch -p1 <qemu-piix-ram-size.patch
+
  
Configure and make Qemu (use the --cc option if your default gcc is newer than version 3.4):
+
Make sure you load the aio(4) kernel module before starting QEMU. Also, QEMU can be build with the kqemu kernel module that enhances QEMU's performance. To load both kernel modules at boot time, add the following lines to <tt>/boot/loader.conf</tt>:
$ ./configure --cc=gcc34 --target-list=i386-softmmu
+
$ make
+
  
The Qemu binary is stored in the i386-softmmu directory.
+
<pre>
 +
aio_load="YES"
 +
kqemu_load="YES"
 +
</pre>
  
 +
You can now use the Qemu binary located in <tt>/usr/local/bin</tt>.
 +
-->
 
=== Creating a hard disk image ===
 
=== Creating a hard disk image ===
  
Line 115: Line 107:
 
Create a boot directory and copy your Linux kernel (vmlinuz) and initramfs (initrd) to it:
 
Create a boot directory and copy your Linux kernel (vmlinuz) and initramfs (initrd) to it:
 
  # mkdir /mnt/rootfs/boot
 
  # mkdir /mnt/rootfs/boot
  # cp vmlinuz vmlinuz
+
  # cp vmlinuz /mnt/rootfs/boot/vmlinuz
  # cp initrd initrd
+
  # cp initrd /mnt/rootfs/boot/initrd
  
 
At this point, you can also copy a complete root filesystem to the disk image.  
 
At this point, you can also copy a complete root filesystem to the disk image.  
Line 133: Line 125:
 
  # exit
 
  # exit
  
=== Starting LinuxBIOS in Qemu ===
+
=== Starting coreboot in QEMU ===
  
Execute Qemu using the following parameters:
+
Execute QEMU using the following parameters:
  $ qemu -L ~ -hda disk.img -nographic
+
  $ qemu -bios path/to/coreboot.rom -hda disk.img -nographic
  
The -L option tells Qemu to look for bios.bin in your HOME directory.  -nographic suppresses the graphical VGA display and connects the virtual machine's serial port to your console.
+
The -bios option tells QEMU to use path/to/coreboot.rom as its BIOSThe -nographic option suppresses the graphical VGA display and connects the virtual machine's serial port to your console. If you want to keep VGA display, you can use "-serial stdio" instead, which only redirects serial to the console.
  
You should now see all sorts of interesting LinuxBIOS messages, followed by Linux kernel boot messages or a FILO prompt.
+
You should now see all sorts of interesting coreboot messages, followed by Linux kernel boot messages or a FILO prompt.
  
 
If you are using FILO, enter at the boot: prompt:
 
If you are using FILO, enter at the boot: prompt:
  boot: hda:/boot/vmlinuz root=/dev/hda initrd=/boot/initrd console=ttyS0
+
 
 +
  kernel hda:/boot/vmlinuz root=/dev/hda
 +
initrd hda:/boot/initrd
 +
boot console=ttyS0
  
 
Example:
 
Example:
  
 
[[Image:Screenshot linuxbios boots qemu.png]]
 
[[Image:Screenshot linuxbios boots qemu.png]]

Latest revision as of 14:22, 9 July 2013

Introduction

If you don't have a mainboard supported by coreboot don't worry: QEMU can help you to emulate one. Using coreboot with QEMU may serve the purpose to familiarize you as a developer with coreboot and may be a reference system during development.

This nice tutorial was written by Alan Carvalho de Assis, with additions by Ed Swierk (but please use the coreboot mailing list rather than emailing the authors directly).

While there are many ways to use coreboot to load and run a Linux kernel, this tutorial covers two of the most common:

  • coreboot with FILO as payload, using FILO to load a Linux kernel (and optional initramfs) from a hard disk image. This approach involves a bit more mechanism (it relies on FILO's built-in disk and filesystem drivers) but it produces a tiny coreboot image.
  • coreboot with a Linux kernel (and optional initramfs) as payload. This cuts FILO out of the picture, but the main challenge with this approach is squeezing the resulting coreboot image into QEMU's BIOS ROM area (currently 2 MB, but easy to extend by patching QEMU).

Requirements

You need the following software packages:

plus a Linux kernel and root filesystem and a working development environment (make, gcc, etc.).

Building or finding a Linux kernel

If you are using FILO, you can simply grab a Linux kernel and initramfs from your favorite distribution.

Otherwise, you will probably need to build a kernel and initramfs from scratch, ensuring that the final coreboot image does not exceed QEMU's BIOS size limit (2MB if qemu-bios-size patch applied, 256KB otherwise). Building the kernel and initramfs is beyond the scope of this tutorial; how you configure them depends on your application.

If you plan to use kexec to chain-boot another Linux kernel, tools from these projects can help automate the process of generating a kernel and initramfs:

Building a FILO payload

If you plan to build your Linux kernel and root filesystem directly into coreboot, you can skip this section.

Download FILO, and cd to the filo directory

First invocation of make creates the config file.

$ make menuconfig

Run make again to create build/filo.elf, the ELF FILO image.

$ make   

You will use this file (filo.elf) as the coreboot payload later on.

Building a Linux kernel payload

If you are using FILO, skip this section.

Download mkelfImage (I used mkelfImage-2.7.tar.gz), decompress it, and cd to the created directory.

Configure and build the mkelfImage binary.

$ ./configure && make

Now use mkelfImage to convert your Linux kernel image (vmlinuz) and initramfs (initrd) into a usable coreboot payload (linux.elf):

$ mkelfImage --append="console=ttyS0" --initrd=initrd vmlinuz linux.elf

Note: disable CONFIG_WRITE_HIGH_TABLES. Building coreboot with this option enabled crashes during elf image execution.

Building coreboot

See the Build HOWTO for information on how to build coreboot for this board.

This creates the coreboot image (build/coreboot.rom).

Building Qemu

Qemu used to require patches to work with coreboot, but any current standard build (as packaged by distributions) should be good enough.

Creating a hard disk image

If you are using FILO, you must create a hard disk image containing the Linux kernel and optional initramfs that FILO loads.

Whether or not you use FILO, you may also wish to populate the disk image with the root filesystem of whatever Linux distribution you want to run.

Create an empty disk image:

$ qemu-img create -f raw disk.img 200M

Format it:

$ mkfs.ext2 -F disk.img 

The remaining steps must be performed as root. Create a temporary mountpoint and mount the image:

# mkdir /mnt/rootfs
# mount -o loop disk.img /mnt/rootfs

Create a boot directory and copy your Linux kernel (vmlinuz) and initramfs (initrd) to it:

# mkdir /mnt/rootfs/boot
# cp vmlinuz /mnt/rootfs/boot/vmlinuz
# cp initrd /mnt/rootfs/boot/initrd

At this point, you can also copy a complete root filesystem to the disk image.

# cp -R /* /mnt/rootfs 

Alternatively, with Debian you can use the debootstrap command to create a basic root filesystem:

# debootstrap --arch i386 sarge /mnt/rootfs http://ftp.debian.org/debian/ 

If you are using a debootstrap filesystem, open the file /mnt/rootfs/etc/inittab and change runlevel to level 1:

id:1:initdefault: 

cd out of /mnt/rootfs and umount it:

# umount /mnt/rootfs

Exit from the root account:

# exit

Starting coreboot in QEMU

Execute QEMU using the following parameters:

$ qemu -bios path/to/coreboot.rom -hda disk.img -nographic

The -bios option tells QEMU to use path/to/coreboot.rom as its BIOS. The -nographic option suppresses the graphical VGA display and connects the virtual machine's serial port to your console. If you want to keep VGA display, you can use "-serial stdio" instead, which only redirects serial to the console.

You should now see all sorts of interesting coreboot messages, followed by Linux kernel boot messages or a FILO prompt.

If you are using FILO, enter at the boot: prompt:

kernel hda:/boot/vmlinuz root=/dev/hda
initrd hda:/boot/initrd
boot console=ttyS0

Example:

Screenshot linuxbios boots qemu.png