Difference between revisions of "Step-by-step Cross-compiling a Kernel"

From odroid US
Jump to: navigation, search
(Created page with "THIS IS IN PROGRESS: PLEASE DO NOT EDIT wget https://launchpadlibrarian.net/129963014/gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar.xz xz -d gcc-linaro-arm-...")
 
Line 1: Line 1:
 
THIS IS IN PROGRESS: PLEASE DO NOT EDIT
 
THIS IS IN PROGRESS: PLEASE DO NOT EDIT
  
 +
=== Introduction ===
 +
This tutorial is for developers
  
 +
These procedures assume you have an Debian-based distribution loaded on your host and your odroid.  The kernel building is not different between the distros, but getting ready to build is. 
  
 +
Debian/Ubuntu/Mint and others use "Debian packages", .deb files.  They use tools like dpkg, apt, synaptic and so on to manage a package database.
 +
 +
RedHat, Centos, Fedora and Gentoo would not know about apt-get and friends -- so these instructions will not be of much use.
 +
 +
 +
 +
=== Setting up the Toolchain ===
 +
If you are happy with your arm cross-compiler, you can skip this step.  Some people prefer the CodeSourcery toolchains, but the free version does not support hard floating point.
 +
 +
The kernel is much easier to build than a whole root file system because there are few dependencies.  We need a compiler that can generate code for the cortex-a9.  We prefer hard-float (armhf rather than armel in Debian lingo)
 +
 +
On your Linux host, setup a shared work area
 +
<pre>
 +
sudo mkdir -p /usr/local/arm >/dev/null
 +
sudo chmod 777 /usr/local/arm
 +
cd /usr/local/arm
 +
</pre>
 +
 +
 +
On your Linux host, get the toolchain and expand it.
 +
<pre>
 +
cd /usr/local/arm
 
wget https://launchpadlibrarian.net/129963014/gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar.xz
 
wget https://launchpadlibrarian.net/129963014/gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar.xz
 
xz -d gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar.xz  
 
xz -d gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar.xz  
 
tar -xvf gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar
 
tar -xvf gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar
 +
</pre>
  
−
sudo mkdir -p /usr/local/arm >/dev/null
+
I need to change compilers depending on the project I'm working on, so I prefer to use a symlink to select the 'active' version.
 +
<pre>
 
ln -s gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux /usr/local/arm/toolchain
 
ln -s gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux /usr/local/arm/toolchain
 +
</pre>
  
−
Setup the c-compiler cache
+
Setup the c-compiler cache (optional)
 
<pre>
 
<pre>
 
cd /usr/local/arm/toolchain
 
cd /usr/local/arm/toolchain
 
mkdir bin-ccache
 
mkdir bin-ccache
 +
# you may already have ccache installed, but for the sake of illustration...
 +
sudo apt-get install ccache
 
ln -s $(which ccache) arm-linux-gnueabihf-gcc
 
ln -s $(which ccache) arm-linux-gnueabihf-gcc
 
ln -s $(which ccache) arm-linux-gnueabihf-g++
 
ln -s $(which ccache) arm-linux-gnueabihf-g++
Line 20: Line 50:
 
</pre>
 
</pre>
  
 +
Check your PATH and update it as shown.  It is convenient to edit your ~/.bashrc file and re-launch a shell rather than just export.
 +
<pre>
 
export PATH=/usr/local/arm/toolchain/bin-ccache:/usr/local/arm/toolchain/bin:$PATH
 
export PATH=/usr/local/arm/toolchain/bin-ccache:/usr/local/arm/toolchain/bin:$PATH
 +
</pre>
  
 +
=== Grabbing the source ===
 +
Go to a convenient work area, here I show $HOME/work
 +
<pre>
 +
cd $HOME
 +
mkdir work
 +
cd work
 +
</pre>
  
 
Get the kernel snapshot, and unzip it
 
Get the kernel snapshot, and unzip it
Line 30: Line 70:
  
  
−
Move into the kernel source directory and set up
+
Move into the kernel source directory and set up.  You could edit your .bashrc and add the ARCH and CROSS_COMPILE variables -- but remember that you did it.  Some x86 packages will fail to build with CROSS_COMPILE and/or ARCH set... (vmware is the worst offender I know)
 
<pre>
 
<pre>
 
cd linux-odroid-3.0.y/
 
cd linux-odroid-3.0.y/
Line 37: Line 77:
 
</pre>
 
</pre>
  
−
Select the configuration you want, and build it
+
Select the configuration you want, and build it (you can see the alternatives in ./arch/arm/configs/odroid*)
 
<pre>
 
<pre>
 
make odroidu2_ubuntu_defconfig  
 
make odroidu2_ubuntu_defconfig  
Line 43: Line 83:
 
</pre>
 
</pre>
  
−
Make a directory for the kernel modules and let the kernel make system strip and copy them out.
+
Make a directory for the kernel modules and let the kernel make system strip and copy them out.  Create a tarball for quick copy/transfer.
 
<pre>
 
<pre>
 
mkdir ../rfs
 
mkdir ../rfs
Line 57: Line 97:
 
</pre>
 
</pre>
  
−
Copy our new kernel and modules to the target.  This method copies over the network.  The thing to remember is that the kernel goes on the boot partition and the kernel modules go on the rootfs partition
+
Copy our new kernel and modules to the target.  This method copies over the network.  The thing to remember is that the kernel goes on the boot partition and the kernel modules go on the rootfs partition.  Here odroidu2 is the name of my odroid target, defined in /etc/hosts.  You can do ifconfig on your odroid to see what IP Address it is using and then use it explicitly instead of the technique I show here (the dotted quad instead of odroidu2)
 
<pre>
 
<pre>
 
scp modules.tgz root@odroidu2:/
 
scp modules.tgz root@odroidu2:/
Line 63: Line 103:
 
</pre>
 
</pre>
  
−
Now go to the odroid Linux console and expand the kernel modules and reboot
+
Now go to the odroid Linux console, expand the kernel modules tarball and reboot
 
<pre>
 
<pre>
 
tar -xvzf modules.tgz  
 
tar -xvzf modules.tgz  

Revision as of 20:45, 2 February 2013

THIS IS IN PROGRESS: PLEASE DO NOT EDIT

Introduction

This tutorial is for developers

These procedures assume you have an Debian-based distribution loaded on your host and your odroid. The kernel building is not different between the distros, but getting ready to build is.

Debian/Ubuntu/Mint and others use "Debian packages", .deb files. They use tools like dpkg, apt, synaptic and so on to manage a package database.

RedHat, Centos, Fedora and Gentoo would not know about apt-get and friends -- so these instructions will not be of much use.


Setting up the Toolchain

If you are happy with your arm cross-compiler, you can skip this step. Some people prefer the CodeSourcery toolchains, but the free version does not support hard floating point.

The kernel is much easier to build than a whole root file system because there are few dependencies. We need a compiler that can generate code for the cortex-a9. We prefer hard-float (armhf rather than armel in Debian lingo)

On your Linux host, setup a shared work area 

sudo mkdir -p /usr/local/arm >/dev/null 
sudo chmod 777 /usr/local/arm
cd /usr/local/arm


On your Linux host, get the toolchain and expand it. 

cd /usr/local/arm
wget https://launchpadlibrarian.net/129963014/gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar.xz
xz -d gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar.xz 
tar -xvf gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux.tar

I need to change compilers depending on the project I'm working on, so I prefer to use a symlink to select the 'active' version. 

ln -s gcc-linaro-arm-linux-gnueabihf-4.7-2013.01-20130125_linux /usr/local/arm/toolchain

Setup the c-compiler cache (optional) 

cd /usr/local/arm/toolchain
mkdir bin-ccache
# you may already have ccache installed, but for the sake of illustration...
sudo apt-get install ccache
ln -s $(which ccache) arm-linux-gnueabihf-gcc
ln -s $(which ccache) arm-linux-gnueabihf-g++
ln -s $(which ccache) arm-linux-gnueabihf-cpp
ln -s $(which ccache) arm-linux-gnueabihf-c++

Check your PATH and update it as shown. It is convenient to edit your ~/.bashrc file and re-launch a shell rather than just export. 

export PATH=/usr/local/arm/toolchain/bin-ccache:/usr/local/arm/toolchain/bin:$PATH

Grabbing the source

Go to a convenient work area, here I show $HOME/work 

cd $HOME
mkdir work
cd work

Get the kernel snapshot, and unzip it 

wget --no-check-certificate https://github.com/hardkernel/linux/archive/odroid-3.0.y.zip
unzip odroid-3.0.y.zip


Move into the kernel source directory and set up. You could edit your .bashrc and add the ARCH and CROSS_COMPILE variables -- but remember that you did it. Some x86 packages will fail to build with CROSS_COMPILE and/or ARCH set... (vmware is the worst offender I know) 

cd linux-odroid-3.0.y/
export CROSS_COMPILE=arm-linux-gnueabihf-
export ARCH=arm

Select the configuration you want, and build it (you can see the alternatives in ./arch/arm/configs/odroid*) 

make odroidu2_ubuntu_defconfig 
make -j8 zImage

Make a directory for the kernel modules and let the kernel make system strip and copy them out. Create a tarball for quick copy/transfer. 

mkdir ../rfs
export INSTALL_MOD_PATH=$PWD/../rfs
make modules_install
cd ../rfs
# remove symlinks that point to files we do not need in root file system
find . -name source | xargs rm
find . -name build | xargs rm
# Compress
sudo tar -cvzf ../modules.tgz .
cd ../

Copy our new kernel and modules to the target. This method copies over the network. The thing to remember is that the kernel goes on the boot partition and the kernel modules go on the rootfs partition. Here odroidu2 is the name of my odroid target, defined in /etc/hosts. You can do ifconfig on your odroid to see what IP Address it is using and then use it explicitly instead of the technique I show here (the dotted quad instead of odroidu2) 

scp modules.tgz root@odroidu2:/
scp linux-odroid-3.0.y/arch/arm/boot/zImage  root@odroidu2:/boot

Now go to the odroid Linux console, expand the kernel modules tarball and reboot 

tar -xvzf modules.tgz 
rm modules.tgz
sync
reboot

Check the kernel version, with uname -a 

Linux odroidu2-1 3.0.61 #1 SMP Sat Feb 2 15:28:35 PST 2013 armv7l GNU/Linux
Retrieved from "http://odroid.us/mediawiki/index.php?title=Step-by-step_Cross-compiling_a_Kernel&oldid=254"