Difference between revisions of "Raspberry Pi Kernel Compilation"

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m (Mortense moved page RPi Kernel Compilation to Raspberry Pi Kernel Compilation: Expansion (there is no need for obfuscation).)
 
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= Overview =
 
= Overview =
This page explains how to rebuild the kernel image for the RPi. There are two possible routes available:  
+
This page explains how to rebuild the kernel image for the Raspberry Pi. There are two possible routes available:  
 
# Compile on the Raspberry Pi itself
 
# Compile on the Raspberry Pi itself
 
# Cross compile on another Linux system
 
# Cross compile on another Linux system
  
Both of these routes are covered below, however, you are strongly recommended to follow the cross compilation route. The low processing power of the RPi means that a local compile will take many hours.
+
Both of these routes are covered below, however, you are strongly recommended to follow the cross-compilation route. The low processing power of the Raspberry Pi means that a local compile will take many hours. A compilation of the latest kernel and modules took about 752 minutes (12h30m)!
 +
 
 +
If you want to compile an upstream kernel, rather than the Raspberry Pi Foundation's downstream kernel, please see [[RPi_Upstream_Kernel_Compilation]] for a few tips.
  
 
== Example Checklist/Roadmap ==
 
== Example Checklist/Roadmap ==
 
This section serves to hold a new user's hand just a bit more than some of the other more generic information below in the document. To get more information on the steps in the roadmap, search this page for additional details. It assumes you can navigate filesystems, move files across systems, and have a general understanding of compiling linux kernels, filesystems, partitions, and block devices.
 
This section serves to hold a new user's hand just a bit more than some of the other more generic information below in the document. To get more information on the steps in the roadmap, search this page for additional details. It assumes you can navigate filesystems, move files across systems, and have a general understanding of compiling linux kernels, filesystems, partitions, and block devices.
  
This series of steps yielded a successful custom/updated hardfp kernel to a stock Raspbian installation, cross compiled from an amd64 Debian system without regression on any kernel configuration options or requiring modified boot parameters. Be aware that in the worst case, you may need to overlay a stock set of kernel/modules/firmware on the Raspberry Pi if something fails. If you do not know how to do this, then a reimage of the SD card may be necessary. Assuming this is not an issue for your configuration, continue onward:
+
This series of steps yielded a successful custom/updated hardfp kernel to a stock Raspbian installation, cross compiled from an AMD 64-bit Debian system without regression on any kernel configuration options or requiring modified boot parameters. Be aware that in the worst case, you may need to overlay a stock set of kernel/modules/firmware on the Raspberry Pi if something fails. If you do not know how to do this, then a reimage of the SD card may be necessary. Assuming this is not an issue for your configuration, continue onward:
# Get the latest raspberrypi kernel source (git://github.com/raspberrypi/linux.git)
+
# Get the latest Raspberry Pi kernel source (https://github.com/raspberrypi/linux)
# Set an environment variable KERNEL_SRC to point to the location of the source (e.g. KERNEL_SRC=/home/me/linux/)
+
# Set an environment variable KERNEL_SRC to point to the location of the source (for example, KERNEL_SRC=/home/me/linux/ )
# Get the latest raspberrypi compiler (git clone git://github.com/raspberrypi/tools.git)
+
# Get the latest Raspberry Pi compiler (git clone https://github.com/raspberrypi/tools)
# Set an environment variable CCPREFIX to point to the location of tools (e.g. CCPREFIX=/home/me/tools/arm-bcm2708/arm-bcm2708-linux-gnueabi/bin/arm-bcm2708-linux-gnueabi-)
+
# Set an environment variable CCPREFIX to point to the location of tools (for example, CCPREFIX=/home/me/tools/arm-bcm2708/arm-bcm2708-linux-gnueabi/bin/arm-bcm2708-linux-gnueabi- )
 
# From the kernel clone location, clean the kernel source with "make mrproper"
 
# From the kernel clone location, clean the kernel source with "make mrproper"
 
# Pull the /proc/config.gz from the running Raspbian installation
 
# Pull the /proc/config.gz from the running Raspbian installation
# Prime kernel with the old config by running "ARCH=arm CROSS_COMPILE=${CCPREFIX} make oldconfig"
+
# Prime the kernel with the old configuration by running "ARCH=arm CROSS_COMPILE=${CCPREFIX} make oldconfig"
# Modify the kernel config by either modifying the .config file or using "ARCH=arm CROSS_COMPILE=${CCPREFIX} make menuconfig"
+
# Modify the kernel configuration by either modifying the .config file or using "ARCH=arm CROSS_COMPILE=${CCPREFIX} make menuconfig"
 
# Build the new kernel by using "ARCH=arm CROSS_COMPILE=${CCPREFIX} make"
 
# Build the new kernel by using "ARCH=arm CROSS_COMPILE=${CCPREFIX} make"
# Set an environment variable MODULES_TEMP to point to the location of the source (e.g. MODULES_TEMP=/home/me/modules/)
+
# Set an environment variable, MODULES_TEMP, to point to the location of the source (for example, MODULES_TEMP=/home/me/modules/ )
# Set aside the new kernel modules by using "ARCH=arm CROSS_COMPILE=${CCPREFIX} modules_install INSTALL_MOD_PATH=${MODULES_TEMP} make"
+
# Set aside the new kernel modules by using "ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=${MODULES_TEMP} make modules_install"
 
# From the tools clone location, in the mkimage directory, run "./imagetool-uncompressed.py ${KERNEL_SRC}/arch/arm/boot/zImage"
 
# From the tools clone location, in the mkimage directory, run "./imagetool-uncompressed.py ${KERNEL_SRC}/arch/arm/boot/zImage"
 
# Move the resulting kernel.img to the Raspberry Pi's /boot/ directory
 
# Move the resulting kernel.img to the Raspberry Pi's /boot/ directory
Line 38: Line 40:
 
#* ...
 
#* ...
 
# Move the modules archive to the Raspberry Pi and extract them such that the aforementioned firmware and modules directories overwrite /lib/firmware and /lib/modules
 
# Move the modules archive to the Raspberry Pi and extract them such that the aforementioned firmware and modules directories overwrite /lib/firmware and /lib/modules
# Get the latest raspberrypi firmware (git://github.com/raspberrypi/firmware.git)
+
# Get the latest Raspberry Pi firmware (git://github.com/raspberrypi/firmware.git)
# Transfer the following files from the firmware/boot directory to the Raspberry pi /boot directory:
+
# Transfer the following files from the firmware/boot directory to the Raspberry Pi /boot directory:
 
#* bootcode.bin
 
#* bootcode.bin
 
#* fixup.dat
 
#* fixup.dat
 
#* start.elf
 
#* start.elf
# Transfer the firmware/hardfp/opt directory to the Raspberry pi /opt directory
+
# Transfer the firmware/hardfp/opt directory to the Raspberry Pi /opt directory
 
# Reboot the Raspberry Pi
 
# Reboot the Raspberry Pi
 
The Raspberry Pi should now boot with the newly configured/recompiled kernel.
 
The Raspberry Pi should now boot with the newly configured/recompiled kernel.
  
 
= Get the kernel source =
 
= Get the kernel source =
The kernel source should be downloaded from the [https://github.com/raspberrypi/linux RPI linux section on GitHub]. Although you could just compile the vanilla kernel from [http://www.kernel.org/ Kernel.org], it will not have the necessary drivers and modules for the Broadcom SoC on the RPi. You can however apply patches from the vanilla kernel to the RPi one - be prepared for potential compiler grumbles though!
+
The kernel source should be downloaded from the [https://github.com/raspberrypi/linux Raspberry Pi Linux section on GitHub]. Although you could just compile the vanilla kernel from [http://www.kernel.org/ Kernel.org], it will not have the necessary drivers and modules for the Broadcom SoC on the Raspberry Pi. You can however apply patches from the vanilla kernel to the Raspberry Pi one - be prepared for potential compiler grumbles though!
  
At the time of writing, two branches of interest are available:
+
On Jan 2014, the current is rpi-3.10.y. You can check this and other available versions by browsing [https://github.com/raspberrypi/linux Raspberry Pi Linux section on GitHub]
* '''rpi-3.2.27''' - This is the version of the kernel currently used in Raspbian, but not exactly the same - Raspbian stock kernel image (the one available from the foundation's website) has a 3.2.27+ version marking. Please see [http://www.raspberrypi.org/phpBB3/viewtopic.php?f=66&t=26616 this post] for more details.
+
* '''rpi-3.6-y''' - This is a development branch based on the current vanilla kernel. It will eventually replace the 3.2 branch. At the time of writing, the exact version is 3.6.11.
+
  
You can download the source directly using git. For the 3.2 branch:
+
You can download the source directly using Git. For the 3.10 branch:
 
<pre>
 
<pre>
 +
git init
 
git clone --depth 1 git://github.com/raspberrypi/linux.git
 
git clone --depth 1 git://github.com/raspberrypi/linux.git
git checkout rpi-3.2.27
 
 
</pre>
 
</pre>
and for the 3.6 branch:
+
And for the other stable code branch, change the numbers in the following to suit:
 
<pre>
 
<pre>
 +
git init
 
git fetch git://github.com/raspberrypi/linux.git rpi-3.6.y:refs/remotes/origin/rpi-3.6.y
 
git fetch git://github.com/raspberrypi/linux.git rpi-3.6.y:refs/remotes/origin/rpi-3.6.y
 
git checkout rpi-3.6.y
 
git checkout rpi-3.6.y
 
</pre>
 
</pre>
Or you can download a tarball from the website using these links: [https://github.com/raspberrypi/linux/archive/rpi-3.2.27.tar.gz rpi-3.2.27] [https://github.com/raspberrypi/linux/archive/rpi-3.6.y.tar.gz rpi-3.6.y]
+
 
 +
Or you can download a tarball from the same website:
  
 
= Get a compiler =
 
= Get a compiler =
 
Next, you will need to get a version of GCC in order to build the kernel.
 
Next, you will need to get a version of GCC in order to build the kernel.
  
== On the RPi ==
+
== 1. On the Raspberry Pi ==
  
=== Raspbian ===
+
=== Raspbian and PiBang ===
 
<pre>
 
<pre>
 
apt-get update
 
apt-get update
 
apt-get -y dist-upgrade
 
apt-get -y dist-upgrade
apt-get -y install gcc make
+
apt-get -y install gcc make bc screen ncurses-dev
 
</pre>
 
</pre>
  
Line 84: Line 86:
 
</pre>
 
</pre>
  
== Cross compiling from Linux ==
+
=== openSUSE Linux ===
Please note that when cross-compiling, your compiler may not target the correct ARM processor by default. This will at best reduce performance, or worse, compile for a much newer processor resulting in illegal instructions in your code. The pre-built compiler or a custom-built compiler are recommended because of this. (For example, the latest GCC Linaro binary targets armv7-a by default, whereas the RPi requires armv6kz). It is possible to add extra compiler options to the <tt>HOSTCFLAGS</tt> line in <tt>Makefile</tt>. The correct flags are shown on the [[RPi_Software#Compiler|software page]] - note that you may also need to add <tt>-marm</tt> if your compiler produces Thumb code by default.
+
Detailed openSUSE Raspberry Pi 12.3 Image 20130407 + 3.8.8 kernel hack tutorial witten (2013-04-22 updated)
 +
see: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=87&t=40664&p=331953#p331953
 +
The kernel compile takes about 22 hours on Raspberry Pi Model B due massive module compiles. Include all IP_VS, ARPD, Fuse-zfs, Zram and more :-)
 +
 
 +
This works as well for Debian, Fedora Remix and others (just the package install command differs):
 +
zypper install u-boot-tools sudo gcc automake autoconf bison gettext flex libncurses5 ncurses-devel
 +
 
 +
<pre>
 +
cd /usr/src
 +
mkdir GIT; cd GIT; git init; D=`date +"%m-%d-%Y"`
 +
git fetch git://github.com/raspberrypi/linux.git rpi-3.8.y:refs/remotes/origin/rpi-3.8.y
 +
git checkout rpi-3.8.y
 +
tar cpf rpi-3.8.y.$D.tar  rpi-3.8.y
 +
 
 +
cd /usr/src
 +
tar xpf  GIT/rpi-3.8.y.$D.tar
 +
rm linux
 +
ln -s linux-rpi-3.8.y linux
 +
 
 +
cd /usr/src/linux
 +
kversion=$(make -s kernelrelease)
 +
cp linux/.config .config_$kversion
 +
 
 +
cd /usr/src/
 +
# Get config-3.8.7.ipvs+krb5+arpd.tar.bz2 from the tutorial:
 +
wget http://www.raspberrypi.org/phpBB3/download/file.php?id=3174
 +
# Copy the .config file to /usr/src/linux:
 +
tar xpfj config-3.8.7.ipvs+krb5+arpd.tar.bz2
 +
 
 +
 
 +
#Make the kernel and go sleep :-)
 +
cd linux
 +
make oldconfig
 +
nohup make zImage dep modules &
 +
 
 +
#The next day: Install it.
 +
cd /usr/src/linux
 +
kversion=$(make -s kernelrelease)
 +
echo $kversion
 +
mkdir -p  /boot/$kversion
 +
make ARCH=arm INSTALL_PATH=/boot/ install
 +
cp System.map /boot/System.map-$kversion
 +
cp System.map-$kversion /boot/System.map
 +
make ARCH=arm modules_install INSTALL_MOD_PATH=/
 +
make ARCH=arm INSTALL_PATH=/boot/ zinstall
 +
cp .config /boot/config-$kversion
 +
cp ./Module.symvers  /boot/symvers-$kversion
 +
cp arch/arm/boot/Image /boot/kernel.img
 +
</pre>
 +
 
 +
== 2. Cross compiling from Linux ==
 +
Please note that when cross-compiling, your compiler may not target the correct ARM processor by default. This will at best reduce performance, or worse, compile for a much newer processor resulting in illegal instructions in your code. The pre-built compiler or a custom-built compiler are recommended because of this. (For example, the latest GCC Linaro binary targets armv7-a by default, whereas the Raspberry Pi requires armv6kz). It is possible to add extra compiler options to the <tt>HOSTCFLAGS</tt> line in <tt>Makefile</tt>. The correct flags are shown on the [[RPi_Software#Compiler|software page]] - note that you may also need to add <tt>-marm</tt> if your compiler produces Thumb code by default.
  
 
=== Use the provided compiler ===
 
=== Use the provided compiler ===
Download the pre-built bmc2708 compiler from the [https://github.com/raspberrypi/tools/tree/master/arm-bcm2708/arm-bcm2708hardfp-linux-gnueabi RPI tools section on GitHub].
+
Download the pre-built bmc2708 compiler from the [https://github.com/raspberrypi/tools/tree/master/arm-bcm2708/arm-bcm2708hardfp-linux-gnueabi Raspberry Pi tools section on GitHub].
 
<pre>
 
<pre>
git clone git://github.com/raspberrypi/tools.git
+
git clone git://github.com/raspberrypi/tools.git --depth 1
 
</pre>
 
</pre>
or you can download a tarball from the website using [https://github.com/raspberrypi/tools/archive/master.tar.gz this link].
+
 
 +
Or you can download a tarball from the website using [https://github.com/raspberrypi/tools/archive/master.tar.gz this link].
  
 
=== Custom-built Linaro GCC ===
 
=== Custom-built Linaro GCC ===
Line 107: Line 161:
 
</pre>
 
</pre>
  
Crossdev should create a cross-toolchain using the latest stable versions of the required packages. If it fails, you can specify exact versions by removing the "-S" flag and adding the "--b", "--g", "--k" and "--l" flags. On 2012-05-06, <tt>cross -S -v -A gnueabi arm</tt> works just fine.
+
Crossdev should create a cross-toolchain using the latest stable versions of the required packages. If it fails, you can specify exact versions by removing the "-S" flag and adding the "--b", "--g", "--k" and "--l" flags. On 2012-05-06, <tt>cross -S -v -A gnueabi arm</tt> works just fine.
  
 
=== Arch Linux ===
 
=== Arch Linux ===
Line 114: Line 168:
 
</pre>
 
</pre>
  
== Cross compiling from OSX ==
+
== Cross compiling from OS X ==
 
=== Macports ===
 
=== Macports ===
The Kernel source requires a case-sensitive filesystem. If you do not have a HFS+ Case-sensitive partition that can be used, create a disk image with the appropriate format.
+
The kernel source requires a case-sensitive filesystem. If you do not have a HFS+ case-sensitive partition that can be used, create a disk image with the appropriate format.
Ensure latest Xcode and command line tools are installed from [http://developer.apple.com/downloads Apple Developer Connection]
+
Ensure the latest versin of Xcode and command line tools are installed from [http://developer.apple.com/downloads Apple Developer Connection]
 
Install [http://guide.macports.org/#installing macports]
 
Install [http://guide.macports.org/#installing macports]
 
<pre>
 
<pre>
Line 147: Line 201:
 
to
 
to
 
  NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) -Dlinux
 
  NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) -Dlinux
 +
 +
'''Complete script''' requires raspberrypi.config to be in the same folder that you execute from.
 +
<pre>
 +
sudo port install arm-none-eabi-gcc
 +
sudo port install arm-none-eabi-binutils
 +
sudo port install libelf && sudo ln -s /opt/local/include/libelf /usr/include/libelf
 +
sudo curl http://opensource.apple.com/source/dtrace/dtrace-48/sys/elftypes.h?txt -o  /usr/include/elftypes.h
 +
sudo curl http://opensource.apple.com/source/dtrace/dtrace-48/sys/elf.h?txt -o /usr/include/elf.h
 +
#code to append to elf.h
 +
echo "
 +
#define R_386_NONE 0
 +
#define R_386_32 1
 +
#define R_386_PC32 2
 +
#define R_ARM_NONE 0
 +
#define R_ARM_PC24 1
 +
#define R_ARM_ABS32 2
 +
#define R_MIPS_NONE 0
 +
#define R_MIPS_16 1
 +
#define R_MIPS_32 2
 +
#define R_MIPS_REL32 3
 +
#define R_MIPS_26 4
 +
#define R_MIPS_HI16 5
 +
#define R_MIPS_LO16 6" > elf-append.h
 +
sudo -s 'cat elf-append.h >> /usr/include/elf.h'
 +
 +
#Make a case sensitive 3&nbsp;GB disk image, raspberrypi-kernel, and attach it:
 +
hdiutil create -size 10g -type SPARSEBUNDLE -nospotlight -volname raspberrypi-kernel -fs "Case-sensitive Journaled HFS+" -attach ./raspberrypi-kernel.dmg
 +
cp raspberrypi.config /Volumes/raspberrypi-kernel/
 +
mkdir /Volumes/raspberrypi-kernel/src
 +
cd /Volumes/raspberrypi-kernel/src
 +
 +
#Get source, either 1. from a ZIP file (faster), or 2. from Git
 +
#1. From a ZIP file
 +
curl https://codeload.github.com/raspberrypi/linux/zip/rpi-3.6.y -o ./rpi-3.6.y.zip
 +
unzip rpi-3.6.y.zip
 +
#2. From Git (disabled)
 +
#git init
 +
#git fetch git://github.com/raspberrypi/linux.git rpi-3.6.y:refs/remotes/origin/rpi-3.6.y
 +
#git checkout rpi-3.6.y
 +
 +
cpu=$(sysctl hw.ncpu | awk '{print $2}')
 +
cpup1=$((cpu+1))
 +
 +
cd /Volumes/raspberrypi-kernel/src/linux-rpi-3.6.y/
 +
export CCPREFIX=/opt/local/bin/arm-none-eabi-
 +
make mrproper
 +
cp /Volumes/raspberrypi-kernel/raspberrypi.config .config
 +
#Answer yes to all config options
 +
#yes "" | make ARCH=arm CROSS_COMPILE=${CCPREFIX} oldconfig
 +
make ARCH=arm CROSS_COMPILE=${CCPREFIX} -j$cpup1
 +
#make ARCH=arm CROSS_COMPILE=${CCPREFIX} modules -j$cpup1
 +
</pre>
  
 
=== Yagarto ===
 
=== Yagarto ===
Line 157: Line 263:
 
</pre>
 
</pre>
  
Next, in all cases, you will want to get a working kernel configuration to start from. You can get the one running on the RPi by typing the following (on the RPi):
+
Next, in all cases, you will want to get a working kernel configuration to start from. You can get the one running on the Raspberry Pi by typing the following (on the Raspberry Pi):
 
<pre>
 
<pre>
 
zcat /proc/config.gz > .config
 
zcat /proc/config.gz > .config
 
</pre>
 
</pre>
then copy <tt>.config</tt> into your build directory.
+
Then copy <tt>.config</tt> into your build directory.
  
 
Alternatively, the default configuration is available in the downloaded kernel source in <tt>arch/arm/configs/bcmrpi_defconfig</tt>. Just copy this to <tt>.config</tt> in the build directory.
 
Alternatively, the default configuration is available in the downloaded kernel source in <tt>arch/arm/configs/bcmrpi_defconfig</tt>. Just copy this to <tt>.config</tt> in the build directory.
Line 170: Line 276:
 
</pre>
 
</pre>
  
If you are building on the RPi, remove <tt>ARCH=arm CROSS_COMPILE=${CCPREFIX}</tt> from each command.
+
If you are building on the Raspberry Pi, remove <tt>ARCH=arm CROSS_COMPILE=${CCPREFIX}</tt> from each command.
  
 
Ensure that your configuration file is up-to-date:
 
Ensure that your configuration file is up-to-date:
Line 183: Line 289:
 
</pre>
 
</pre>
  
Now you are ready to build:
+
Now you are ready to build:<br>
 +
(On the Raspberry Pi, type 'screen' to open a virtual screen. If you use it you can disconnect from the Raspberry Pi and compile overnight...)
 
<pre>
 
<pre>
 
make ARCH=arm CROSS_COMPILE=${CCPREFIX}
 
make ARCH=arm CROSS_COMPILE=${CCPREFIX}
 
</pre>
 
</pre>
If you are on a multi-core system, you can make the build faster by appending <tt>-j<N></tt> where <tt>N</tt> is the number of cores on your system plus one.
+
If you are on a multi-core system, you can make the build faster by appending <tt>-j<N></tt> where <tt><N></tt> is the number of cores on your system plus one (that is, -j3 for two cores).
  
 
Find something else to get on with while the compilation takes place. On an average PC with the default configuration, this should take about 15 minutes.
 
Find something else to get on with while the compilation takes place. On an average PC with the default configuration, this should take about 15 minutes.
 +
 +
The modules will be build with the following command.
 +
<pre>
 +
make ARCH=arm CROSS_COMPILE=${CCPREFIX} modules
 +
</pre>
  
 
= Transfer the build =
 
= Transfer the build =
Copy your new <tt>kernel.img</tt> file into the RPi boot partition, though preferably as a new file (such as <tt>kernel_new.img</tt>) just in case it doesn't work. If you're building on the RPi, just copy the file to <tt>/boot</tt>. If you use a different filename, edit <tt>config.txt</tt> change the kernel line:
+
The fully built kernel will be <tt>arch/arm/boot/Image</tt>. Copy your new kernel file into the Raspberry Pi boot partition, though preferably as a new file (such as <tt>kernel_new.img</tt>) just in case it doesn't work. If you're building on the Raspberry Pi, just copy the file to <tt>/boot</tt>. If you use a different filename, edit <tt>config.txt</tt> change the kernel line:
 
<pre>
 
<pre>
 
kernel=kernel_new.img
 
kernel=kernel_new.img
Line 198: Line 310:
 
</pre>
 
</pre>
  
Now you need to transfer the modules. In the build directory, run the following (substituting <tt><modules_path></tt> for a folder somewhere (e.g. <tt>~/modules</tt>):
+
Now you need to transfer the modules. Set an environment variable that points to a temporary module path.
 
<pre>
 
<pre>
make ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=<modules_path> modules_install
+
export MODULES_TEMP=~/modules
 
</pre>
 
</pre>
  
The contents of this directory should then be copied into the RPi root directory. NOTE: If you have rebuilt the new kernel with exactly the same version as the one that's running, you'll need to remove the old modules first. Ideally this should be done offline by mounting the SD card on another system.
+
In the build directory, run the following command:
 +
<pre>
 +
make ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=${MODULES_TEMP} modules_install
 +
</pre>
 +
 
 +
The contents of this directory, a single <pre>lib</pre> directory, should then be copied into the Raspberry Pi root directory, merging or overwriting <pre>/lib</pre>
 +
NOTE: If you have rebuilt the new kernel with exactly the same version as the one that's running, you'll need to remove the old modules first. Ideally this should be done offline by mounting the SD card on another system.
 +
 
 +
NOTE: The lib directory will have symlinks back to the kernel sources (lib/modules/<kernel-version>/source and lib/modules/<kernel-version>/build). If you have limited space on the SD card and don't intend to compile modules on the Raspberry Pi itself, you will probably want to remove those links before you transfer the lib directory. The size difference can be many hundreds of MB.
  
Your RPi should now be ready to boot the new kernel. However, at this point it's recommended that you update your GPU firmware and libraries. '''This is required if you've just moved from 3.2 to 3.6 as the firmware interface has changed'''.
+
Your Raspberry Pi should now be ready to boot the new kernel. However, at this point it's recommended that you update your GPU firmware and libraries. '''This is required if you've just moved from 3.2 to 3.6 as the firmware interface has changed'''.
  
 
= Get the firmware =
 
= Get the firmware =
 
The firmware and boot files should be updated at the same time to ensure that your new kernel works properly. Again, two branches are available:
 
The firmware and boot files should be updated at the same time to ensure that your new kernel works properly. Again, two branches are available:
* '''master''' - This is the version of firmware currently used in Raspbian (i.e. it works with the 3.2 kernel).
+
* '''master''' - This is the version of firmware currently used in Raspbian (that is, it works with the 3.2 kernel).
 
* '''next''' - This is a development branch which provides a newer GPU firmware to work with the updated drivers in the 3.6 kernel.
 
* '''next''' - This is a development branch which provides a newer GPU firmware to work with the updated drivers in the 3.6 kernel.
  
You can either download the source directly using git:
+
You can either download the source directly using Git:
You can download the firmware directly using git. For the master branch:
+
You can download the firmware directly using Git. For the master branch:
 
<pre>
 
<pre>
 
git clone git://github.com/raspberrypi/firmware.git
 
git clone git://github.com/raspberrypi/firmware.git
 
</pre>
 
</pre>
and for the next branch:
+
And for the next branch:
 
<pre>
 
<pre>
 
git fetch git://github.com/raspberrypi/firmware.git next:refs/remotes/origin/next
 
git fetch git://github.com/raspberrypi/firmware.git next:refs/remotes/origin/next
Line 224: Line 344:
  
 
= Transfer the firmware =
 
= Transfer the firmware =
Firstly, update the required boot files in the RPi <tt>boot</tt> directory with those you've downloaded. These are:
+
Firstly, update the required boot files in the Raspberry Pi <tt>boot</tt> directory with those you've downloaded. These are:
 
* bootcode.bin
 
* bootcode.bin
 
* fixup.dat
 
* fixup.dat
 
* start.elf
 
* start.elf
  
Next, you need to copy the VC libraries over. There are two copies of this: one for hard float and one for soft float. To find the correct one, run the following command (substituting the program name for your compiler binary as required):
+
Next, you need to copy the VC libraries over. There are two copies of this: one for hard float and one for soft float. To find the correct one, run the following command:
 
<pre>
 
<pre>
arm-none-linux-gnueabi-gcc -v 2>&1 | grep hard
+
${CCPREFIX}gcc -v 2>&1 | grep hard
 
</pre>
 
</pre>
  
 
If something prints out, and you can see <tt>--with-float=hard</tt>, you need the hard float ones. NOTE: The current version of Raspbian uses hard float.
 
If something prints out, and you can see <tt>--with-float=hard</tt>, you need the hard float ones. NOTE: The current version of Raspbian uses hard float.
  
Remove the <tt>/opt/vc</tt> directory from the RPi root, then:
+
Remove the <tt>/opt/vc</tt> directory from the Raspberry Pi root, then:
* For hard float, copy <tt>vc</tt> from the <tt>hardfp/opt</tt> directory into <tt>/opt</tt> in the RPi root directory
+
* For hard float, copy <tt>vc</tt> from the <tt>hardfp/opt</tt> directory into <tt>/opt</tt> in the Raspberry Pi root directory
* Otherwise copy <tt>vc</tt> from the top-level <tt>opt</tt> directory into <tt>/opt</tt> in the RPi root directory.
+
* Otherwise copy <tt>vc</tt> from the top-level <tt>opt</tt> directory into <tt>/opt</tt> in the Raspberry Pi root directory.
 +
 
 +
Note: The hard float vs soft float here refers only to the kernel itself, not the functionality it provides. Your applications will still be able to use hard floats. The kernel doesn't use floats anyway, so it is not something to worry about as long as you select the correct <tt>vc</tt> directory to copy.
  
 
= Test your build =
 
= Test your build =
Power cycle your RPi and check the following:
+
Power cycle your Raspberry Pi and check the following:
 
* If you have the serial port on the GPIO expander wired up, you should see the kernel booting.
 
* If you have the serial port on the GPIO expander wired up, you should see the kernel booting.
 
* The screen works - the kernel boots and you get a login prompt.
 
* The screen works - the kernel boots and you get a login prompt.
Line 247: Line 369:
 
* Run <tt>uname -a</tt> and check that your new kernel is the one that's running.
 
* Run <tt>uname -a</tt> and check that your new kernel is the one that's running.
 
* Make sure you don't have any odd error messages during boot that may indicate a module isn't working properly. If you see <tt>missed completion of cmd 18</tt> regarding DMA transfers to the SD card, you can safely ignore it.
 
* Make sure you don't have any odd error messages during boot that may indicate a module isn't working properly. If you see <tt>missed completion of cmd 18</tt> regarding DMA transfers to the SD card, you can safely ignore it.
 +
 +
= Build modules for the running kernel =
 +
[https://github.com/notro/rpi-source/wiki rpi-source] downloads a matching source for the running kernel.
 +
It supports rpi-update kernels and Raspian kernels.
 +
 +
Examples: https://github.com/notro/rpi-source/wiki/Examples-on-how-to-build-various-modules
 +
 +
= Easy kernel building with rpi-build =
 +
Now it's easy for everyone to build, install and distribute Linux kernels for the Raspberry Pi.
 +
 +
rpi-build installs all prerequisites and downloads all necessary source files.
 +
 +
Wiki with examples: https://github.com/notro/rpi-build/wiki
 +
 +
Build and install the latest Raspberry Pi/Linux kernel on the Raspberry Pi (~11 hours)
 +
<pre>
 +
rpi-build use[stdlib] rpi_linux build
 +
rpi-build use[stdlib] rpi_linux install
 +
</pre>
 +
From a build machine (cross compiling)
 +
<pre>
 +
rpi-build use[stdlib] rpi_linux build
 +
rpi-build use[stdlib] rpi_linux install SSHIP=<Raspberry Pi IP address>
 +
</pre>
 +
Upload the kernel to GitHub
 +
<pre>
 +
rpi-build use[stdlib] rpi_linux commit COMMIT_MESSAGE="First release" FW_REPO=<path to Git repository>
 +
rpi-build use[stdlib] rpi_linux push
 +
</pre>
 +
Install the kernel from GitHub
 +
<pre>
 +
sudo REPO_URI=<github repo url> rpi-update
 +
</pre>
 +
  
 
{{Template:Raspberry Pi}}
 
{{Template:Raspberry Pi}}
 
[[Category:RaspberryPi]]
 
[[Category:RaspberryPi]]
 +
[[Category:Linux-kernel]]

Latest revision as of 14:55, 11 July 2014

Back to the Hub.


Software & Distributions:

Software - an overview.

Distributions - operating systems and development environments for the Raspberry Pi.

Kernel Compilation - advice on compiling a kernel.

Performance - measures of the Raspberry Pi's performance.

Programming - programming languages that might be used on the Raspberry Pi.

Overview

This page explains how to rebuild the kernel image for the Raspberry Pi. There are two possible routes available:

  1. Compile on the Raspberry Pi itself
  2. Cross compile on another Linux system

Both of these routes are covered below, however, you are strongly recommended to follow the cross-compilation route. The low processing power of the Raspberry Pi means that a local compile will take many hours. A compilation of the latest kernel and modules took about 752 minutes (12h30m)!

If you want to compile an upstream kernel, rather than the Raspberry Pi Foundation's downstream kernel, please see RPi_Upstream_Kernel_Compilation for a few tips.

Example Checklist/Roadmap

This section serves to hold a new user's hand just a bit more than some of the other more generic information below in the document. To get more information on the steps in the roadmap, search this page for additional details. It assumes you can navigate filesystems, move files across systems, and have a general understanding of compiling linux kernels, filesystems, partitions, and block devices.

This series of steps yielded a successful custom/updated hardfp kernel to a stock Raspbian installation, cross compiled from an AMD 64-bit Debian system without regression on any kernel configuration options or requiring modified boot parameters. Be aware that in the worst case, you may need to overlay a stock set of kernel/modules/firmware on the Raspberry Pi if something fails. If you do not know how to do this, then a reimage of the SD card may be necessary. Assuming this is not an issue for your configuration, continue onward:

  1. Get the latest Raspberry Pi kernel source (https://github.com/raspberrypi/linux)
  2. Set an environment variable KERNEL_SRC to point to the location of the source (for example, KERNEL_SRC=/home/me/linux/ )
  3. Get the latest Raspberry Pi compiler (git clone https://github.com/raspberrypi/tools)
  4. Set an environment variable CCPREFIX to point to the location of tools (for example, CCPREFIX=/home/me/tools/arm-bcm2708/arm-bcm2708-linux-gnueabi/bin/arm-bcm2708-linux-gnueabi- )
  5. From the kernel clone location, clean the kernel source with "make mrproper"
  6. Pull the /proc/config.gz from the running Raspbian installation
  7. Prime the kernel with the old configuration by running "ARCH=arm CROSS_COMPILE=${CCPREFIX} make oldconfig"
  8. Modify the kernel configuration by either modifying the .config file or using "ARCH=arm CROSS_COMPILE=${CCPREFIX} make menuconfig"
  9. Build the new kernel by using "ARCH=arm CROSS_COMPILE=${CCPREFIX} make"
  10. Set an environment variable, MODULES_TEMP, to point to the location of the source (for example, MODULES_TEMP=/home/me/modules/ )
  11. Set aside the new kernel modules by using "ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=${MODULES_TEMP} make modules_install"
  12. From the tools clone location, in the mkimage directory, run "./imagetool-uncompressed.py ${KERNEL_SRC}/arch/arm/boot/zImage"
  13. Move the resulting kernel.img to the Raspberry Pi's /boot/ directory
  14. Package up the modules into an archive such that at the top level, the structure looks like this:
    • ./firmware
    • ./firmware/brcm
    • ./firmware/edgeport
    • ./firmware/emi26
    • ...
    • ./modules
    • ./modules/3.6.11+
    • ./modules/3.6.11+/kernel
    • ./modules/3.6.11+/kernel/lib
    • ./modules/3.6.11+/kernel/fs
    • ...
  15. Move the modules archive to the Raspberry Pi and extract them such that the aforementioned firmware and modules directories overwrite /lib/firmware and /lib/modules
  16. Get the latest Raspberry Pi firmware (git://github.com/raspberrypi/firmware.git)
  17. Transfer the following files from the firmware/boot directory to the Raspberry Pi /boot directory:
    • bootcode.bin
    • fixup.dat
    • start.elf
  18. Transfer the firmware/hardfp/opt directory to the Raspberry Pi /opt directory
  19. Reboot the Raspberry Pi

The Raspberry Pi should now boot with the newly configured/recompiled kernel.

Get the kernel source

The kernel source should be downloaded from the Raspberry Pi Linux section on GitHub. Although you could just compile the vanilla kernel from Kernel.org, it will not have the necessary drivers and modules for the Broadcom SoC on the Raspberry Pi. You can however apply patches from the vanilla kernel to the Raspberry Pi one - be prepared for potential compiler grumbles though!

On Jan 2014, the current is rpi-3.10.y. You can check this and other available versions by browsing Raspberry Pi Linux section on GitHub

You can download the source directly using Git. For the 3.10 branch:

git init
git clone --depth 1 git://github.com/raspberrypi/linux.git

And for the other stable code branch, change the numbers in the following to suit:

git init
git fetch git://github.com/raspberrypi/linux.git rpi-3.6.y:refs/remotes/origin/rpi-3.6.y
git checkout rpi-3.6.y

Or you can download a tarball from the same website:

Get a compiler

Next, you will need to get a version of GCC in order to build the kernel.

1. On the Raspberry Pi

Raspbian and PiBang

apt-get update
apt-get -y dist-upgrade
apt-get -y install gcc make bc screen ncurses-dev

Arch Linux

pacman -Syu
pacman -S gcc make

openSUSE Linux

Detailed openSUSE Raspberry Pi 12.3 Image 20130407 + 3.8.8 kernel hack tutorial witten (2013-04-22 updated) see: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=87&t=40664&p=331953#p331953 The kernel compile takes about 22 hours on Raspberry Pi Model B due massive module compiles. Include all IP_VS, ARPD, Fuse-zfs, Zram and more :-)

This works as well for Debian, Fedora Remix and others (just the package install command differs):

zypper install u-boot-tools sudo gcc automake autoconf bison gettext flex libncurses5 ncurses-devel
cd /usr/src
mkdir GIT; cd GIT; git init; D=`date +"%m-%d-%Y"`
git fetch git://github.com/raspberrypi/linux.git rpi-3.8.y:refs/remotes/origin/rpi-3.8.y
git checkout rpi-3.8.y
tar cpf rpi-3.8.y.$D.tar   rpi-3.8.y

cd /usr/src
tar xpf  GIT/rpi-3.8.y.$D.tar
rm linux
ln -s linux-rpi-3.8.y linux

cd /usr/src/linux
kversion=$(make -s kernelrelease)
cp linux/.config .config_$kversion

cd /usr/src/
# Get config-3.8.7.ipvs+krb5+arpd.tar.bz2 from the tutorial:
wget http://www.raspberrypi.org/phpBB3/download/file.php?id=3174
# Copy the .config file to /usr/src/linux: 
tar xpfj config-3.8.7.ipvs+krb5+arpd.tar.bz2


#Make the kernel and go sleep :-)
cd linux
make oldconfig
nohup make zImage dep modules &

#The next day: Install it.
cd /usr/src/linux
kversion=$(make -s kernelrelease)
echo $kversion
mkdir -p  /boot/$kversion
make ARCH=arm INSTALL_PATH=/boot/ install
cp System.map /boot/System.map-$kversion
cp System.map-$kversion /boot/System.map
make ARCH=arm modules_install INSTALL_MOD_PATH=/
make ARCH=arm INSTALL_PATH=/boot/ zinstall
cp .config /boot/config-$kversion
cp ./Module.symvers  /boot/symvers-$kversion
cp arch/arm/boot/Image /boot/kernel.img

2. Cross compiling from Linux

Please note that when cross-compiling, your compiler may not target the correct ARM processor by default. This will at best reduce performance, or worse, compile for a much newer processor resulting in illegal instructions in your code. The pre-built compiler or a custom-built compiler are recommended because of this. (For example, the latest GCC Linaro binary targets armv7-a by default, whereas the Raspberry Pi requires armv6kz). It is possible to add extra compiler options to the HOSTCFLAGS line in Makefile. The correct flags are shown on the software page - note that you may also need to add -marm if your compiler produces Thumb code by default.

Use the provided compiler

Download the pre-built bmc2708 compiler from the Raspberry Pi tools section on GitHub.

git clone git://github.com/raspberrypi/tools.git --depth 1

Or you can download a tarball from the website using this link.

Custom-built Linaro GCC

See Linaro GCC Compilation.

Ubuntu

apt-get install gcc-arm-linux-gnueabi make ncurses-dev

Gentoo Linux

crossdev -S -v -t arm-unknown-linux-gnueabi

Crossdev should create a cross-toolchain using the latest stable versions of the required packages. If it fails, you can specify exact versions by removing the "-S" flag and adding the "--b", "--g", "--k" and "--l" flags. On 2012-05-06, cross -S -v -A gnueabi arm works just fine.

Arch Linux

yaourt -S arm-linux-gnueabi-gcc

Cross compiling from OS X

Macports

The kernel source requires a case-sensitive filesystem. If you do not have a HFS+ case-sensitive partition that can be used, create a disk image with the appropriate format. Ensure the latest versin of Xcode and command line tools are installed from Apple Developer Connection Install macports

port install arm-none-eabi-gcc
port install arm-none-eabi-binutils

If you get an error message that elf.h is missing

sudo port install libelf && sudo ln -s /opt/local/include/libelf /usr/include/libelf

From opensource.apple.com, download and copy elf.h and elftypes.h to /usr/include

Edit elf.h and add

#define R_386_NONE        0
#define R_386_32          1
#define R_386_PC32        2
#define R_ARM_NONE        0
#define R_ARM_PC24        1
#define R_ARM_ABS32       2
#define R_MIPS_NONE       0
#define R_MIPS_16         1
#define R_MIPS_32         2
#define R_MIPS_REL32      3
#define R_MIPS_26         4
#define R_MIPS_HI16       5
#define R_MIPS_LO16       6

If you get a "SEGMENT_SIZE is undeclared" error open the Makefile and change the line:

NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)

to

NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) -Dlinux

Complete script requires raspberrypi.config to be in the same folder that you execute from.

sudo port install arm-none-eabi-gcc
sudo port install arm-none-eabi-binutils
sudo port install libelf && sudo ln -s /opt/local/include/libelf /usr/include/libelf
sudo curl http://opensource.apple.com/source/dtrace/dtrace-48/sys/elftypes.h?txt -o  /usr/include/elftypes.h
sudo curl http://opensource.apple.com/source/dtrace/dtrace-48/sys/elf.h?txt -o /usr/include/elf.h
#code to append to elf.h
echo "
#define R_386_NONE 0
#define R_386_32 1
#define R_386_PC32 2
#define R_ARM_NONE 0
#define R_ARM_PC24 1
#define R_ARM_ABS32 2
#define R_MIPS_NONE 0
#define R_MIPS_16 1
#define R_MIPS_32 2
#define R_MIPS_REL32 3
#define R_MIPS_26 4
#define R_MIPS_HI16 5
#define R_MIPS_LO16 6" > elf-append.h
sudo -s 'cat elf-append.h >> /usr/include/elf.h'

#Make a case sensitive 3 GB disk image, raspberrypi-kernel, and attach it:
hdiutil create -size 10g -type SPARSEBUNDLE -nospotlight -volname raspberrypi-kernel -fs "Case-sensitive Journaled HFS+" -attach ./raspberrypi-kernel.dmg
cp raspberrypi.config /Volumes/raspberrypi-kernel/
mkdir /Volumes/raspberrypi-kernel/src
cd /Volumes/raspberrypi-kernel/src

#Get source, either 1. from a ZIP file (faster), or 2. from Git
#1. From a ZIP file
curl https://codeload.github.com/raspberrypi/linux/zip/rpi-3.6.y -o ./rpi-3.6.y.zip
unzip rpi-3.6.y.zip
#2. From Git (disabled)
#git init
#git fetch git://github.com/raspberrypi/linux.git rpi-3.6.y:refs/remotes/origin/rpi-3.6.y
#git checkout rpi-3.6.y

cpu=$(sysctl hw.ncpu | awk '{print $2}')
cpup1=$((cpu+1))

cd /Volumes/raspberrypi-kernel/src/linux-rpi-3.6.y/
export CCPREFIX=/opt/local/bin/arm-none-eabi-
make mrproper
cp /Volumes/raspberrypi-kernel/raspberrypi.config .config
#Answer yes to all config options
#yes "" | make ARCH=arm CROSS_COMPILE=${CCPREFIX} oldconfig
make ARCH=arm CROSS_COMPILE=${CCPREFIX} -j$cpup1
#make ARCH=arm CROSS_COMPILE=${CCPREFIX} modules -j$cpup1

Yagarto

Download and install from here.

Perform the compilation

Firstly, ensure your build directory is clean:

make mrproper

Next, in all cases, you will want to get a working kernel configuration to start from. You can get the one running on the Raspberry Pi by typing the following (on the Raspberry Pi):

zcat /proc/config.gz > .config

Then copy .config into your build directory.

Alternatively, the default configuration is available in the downloaded kernel source in arch/arm/configs/bcmrpi_defconfig. Just copy this to .config in the build directory.

From this point on, if you are cross-compiling, set an environment variable CCPREFIX that points to the prefix of your compiler binary as each compiler will be named slightly differently.

export CCPREFIX=/path/to/your/compiler/binary/prefix-of-binary-

If you are building on the Raspberry Pi, remove ARCH=arm CROSS_COMPILE=${CCPREFIX} from each command.

Ensure that your configuration file is up-to-date:

make ARCH=arm CROSS_COMPILE=${CCPREFIX} oldconfig

If any configuration options have been added, you will be asked what set each option to. If you don't know the answer, just press enter to accept the default.

Optionally, if you want to make changes to the configuration, run this next:

make ARCH=arm CROSS_COMPILE=${CCPREFIX} menuconfig

Now you are ready to build:
(On the Raspberry Pi, type 'screen' to open a virtual screen. If you use it you can disconnect from the Raspberry Pi and compile overnight...)

make ARCH=arm CROSS_COMPILE=${CCPREFIX}

If you are on a multi-core system, you can make the build faster by appending -j<N> where <N> is the number of cores on your system plus one (that is, -j3 for two cores).

Find something else to get on with while the compilation takes place. On an average PC with the default configuration, this should take about 15 minutes.

The modules will be build with the following command.

make ARCH=arm CROSS_COMPILE=${CCPREFIX} modules

Transfer the build

The fully built kernel will be arch/arm/boot/Image. Copy your new kernel file into the Raspberry Pi boot partition, though preferably as a new file (such as kernel_new.img) just in case it doesn't work. If you're building on the Raspberry Pi, just copy the file to /boot. If you use a different filename, edit config.txt change the kernel line:

kernel=kernel_new.img
#kernel=kernel.img

Now you need to transfer the modules. Set an environment variable that points to a temporary module path.

export MODULES_TEMP=~/modules

In the build directory, run the following command:

make ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=${MODULES_TEMP} modules_install
The contents of this directory, a single
lib
directory, should then be copied into the Raspberry Pi root directory, merging or overwriting
/lib

NOTE: If you have rebuilt the new kernel with exactly the same version as the one that's running, you'll need to remove the old modules first. Ideally this should be done offline by mounting the SD card on another system.

NOTE: The lib directory will have symlinks back to the kernel sources (lib/modules/<kernel-version>/source and lib/modules/<kernel-version>/build). If you have limited space on the SD card and don't intend to compile modules on the Raspberry Pi itself, you will probably want to remove those links before you transfer the lib directory. The size difference can be many hundreds of MB.

Your Raspberry Pi should now be ready to boot the new kernel. However, at this point it's recommended that you update your GPU firmware and libraries. This is required if you've just moved from 3.2 to 3.6 as the firmware interface has changed.

Get the firmware

The firmware and boot files should be updated at the same time to ensure that your new kernel works properly. Again, two branches are available:

  • master - This is the version of firmware currently used in Raspbian (that is, it works with the 3.2 kernel).
  • next - This is a development branch which provides a newer GPU firmware to work with the updated drivers in the 3.6 kernel.

You can either download the source directly using Git: You can download the firmware directly using Git. For the master branch:

git clone git://github.com/raspberrypi/firmware.git

And for the next branch:

git fetch git://github.com/raspberrypi/firmware.git next:refs/remotes/origin/next

Or you can download a tarball from the website using these links: master next

Transfer the firmware

Firstly, update the required boot files in the Raspberry Pi boot directory with those you've downloaded. These are:

  • bootcode.bin
  • fixup.dat
  • start.elf

Next, you need to copy the VC libraries over. There are two copies of this: one for hard float and one for soft float. To find the correct one, run the following command:

${CCPREFIX}gcc -v 2>&1 | grep hard

If something prints out, and you can see --with-float=hard, you need the hard float ones. NOTE: The current version of Raspbian uses hard float.

Remove the /opt/vc directory from the Raspberry Pi root, then:

  • For hard float, copy vc from the hardfp/opt directory into /opt in the Raspberry Pi root directory
  • Otherwise copy vc from the top-level opt directory into /opt in the Raspberry Pi root directory.

Note: The hard float vs soft float here refers only to the kernel itself, not the functionality it provides. Your applications will still be able to use hard floats. The kernel doesn't use floats anyway, so it is not something to worry about as long as you select the correct vc directory to copy.

Test your build

Power cycle your Raspberry Pi and check the following:

  • If you have the serial port on the GPIO expander wired up, you should see the kernel booting.
  • The screen works - the kernel boots and you get a login prompt.
  • The VC interface is working - if the 'OK' LED flashes regularly eight or so times every few seconds once the OS has booted, it's not. You can also test this by running vcgencmd measure_temp. If it prints "VCHI initialization failed", you have the a mismatch between the firmware, the VC libraries, and the kernel driver.
  • Run uname -a and check that your new kernel is the one that's running.
  • Make sure you don't have any odd error messages during boot that may indicate a module isn't working properly. If you see missed completion of cmd 18 regarding DMA transfers to the SD card, you can safely ignore it.

Build modules for the running kernel

rpi-source downloads a matching source for the running kernel. It supports rpi-update kernels and Raspian kernels.

Examples: https://github.com/notro/rpi-source/wiki/Examples-on-how-to-build-various-modules

Easy kernel building with rpi-build

Now it's easy for everyone to build, install and distribute Linux kernels for the Raspberry Pi.

rpi-build installs all prerequisites and downloads all necessary source files.

Wiki with examples: https://github.com/notro/rpi-build/wiki

Build and install the latest Raspberry Pi/Linux kernel on the Raspberry Pi (~11 hours)

rpi-build use[stdlib] rpi_linux build
rpi-build use[stdlib] rpi_linux install

From a build machine (cross compiling)

rpi-build use[stdlib] rpi_linux build
rpi-build use[stdlib] rpi_linux install SSHIP=<Raspberry Pi IP address>

Upload the kernel to GitHub

rpi-build use[stdlib] rpi_linux commit COMMIT_MESSAGE="First release" FW_REPO=<path to Git repository>
rpi-build use[stdlib] rpi_linux push

Install the kernel from GitHub

sudo REPO_URI=<github repo url> rpi-update