Building a Cross Compiler
This document will help you build Debian packages of a cross-compilation toolchain. It is based on a HOWTO by Josh Triplett, with his kind permission.
Note that most sensible cross-toolchain combinations within Debian are built by the Embedded Debian Project, so you may well just be able to apt-get what you need on their Toolchains page: http://www.emdebian.org/tools/crosstools.html . They also maintain scripts which effectively do what this page describes. Take a look at the 'buildcross' package from Debian experimental, which will build a whole range of toolchains.
Commands you need to run as root assume you have already set up sudo on your system.
We will be building a cross-compiler from the gcc-4.1 package. Specific version numbers for packages are listed as VERSION; substitute the version number of the latest package in unstable (or testing).
Notes for Debian unstable
We build gcc-4.4 whose cross package additionally build-depends on gcc-4.4-source which you henceforth must install.
The package linux-kernel-headers is now called linux-libc-dev instead.
The three packages libc6-dev, libc6, linux-libc-dev have additional dependencies, so you need to get the (native for the target arch) gcc-4.4-base, libc-bin, libc-dev-bin and libgcc2 (libgcc1, libgcc4, whatever your target needs) packages additionally. Now, dpkg-cross refuses to convert those without “any useful files”, so you need to pass the -A option in addition to -b and -a $ARCH.
A bit uglily, you get libgcc2-m68k-cross depending on gcc-4.4-base-m68k-cross from dpkg-cross and later, after compiling, libgcc2-m68k-cross depending on gcc-4.4-m68k-linux-gnu-base. Just remove the dpkg-cross-generated one once you got the new ones.
Build a cross-compilation toolchain
Create a working directory
mkdir -p ~/src/cross-toolchain cd ~/src/cross-toolchain
Some useful variables
These will be used in the commands in this document. Replace "arm" with the architecture for which you are building a cross-compiler.
unset ARCH # make sure it’s not exported ARCH=arm # set to the value we want to use
Get the source for binutils and GCC
apt-get source binutils gcc-4.1
Install Build-Depends
sudo apt-get build-dep binutils gcc-4.1
Note that gcc-4.1 may have build-dependencies that apt-get can't figure out; this is not a problem, just make sure you install all the ones that apt-get understands. Unfortunately, apt-get build-dep may give an error if such a situation arises; in this case, take the list of packages apt-get provided before giving an error, and install them using "sudo apt-get install pkg1 pkg2 pkg3 ...".
Install fakeroot
fakeroot allows you to build packages without being root.
sudo apt-get install fakeroot
Install dpkg-cross
dpkg-cross adds cross-compilation support to some of the basic Debian package tools. dpkg-cross can also convert packages designed for the target architecture into packages usable for cross-compilation to that architecture.
sudo apt-get install dpkg-cross
Build and install binutils
cd binutils-VERSION export TARGET=$(dpkg-architecture -a$ARCH -qDEB_HOST_GNU_TYPE 2>/dev/null) # this is for binutils <= 2.20 #fakeroot debian/rules binary-cross >../binutils.build 2>&1 || echo 'Build error' # this is for binutils >= 2.21 dpkg-buildpackage -b -uc -us -rfakeroot >../binutils.build 2>&1 || echo 'Build error' unset TARGET cd .. sudo dpkg -i binutils-$ARCH-linux-gnu_VERSION_HOSTARCH.deb
Convert library packages
You will need cross-compilation packages for various libraries; dpkg-cross can convert native packages for the target architecture into packages usable for cross-compilation. Note that the mirror ftp.us.debian.org only has amd64 and i386 packages, so to build a cross-compilation toolchain for another architecture (e.g. arm), you will have to use a mirror other than ftp.us.debian.org.
wget http://ftp.XX.debian.org/debian/pool/main/g/glibc/libc6-dev_VERSION_$ARCH.deb wget http://ftp.XX.debian.org/debian/pool/main/g/glibc/libc6_VERSION_$ARCH.deb wget http://ftp.XX.debian.org/debian/pool/main/l/linux-kernel-headers/linux-kernel-headers_VERSION_$ARCH.deb dpkg-cross -a $ARCH -b l*.deb sudo dpkg -i l*$ARCH-cross*.deb
It may be needed to download and convert libc-bin and libc-dev-bin packages too, otherwise the packages’ dependencies can maybe not be resolved. Use dpkg-cross -a m68k -A -b l*.deb in that case.
If you have an architecture that needs a libgcc[124] package, such as libgcc2-m68k-cross, installed to build gcc itself, it’s useful to install that from a previous build first (otherwise, convert it now, the same way).
Build and install GCC
Now that you have all the necessary prerequisites, you can build a cross-compiling GCC.
cd gcc-VERSION export GCC_TARGET=$ARCH debian/rules control dpkg-buildpackage -us -uc -rfakeroot -b > ../gcc.build 2>&1 || echo 'Build error' cd .. sudo dpkg -i *-VERSION-$ARCH-linux-gnu*.deb *-$ARCH-cross_VERSION*.deb
If you run into this error, or a similar one…
dh_strip -plibgcc2-m68k-cross --dbg-package=libgcc2-dbg-m68k-cross objcopy: Unable to recognise the format of the input file `debian/libgcc2-m68k-cross/usr/m68k-linux-gnu/lib/libgcc_s.so.2' dh_strip: objcopy --only-keep-debug debian/libgcc2-m68k-cross/usr/m68k-linux-gnu/lib/libgcc_s.so.2 debian/libgcc2-dbg-m68k-cross/usr/lib/debug//usr/m68k-linux-gnu/lib/libgcc_s.so.2 returned exit code 1 make[1]: *** [stamps/08-binary-stamp-libgcc] Error 2 make[1]: Leaving directory `/home/tg/X/gcc-4.4-4.4.5' make: *** [binary] Error 2 dpkg-buildpackage: error: fakeroot debian/rules binary gave error exit status 2
… then this will help:
tg@zigo:~/X/gcc-4.4-4.4.5 $ sudo apt-get install binutils-multiarch [sudo] password for tg: Reading package lists... Done Building dependency tree Reading state information... Done Starting Starting 2 Done The following NEW packages will be installed: binutils-multiarch 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 0 B/2127 kB of archives. After this operation, 7164 kB of additional disk space will be used. Selecting previously deselected package binutils-multiarch. (Reading database ... 32493 files and directories currently installed.) Unpacking binutils-multiarch (from .../binutils-multiarch_2.21.0.20110216-2_amd64.deb) ... Adding 'diversion of /usr/bin/nm to /usr/bin/nm.single by binutils-multiarch' Adding 'diversion of /usr/bin/objdump to /usr/bin/objdump.single by binutils-multiarch' Adding 'diversion of /usr/bin/objcopy to /usr/bin/objcopy.single by binutils-multiarch' Adding 'diversion of /usr/bin/strings to /usr/bin/strings.single by binutils-multiarch' Adding 'diversion of /usr/bin/strip to /usr/bin/strip.single by binutils-multiarch' Adding 'diversion of /usr/bin/size to /usr/bin/size.single by binutils-multiarch' Adding 'diversion of /usr/bin/ar to /usr/bin/ar.single by binutils-multiarch' Adding 'diversion of /usr/bin/ranlib to /usr/bin/ranlib.single by binutils-multiarch' Adding 'diversion of /usr/bin/addr2line to /usr/bin/addr2line.single by binutils-multiarch' Adding 'diversion of /usr/bin/gprof to /usr/bin/gprof.single by binutils-multiarch' Adding 'diversion of /usr/bin/readelf to /usr/bin/readelf.single by binutils-multiarch' Setting up binutils-multiarch (2.21.0.20110216-2) ...
Test the cross-compile environment
Test compilation
Create a file "hello.c", containing the following code:
#include <stdio.h> int main() { printf("Hello cross-compiling world!\n"); return 0; }
Compile it statically with the new cross-compiler.
$ARCH-linux-gnu-gcc -static hello.c -o hello
Check the binary's type with "file".
file hello
You should see something like:
hello: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 (SYSV), for GNU/Linux 2.2.0, statically linked, not stripped
for the PowerPC architecture.
Install qemu
qemu is an emulator for various architectures. It supports both whole-system emulation as well as single-program emulation with system-call conversion.
sudo apt-get install qemu
Run the test program with qemu
To run the test program with qemu, just prefix it with "qemu-$ARCH" (assuming of course that your architecture is supported by qemu).
qemu-$ARCH ./hello
You should see:
Hello cross-compiling world!
Get all the libraries you need
apt-cross is in Lenny but no longer in Squeeze. pdebuild-cross in Squeeze contains an early version of xapt or you can use the xapt xapt package from experimental until Squeeze is released.
apt-cross reminders:
apt-get install apt-cross dpkg-cross
Update
apt-cross -a $ARCH -u
Fetch your cross favorite library
apt-cross -a $ARCH -i $LIBRARY