This is provided to allow existing linux kernel developers experiment with the updated version of GCC (besides the complicated building instructions the code just has a small patch for a known issue with android and 4.6.* otherwise is directly from GNU (see build information below)
The packages I'm also providing to help developers current on windows (With cygwin but no other virtual environment) to start exploring android Linux kernel development for their devices. (In addition to a OSX toolchain for more advanced mac users)
due to the slight differences between kernels on different devices this How To is intended to be used for advanced users who can adjust for the differences required for the devices specific kernel.
I may add additional guides to this thread if I find a need for them.
I have two versions of a GCC-4.6.3 toolchain
1) For x86 linux: toolchain-4.6.3.tar.bz2 (Sha1: c8c57aba6ad92e9acddf29ba8620ba880be09a81)
2) For Cygwin (windows): toolchain-4.6.3.cygwin.tar.bz2 (Sha1: 6947e1c1ba95195019f542eb8ba0708667b63eca)
3) For OSX (mac/darwin): toolchain-4.6.3.darwin.tar.bz2 (Sha1: 9a977f0672863fdd9501383a6ad1e30723281f68)
> The linux version was built via this script: http://pastebin.com/b2dZ8YtG (or in the included toolchain_notes.txt)
> The cygwin/darwin version uses the same source however has a slightly modified script (see the included toolchain_notes.txt for the updated script)
Note I have a 64bit debian linux box, and a 64bit version of WIndows7 Pro running cygwin, while I believe these binaries ought to be compatible with all x86 linux and cygwin installs these have not been tested by a wide number of people yet.
> Linux users: If you have a working android build environment likely no additional requirements are needed. In addition you must build any kernel/android utilities from a case sensitive filesystem or disk image.
> OSx users: the cygwin packages will give you an idea of what is required, please also see the README in the tar.bz2 about manually installing elf.h
> Cygwin users: as its unlikely you have compiled a kernel with cygwin up to this point you may wish to ensure the following packages are installed (as well as any cygwin recommends to be used with them):
vimCygwin users must also set their NTFS file partition to allow case sensitive files:
To do this open regedit and change:
Advanced Kernel Building Guide
after this reboot and the NTFS kernel will allow cygwin to use case sensitive files (ie 'AbC' and 'aBc' as two different files)
Since may devices are slightly different this can only be a high level kernel building guide
Please ask for any specific directions from the current kernel maintainer.
To most people who have built kernels before this will look familiar, the most important part is preparing your local environment to use the new toolchain,
1) If you have not already download the tar.bz2 above, (pick the one for the computer you are preparing to build kernels on)
2) extract the file (for the sake of this guide I will assume it is extracted into a ~/android directory)
ie on cygwin you might:
mkdir -p ~/android
tar -xjvf toolchain-4.6.3.cygwin.tar.bz2
Note: steps one and two are just properly installing the toolchain, you will not need
to repeat them to build a different kernel.
2.b) OSX Only: check elf.h
open ~/android/toolchain-4.6.3/README in a text editor and check if elf.h is installed, otherwise manually install it as per the readme
3) fetch your kernel source into the ~/android directory and change into the
source codes root directory
(this can be via a git repo or tarball)
example if you wanted my ACER a100/a500 source you might run:
git clone git://github.com/ezterry/AcerTabKernel.git
change this to match the source you are fetching
4) In the root directory of the kernel source (~/android/AcerTabKernel in the about a100/a500 example) update the environment for the cross compiler
add the toolchain to your path:
export PATH=$HOME/android/toolchain-4.6.3/bin:$PATHset the cross compile:
export ARCH=arm(this will need to be done once for each terminal you use to run any of the following make commands)
5) Grab your configuration
From the device:
adb pull /proc/config.gz
gzip -dc config.gz > .config
or from a prepared configuration if it's included in your code base by running
example for the a100/a500 code base is 'make vangogh_defconfig' for the a100 and 'make picasso_defconfig' for the a500
6) Customize configuration
just run menuconfig and use the UI to update settings
make menuconfig7) building the kernel (zImage)
This is normal at this point with 'make -j'
so for a quad core CPU you can run
make -j5(note: the wrong number in the -j argument will not harm the build but may slow down the building process by either using too few threads or needing to keep track of too many)
8) If it worked you will now have the kernel in arch/arm/boot/zImage
this can be injected into the boot.img (as the kernel, using an existing ramdisk) as is
If it failed for your kernel your kernel source may need one of the common patches
9) Building modules
the following will prepare the modules in subdirectory mod:
make modulesAfter these commands [if no errors] you can simply copy the contents of mod/ to /system/lib/modules on your device, note it is recommended usually to remove the existing contents of /system/lib/modules unless there is a closed source module required from the previous build despite the new kernel.
rm -rf mod
cp `find ./ | grep .ko$` modules.order mod/
Common Patches Required
If your kernel has not been built for the new toolchain or on cygwin before you may require some of these common patchs: (I've thus far only tested this on my Acer A100/A500 source)
wireless/bcm4329 for GCC-4.6.3:
linux kernel module patch for cygwin (broken elf.h):
Error compiling security/smc/bridge_pub2sec.S (I required the cygwin elf patch and this patch to build the Franco galaxy nexus kernel)
(use 'git am 0001-Fix-build-error-with-4.6.3-toolchain-smc-0.patch' to apply)
OSX stat patches (fixes errors between GNU and BSD stat):
Errors loading newly built modules (modules appear to build cleanly but wont install):
simply add -fno-pic to CFLAGS_MODULE
(I can add others here if highlighted to me, and as I find them)
Other Toolchain uses
The linux toolchain can be used to build android components, however this requires various manipulation to the android /build git repository as currently various other toolchains have hard coded paths into the prebuilt repo. If you intend to incorporate this into your build it may be best to inject the toolchain into your prebuilt repo rather than expect your users to download the links above, ensure to keep the compile notes as it explains how to get the source code to the toolchains)
On cygwin/osx it may also be possible to build android applications however I've not yet tested this as the scripts to make a proper build are complex when attempted outside the android build tree.