Thursday, September 6, 2012

aarch64 toolchain

In the last months there has been movement towards merging a new architecture in the mainline kernel, called aarch64. Along with it, they came the binutils and gcc ports.
Given that I have never touched a bare metal toolchain, I thought this was a good thing to pass the time, so I started playing with these pieces and got to compile binutils, gcc and the kernel, from the patches submitted. Now it is easier given that binutils support was merged.

I don't really use cvs, just downloaded the latest snapshot of binutils (2.22.90 doesn't have aarch64):

Assuming you are at /my_tc, you create build/binutils and compile from there, your source is at /my_tc/binutils-latest/.
$ cd /my_tc/build/binutils/ 
$ /my_tc/binutils-latest/configure --prefix=/my_tc/out --target=aarch64-none-linux-gnu --disable-werror
$ make -j4 && make install
And for gcc:
svn checkout
Assuming you are at /my_tc, you create build/gcc and compile from there, your source is at /my_tc/aarch64-branch/.
$ cd /my_tc/build/gcc/ 
$ /my_tc/aarch64-branch/configure --prefix=/my_tc/out --target=aarch64-none-linux-gnu --disable-nls --enable-languages=c --disable-threads --without-headers --with-newlib --disable-shared --disable-libmudflap --disable-libssp --disable-libgomp  --disable-libquadmath
$ make -j4 && make install

$ export PATH=/my_tc/out/bin:$PATH
$ export CROSS_COMPILE=aarch64-none-linux-gnu-
$ export ARCH=arm64
Get the kernel:
$ git clone git://
$ cd linux-aarch64
$ make allnoconfig && make -j4
And now you have a compiled kernel with a bare metal toolchain. You can play with the menuconfig or just go randconfig and fix some of the bugs too.


Back then when aarch64 binutils wasn't merged, I had to download and patch binutils code and regenerate the makefile and include files. Something like:
1. Download binutils-2.22.90, patch it with aarch64 changes.
2. automake on bfd/, binutils/, gas/, ld/ and opcodes/; automake must be 1.11.1.
3. autoconf on top configure file, bfd/ and opcodes/; autoconf must be 2.64.
4. configure and make, and wait for it to break or just run configure inside bfd in order to get a Makefile there.
5. cd bfd/; make headers and cd -, this will generate some missing symbols.
6. Now you can either clean your previous failed build or continue it.
And then follow the steps to compile binutils, gcc and kernel.

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