I recently got interested in the technical details of how ARM OS's work, so I decided to try my hand at writing a simple one.  This blog post is not about the OS itself, but about setting up the development environment.

In my case, I'm developing in a terminal session, on FreeBSD 10 on an AMD-64 host, so I'll need to cross-compile all my code.  Luckily, the ports tree includes gcc-arm-embedded a port of the launchpad ARM cross tools.  It's easy to install:

pkg install gcc-arm-embedded

This package includes all the tools which are needed:

-rwxr-xr-x 1 root wheel 711488 Oct 3 11:17 arm-none-eabi-addr2line
-rwxr-xr-x 2 root wheel 740040 Oct 3 11:17 arm-none-eabi-ar
-rwxr-xr-x 2 root wheel 1298680 Oct 3 11:17 arm-none-eabi-as
-rwxr-xr-x 2 root wheel 620816 Oct 3 11:17 arm-none-eabi-c++
-rwxr-xr-x 1 root wheel 710528 Oct 3 11:17 arm-none-eabi-c++filt
-rwxr-xr-x 1 root wheel 620608 Oct 3 11:17 arm-none-eabi-cpp
-rwxr-xr-x 1 root wheel 29416 Oct 3 11:17 arm-none-eabi-elfedit
-rwxr-xr-x 2 root wheel 620816 Oct 3 11:17 arm-none-eabi-g++
-rwxr-xr-x 2 root wheel 620608 Oct 3 11:17 arm-none-eabi-gcc
-rwxr-xr-x 2 root wheel 620608 Oct 3 11:17 arm-none-eabi-gcc-4.8.4
-rwxr-xr-x 1 root wheel 24480 Oct 3 11:17 arm-none-eabi-gcc-ar
-rwxr-xr-x 1 root wheel 24448 Oct 3 11:17 arm-none-eabi-gcc-nm
-rwxr-xr-x 1 root wheel 24448 Oct 3 11:17 arm-none-eabi-gcc-ranlib
-rwxr-xr-x 1 root wheel 271072 Oct 3 11:17 arm-none-eabi-gcov
-rwxr-xr-x 1 root wheel 3992568 Oct 3 11:17 arm-none-eabi-gdb
-rwxr-xr-x 1 root wheel 776672 Oct 3 11:17 arm-none-eabi-gprof
-rwxr-xr-x 4 root wheel 1025912 Oct 3 11:17 arm-none-eabi-ld
-rwxr-xr-x 4 root wheel 1025912 Oct 3 11:17 arm-none-eabi-ld.bfd
-rwxr-xr-x 2 root wheel 722928 Oct 3 11:17 arm-none-eabi-nm
-rwxr-xr-x 2 root wheel 906848 Oct 3 11:17 arm-none-eabi-objcopy
-rwxr-xr-x 2 root wheel 1123424 Oct 3 11:17 arm-none-eabi-objdump
-rwxr-xr-x 2 root wheel 740056 Oct 3 11:17 arm-none-eabi-ranlib
-rwxr-xr-x 1 root wheel 365208 Oct 3 11:17 arm-none-eabi-readelf
-rwxr-xr-x 1 root wheel 712976 Oct 3 11:17 arm-none-eabi-size
-rwxr-xr-x 1 root wheel 712080 Oct 3 11:17 arm-none-eabi-strings
-rwxr-xr-x 2 root wheel 906864 Oct 3 11:17 arm-none-eabi-strip

Additionally, an ARM simulator such as QEMU will be needed.  FreeBSD also include that port:

pkg install qemu-devel

I can easily use BSD Make, however I prefer GNU Make, so I've installed that too

pkg install gmake

With these tools installed, I have enough to cross-compile ARM assembler and C code, link it, and run it in QEMU and debug with GDB.