Obtaining an ARMv4 Toolchain

Since I sometimes work on technology considered antique, I need ARMv4 toolchains for systems such as the Gemini or Integrator AP/CP

The ARMv4 Instruction Set Architecture (ISA) also referred to as "ARM8 family" which is a bit confusing. It is used in StrongARM and Faraday Seminconductors FA526 such as in Gemini or iPAQ.

This is for userspace, even a tiny InitramFS using just BusyBox will need a proper toolchain linked to some fairly recent Linux UAPI headers. For compiling just the kernel or U-Boot you can just use the latest Linaro GCC toolchain since the kernel does not utilize libgcc.a and other glibc parts of the toolchain, neither does U-Boot these days.

Getting a proper cross compiler for ARMv4 can be tricky.

Using OpenWrt's Toolchain

Nowadays I find it easiest to just build OpenWrt and use as userspace, and it includes an ARMv4 toolchain that gets built with OpenWrt. There are build options in the menuconfig of OpenWrt to package and export the toolchain for your target, so if you select an ARMv4 target this will solve itself.

Using OpenEmbeddeds Toolchain

Recently I have been building my ARMv4 toolchains using OpenEmbedded. This gives you a GCC 7.2.0 or later toolchain as of writing. This is the simplified procedure:

Follow the steps from OpenEmbeddeds getting started documentation to obtain prerequisites.
Follow the OE-Core Standalone Setup procedure. I don't care with checking out stable branches, I just use the master. I guess sometimes that breaks. STOP before the step where you source the config.
Edit the conf/local.conf file, enable the QEMU ARM machine by uncommenting the line:
```
      MACHINE ?= "qemuarm"
    
```
Your host environment can conflict with OpenEmbedded (especially by picking up the wrong hosttools) so make sure you initialize it like this:
```
      export PATH=/usr/bin:/usr/sbin
      source ./oe-init-build-env build-armv4-toolchain
      bitbake meta-toolchain
    
```
Then it should build for hours. It downloads the entire universe to your machine and build it from scratch using canadian cross and other magic techniques I don't understand. Hopefully it doesn't break. If it breaks, that sucks. Especially for you, since you have to find the problem.
At the end OpenEmbedded will (hopefully) populate an SDK that magically appears in tmp-glibc/deploy/sdk/oecore-x86_64-armv4-toolchain-nodistro.0.sh this is an installer! You can just run it!
I chose to install into /var/linus/oecore-x86_64-armv4-toolchain-nodistro since I like to keep the compilers on a local SSD. It goes:

    $ ./oecore-x86_64-armv4-toolchain-nodistro.0.sh
    OpenEmbedded SDK installer version nodistro.0
    =============================================
    Enter target directory for SDK (default: /usr/local/oecore-x86_64): /var/linus/oecore-x86_64-armv4-toolchain-nodistro
    You are about to install the SDK to "/var/linus/oecore-x86_64-armv4-toolchain-nodistro". Proceed[Y/n]? Y
    Extracting SDK.....................done
    Setting it up...done
    SDK has been successfully set up and is ready to be used.
    Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g.
     $ . /var/linus/oecore-x86_64-armv4-toolchain-nodistro/environment-setup-armv4-oe-linux-gnueabi

I haven't had any major problems with this toolchain, it works great and uses very recent kernel APIs. The target C library is in oecore-x86_64-armv4-toolchain-nodistro/sysroots/armv4-oe-linux-gnueabi and as it is modern, all you need to do to get compilation working is to pass the magical --sysroot=/var/linus/oecore-x86_64-armv4-toolchain-nodistro/sysroots/armv4-oe-linux-gnueabi parameter to the compiler and linker (CFLAGS and LDFLAGS respectively) and all just works.

Prebuilt OE Toolchain

x86_64 GCC 7.2.0 OE ARMv4 Toolchain built 2017-11-11 - this had to be renamed because of mimetype and server problems, it is a .sh file you should rename it something like foo.sh make it executable and run it as per above

Unpack with bunzip2, then run to install.

Toolchain from Aboriginal

I used to just use Rob Landleys precompiled ARMv4TL (ARMv4 Thumb Little-Endian) compiler for the Integrator U-Boot and userspace rootfs compilation. Presumably you can use the plain ARMv4L version as well, and if you mounted core module is ARMv5 or ARMv6 or whatever you can use the other compiler variants in Rob's download directory. Just unpack the toolchain and make sure the /bin subdir is added to your $PATH and you are ready to go.

The problem is that Rob's project is decomissioned.