Greenforce Clang

To get started with Greenforce Clang, you'll need to get familiar with Building Linux with Clang/LLVM.

This is how you start initializing the Greenforce Clang to your local or server, use a command like this:

# Create a directory for the source files
mkdir -p ~/toolchains/greenforce-clang

Then to download:

wget -c https://github.com/greenforce-project/clang-llvm/releases/download/04102023/greenforce-clang-18.0.0-04102023-1050.tar.zst -O - | tar -xz -C ~/toolchains/greenforce-clang

For more information, see clang-18.0.0-04102023-1050-info.txt regarding the majority changes each week.

Host compatibility

This toolchain is built on Ubuntu 22.04.3 LTS, which uses glibc 2.35. Compatibility with older distributions cannot be guaranteed. Other libc implementations (such as musl) are not supported.

Building Linux

Make sure you have this toolchain in your PATH:

export PATH="~/toolchains/greenforce-clang/bin:/usr/bin/core_perl:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

For an AArch64 cross-compilation setup, you must set the following variables. Some of them can be environment variables, but some must be passed directly to make as a command-line argument. It is recommended to pass all of them as make arguments to avoid confusing errors:

• CC=clang (must be passed directly to make)
• CROSS_COMPILE=aarch64-linux-gnu-
• If your kernel has a 32-bit vDSO: CROSS_COMPILE_ARM32=arm-linux-gnueabi-

Optionally, you can also choose to use as many LLVM tools as possible to reduce reliance on binutils. All of these must be passed directly to make:

• AR=llvm-ar
• NM=llvm-nm
• OBJCOPY=llvm-objcopy
• OBJDUMP=llvm-objdump
• STRIP=llvm-strip

Note, however, that additional kernel patches may be required for these LLVM tools to work. It is also possible to replace the binutils linkers (lf.bfd and ld.gold) with lld and use Clang's integrated assembler for inline assembly in C code, but that will require many more kernel patches and it is currently impossible to use the integrated assembler for all assembly code in the kernel.

Android kernels older than 4.14 will require patches for compiling with any Clang toolchain to work; those patches are out of the scope of this project. See android-kernel-clang for more information.

Android kernels 4.19 and newer use the upstream variable CROSS_COMPILE_COMPAT. When building these kernels, replace CROSS_COMPILE_ARM32 in your commands and scripts with CROSS_COMPILE_COMPAT.

Differences from other toolchains

Greenforce Clang has been designed to be easy-to-use compared to other toolchains, such as AOSP Clang. The differences are as follows:

• CLANG_TRIPLE does not need to be set because we don't use AOSP binutils.
• LD_LIBRARY_PATH does not need to be set because we set library load paths in the toolchain.
• No separate GCC/binutils toolchains are necessary; all tools are bundled.