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https://github.com/dslm4515/CMLFS

Clang-Built Musl Linux From Scratch
https://github.com/dslm4515/CMLFS

clang lfs llvm musl musl-libc

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Clang-Built Musl Linux From Scratch

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# CMLFS - Clang Musl Linux From Scratch



CMLFS can either mean "Clang-built Musl Linux from Scratch" or "Clang MLFS". It started as a hobby to see if a Linux system can be built with clang as primary toolchain and GCC as secondary (for packages that cannot be built with clang). This is based on [Linux From Scratch](www.linuxfromscratch.org) and my previous work [MLFS](https://github.com/dslm4515/Musl-LFS). Big thanks to [Chimera-Linux](https://chimera-linux.org) that had patches that fixed a lot of issues.



## DISCLAIMER



Use at you own risk. This builds a Unix-like system that may not be stable enough as a 'daily driver' for most users. Security-hardening of the built system is beyound the scope of this project. This repo started as means to backup and archive my work.



## Getting Started



The master branch may be unstable when I am working on upgrading CMLFS. 



To build this project, pick a branch other than master OR choose a tag. Each branch & tag are based on the LLVM version.

As of this writing, llvm-15.0.6 is stable. Older branches maybe incomplete or unstable (may not compile).



When I have time later, I will write a more thorough introduction for users new to CMLFS.



## Specification

    

  • C Runtime Library (system libc): Musl 
    • 

  • Default C Compiler: clang (LLVM)
    • 

  • Default C++ compiler: clang++ (LLVM)
    • 

  • Default linker: lld (LLVM)
    • 

  • Default binary tools: elftoolchain
    • 

  • Secondary C Compiler: GCC
    • 

  • Secondary C++ compiler: GCC
    • 

  • Secondary binary tools: GNU Binutils & LLVM
    • 

  • Secondary linker(s): bfd, gold
    • 

  • C++ standard library: libcxx (LLVM)
    • 

  • C++ ABI library: libcxxabi (LLVM)
    • 

  • Unwinding Library: libunwind (LLVM)
    • 

  • Init system: skarnet's S6 & S6-rc
    • 

  • Device manager: Udev 
    • 

  • TLS Implementaion: LibreSSL
    • 

  • Secondary TLS Implementaion: OpenSSL
    • 

  • System Shell: Bash 
    • 

  • System Gettext: gettext-tiny
    • 

  • Curses Library: netbsd-curses 
    • 




## Supported Architectures



    

  • AMD64/x86_64: Toolchains and final system build sucessfully (musl & glibc hosts) .
    • 

  • i686: Pending
    • 

  • AARCH64/ARM64: Pending
    • 

  • ARMV7L: Pending
    • 




## Goals



    

  •  [x] Build a toolchain (llvmtools) with LLVM+stage1_clang but without GCC
    • 

  •  [x] Build final root filesystem with LLVM
    • 

  •  [x] Set default linker as lld(LLVM)
    • 

  •  [x] Set default C++ standard library as libcxx(LLVM)
    • 

  •  [x] Set default C++ ABI library as libcxxabi(LLVM)
    • 

  •  [x] Set default stack unwinding library as libunwind(LLVM)
    • 

  •  [x] Eliminate dependacy on GCC's libgcc_s
    • 

  •  [x] Build GCC as a secondary systen compiler. 
    • 

  •  [x] Build toolchain (llvmtools) with GCC as secondary compiler
    • 

  •  [x] Merge cross-tools build with cgnutools 
    • 

  •  [x] Build successfully on a Glibc host 
    • 

  •  [x] Build final system without GCC 
    • 

  •  [x] Replace binutils with elftoolchain 
    • 

  •  [ ] Reduce LLVM size & build time for cgnutools and llvmtools 
    • 

  •  [ ] Create initramfs with busybox & mdev 
    • 

  •  [ ] Build on aarch64
    • 




## Host System Requirements



    

     
  • CMake
    • 

     
  • Ninja/Samurai
    • 

     
  • wget/cURL
    • 




## Required Base Development tools (may refer to LFS)

    

     
  • bash 3.2 (/bin/sh should be a symbolic or hard link to bash) 
    • 

     
  • binutils 2.25 
    • 

     
  • bison 2.7 (/usr/bin/yacc should be a link to bison or small script that executes bison) 
    • 

     
  • bzip2 1.0.4 
    • 

     
  • coreutils 6.9 
    • 

     
  • diffutils 2.8.1 
    • 

     
  • findutils 4.2.31 
    • 

     
  • gawk 4.0.1 (/usr/bin/awk should be a link to gawk) 
    • 

     
  • GCC 6.2 (including the C++ compiler, g++) 
    • 

     
  • Glibc 2.11 / Musl Libc 1.20 
    • 

     
  • Grep 2.5.1a 
    • 

     
  • gzip 1.3.12 
    • 

     
  • linux kernel 3.2 (not sure if it matters, as most distros are running 4.x/5.x kernels
    • 

     
  • m4 1.4.10
    • 

     
  • make 4.0 
    • 

     
  • patch 2.5.4 
    • 

     
  • Python 3.4 
    • 

     
  • sed 4.1.5 
    • 

     
  • tar 1.22 
    • 

     
  • texinfo 4.7 
    • 

      
  • xz 5.0.0 
    • 



 * (if hostdistro is MLFS/LFS, then all development packages are installed)



## Current Method



Build 'cross-tools' with [Mussel](https://github.com/firasuke/mussel) to cross-compile a stage0 LLVM+clang. This stage0 clang will still link to `libgcc_s` [in cgnutools] but will later be used to build a stage1 clang free of `libbgcc_s`. The goal is to build clang+friends with clang and not GCC.



* Some packages can be built once to be used by the toolchain [llvmtools] and the final system, but will be built twice to make it easy to implement a package managment system [which is outside the scope of this project]. 



    

  1. Bootstrap build of cgnutools with mussel
    2. 

  2. Use mussel-built toolchain (cgnutools) to build stage0 LLVM+clang
    3. 

  3. Use cgnutools to build stage1 LLVM+clang with sysroot at llvmtools with stage0 LLVM+clang
    4. 

  4. Build enough of llvmtools to enter a chroot with stage1 LLVM+clang
    5. 

  5. Build the rest of llvmtools under chroot 
    6. 

  6. Build final system with llvmtools 
    7. 




## Issues

    

  • Test for C++11/14 fails when testing stage0 & stage1 LLVM's. Not sure what issue this will cause or if test needs to be revised..
    • 

  • Coreutils will not build for llvmtools under 32-bit x86 (i386/i586/i686)
    • 

  • Ninja for llvmtools fails to compile with python3. For now use cmake instead of python3
    •  




## Change log



    

  • 4.0.0: Upgraded to LLVM 17.0.5 
    • 

  • 3.0.0: Upgraded to LLVM-15.0.6. cgnutools is now bootstrapped with mussel. Replaced binutils with elftoolchain. Most of llvmtools will be build under chroot to avoid contamination from host. 
    • 

  • 2.0.0: Upgraded to LLVM-12.0.0. Upgraded GCC to 10.3.1-x Replace ninja with samurai. Replace zlib with zlib-ng. Patched elfutils to build libelf under clang. No longer using /llvmtools/gnu and /opt/gnu.
    • 

  • 1.2.0: Incomplete: LLVM-11.0.0, Install GCC & Binutils in /llvmtools & /usr instead of /llvmtools/gnu and /opt/gnu 
    • 

  • 1.1.0: Sucessfully merged cross-tools and cgnutools to include GCC & binutils.
    • 

  • 1.0.0: Sucessfully built on x86_64. GCC built as secondary compiler in /opt/gnu 
    • 

  • 0.1.3: Configure Stage1 clang correctly with x86_64-pc-linux-musl.cfg.
    • 

  • 0.1.2: Use stage0 to build a stage1 clang...Stage1 clang will be used in chroot. Stage1 clang fails to compile
    • 

  • 0.1.1: Build stage0 clang by building clang, lld, compiler-rt, libunwind, libcxxabi, libcxx together in llvm source tree. Stage0 builds binaries with host's dynamic linker in /lib
    • 

  • 0.1.0: Build cross-tools with GCC to build stage 1 clang... first build libunwind, libcxxabi & libcxx - stage1 Clang broken
    • 

  • 0.0.0: First attempt, modeled afer Genshen's repo: Stage 2 clang fails to build.
    • 




## Projects of Interest

    

  •  [Mussel](https://github.com/firasuke/mussel)
    • 

  •  [Musl Linux From Scratch](https://github.com/dslm4515/Musl-LFS) - Based on LFS, but uses Musl instead of Glibc 
    • 

  •  [Beyond MLFS](https://github.com/dslm4515/BMLFS) - The Musl version of LFS's BLFS 
    • 

  •  [MLFS-S6-Bootscripts](https://github.com/dslm4515/MLFS-S6-Bootscripts) - Boot scripts for CMLFS/MLFS/LFS using skarnet's S6+S6-rc init system 
    • 

  •  [MLFS-Pkgtool](https://github.com/dslm4515/MLFS-pkgtool) - Musl LFS with Slackware's pkgtools 
    • 

  •  [Genshen's docker-clang-toolchain](https://github.com/genshen/docker-clang-toolchain)
    • 

  •  [Build a freestanding libc++](https://blogs.gentoo.org/gsoc2016-native-clang/2016/05/05/build-a-freestanding-libcxx/) 
    •