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crux-bitcode

crux-bitcode is a CRUX Linux Docker image to make generating LLVM bitcode from (some) open-source software easy by using CRUX's ports system and GLLVM. build-bitcode.sh can build software in the official ports tree (with some caveats) into bitcode.

LLVM/Clang version: 12.0.0.

Requirements

Docker. The first run may be slow as the (large) image is downloaded.

Usage

  1. Create a list of desired ports in a file pkgs.txt (modify included file). (The full list of possibilities can be seen by running ls ports/*/.)
  2. Run ./build-bitcode.sh.
  3. unzip the generated bitcode-XYZ.zip.

An info.txt file is provided alongside the bitcode files containing (an estimate of) the lines of C/C++ code used to generate each bitcode file. This is calculated by counting the lines of code in the files mentioned in the debug information. info.txt also includes the user-defined CFLAGS and CXXFLAGS.

Customisation

  • build-bitcode.sh copies ports into the container, so ports can be modified, and new ports can be created or copied from elsewhere.
  • build-bitcode.sh copies pkgmk.conf into the container (run the image and man pkgmk.conf for more information).

Caveats

Some ports may not respect CFLAGS/CXXFLAGS nor CC/CXX. The image attempts to resolve this by intercepting calls to the compiler (see image/cc.lua, image/cxx.lua). Some ports may need to have their Pkgfile modified, or a patch added, if problems arise.

Packages that cannot be built

These packages have some known problem building bitcode or building bitcode according to user parameters. They can still be used as dependencies though.

  • nss: can produce bitcode, but not with user-defined CFLAGS.
  • firefox: appears to fail at the last step; needs investigation.
  • qt5: does not produce bitcode for some/all binaries; needs investigation
    • Can be used as a dependency
  • qownnotes: same problem as qt5
  • bc: will not build on Apple Silicon
    • ARM build may be worthwhile

LLVM/Clang version

If LLVM or Clang (or their runtime dependencies) are included in pkgs.txt, then version 10 is used. The ports directory is "frozen" (modulo required fixes) whereas the image/ports directory is not. LLVM and Clang (and dependencies) in image/ports are updated as necessary.

Thus there is a tension where LLVM/Clang ports, when building bitcode, are of different versions to the included LLVM/Clang. If LLVM (or Clang) is built, explicitly or as a dependency, the container will use the newly built LLVM (or Clang) and not the one included in the image. This can be an older version.

TODO

  • Ability to run build-bitcode.sh from anywhere.
  • Command line options for build-bitcode.sh and build-bitcode.lua.
  • Reduce image size.
  • Test more ports.
  • Remove more non-C/C++ ports.
  • Nicer error handling.
  • Would be nice if sources are archived to "freeze" the port tree.
  • Always use included LLVM/Clang, never a version built by the user.