Integration of the LLVM sanitizers with the base system


February 01, 2019 posted by Kamil Rytarowski

Over the past month I've merged the LLVM compiler-rt sanitizers (LLVM svn r350590) with the base system. I've also managed to get a functional set of Makefile rules to build all of them, namely:
  • ASan
  • UBSan
  • TSan
  • MSan
  • libFuzzer
  • SafeStack
  • XRay
In all supported variations and modes that are supported by the original LLVM compiler-rt package.

Integration of sanitizers with the base system

I've submitted a patch for internal review but I was asked to push it through tech-toolchain@ first. I'm still waiting for active feedback on moving it in the proper direction.

The final merge of build rules will be done once we get LLVM 8.0(rc2) in the base as there is a small ABI mismatch between Clang/LLVM (7.0svn) and compilr-rt (8.0svn). I've ported/adapted-with-a-hack all the upstream tests for supported sanitizers to be executed against the newly integrated ones with the base system and everything has been adjusted to pass with a few exceptions that still need to be fixed: ASan dynamic (.so) tests are still crashy and UBSan tests where around 1/3 of them are failing due to an ABI mismatch. This caused by a number of new features for UBSan that are not supported by older Clang/LLVM.

Changes intergrated with LLVM projects

There has been a branching of LLVM 8.0 in the middle of January, causing a lot of breakage that required collaboration with the LLVM people to get things back into proper shape. I've also taken part in the LLD porting effort with Michal Gorny.

Post branching point there was also a refactoring of existing features in compiler-rt, such as LSan, SafeStack and Scudo. I had to apply appropriate patches in these sanitizers and temporarily disable LSan until it can be fully ported.

Changes in the base system

Out of the context of sanitizer I've fixed two bugs that relate to my previous work on interfaces for debuggers:

  • PR kern/53817 Random panics in vfs_mountroot()
  • PR lib/53343 t_ptrace_wait*:traceme_vfork_crash_bus test cases fail

Plan for the next milestone

Collect feedback for the patch integrating LLVM sanitizers and merge the final version with the base system.

Return to ptrace(2) kernel fixes and start the work with a focus on improving correctness of signal handling.

This work was sponsored by The NetBSD Foundation.

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