[TSan][Darwin] Avoid crashes due to interpreting non-zero shadow content as a pointer

We would like to use TLS to store the ThreadState object (or at least a
reference ot it), but on Darwin accessing TLS via __thread or manually
by using pthread_key_* is problematic, because there are several places
where interceptors are called when TLS is not accessible (early process
startup, thread cleanup, ...).

Previously, we used a "poor man's TLS" implementation, where we use the
shadow memory of the pointer returned by pthread_self() to store a
pointer to the ThreadState object.

The problem with that was that certain operations can populate shadow
bytes unbeknownst to TSan, and we later interpret these non-zero bytes
as the pointer to our ThreadState object and crash on when dereferencing
the pointer.

This patch changes the storage location of our reference to the
ThreadState object to "real" TLS.  We make this work by artificially
keeping this reference alive in the pthread_key destructor by resetting
the key value with pthread_setspecific().

This change also fixes the issue were the ThreadState object is
re-allocated after DestroyThreadState() because intercepted functions
can still get called on the terminating thread after the

Radar-Id: rdar://problem/72010355

Reviewed By: dvyukov

Differential Revision: https://reviews.llvm.org/D110236
1 file changed
tree: 794402f476a4319fa1c86b42612eb4a90e63aa62
  1. .github/
  2. clang/
  3. clang-tools-extra/
  4. cmake/
  5. compiler-rt/
  6. cross-project-tests/
  7. flang/
  8. libc/
  9. libclc/
  10. libcxx/
  11. libcxxabi/
  12. libunwind/
  13. lld/
  14. lldb/
  15. llvm/
  16. mlir/
  17. openmp/
  18. polly/
  19. pstl/
  20. runtimes/
  21. utils/
  22. .arcconfig
  23. .arclint
  24. .clang-format
  25. .clang-tidy
  26. .git-blame-ignore-revs
  27. .gitignore
  28. .mailmap
  30. README.md
  31. SECURITY.md

The LLVM Compiler Infrastructure

This directory and its sub-directories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

The README briefly describes how to get started with building LLVM. For more information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.

Getting Started with the LLVM System

Taken from https://llvm.org/docs/GettingStarted.html.


Welcome to the LLVM project!

The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer. It also contains basic regression tests.

C-like languages use the Clang front end. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

Other components include: the libc++ C++ standard library, the LLD linker, and more.

Getting the Source Code and Building LLVM

The LLVM Getting Started documentation may be out of date. The Clang Getting Started page might have more accurate information.

This is an example work-flow and configuration to get and build the LLVM source:

  1. Checkout LLVM (including related sub-projects like Clang):

    • git clone https://github.com/llvm/llvm-project.git

    • Or, on windows, git clone --config core.autocrlf=false https://github.com/llvm/llvm-project.git

  2. Configure and build LLVM and Clang:

    • cd llvm-project

    • cmake -S llvm -B build -G <generator> [options]

      Some common build system generators are:

      • Ninja --- for generating Ninja build files. Most llvm developers use Ninja.
      • Unix Makefiles --- for generating make-compatible parallel makefiles.
      • Visual Studio --- for generating Visual Studio projects and solutions.
      • Xcode --- for generating Xcode projects.

      Some common options:

      • -DLLVM_ENABLE_PROJECTS='...' --- semicolon-separated list of the LLVM sub-projects you'd like to additionally build. Can include any of: clang, clang-tools-extra, compiler-rt,cross-project-tests, flang, libc, libclc, libcxx, libcxxabi, libunwind, lld, lldb, mlir, openmp, polly, or pstl.

        For example, to build LLVM, Clang, libcxx, and libcxxabi, use -DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi".

      • -DCMAKE_INSTALL_PREFIX=directory --- Specify for directory the full path name of where you want the LLVM tools and libraries to be installed (default /usr/local).

      • -DCMAKE_BUILD_TYPE=type --- Valid options for type are Debug, Release, RelWithDebInfo, and MinSizeRel. Default is Debug.

      • -DLLVM_ENABLE_ASSERTIONS=On --- Compile with assertion checks enabled (default is Yes for Debug builds, No for all other build types).

    • cmake --build build [-- [options] <target>] or your build system specified above directly.

      • The default target (i.e. ninja or make) will build all of LLVM.

      • The check-all target (i.e. ninja check-all) will run the regression tests to ensure everything is in working order.

      • CMake will generate targets for each tool and library, and most LLVM sub-projects generate their own check-<project> target.

      • Running a serial build will be slow. To improve speed, try running a parallel build. That's done by default in Ninja; for make, use the option -j NNN, where NNN is the number of parallel jobs, e.g. the number of CPUs you have.

    • For more information see CMake

Consult the Getting Started with LLVM page for detailed information on configuring and compiling LLVM. You can visit Directory Layout to learn about the layout of the source code tree.