Sanitizers Support

The rustc compiler contains support for following sanitizers:

How to use the sanitizers?

To enable a sanitizer compile with -Z sanitizer=... option, where value is one of address, cfi, hwaddress, kcfi, leak, memory or thread. For more details on how to use sanitizers please refer to the sanitizer flag in the unstable book.

How are sanitizers implemented in rustc?

The implementation of sanitizers (except CFI) relies almost entirely on LLVM. The rustc is an integration point for LLVM compile time instrumentation passes and runtime libraries. Highlight of the most important aspects of the implementation:

  • The sanitizer runtime libraries are part of the compiler-rt project, and will be built on supported targets when enabled in config.toml:

    sanitizers = true

    The runtimes are placed into target libdir.

  • During LLVM code generation, the functions intended for instrumentation are marked with appropriate LLVM attribute: SanitizeAddress, SanitizeHWAddress, SanitizeMemory, or SanitizeThread. By default all functions are instrumented, but this behaviour can be changed with #[no_sanitize(...)].

  • The decision whether to perform instrumentation or not is possible only at a function granularity. In the cases were those decision differ between functions it might be necessary to inhibit inlining, both at MIR level and LLVM level.

  • The LLVM IR generated by rustc is instrumented by dedicated LLVM passes, different for each sanitizer. Instrumentation passes are invoked after optimization passes.

  • When producing an executable, the sanitizer specific runtime library is linked in. The libraries are searched for in the target libdir. First relative to the overridden system root and subsequently relative to the default system root. Fall-back to the default system root ensures that sanitizer runtimes remain available when using sysroot overrides constructed by cargo -Z build-std or xargo.

Testing sanitizers

Sanitizers are validated by code generation tests in tests/codegen/sanitize*.rs and end-to-end functional tests in tests/ui/sanitize/ directory.

Testing sanitizer functionality requires the sanitizer runtimes (built when sanitizer = true in config.toml) and target providing support for particular sanitizer. When sanitizer is unsupported on given target, sanitizers tests will be ignored. This behaviour is controlled by compiletest needs-sanitizer-* directives.

Enabling sanitizer on a new target

To enable a sanitizer on a new target which is already supported by LLVM:

  1. Include the sanitizer in the list of supported_sanitizers in the target definition. rustc --target .. -Zsanitizer=.. should now recognize sanitizer as supported.
  2. Build the runtime for the target and include it in the libdir.
  3. Teach compiletest that your target now supports the sanitizer. Tests marked with needs-sanitizer-* should now run on the target.
  4. Run tests ./x test --force-rerun tests/ui/sanitize/ to verify.
  5. --enable-sanitizers in the CI configuration to build and distribute the sanitizer runtime as part of the release process.

Additional Information