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| -rw-r--r-- | docs/CODE_QUALITY.md | 5 | ||||
| -rw-r--r-- | docs/TESTING_WITH_SANITIZERS.md | 88 |
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diff --git a/docs/CODE_QUALITY.md b/docs/CODE_QUALITY.md index 18363f0f1b..a3bdfaad8e 100644 --- a/docs/CODE_QUALITY.md +++ b/docs/CODE_QUALITY.md @@ -64,5 +64,10 @@ available functionality: of active alerts can be found [here](https://lgtm.com/projects/g/systemd/systemd/alerts/?mode=list). +15. Each PR is automatically tested with [Address Sanitizer](https://clang.llvm.org/docs/AddressSanitizer.html) + and [Undefined Behavior Sanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html). + See [Testing systemd using sanitizers](https://systemd.io/TESTING_WITH_SANITIZERS) + for more information. + Access to Coverity and oss-fuzz reports is limited. Please reach out to the maintainers if you need access. diff --git a/docs/TESTING_WITH_SANITIZERS.md b/docs/TESTING_WITH_SANITIZERS.md new file mode 100644 index 0000000000..7cb879aaf3 --- /dev/null +++ b/docs/TESTING_WITH_SANITIZERS.md @@ -0,0 +1,88 @@ +--- +title: Testing systemd using sanitizers +--- + +# Testing systemd using sanitizers + +To catch the *nastier* kind of bugs, you can run your code with [Address Sanitizer](https://clang.llvm.org/docs/AddressSanitizer.html) +and [Undefined Behavior Sanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html). +This is mostly done automagically by various CI systems for each PR, but you may +want to do it locally as well. The process slightly varies depending on the +compiler you want to use and which part of the test suite you want to run. + +## gcc +gcc compiles in sanitizer libraries dynamically by default, so you need to get +the shared libraries first - on Fedora these are shipped as a separate packages +(`libasan` for Address Sanitizer and `libubsan` for Undefined Behavior Sanitizer). + +The compilation itself is then a matter of simply adding `-Db_sanitize=address,undefined` +to `meson`. That's it - following executions of `meson test` and integrations tests +under `test/` subdirectory will run with sanitizers enabled. However, to get +truly useful results, you should tweak the runtime configuration of respective +sanitizers; e.g. in systemd we set the following environment variables: + +```bash +ASAN_OPTIONS=strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1 +UBSAN_OPTIONS=print_stacktrace=1:print_summary=1:halt_on_error=1 +``` +## clang +In case of clang things are somewhat different - the sanitizer libraries are +compiled in statically by default. This is not an issue if you plan to run +only the unit tests, but for integration tests you'll need to convince clang +to use the dynamic versions of sanitizer libraries. + +First of all, pass `-shared-libsan` to both `clang` and `clang++`: + +```bash +CFLAGS=-shared-libasan +CXXFLAGS=-shared-libasan +``` + +The `CXXFLAGS` are necessary for `src/libsystemd/sd-bus/test-bus-vtable-cc.c`. Compilation +is then the same as in case of gcc, simply add `-Db_sanitize=address,undefined` +to the `meson` call and use the same environment variables for runtime configuration. + +```bash +ASAN_OPTIONS=strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1 +UBSAN_OPTIONS=print_stacktrace=1:print_summary=1:halt_on_error=1 +``` + +After this, you'll probably notice that all compiled binaries complain about +missing `libclang_rt.asan*` library. To fix this, you have to install clang's +runtime libraries, usually shipped in the `compiler-rt` package. As these libraries +are installed in a non-standard location (non-standard for `ldconfig`), you'll +need to manually direct binaries to the respective runtime libraries. + +``` +# Optionally locate the respective runtime DSO +$ ldd build/systemd | grep libclang_rt.asan + libclang_rt.asan-x86_64.so => not found + libclang_rt.asan-x86_64.so => not found +$ find /usr/lib* /usr/local/lib* -type f -name libclang_rt.asan-x86_64.so 2>/dev/null +/usr/lib64/clang/7.0.1/lib/libclang_rt.asan-x86_64.so + +# Set the LD_LIBRARY_PATH accordingly +export LD_LIBRARY_PATH=/usr/lib64/clang/7.0.1/lib/ + +# If the path is correct, the "not found" message should change to an actual path +$ ldd build/systemd | grep libclang_rt.asan + libclang_rt.asan-x86_64.so => /usr/lib64/clang/7.0.1/lib/libclang_rt.asan-x86_64.so (0x00007fa9752fc000) +``` + +This should help binaries to correctly find necessary sanitizer DSOs. + +Also, to make the reports useful, `llvm-symbolizer` tool is required (usually +part of the `llvm` package). + +## Background notes +The reason why you need to force dynamic linking in case of `clang` is that some +applications make use of `libsystemd`, which is compiled with sanitizers as well. +However, if a *standard* (uninstrumented) application loads an instrumented library, +it will immediately fail due to unresolved symbols. To fix/workaround this, you +need to pre-load the ASan DSO using `LD_PRELOAD=/path/to/asan/dso`, which will +make things work as expected in most cases. This will, obviously, not work with +statically linked sanitizer libraries. + +These shenanigans are performed automatically when running the integration test +suite (i.e. `test/TEST-??-*`) and are located in `test/test-functions` (mainly, +but not only, in the `create_asan_wrapper` function). |