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Diffstat (limited to 'docs/MemorySanitizer.rst')
| -rw-r--r-- | docs/MemorySanitizer.rst | 46 |
1 files changed, 13 insertions, 33 deletions
diff --git a/docs/MemorySanitizer.rst b/docs/MemorySanitizer.rst index 9d6c22d..007e086 100644 --- a/docs/MemorySanitizer.rst +++ b/docs/MemorySanitizer.rst @@ -16,8 +16,7 @@ Typical slowdown introduced by MemorySanitizer is **3x**. How to build ============ -Follow the `clang build instructions <../get_started.html>`_. CMake -build is supported. +Build LLVM/Clang with `CMake <http://llvm.org/docs/CMake.html>`_. Usage ===== @@ -111,32 +110,12 @@ Origin Tracking MemorySanitizer can track origins of unitialized values, similar to Valgrind's --track-origins option. This feature is enabled by -``-fsanitize-memory-track-origins`` Clang option. With the code from +``-fsanitize-memory-track-origins=2`` (or simply +``-fsanitize-memory-track-origins``) Clang option. With the code from the example above, .. code-block:: console - % clang -fsanitize=memory -fsanitize-memory-track-origins -fno-omit-frame-pointer -g -O2 umr.cc - % ./a.out - WARNING: MemorySanitizer: use-of-uninitialized-value - #0 0x7f7893912f0b in main umr2.cc:6 - #1 0x7f789249b76c in __libc_start_main libc-start.c:226 - - Uninitialized value was created by a heap allocation - #0 0x7f7893901cbd in operator new[](unsigned long) msan_new_delete.cc:44 - #1 0x7f7893912e06 in main umr2.cc:4 - -Origin tracking has proved to be very useful for debugging MemorySanitizer -reports. It slows down program execution by a factor of 1.5x-2x on top -of the usual MemorySanitizer slowdown. - -MemorySanitizer can provide even more information with -``-fsanitize-memory-track-origins=2`` flag. In this mode reports -include information about intermediate stores the uninitialized value went -through. - -.. code-block:: console - % cat umr2.cc #include <stdio.h> @@ -163,6 +142,15 @@ through. #0 0x7f7893901cbd in operator new[](unsigned long) msan_new_delete.cc:44 #1 0x7f7893912e06 in main umr2.cc:4 +By default, MemorySanitizer collects both allocation points and all +intermediate stores the uninitialized value went through. Origin +tracking has proved to be very useful for debugging MemorySanitizer +reports. It slows down program execution by a factor of 1.5x-2x on top +of the usual MemorySanitizer slowdown. + +Clang option ``-fsanitize-memory-track-origins=1`` enabled a slightly +faster mode when MemorySanitizer collects only allocation points but +not intermediate stores. Handling external code ============================ @@ -177,15 +165,7 @@ interceptors for the most common libc functions. They make it possible to run MemorySanitizer-instrumented programs linked with uninstrumented libc. For example, the authors were able to bootstrap MemorySanitizer-instrumented Clang compiler by linking it with -self-built instrumented libcxx (as a replacement for libstdc++). - -In the case when rebuilding all program dependencies with -MemorySanitizer is problematic, an experimental MSanDR tool can be -used. It is a DynamoRio-based tool that uses dynamic instrumentation -to avoid false positives due to uninstrumented code. The tool simply -marks memory from instrumented libraries as fully initialized. See -`http://code.google.com/p/memory-sanitizer/wiki/Running#Running_with_the_dynamic_tool` -for more information. +self-built instrumented libc++ (as a replacement for libstdc++). Supported Platforms =================== |
