Add GWP-ASan fuzz target to compiler-rt/tools.

[hctim]

Summary

@eugenis to approve addition of //compiler-rt/tools.
@pree-jackie please confirm that this WFY.

D66494 introduced the GWP-ASan stack_trace_compressor_fuzzer. Building fuzz
targets in compiler-rt is a new affair, and has some challenges:

• If the host compiler doesn't have compiler-rt, the -fsanitize=fuzzer may not be able to link against libclang_rt.fuzzer*.
• Things in compiler-rt generally aren't built when you want to build with sanitizers using -DLLVM_USE_SANITIZER. This tricky to work around, so we create the new tools directory so that we can build fuzz targets with sanitizers. This has the added bonus of fixing the problem above as well, as we can now just guard the fuzz target build to only be done with -DLLVM_USE_SANITIZE_COVERAGE=On.

[pree-jackie]

This builds llvm fine, thanks a lot for working on this :)

[eugenis]

LGTM

[hctim]

Submission is broken currently due to the upstream SVN issues. Will submit when it's available. Thanks for your patience.

compiler-rt/CMakeLists.txt

if (COMPILER_RT_STANDALONE_BUILD)
     if (EXISTS ${LLVM_MAIN_SRC_DIR}/utils/llvm-lit)
       add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/llvm-lit ${CMAKE_CURRENT_BINARY_DIR}/llvm-lit)
     elseif(NOT EXISTS ${LLVM_EXTERNAL_LIT})
       message(WARNING "Could not find LLVM source directory and LLVM_EXTERNAL_LIT does not"
                        "point to a valid file.  You will not be able to run tests.")
     endif()
   endif()
 endif()
+
+add_subdirectory(tools)

compiler-rt/lib/gwp_asan/CMakeLists.txt

add_compiler_rt_object_libraries(RTGwpAsanBacktraceLibc
       SOURCES optional/backtrace_linux_libc.cpp
       ADDITIONAL_HEADERS ${GWP_ASAN_BACKTRACE_HEADERS}
       CFLAGS ${GWP_ASAN_CFLAGS})
   add_compiler_rt_object_libraries(RTGwpAsanBacktraceSanitizerCommon
       ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
       SOURCES optional/backtrace_sanitizer_common.cpp
       ADDITIONAL_HEADERS ${GWP_ASAN_BACKTRACE_HEADERS}
       CFLAGS ${GWP_ASAN_CFLAGS} ${SANITIZER_COMMON_CFLAGS})
-
-  # Build the stack trace compressor fuzzer. Note that clang versions 4.* did
-  # not have -fsanitize=fuzzer, and Clang versions 5.* didn't have
-  # -fsanitize=fuzzer-no-link. In general, the way we build fuzz targets in LLVM
-  # core is to link it against a dummy main when DLLVM_USE_SANITIZE_COVERAGE
-  # isn't specified. Instead, here we only build fuzz targets if clang version
-  # is >= 6.0.
-  if (COMPILER_RT_BUILD_LIBFUZZER AND
-      "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND
-      NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.0)
-    add_executable(stack_trace_compressor_fuzzer
-        stack_trace_compressor_fuzzer.cpp
-        ${GWP_ASAN_SOURCES}
-        ${GWP_ASAN_HEADERS})
-    set_target_properties(
-        stack_trace_compressor_fuzzer PROPERTIES FOLDER "Fuzzers")
-    target_compile_options(
-        stack_trace_compressor_fuzzer PRIVATE -fsanitize=fuzzer-no-link)
-    set_target_properties(
-        stack_trace_compressor_fuzzer PROPERTIES LINK_FLAGS -fsanitize=fuzzer)
-    add_dependencies(stack_trace_compressor_fuzzer fuzzer)
-    add_dependencies(gwp_asan stack_trace_compressor_fuzzer)
-  endif()
 endif()
 
 if(COMPILER_RT_INCLUDE_TESTS)
   add_subdirectory(tests)
 endif()

compiler-rt/tools/CMakeLists.txt

+add_subdirectory(gwp_asan)

compiler-rt/tools/gwp_asan/CMakeLists.txt

+# Build the stack trace compressor fuzzer. This will require Clang >= 6.0.0, as
+# -fsanitize=fuzzer-no-link was not a valid command line flag prior to this.
+if (LLVM_USE_SANITIZE_COVERAGE)
+  add_executable(stack_trace_compressor_fuzzer
+      ../../lib/gwp_asan/stack_trace_compressor.cpp
+      ../../lib/gwp_asan/stack_trace_compressor.h
+      stack_trace_compressor_fuzzer.cpp)
+  set_target_properties(
+      stack_trace_compressor_fuzzer PROPERTIES FOLDER "Fuzzers")
+  target_compile_options(
+      stack_trace_compressor_fuzzer PRIVATE -fsanitize=fuzzer-no-link)
+  set_target_properties(
+      stack_trace_compressor_fuzzer PROPERTIES LINK_FLAGS -fsanitize=fuzzer)
+  target_include_directories(
+      stack_trace_compressor_fuzzer PRIVATE ../../lib/)
+
+  if (TARGET gwp_asan)
+    add_dependencies(gwp_asan stack_trace_compressor_fuzzer)
+  endif()
+endif()

compiler-rt/tools/gwp_asan/stack_trace_compressor_fuzzer.cpp

 #include <cstddef>
 #include <cstdint>
 #include <cstdio>
 #include <cstdlib>
 #include <vector>
 
 #include "gwp_asan/stack_trace_compressor.h"
 
 constexpr size_t kBytesForLargestVarInt = (sizeof(uintptr_t) * 8) / 7 + 1;
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   size_t BufferSize = kBytesForLargestVarInt * Size / sizeof(uintptr_t);
   std::vector<uint8_t> Buffer(BufferSize);
   std::vector<uint8_t> Buffer2(BufferSize);
 
   // Unpack the fuzz bytes.
   gwp_asan::compression::unpack(Data, Size,
                                 reinterpret_cast<uintptr_t *>(Buffer2.data()),
                                 BufferSize / sizeof(uintptr_t));
 
   // Pack the fuzz bytes.
   size_t BytesWritten = gwp_asan::compression::pack(
       reinterpret_cast<const uintptr_t *>(Data), Size / sizeof(uintptr_t),
       Buffer.data(), BufferSize);
 
   // Unpack the compressed buffer.
   size_t DecodedElements = gwp_asan::compression::unpack(
       Buffer.data(), BytesWritten,
       reinterpret_cast<uintptr_t *>(Buffer2.data()),
       BufferSize / sizeof(uintptr_t));
 
   // Ensure that every element was encoded and decoded properly.
   if (DecodedElements != Size / sizeof(uintptr_t))
     abort();
 
   // Ensure that the compression and uncompression resulted in the same trace.
   const uintptr_t *FuzzPtrs = reinterpret_cast<const uintptr_t *>(Data);
   const uintptr_t *DecodedPtrs =
       reinterpret_cast<const uintptr_t *>(Buffer2.data());
   for (size_t i = 0; i < Size / sizeof(uintptr_t); ++i) {
     if (FuzzPtrs[i] != DecodedPtrs[i]) {
       fprintf(stderr, "FuzzPtrs[%zu] != DecodedPtrs[%zu] (0x%zx vs. 0x%zx)", i,
               i, FuzzPtrs[i], DecodedPtrs[i]);
       abort();
     }
   }
 
   return 0;
 }