[cfe-dev] AddressSanitizer

Vitaly Buka via cfe-dev cfe-dev at lists.llvm.org
Thu Nov 19 22:17:43 PST 2020 

I guess the problem is the following:
Stage2 builds libomp.so instrumented with AddressSanitizer. Then omp tests
are compiled without -fsanitize=address and load instrumented libomp.so
which fails on missing symbols.

You can try to solve this in two ways:
1. Disable sanitizers on libomp.so even -DLLVM_USE_SANITIZER= is set. That
can be hard if it uses some part of llvm as dependency. If so, you can try
to build non-instrumented libomp.so using ExternalProject_Add.
Should work but sanitizer will cover only the compiler binary not libomp.so.

2. Use asan in all tests e.g. with -DOPENMP_TEST_FLAGS=-fsanitize=address
(better to do so in cmake file). Problem here is that stage2 does not build
asan because it uses LLVM_USE_SANITIZER. We can just use stage1 compiler
which contains asan libs.  With a hack like this:

if(LLVM_USE_SANITIZER)
  set(OPENMP_TEST_C_COMPILER ${CMAKE_C_COMPILER})
  set(OPENMP_TEST_CXX_COMPILER ${CMAKE_CXX_COMPILER})

  set(saved_CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
  set(saved_CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})

  unset(CMAKE_C_FLAGS)
  append_common_sanitizer_flags()
  set(OPENMP_TEST_FLAGS "${CMAKE_C_FLAGS} -fsanitize=address
${OPENMP_TEST_FLAGS}")

  set(CMAKE_C_FLAGS ${saved_CMAKE_C_FLAGS})
  set(CMAKE_CXX_FLAGS ${saved_CMAKE_CXX_FLAGS})
endif()

I can run most of the test:

  Unsupported      :  39
  Passed           : 241
  Expectedly Failed:   2
  Failed           :  33 (it was 270+ before)

then you can fix or disable failing tests





On Thu, 22 Oct 2020 at 05:31, Bryan Chan <bryanpkc at gmail.com> wrote:

> Hi Vitaly,
>
> This is the CMake command line I used:
>
> cmake -G Ninja -DCMAKE_BUILD_TYPE=Release
> -DCMAKE_INSTALL_PREFIX=$HOME/stage2 \
>       -DCMAKE_C_COMPILER=$HOME/stage1/bin/clang \
>       -DCMAKE_CXX_COMPILER=$HOME/stage1/bin/clang++ \
>       -DCOMPILER_RT_BUILD_BUILTINS=off -DCOMPILER_RT_BUILD_PROFILE=on \
>       -DCOMPILER_RT_BUILD_SANITIZERS=on -DCOMPILER_RT_BUILD_XRAY=off \
>       -DLLVM_ENABLE_PROJECTS="clang;compiler-rt;lld;openmp" \
>       -DLLVM_ENABLE_ASSERTIONS=on -DLLVM_OPTIMIZED_TABLEGEN=on \
>       -DLLVM_STATIC_LINK_CXX_STDLIB=on
> -DLLVM_TARGETS_TO_BUILD="AArch64;X86" \
>       -DLLVM_USE_LINKER=gold -DLLVM_USE_SANITIZER=Address ../llvm
>
> Stage 1 was built from the same source using the same CMake command,
> without
> -DLLVM_USE_SANITIZER. CMAKE_C_FLAGS and CMAKE_CXX_FLAGS contained some
> hardening options like "-fstack-protector-strong -D_FORTIFY_SOURCE=2" which
> I omitted for brevity. I am building on an AArch64 CentOS system.
>
> The Builtins-aarch64-linux test failures have disappeared after I set the
> PATH and LD_LIBRARY_PATH environment variables to point to $HOME/stage1/bin
> and $HOME/stage1/lib. But I still see the tools/gold/X86 and OpenMP test
> failures.
>
> Thanks,
> --
> Bryan
>
>
> On Wed, Oct 21, 2020 at 3:03 PM Vitaly Buka <vitalybuka at google.com> wrote:
>
>> Can you please share the full cmake command line?
>>
>> On Wed, 21 Oct 2020 at 11:28, Kostya Serebryany <kcc at google.com> wrote:
>>
>>> +Vitaly Buka <vitalybuka at google.com> to help with the links to build
>>> bots.
>>> Not sure if any of those cover OpenMP.
>>>
>>> On Wed, Oct 21, 2020 at 5:50 AM Bryan Chan <bryanpkc at gmail.com> wrote:
>>>
>>>> Thanks Kostya, using Clang to build itself with ASan enabled, and
>>>> running my
>>>> build container in privileged mode, helped solve a lot of the problems.
>>>> But I
>>>> now encounter a lot of link errors while testing my stage-2 build:
>>>>
>>>> FAIL: libomp :: api/has_openmp.c (52345 of 54886)
>>>> ******************** TEST 'libomp :: api/has_openmp.c' FAILED
>>>> ********************
>>>> Script:
>>>> --
>>>> : 'RUN': at line 1';   /home/bryanpkc/llvm-project/build/./bin/clang
>>>> -fopenmp -pthread -fno-experimental-isel  -I
>>>> /home/bryanpkc/llvm-project/openmp/runtime/test -I
>>>> /home/bryanpkc/llvm-project/build/projects/openmp/runtime/src -L
>>>> /home/bryanpkc/llvm-project/build/lib  -I /h
>>>> ome/bryanpkc/llvm-project/openmp/runtime/test/ompt
>>>> /home/bryanpkc/llvm-project/openmp/runtime/test/api/has_openmp.c -o
>>>> /home/bryanpkc/llvm-project/build/projects/openmp/runtime/test/api/Output/has_openmp.c.tmp
>>>> -lm -latomic &&
>>>> /home/bryanpkc/llvm-project/build/projects/openmp/runtime/test/api/Output/has_openmp.c.tmp
>>>> --
>>>> Exit Code: 1
>>>>
>>>> Command Output (stdout):
>>>> --
>>>> $ ":" "RUN: at line 1"
>>>> $ "/home/bryanpkc/llvm-project/build/./bin/clang" "-fopenmp" "-pthread"
>>>> "-fno-experimental-isel" "-I"
>>>> "/home/bryanpkc/llvm-project/openmp/runtime/test" "-I"
>>>> "/home/bryanpkc/llvm-project/build/projects/openmp/runtime/src" "-L"
>>>> "/home/bryanpkc/llvm-project/build/lib" "-I"
>>>> "/home/bryanpkc/llvm-project/openmp/runtime/test/ompt"
>>>> "/home/bryanpkc/llvm-project/openmp/runtime/test/api/has_openmp.c" "-o"
>>>> "/home/bryanpkc/llvm-project/build/projects/openmp/runtime/test/api/Output/has_openmp.c.tmp"
>>>> "-lm" "-latomic"
>>>> # command stderr:
>>>> /usr/bin/ld: /home/bryanpkc/llvm-project/build/lib/libomp.so: undefined
>>>> reference to `__asan_load_cxx_array_cookie'
>>>> /usr/bin/ld: /home/bryanpkc/llvm-project/build/lib/libomp.so: undefined
>>>> reference to `__asan_set_shadow_f8'
>>>> /usr/bin/ld: /home/bryanpkc/llvm-project/build/lib/libomp.so: undefined
>>>> reference to `__asan_stack_malloc_8'
>>>> /usr/bin/ld: /home/bryanpkc/llvm-project/build/lib/libomp.so: undefined
>>>> reference to `__asan_stack_malloc_2'
>>>> /usr/bin/ld: /home/bryanpkc/llvm-project/build/lib/libomp.so: undefined
>>>> reference to `__asan_unregister_globals'
>>>>
>>>> This type of failures are affecting multiple groups of tests:
>>>>
>>>> Builtins-aarch64-linux :: *
>>>> LLVM :: tools/gold/X86/*
>>>> libomp :: *
>>>> libomptarget :: *
>>>>
>>>> Any ideas? Could you point me to the build bot that has a good
>>>> Clang/LLVM/OpenMP
>>>> configuration with ASan enabled? Unfortunately the documentation at
>>>> https://llvm.org/docs/CMake.html is not clear on how to get this
>>>> working.
>>>>
>>>> --
>>>> Bryan
>>>>
>>>>
>>>> On Tue, Oct 20, 2020 at 12:33 PM Kostya Serebryany <kcc at google.com>
>>>> wrote:
>>>>
>>>>> Hi Bryan,
>>>>>
>>>>> Yes, building LLVM with GCC+ASAN is a warranty void zone.
>>>>> It can probably be made to work with some effort, but unless someone
>>>>> is willing to
>>>>> maintain a public bot with this build, it will remain unsupported.
>>>>>
>>>>> Building LLVM with LLVM+ASAN is fully supported, and the bots are
>>>>> maintained.
>>>>>
>>>>> thanks!
>>>>>
>>>>> --kcc
>>>>>
>>>>>
>>>>> On Tue, Oct 20, 2020 at 7:39 AM Bryan Chan via cfe-dev <
>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>
>>>>>> Hi lists,
>>>>>>
>>>>>> I am encountering a large number of check-clang failures after
>>>>>> building Clang/LLVM with -DLLVM_USE_SANITIZER=Address. I have
>>>>>> reported the issue on Bugzilla (
>>>>>> https://bugs.llvm.org/show_bug.cgi?id=47678). I cannot even
>>>>>> compile helloworld.c with the resulting clang tool without a lot of false
>>>>>> positives from ASan. Is it because I am not supposed to use GCC's
>>>>>> AddressSanitizer when building Clang?
>>>>>>
>>>>>> --
>>>>>> Bryan
>>>>>> _______________________________________________
>>>>>> cfe-dev mailing list
>>>>>> cfe-dev at lists.llvm.org
>>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>
>>>>>
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