Re: [PATCH 01/19] configure: add --enable-tsan flag + fiber annotations for coroutine-ucontext

[Philippe Mathieu-Daudé]

Hi Robert,

On 5/22/20 6:07 PM, Robert Foley wrote:
> From: Lingfeng Yang <address@hidden>
> 
> We tried running QEMU under tsan in 2016, but tsan's lack of support for
> longjmp-based fibers was a blocker:
>   https://groups.google.com/forum/#!topic/thread-sanitizer/se0YuzfWazw
> 
> Fortunately, thread sanitizer gained fiber support in early 2019:
>   https://reviews.llvm.org/D54889
> 
> This patch brings tsan support upstream by importing the patch that annotated
> QEMU's coroutines as tsan fibers in Android's QEMU fork:
>   https://android-review.googlesource.com/c/platform/external/qemu/+/844675
> 
> Tested with '--enable-tsan --cc=clang-9 --cxx=clang++-9 --disable-werror'
> configure flags.
> 
> Signed-off-by: Lingfeng Yang <address@hidden>
> Signed-off-by: Emilio G. Cota <address@hidden>
> [cota: minor modifications + configure changes]
> Signed-off-by: Robert Foley <address@hidden>
> [RF: minor changes to clean up checkpatch warnings/errors]
> ---
>  configure                 | 39 ++++++++++++++++
>  util/coroutine-ucontext.c | 97 +++++++++++++++++++++++++++++++++++----
>  2 files changed, 127 insertions(+), 9 deletions(-)
> 
> diff --git a/configure b/configure
> index 26084fc53a..c95c54fb48 100755
> --- a/configure
> +++ b/configure
> @@ -395,6 +395,7 @@ gprof="no"
>  debug_tcg="no"
>  debug="no"
>  sanitizers="no"
> +tsan="no"
>  fortify_source=""
>  strip_opt="yes"
>  tcg_interpreter="no"
> @@ -1150,6 +1151,10 @@ for opt do
>    ;;
>    --disable-sanitizers) sanitizers="no"
>    ;;
> +  --enable-tsan) tsan="yes"
> +  ;;
> +  --disable-tsan) tsan="no"
> +  ;;
>    --enable-sparse) sparse="yes"
>    ;;
>    --disable-sparse) sparse="no"
> @@ -1750,6 +1755,7 @@ Advanced options (experts only):
>    --with-pkgversion=VERS   use specified string as sub-version of the package
>    --enable-debug           enable common debug build options
>    --enable-sanitizers      enable default sanitizers
> +  --enable-tsan            enable thread sanitizer
>    --disable-strip          disable stripping binaries
>    --disable-werror         disable compilation abort on warning
>    --disable-stack-protector disable compiler-provided stack protection
> @@ -6176,6 +6182,27 @@ if test "$fuzzing" = "yes" ; then
>    fi
>  fi
>  
> +# Thread sanitizer is, for now, much noisier than the other sanitizers;
> +# keep it separate until that is not the case.
> +have_tsan=no
> +have_tsan_iface_fiber=no
> +if test "$tsan" = "yes" ; then
> +  write_c_skeleton
> +  if compile_prog "$CPU_CFLAGS -Werror -fsanitize=thread" "" ; then
> +      have_tsan=yes
> +  fi
> +  cat > $TMPC << EOF
> +#include <sanitizer/tsan_interface.h>
> +int main(void) {
> +  __tsan_create_fiber(0);
> +  return 0;
> +}
> +EOF
> +  if compile_prog "$CPU_CFLAGS -Werror -fsanitize=thread" "" ; then
> +      have_tsan_iface_fiber=yes
> +  fi
> +fi
> +
>  ##########################################
>  # check for libpmem
>  
> @@ -6277,6 +6304,14 @@ if test "$have_asan" = "yes"; then
>             "Without code annotation, the report may be inferior."
>    fi
>  fi
> +if test "$have_tsan" = "yes" ; then
> +  if test "$have_tsan_iface_fiber" = "yes" ; then
> +    QEMU_CFLAGS="-fsanitize=thread $QEMU_CFLAGS"
> +    QEMU_LDFLAGS="-fsanitize=thread $QEMU_LDFLAGS"
> +  else
> +    echo "Cannot enable TSAN due to missing fiber annotation interface."

I tried your series and there were no changes anywhere, then I looked at
how TSan work, started to debug, to finally realize my build was not
using TSan (clang8). Please use to something such:

     if test "$tsan" = "yes" ; then
        error_exit "Cannot enable TSAN due to missing fiber" \
                   "annotation interface."
     fi

> +  fi
> +fi
>  if test "$have_ubsan" = "yes"; then
>    QEMU_CFLAGS="-fsanitize=undefined $QEMU_CFLAGS"
>    QEMU_LDFLAGS="-fsanitize=undefined $QEMU_LDFLAGS"
> @@ -7365,6 +7400,10 @@ if test "$have_asan_iface_fiber" = "yes" ; then
>      echo "CONFIG_ASAN_IFACE_FIBER=y" >> $config_host_mak
>  fi
>  
> +if test "$have_tsan" = "yes" && test "$have_tsan_iface_fiber" = "yes" ; then
> +    echo "CONFIG_TSAN=y" >> $config_host_mak
> +fi
> +
>  if test "$has_environ" = "yes" ; then
>    echo "CONFIG_HAS_ENVIRON=y" >> $config_host_mak
>  fi
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