[ubsan] Link shared runtime library with a version script.

[eugenis]

Summary

Do not reexport libgcc.a symbols and random sanitizer internal symbols
by applying a version script to the shared library build.

This fixes unwinder conflicts on Android that are created by reexporting
the unwinder interface from libgcc_real.a. The same is already done in
asan and hwasan.

[phosek]

We're seeing a link failure after this change:

FAILED: /b/s/w/ir/k/recipe_cleanup/clangpp19QX/llvm_build_dir/lib/clang/11.0.0/lib/x86_64-unknown-fuchsia/libclang_rt.ubsan_standalone.so 
: && /b/s/w/ir/k/recipe_cleanup/clangpp19QX/llvm_build_dir/./bin/clang++ --target=x86_64-unknown-fuchsia --sysroot=/b/s/w/ir/k/cipd/sdk/arch/x64/sysroot -fPIC -I/b/s/w/ir/k/cipd/sdk/pkg/fdio/include -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -ffunction-sections -fdata-sections -ffile-prefix-map=/b/s/w/ir/k/recipe_cleanup/clangpp19QX/llvm_build_dir/runtimes/runtimes-x86_64-unknown-fuchsia-bins=../recipe_cleanup/clangpp19QX/llvm_build_dir/runtimes/runtimes-x86_64-unknown-fuchsia-bins -ffile-prefix-map=/b/s/w/ir/k/llvm-project/= -no-canonical-prefixes -Wall -std=c++14 -Wno-unused-parameter -O2 -g  -L/b/s/w/ir/k/cipd/sdk/arch/x64/lib    -Wl,--version-script,/b/s/w/ir/k/recipe_cleanup/clangpp19QX/llvm_build_dir/runtimes/runtimes-x86_64-unknown-fuchsia-bins/compiler-rt/lib/ubsan/clang_rt.ubsan_standalone-dynamic-x86_64.vers -shared -Wl,-soname,libclang_rt.ubsan_standalone.so -o /b/s/w/ir/k/recipe_cleanup/clangpp19QX/llvm_build_dir/lib/clang/11.0.0/lib/x86_64-unknown-fuchsia/libclang_rt.ubsan_standalone.so compiler-rt/lib/sanitizer_common/CMakeFiles/RTSanitizerCommon.x86_64.dir/sanitizer_allocator.cpp.obj compiler-rt/lib/sanitizer_common/CMakeFiles/RTSanitizerCommon.x86_64.dir/sanitizer_common.cpp.obj compiler-rt/lib/sanitizer_common/CMakeFiles/RTSanitizerCommon.x86_64.dir/sanitizer_deadlock_detector1.cpp.obj compiler-rt/lib/sanitizer_common/CMakeFiles/RTSanitizerCommon.x86_64.dir/sanitizer_deadlock_detector2.cpp.obj compiler-rt/lib/sanitizer_common/CMakeFiles/RTSanitizerCommon.x86_64.dir/sanitizer_errno.cpp.obj compiler-rt/lib/sanitizer_common/CMakeFiles/RTSanitizerCommon.x86_64.dir/sanitizer_file.cpp.obj 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compiler-rt/lib/ubsan/CMakeFiles/RTUbsan_standalone.x86_64.dir/ubsan_init_standalone.cpp.obj compiler-rt/lib/ubsan/CMakeFiles/RTUbsan_standalone.x86_64.dir/ubsan_signals_standalone.cpp.obj compiler-rt/lib/interception/CMakeFiles/RTInterception.x86_64.dir/interception_linux.cpp.obj compiler-rt/lib/interception/CMakeFiles/RTInterception.x86_64.dir/interception_mac.cpp.obj compiler-rt/lib/interception/CMakeFiles/RTInterception.x86_64.dir/interception_win.cpp.obj compiler-rt/lib/interception/CMakeFiles/RTInterception.x86_64.dir/interception_type_test.cpp.obj compiler-rt/lib/ubsan/CMakeFiles/RTUbsan_dynamic_version_script_dummy.x86_64.dir/dummy.cpp.obj -L/b/s/w/ir/k/cipd/sdk/arch/x64/lib  -L/b/s/w/ir/k/cipd/sdk/arch/x64/sysroot/lib /b/s/w/ir/k/recipe_cleanup/clangpp19QX/llvm_build_dir/lib/x86_64-unknown-fuchsia/c++/libunwind.a /b/s/w/ir/k/recipe_cleanup/clangpp19QX/llvm_build_dir/lib/x86_64-unknown-fuchsia/c++/libc++abi.so.1.0 -lc -lzircon -ldl -lrt -lpthread /b/s/w/ir/k/recipe_cleanup/clangpp19QX/llvm_build_dir/lib/clang/11.0.0/lib/x86_64-unknown-fuchsia/libclang_rt.builtins.a -lc && :
ld.lld: error: unable to find library -lc++

It seems like this change introduced a C++ standard library dependency to libclang_rt.ubsan_standalone.so?

[eugenis]

Sorry about that! Any idea why this is happening? I don't see any "-lc++" on the linker command line, but the driver should add it anyway when you link with "clang++" AFAIK.

[phosek]

In D78325#1989273, @eugenis wrote:

Sorry about that! Any idea why this is happening? I don't see any "-lc++" on the linker command line, but the driver should add it anyway when you link with "clang++" AFAIK.

I compared the two builds from before and after, and it seems like -nodefaultlibs got dropped which explains why -lc++ is not being linked in:

Before:

LINK_FLAGS = -L/usr/local/google/home/phosek/clang-llvm/sdk/arch/x64/lib    -nodefaultlibs -Wl,-z,text -Wl,-z,defs,-z,now,-z,relro

After:

LINK_FLAGS = -L/usr/local/google/home/phosek/clang-llvm/sdk/arch/x64/lib    -Wl,--version-script,/src/clang-llvm/llvm-build/fuchsia2/runtimes/runtimes-x86_64-unknown-fuchsia-bins/compiler-rt/lib/ubsan/clang_rt.ubsan_standalone-dynamic-x86_64.vers

I believe this is because ${SANITIZER_COMMON_LINK_FLAGS} got replaced with ${UBSAN_LINK_FLAGS} ${VERSION_SCRIPT_FLAG}, and ${UBSAN_LINK_FLAGS} doesn't contain -nodefaultlibs. In fact, I don't even see ${UBSAN_LINK_FLAGS} being set in ubsan\CMakeLists.txt, it's only set in ubsan_minimal\CMakeLists.txt, so we probably need to add set(UBSAN_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS}) to this file as well.

[ro]

This patch broke the Solaris builds:

[2307/5232] Linking CXX shared library lib/clang/11.0.0/lib/sunos/libclang_rt.ubsan_standalone-i386.so
FAILED: lib/clang/11.0.0/lib/sunos/libclang_rt.ubsan_standalone-i386.so
[...]
ld: fatal: option --version-script requires option -z gnu-version-script-compat to be specified
collect2: error: ld returned 1 exit status

For some reason it didn't carry over the Solaris suport to add that linker flag present in compiler-rt/lib/asan/CMakeLists.txt.

[eugenis]

I've copied the code from hwasan, which does not have the solaris check.
See D78510.

[ro]

In D78325#1992966, @eugenis wrote:

I've copied the code from hwasan, which does not have the solaris check.
See D78510.

So of the two uses of --version-script you took the one that isn't used on Solaris since it's practically guaranteed that hwasan will never be supported there ;-)

compiler-rt/lib/ubsan/CMakeLists.txt

if(COMPILER_RT_HAS_UBSAN)
     add_compiler_rt_runtime(clang_rt.ubsan_standalone_cxx
       STATIC
       ARCHS ${UBSAN_SUPPORTED_ARCH}
       OBJECT_LIBS RTUbsan_cxx
       CFLAGS ${UBSAN_CXXFLAGS}
       PARENT_TARGET ubsan)
 
     if (FUCHSIA OR UNIX)
+      file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/dummy.cpp "")
+      add_compiler_rt_object_libraries(RTUbsan_dynamic_version_script_dummy
+        ARCHS ${UBSAN_SUPPORTED_ARCH}
+        SOURCES ${CMAKE_CURRENT_BINARY_DIR}/dummy.cpp
+        CFLAGS ${UBSAN_CFLAGS})
+
+      foreach(arch ${UBSAN_SUPPORTED_ARCH})
+        add_sanitizer_rt_version_list(clang_rt.ubsan_standalone-dynamic-${arch}
+                                      LIBS clang_rt.ubsan_standalone-${arch}
+                                           clang_rt.ubsan_standalone_cxx-${arch}
+                                      EXTRA ubsan.syms.extra)
+        set(VERSION_SCRIPT_FLAG
+            -Wl,--version-script,${CMAKE_CURRENT_BINARY_DIR}/clang_rt.ubsan_standalone-dynamic-${arch}.vers)
+        set_property(SOURCE
+          ${CMAKE_CURRENT_BINARY_DIR}/dummy.cpp
+          APPEND PROPERTY
+          OBJECT_DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/clang_rt.ubsan_standalone-dynamic-${arch}.vers)
+
         add_compiler_rt_runtime(clang_rt.ubsan_standalone
           SHARED
-        ARCHS ${UBSAN_SUPPORTED_ARCH}
+          ARCHS ${arch}
           OBJECT_LIBS RTSanitizerCommon
                 RTSanitizerCommonLibc
                 RTSanitizerCommonCoverage
                 RTSanitizerCommonSymbolizer
                 RTUbsan
                 RTUbsan_cxx
                 RTUbsan_standalone
                 RTInterception
+                RTUbsan_dynamic_version_script_dummy
           CFLAGS ${UBSAN_CFLAGS}
-        LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS}
+          LINK_FLAGS ${UBSAN_LINK_FLAGS} ${VERSION_SCRIPT_FLAG}
           LINK_LIBS ${UBSAN_DYNAMIC_LIBS}
           PARENT_TARGET ubsan)
+      endforeach()
 
       set(ARCHS_FOR_SYMBOLS ${UBSAN_SUPPORTED_ARCH})
       list(REMOVE_ITEM ARCHS_FOR_SYMBOLS i386)
       add_sanitizer_rt_symbols(clang_rt.ubsan_standalone
         ARCHS ${ARCHS_FOR_SYMBOLS}
         PARENT_TARGET ubsan
         EXTRA ubsan.syms.extra)
       add_sanitizer_rt_symbols(clang_rt.ubsan_standalone_cxx
         ARCHS ${ARCHS_FOR_SYMBOLS}
         PARENT_TARGET ubsan
         EXTRA ubsan.syms.extra)
     endif()
   endif()
 endif()