avoid interposition (linux only)

Author: malytomas

cmake/cage_build_configuration.cmake

@@ -75,6 +75,9 @@ macro(cage_build_configuration)
 		set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /MP")
 		set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /MP")
 	else()
+		# make runtime loader look for local symbols first
+		set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Bsymbolic")
+
 		# link time optimizations
 		set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -flto")
 		set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -flto")

sources/CMakeLists.txt

@@ -29,8 +29,9 @@ if(MSVC)
 	target_compile_definitions(cage-core PUBLIC "CAGE_API_IMPORT=__declspec(dllimport)")
 	target_compile_definitions(cage-core PUBLIC "CAGE_FORCE_INLINE=__forceinline")
 else()
-	target_compile_definitions(cage-core PUBLIC "CAGE_API_EXPORT=[[gnu::visibility(\"default\")]]")
-	target_compile_definitions(cage-core PUBLIC "CAGE_API_IMPORT=[[gnu::visibility(\"default\")]]")
+	# protected, unlike default, prevents interposition
+	target_compile_definitions(cage-core PUBLIC "CAGE_API_EXPORT=[[gnu::visibility(\"protected\")]]")
+	target_compile_definitions(cage-core PUBLIC "CAGE_API_IMPORT=[[gnu::visibility(\"protected\")]]")
 	target_compile_definitions(cage-core PUBLIC "CAGE_FORCE_INLINE=[[gnu::always_inline]]inline")
 endif()
 if(WIN32)