Add support to generate correct code on ARM ELF targets.

Adds -Bsymbolic at link time when producing shared objects
so that the linker will not produce the forbidden relocation
R_ARM_REL32. Do the same also when linking Swift standard
libraries.

Author: tienex

cmake/modules/AddSwift.cmake

@@ -160,8 +160,14 @@ function(_add_variant_link_flags
 
   if("${sdk}" STREQUAL "LINUX")
     list(APPEND result "-lpthread" "-ldl")
+    if("${arch}" MATCHES "^arm")
+      list(APPEND result "-Wl,-Bsymbolic")
+    endif()
   elseif("${sdk}" STREQUAL "FREEBSD")
     # No extra libraries required.
+    if("${arch}" MATCHES "^arm")
+      list(APPEND result "-Wl,-Bsymbolic")
+    endif()
   else()
     list(APPEND result "-lobjc")
   endif()

lib/Driver/ToolChains.cpp

@@ -1047,6 +1047,16 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
     break;
   case LinkKind::DynamicLibrary:
     Arguments.push_back("-shared");
+    switch (getTriple().getArch()) {
+      default:
+        break;
+      case llvm::Triple::arm:
+      case llvm::Triple::armeb:
+        // Avoid emitting R_ARM_REL32 which is not supported by shared objects
+        // on ELF targets.
+        Arguments.push_back("-Wl,-Bsymbolic");
+        break;
+    }
     break;
   }
 

stdlib/public/runtime/CMakeLists.txt

@@ -74,15 +74,30 @@ add_swift_library(swiftRuntime IS_STDLIB IS_STDLIB_CORE
 foreach(sdk ${SWIFT_CONFIGURED_SDKS})
   if("${sdk}" STREQUAL "LINUX" OR "${sdk}" STREQUAL "FREEBSD")
     foreach(arch ${SWIFT_SDK_${sdk}_ARCHITECTURES})
-      set(arch_subdir "${SWIFT_SDK_${sdk}_LIB_SUBDIR}/${arch}")
+      if ("${sdk}" STREQUAL "LINUX" AND "${arch}" STREQUAL "armv7")
+        # Handle special case for ARM on Linux.
+        # FIXME: Find a more elegant way to handle this case.
+        foreach(subarch armv7;armv7l)
+          set(arch_subdir "${SWIFT_SDK_${sdk}_LIB_SUBDIR}/${subarch}")
 
-      # FIXME: We will need a different linker script for 32-bit builds.
-      configure_file(
-          "swift.ld" "${SWIFTLIB_DIR}/${arch_subdir}/swift.ld" COPYONLY)
+          configure_file(
+              "swift.ld" "${SWIFTLIB_DIR}/${arch_subdir}/swift.ld" COPYONLY)
 
-      swift_install_in_component(compiler
-          FILES "swift.ld"
-          DESTINATION "lib/swift/${arch_subdir}")
+          swift_install_in_component(compiler
+              FILES "swift.ld"
+              DESTINATION "lib/swift/${arch_subdir}")
+
+        endforeach()
+      else ()
+        set(arch_subdir "${SWIFT_SDK_${sdk}_LIB_SUBDIR}/${arch}")
+
+        configure_file(
+            "swift.ld" "${SWIFTLIB_DIR}/${arch_subdir}/swift.ld" COPYONLY)
+
+        swift_install_in_component(compiler
+            FILES "swift.ld"
+            DESTINATION "lib/swift/${arch_subdir}")
+      endif ()
 
     endforeach()
   endif()