[ExecutionEngine] Check for libunwind before calling __register_frame

libgcc and libunwind have different flavours of __register_frame. Both
 flavours are already correctly handled, except that the code to handle
the libunwind flavour is guarded by __APPLE__. This change uses the
presence of __unw_add_dynamic_fde in libunwind instead to detect whether
libunwind is used, rather than hardcoding it as Apple vs. non-Apple.

Fixes PR44074.

Thanks to Albert Jin <albert.jin@gmail.com> and Chris Schafmeister
<chris.schaf@verizon.net> for identifying the problem.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D106129

llvm/cmake/config-ix.cmake

@@ -211,6 +211,7 @@ endif()
 # Determine whether we can register EH tables.
 check_symbol_exists(__register_frame "${CMAKE_CURRENT_LIST_DIR}/unwind.h" HAVE_REGISTER_FRAME)
 check_symbol_exists(__deregister_frame "${CMAKE_CURRENT_LIST_DIR}/unwind.h" HAVE_DEREGISTER_FRAME)
+check_symbol_exists(__unw_add_dynamic_fde "${CMAKE_CURRENT_LIST_DIR}/unwind.h" HAVE_UNW_ADD_DYNAMIC_FDE)
 
 check_symbol_exists(_Unwind_Backtrace "unwind.h" HAVE__UNWIND_BACKTRACE)
 check_symbol_exists(getpagesize unistd.h HAVE_GETPAGESIZE)

llvm/cmake/unwind.h

@@ -5,3 +5,4 @@
 // exist in the runtime.
 extern void __register_frame(const void *fde);   // NOLINT
 extern void __deregister_frame(const void *fde); // NOLINT
+extern void __unw_add_dynamic_fde();             // NOLINT

llvm/include/llvm/Config/config.h.cmake

@@ -64,6 +64,9 @@
 /* Define to 1 if we can deregister EH frames on this platform. */
 #cmakedefine HAVE_DEREGISTER_FRAME ${HAVE_DEREGISTER_FRAME}
 
+/* Define if __unw_add_dynamic_fde() is available on this platform. */
+#cmakedefine HAVE_UNW_ADD_DYNAMIC_FDE ${HAVE_UNW_ADD_DYNAMIC_FDE}
+
 /* Define to 1 if you have the <errno.h> header file. */
 #cmakedefine HAVE_ERRNO_H ${HAVE_ERRNO_H}
 

llvm/lib/ExecutionEngine/Orc/TargetProcess/RegisterEHFrames.cpp

@@ -85,11 +85,11 @@ static Error deregisterFrameWrapper(const void *P) {
 }
 #endif
 
-#ifdef __APPLE__
+#ifdef HAVE_UNW_ADD_DYNAMIC_FDE
 
 template <typename HandleFDEFn>
-Error walkAppleEHFrameSection(const char *const SectionStart,
-                              size_t SectionSize, HandleFDEFn HandleFDE) {
+Error walkLibunwindEHFrameSection(const char *const SectionStart,
+                                  size_t SectionSize, HandleFDEFn HandleFDE) {
   const char *CurCFIRecord = SectionStart;
   const char *End = SectionStart + SectionSize;
   uint64_t Size = *reinterpret_cast<const uint32_t *>(CurCFIRecord);
@@ -123,16 +123,19 @@ Error walkAppleEHFrameSection(const char *const SectionStart,
   return Error::success();
 }
 
-#endif // __APPLE__
+#endif // HAVE_UNW_ADD_DYNAMIC_FDE
 
 Error registerEHFrameSection(const void *EHFrameSectionAddr,
                              size_t EHFrameSectionSize) {
-#ifdef __APPLE__
-  // On Darwin __register_frame has to be called for each FDE entry.
-  return walkAppleEHFrameSection(static_cast<const char *>(EHFrameSectionAddr),
-                                 EHFrameSectionSize, registerFrameWrapper);
+  /* libgcc and libunwind __register_frame behave differently. We use the
+   * presence of __unw_add_dynamic_fde to detect libunwind. */
+#ifdef HAVE_UNW_ADD_DYNAMIC_FDE
+  // With libunwind, __register_frame has to be called for each FDE entry.
+  return walkLibunwindEHFrameSection(
+      static_cast<const char *>(EHFrameSectionAddr), EHFrameSectionSize,
+      registerFrameWrapper);
 #else
-  // On Linux __register_frame takes a single argument:
+  // With libgcc, __register_frame takes a single argument:
   // a pointer to the start of the .eh_frame section.
 
   // How can it find the end? Because crtendS.o is linked
@@ -143,9 +146,10 @@ Error registerEHFrameSection(const void *EHFrameSectionAddr,
 
 Error deregisterEHFrameSection(const void *EHFrameSectionAddr,
                                size_t EHFrameSectionSize) {
-#ifdef __APPLE__
-  return walkAppleEHFrameSection(static_cast<const char *>(EHFrameSectionAddr),
-                                 EHFrameSectionSize, deregisterFrameWrapper);
+#ifdef HAVE_UNW_ADD_DYNAMIC_FDE
+  return walkLibunwindEHFrameSection(
+      static_cast<const char *>(EHFrameSectionAddr), EHFrameSectionSize,
+      deregisterFrameWrapper);
 #else
   return deregisterFrameWrapper(EHFrameSectionAddr);
 #endif

llvm/lib/ExecutionEngine/RuntimeDyld/RTDyldMemoryManager.cpp

@@ -67,7 +67,9 @@ static void __deregister_frame(void *p) {
 }
 #endif
 
-#ifdef __APPLE__
+/* libgcc and libunwind __register_frame behave differently. We use the presence
+ * of __unw_add_dynamic_fde to detect libunwind. */
+#ifdef HAVE_UNW_ADD_DYNAMIC_FDE
 
 static const char *processFDE(const char *Entry, bool isDeregister) {
   const char *P = Entry;