COFF: ARM: Fix relocations to thumb code.

Windows ARM is the thumb ARM environment, and pointers to thumb code
needs to have its LSB set. When we apply relocations, we need to
adjust the LSB if it points to an executable section.

llvm-svn: 243560

lld/COFF/Chunks.cpp

@@ -105,6 +105,9 @@ static void applyBranchImm(uint8_t *Off, int32_t V) {
 void SectionChunk::applyRelARM(uint8_t *Off, uint16_t Type, Defined *Sym,
                                uint64_t P) {
   uint64_t S = Sym->getRVA();
+  // Pointer to thumb code must have the LSB set.
+  if (Sym->isExecutable())
+    S |= 1;
   switch (Type) {
   case IMAGE_REL_ARM_ADDR32:    add32(Off, S + Config->ImageBase); break;
   case IMAGE_REL_ARM_ADDR32NB:  add32(Off, S); break;

lld/COFF/Symbols.h

@@ -138,6 +138,10 @@ public:
   // Returns the output section index.
   // Used to implement SECTION relocation type.
   uint64_t getSectionIndex();
+
+  // Returns true if this symbol points to an executable (e.g. .text) section.
+  // Used to implement ARM relocations.
+  bool isExecutable();
 };
 
 // Symbols defined via a COFF object file.

lld/COFF/Writer.cpp

@@ -690,5 +690,12 @@ uint64_t Defined::getSectionIndex() {
   llvm::report_fatal_error("SECTION relocation points to a non-regular symbol");
 }
 
+bool Defined::isExecutable() {
+  const auto X = IMAGE_SCN_MEM_EXECUTE;
+  if (auto *D = dyn_cast<DefinedRegular>(this))
+    return D->getChunk()->getOutputSection()->getPermissions() & X;
+  return isa<DefinedImportThunk>(this);
+}
+
 } // namespace coff
 } // namespace lld

lld/test/COFF/armnt-mov32t-exec.test

@@ -2,7 +2,7 @@
 
 # RUN: yaml2obj < %s > %t.obj
 # RUN: llvm-objdump -d %t.obj | FileCheck %s -check-prefix BEFORE
-# RUN: lld -flavor link /out:%t.exe /subsystem:console /entry:get_function %t.obj
+# RUN: lld -flavor link2 /out:%t.exe /subsystem:console /entry:get_function %t.obj
 # RUN: llvm-objdump -d %t.exe | FileCheck %s -check-prefix AFTER
 
 # BEFORE: Disassembly of section .text: