From 8bc43a142ba4c852820ec1e285f6ead6229baa7c Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Wed, 29 Jul 2015 19:25:00 +0000
Subject: [PATCH] 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                  | 3 +++
 lld/COFF/Symbols.h                   | 4 ++++
 lld/COFF/Writer.cpp                  | 7 +++++++
 lld/test/COFF/armnt-mov32t-exec.test | 2 +-
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/lld/COFF/Chunks.cpp b/lld/COFF/Chunks.cpp
index a68e258efc48..4e41f2fcea9e 100644
--- a/lld/COFF/Chunks.cpp
+++ b/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;
diff --git a/lld/COFF/Symbols.h b/lld/COFF/Symbols.h
index eae1bfa203ed..eb9afd380080 100644
--- a/lld/COFF/Symbols.h
+++ b/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.
diff --git a/lld/COFF/Writer.cpp b/lld/COFF/Writer.cpp
index 62ac95cc95af..4a9c5f896aff 100644
--- a/lld/COFF/Writer.cpp
+++ b/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
diff --git a/lld/test/COFF/armnt-mov32t-exec.test b/lld/test/COFF/armnt-mov32t-exec.test
index 847c7b92a62e..91b814caa5ec 100644
--- a/lld/test/COFF/armnt-mov32t-exec.test
+++ b/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: