6 files changed, 45 insertions, 2 deletions
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 358c036f2a7..5b8b013ad08 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -29,6 +29,7 @@
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCFixupKindInfo.h"
 #include "llvm/MC/MCFragment.h"
+#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionELF.h"
@@ -1107,6 +1108,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
       SectionIndexMap[RelSection] = addToSectionTable(RelSection);
       Relocations.push_back(RelSection);
     }
+
+    OWriter.TargetObjectWriter->addTargetSectionFlags(Ctx, Section);
   }
 
   MCSectionELF *CGProfileSection = nullptr;
diff --git a/llvm/lib/MC/MCELFObjectTargetWriter.cpp b/llvm/lib/MC/MCELFObjectTargetWriter.cpp
index 483ee94c0db..ff53dd7299c 100644
--- a/llvm/lib/MC/MCELFObjectTargetWriter.cpp
+++ b/llvm/lib/MC/MCELFObjectTargetWriter.cpp
@@ -26,3 +26,6 @@ void
 MCELFObjectTargetWriter::sortRelocs(const MCAssembler &Asm,
                                     std::vector<ELFRelocationEntry> &Relocs) {
 }
+
+void MCELFObjectTargetWriter::addTargetSectionFlags(MCContext &Ctx,
+                                                    MCSectionELF &Sec) {}
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index 019b9348a4e..8c88db009bd 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -496,6 +496,12 @@ void MCObjectStreamer::EmitBytes(StringRef Data) {
   MCDataFragment *DF = getOrCreateDataFragment();
   flushPendingLabels(DF, DF->getContents().size());
   DF->getContents().append(Data.begin(), Data.end());
+
+  // EmitBytes might not cover all possible ways we emit data (or could be used
+  // to emit executable code in some cases), but is the best method we have
+  // right now for checking this.
+  MCSection *Sec = getCurrentSectionOnly();
+  Sec->setHasData(true);
 }
 
 void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
diff --git a/llvm/lib/MC/MCSection.cpp b/llvm/lib/MC/MCSection.cpp
index 97bc65387dd..d4f11d10136 100644
--- a/llvm/lib/MC/MCSection.cpp
+++ b/llvm/lib/MC/MCSection.cpp
@@ -23,7 +23,8 @@ using namespace llvm;
 
 MCSection::MCSection(SectionVariant V, SectionKind K, MCSymbol *Begin)
     : Begin(Begin), BundleGroupBeforeFirstInst(false), HasInstructions(false),
-      IsRegistered(false), DummyFragment(this), Variant(V), Kind(K) {}
+      HasData(false), IsRegistered(false), DummyFragment(this), Variant(V),
+      Kind(K) {}
 
 MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) {
   if (!End)
diff --git a/llvm/lib/Target/ARM/ARMTargetObjectFile.cpp b/llvm/lib/Target/ARM/ARMTargetObjectFile.cpp
index d0620761ea9..9c13359cba7 100644
--- a/llvm/lib/Target/ARM/ARMTargetObjectFile.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetObjectFile.cpp
@@ -32,7 +32,8 @@ void ARMElfTargetObjectFile::Initialize(MCContext &Ctx,
                                         const TargetMachine &TM) {
   const ARMBaseTargetMachine &ARM_TM = static_cast<const ARMBaseTargetMachine &>(TM);
   bool isAAPCS_ABI = ARM_TM.TargetABI == ARMBaseTargetMachine::ARMABI::ARM_ABI_AAPCS;
-  //  genExecuteOnly = ARM_TM.getSubtargetImpl()->genExecuteOnly();
+  bool genExecuteOnly =
+      ARM_TM.getMCSubtargetInfo()->hasFeature(ARM::FeatureExecuteOnly);
 
   TargetLoweringObjectFileELF::Initialize(Ctx, TM);
   InitializeELF(isAAPCS_ABI);
@@ -40,6 +41,17 @@ void ARMElfTargetObjectFile::Initialize(MCContext &Ctx,
   if (isAAPCS_ABI) {
     LSDASection = nullptr;
   }
+
+  // Make code section unreadable when in execute-only mode
+  if (genExecuteOnly) {
+    unsigned Type = ELF::SHT_PROGBITS;
+    unsigned Flags =
+        ELF::SHF_EXECINSTR | ELF::SHF_ALLOC | ELF::SHF_ARM_PURECODE;
+    // Since we cannot modify flags for an existing section, we create a new
+    // section with the right flags, and use 0 as the unique ID for
+    // execute-only text
+    TextSection = Ctx.getELFSection(".text", Type, Flags, 0, "", 0U);
+  }
 }
 
 const MCExpr *ARMElfTargetObjectFile::getTTypeGlobalReference(
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
index 7d04c73fb3f..b8ba7584911 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -14,6 +14,7 @@
 #include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -40,6 +41,8 @@ namespace {
 
     bool needsRelocateWithSymbol(const MCSymbol &Sym,
                                  unsigned Type) const override;
+
+    void addTargetSectionFlags(MCContext &Ctx, MCSectionELF &Sec) override;
   };
 
 } // end anonymous namespace
@@ -236,6 +239,21 @@ unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
   }
 }
 
+void ARMELFObjectWriter::addTargetSectionFlags(MCContext &Ctx,
+                                               MCSectionELF &Sec) {
+  // The mix of execute-only and non-execute-only at link time is
+  // non-execute-only. To avoid the empty implicitly created .text
+  // section from making the whole .text section non-execute-only, we
+  // mark it execute-only if it is empty and there is at least one
+  // execute-only section in the object.
+  MCSectionELF *TextSection =
+      static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());
+  if (Sec.getKind().isExecuteOnly() && !TextSection->hasInstructions() &&
+      !TextSection->hasData()) {
+    TextSection->setFlags(TextSection->getFlags() | ELF::SHF_ARM_PURECODE);
+  }
+}
+
 std::unique_ptr<MCObjectTargetWriter>
 llvm::createARMELFObjectWriter(uint8_t OSABI) {
   return llvm::make_unique<ARMELFObjectWriter>(OSABI);