[PAC][ELF][AArch64] Support signed personality function pointer

If function pointer signing is enabled, sign personality function pointer
stored in `.DW.ref.__gxx_personality_v0` section with IA key,
0x7EAD = `ptrauth_string_discriminator("personality")` constant discriminator
and address diversity enabled.

Author: kovdan01

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1218,6 +1218,9 @@ void CodeGenModule::Release() {
                                 "sign-return-address-with-bkey", 1);
 
     if (getTriple().isOSLinux()) {
+      if (LangOpts.PointerAuthCalls)
+        getModule().addModuleFlag(llvm::Module::Min, "ptrauth-sign-personality",
+                                  1);
       assert(getTriple().isOSBinFormatELF());
       using namespace llvm::ELF;
       uint64_t PAuthABIVersion =

clang/test/CodeGen/ptrauth-module-flags.c

@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -triple aarch64-linux-gnu                   -emit-llvm %s  -o - | FileCheck %s --check-prefix=OFF
+// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-calls   -emit-llvm %s  -o - | FileCheck %s --check-prefix=PERSONALITY
+
+// PERSONALITY:      !llvm.module.flags = !{
+// PERSONALITY-SAME: !1
+// PERSONALITY:      !1 = !{i32 8, !"ptrauth-sign-personality", i32 1}
+
+// OFF-NOT: "ptrauth-

llvm/include/llvm/CodeGen/MachineModuleInfoImpls.h

@@ -83,10 +83,14 @@ class MachineModuleInfoELF : public MachineModuleInfoImpl {
   /// extern_weak symbols.
   DenseMap<MCSymbol *, const MCExpr *> AuthPtrStubs;
 
+  /// HasSignedPersonality is true if the corresponding IR module has the
+  /// "ptrauth-sign-personality" flag set to 1.
+  bool HasSignedPersonality = false;
+
   virtual void anchor(); // Out of line virtual method.
 
 public:
-  MachineModuleInfoELF(const MachineModuleInfo &) {}
+  MachineModuleInfoELF(const MachineModuleInfo &);
 
   StubValueTy &getGVStubEntry(MCSymbol *Sym) {
     assert(Sym && "Key cannot be null");
@@ -105,6 +109,8 @@ class MachineModuleInfoELF : public MachineModuleInfoImpl {
   ExprStubListTy getAuthGVStubList() {
     return getSortedExprStubs(AuthPtrStubs);
   }
+
+  bool hasSignedPersonality() const { return HasSignedPersonality; }
 };
 
 /// MachineModuleInfoCOFF - This is a MachineModuleInfoImpl implementation

llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

@@ -52,7 +52,13 @@ class TargetLoweringObjectFileELF : public TargetLoweringObjectFile {
   void emitModuleMetadata(MCStreamer &Streamer, Module &M) const override;
 
   void emitPersonalityValue(MCStreamer &Streamer, const DataLayout &DL,
-                            const MCSymbol *Sym) const override;
+                            const MCSymbol *Sym,
+                            const MachineModuleInfo *MMI) const override;
+
+  virtual void emitPersonalityValueImpl(MCStreamer &Streamer,
+                                        const DataLayout &DL,
+                                        const MCSymbol *Sym,
+                                        const MachineModuleInfo *MMI) const;
 
   /// Given a constant with the SectionKind, return a section that it should be
   /// placed in.

llvm/include/llvm/Target/TargetLoweringObjectFile.h

@@ -82,7 +82,8 @@ class TargetLoweringObjectFile : public MCObjectFileInfo {
   virtual void Initialize(MCContext &ctx, const TargetMachine &TM);
 
   virtual void emitPersonalityValue(MCStreamer &Streamer, const DataLayout &TM,
-                                    const MCSymbol *Sym) const;
+                                    const MCSymbol *Sym,
+                                    const MachineModuleInfo *MMI) const;
 
   /// Emit the module-level metadata that the platform cares about.
   virtual void emitModuleMetadata(MCStreamer &Streamer, Module &M) const {}

llvm/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp

@@ -50,7 +50,8 @@ void DwarfCFIException::endModule() {
   // Emit indirect reference table for all used personality functions
   for (const GlobalValue *Personality : Personalities) {
     MCSymbol *Sym = Asm->getSymbol(Personality);
-    TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym);
+    TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym,
+                              Asm->MMI);
   }
   Personalities.clear();
 }

llvm/lib/CodeGen/MachineModuleInfoImpls.cpp

@@ -14,6 +14,8 @@
 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Module.h"
 #include "llvm/MC/MCSymbol.h"
 
 using namespace llvm;
@@ -59,3 +61,13 @@ MachineModuleInfoImpl::ExprStubListTy MachineModuleInfoImpl::getSortedExprStubs(
   ExprStubs.clear();
   return List;
 }
+
+MachineModuleInfoELF::MachineModuleInfoELF(const MachineModuleInfo &MMI) {
+  const Module *M = MMI.getModule();
+  const auto *Flag = mdconst::extract_or_null<ConstantInt>(
+      M->getModuleFlag("ptrauth-sign-personality"));
+  if (Flag && Flag->getZExtValue() == 1)
+    HasSignedPersonality = true;
+  else
+    HasSignedPersonality = false;
+}

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -413,7 +413,8 @@ MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
 }
 
 void TargetLoweringObjectFileELF::emitPersonalityValue(
-    MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
+    MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym,
+    const MachineModuleInfo *MMI) const {
   SmallString<64> NameData("DW.ref.");
   NameData += Sym->getName();
   MCSymbolELF *Label =
@@ -431,6 +432,13 @@ void TargetLoweringObjectFileELF::emitPersonalityValue(
   Streamer.emitELFSize(Label, E);
   Streamer.emitLabel(Label);
 
+  emitPersonalityValueImpl(Streamer, DL, Sym, MMI);
+}
+
+void TargetLoweringObjectFileELF::emitPersonalityValueImpl(
+    MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym,
+    const MachineModuleInfo *MMI) const {
+  unsigned Size = DL.getPointerSize();
   Streamer.emitSymbolValue(Sym, Size);
 }
 

llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp

@@ -9,6 +9,7 @@
 #include "AArch64TargetObjectFile.h"
 #include "AArch64TargetMachine.h"
 #include "MCTargetDesc/AArch64MCExpr.h"
+#include "MCTargetDesc/AArch64TargetStreamer.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
@@ -29,6 +30,21 @@ void AArch64_ELFTargetObjectFile::Initialize(MCContext &Ctx,
   SupportDebugThreadLocalLocation = false;
 }
 
+void AArch64_ELFTargetObjectFile::emitPersonalityValueImpl(
+    MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym,
+    const MachineModuleInfo *MMI) const {
+  if (!MMI->getObjFileInfo<MachineModuleInfoELF>().hasSignedPersonality()) {
+    TargetLoweringObjectFileELF::emitPersonalityValueImpl(Streamer, DL, Sym,
+                                                          MMI);
+    return;
+  }
+  auto *TS = static_cast<AArch64TargetStreamer *>(Streamer.getTargetStreamer());
+  // The value is ptrauth_string_discriminator("personality")
+  constexpr uint16_t Discriminator = 0x7EAD;
+  TS->emitAuthValue(MCSymbolRefExpr::create(Sym, getContext()), Discriminator,
+                    AArch64PACKey::IA, true, getContext());
+}
+
 const MCExpr *AArch64_ELFTargetObjectFile::getIndirectSymViaGOTPCRel(
     const GlobalValue *GV, const MCSymbol *Sym, const MCValue &MV,
     int64_t Offset, MachineModuleInfo *MMI, MCStreamer &Streamer) const {

llvm/lib/Target/AArch64/AArch64TargetObjectFile.h

@@ -35,6 +35,10 @@ class AArch64_ELFTargetObjectFile : public TargetLoweringObjectFileELF {
                                  MachineModuleInfo *MMI, const MCSymbol *RawSym,
                                  AArch64PACKey::ID Key,
                                  uint16_t Discriminator) const;
+
+  void emitPersonalityValueImpl(MCStreamer &Streamer, const DataLayout &DL,
+                                const MCSymbol *Sym,
+                                const MachineModuleInfo *MMI) const override;
 };
 
 /// AArch64_MachoTargetObjectFile - This TLOF implementation is used for Darwin.