[AArch64] - Return address signing dwarf support

Functions that have signed return addresses need additional dwarf support:
- After signing the LR, and before authenticating it, the LR register is in a
  state the is unusable by a debugger or unwinder
- To account for this a new directive, .cfi_negate_ra_state, is added
- This directive says the signed state of the LR register has now changed,
  i.e. unsigned -> signed or signed -> unsigned
- This directive has the same CFA code as the SPARC directive GNU_window_save
  (0x2d), adding a macro to account for multiply defined codes
- This patch matches the gcc implementation of this support:
  https://patchwork.ozlabs.org/patch/800271/

Differential Revision: https://reviews.llvm.org/D50136

llvm-svn: 343089

3 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index c4744ac5d51..58c400a7132 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -285,6 +285,7 @@ public:
   void EmitCFIUndefined(int64_t Register) override;
   void EmitCFIRegister(int64_t Register1, int64_t Register2) override;
   void EmitCFIWindowSave() override;
+  void EmitCFINegateRAState() override;
   void EmitCFIReturnColumn(int64_t Register) override;
 
   void EmitWinCFIStartProc(const MCSymbol *Symbol, SMLoc Loc) override;
@@ -1564,6 +1565,12 @@ void MCAsmStreamer::EmitCFIWindowSave() {
   EmitEOL();
 }
 
+void MCAsmStreamer::EmitCFINegateRAState() {
+  MCStreamer::EmitCFINegateRAState();
+  OS << "\t.cfi_negate_ra_state";
+  EmitEOL();
+}
+
 void MCAsmStreamer::EmitCFIReturnColumn(int64_t Register) {
   MCStreamer::EmitCFIReturnColumn(Register);
   OS << "\t.cfi_return_column " << Register;
diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index 7093446815f..2899242ee4c 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -1332,6 +1332,10 @@ void FrameEmitterImpl::EmitCFIInstruction(const MCCFIInstruction &Instr) {
     Streamer.EmitIntValue(dwarf::DW_CFA_GNU_window_save, 1);
     return;
 
+  case MCCFIInstruction::OpNegateRAState:
+    Streamer.EmitIntValue(dwarf::DW_CFA_AARCH64_negate_ra_state, 1);
+    return;
+
   case MCCFIInstruction::OpUndefined: {
     unsigned Reg = Instr.getRegister();
     Streamer.EmitIntValue(dwarf::DW_CFA_undefined, 1);
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index fa0d1f46cbb..bb8f3b8ccec 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -565,6 +565,15 @@ void MCStreamer::EmitCFIWindowSave() {
   CurFrame->Instructions.push_back(Instruction);
 }
 
+void MCStreamer::EmitCFINegateRAState() {
+  MCSymbol *Label = EmitCFILabel();
+  MCCFIInstruction Instruction = MCCFIInstruction::createNegateRAState(Label);
+  MCDwarfFrameInfo *CurFrame = getCurrentDwarfFrameInfo();
+  if (!CurFrame)
+    return;
+  CurFrame->Instructions.push_back(Instruction);
+}
+
 void MCStreamer::EmitCFIReturnColumn(int64_t Register) {
   MCDwarfFrameInfo *CurFrame = getCurrentDwarfFrameInfo();
   if (!CurFrame)