Arm-64: Add initial support for PAC-RET

src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.CoreCLR.cs

@@ -511,7 +511,8 @@ private static unsafe void DispatchTailCalls(
             IntPtr callersRetAddr;
             TailCallTls* tls = GetTailCallInfo(callersRetAddrSlot, &callersRetAddr);
             PortableTailCallFrame* prevFrame = tls->Frame;
-            if (callersRetAddr == prevFrame->TailCallAwareReturnAddress)
+            // TODO-PAC: Implement stripping of PAC from return addresses in coreclr
+            if ((callersRetAddr & 0x0000FFFFFFFFFFFF) == (prevFrame->TailCallAwareReturnAddress & 0x0000FFFFFFFFFFFF))
             {
                 prevFrame->NextCall = callTarget;
                 return;

src/coreclr/jit/codegenarm64.cpp

@@ -271,6 +271,10 @@ void CodeGen::genPopCalleeSavedRegistersAndFreeLclFrame(bool jmpEpilog)
         GetEmitter()->emitIns_R_R_I(INS_add, EA_PTRSIZE, REG_SPBASE, REG_SPBASE, spAdjust);
         compiler->unwindAllocStack(spAdjust);
     }
+
+    // TODO-PAC: emit autiasp
+    GetEmitter()->emitIns(INS_autiaz);
+   //compiler->unwindPacSignLR();
 }
 
 //------------------------------------------------------------------------
@@ -523,6 +527,11 @@ void CodeGen::genPrologSaveRegPair(regNumber reg1,
             compiler->unwindSaveRegPair(reg1, reg2, spOffset);
         }
     }
+
+    if (reg2 == REG_LR)
+    {
+        compiler->unwindPacSignLR();
+    }
 }
 
 //------------------------------------------------------------------------
@@ -1398,6 +1407,10 @@ void CodeGen::genFuncletProlog(BasicBlock* block)
 
     compiler->unwindBegProlog();
 
+    // Sign LR as part of Pointer Authentication (PAC) support
+    GetEmitter()->emitIns(INS_paciaz);
+    compiler->unwindPacSignLR();
+
     regMaskTP maskSaveRegsFloat = genFuncletInfo.fiSaveRegs & RBM_ALLFLOAT;
     regMaskTP maskSaveRegsInt   = genFuncletInfo.fiSaveRegs & ~maskSaveRegsFloat;
 
@@ -1721,6 +1734,10 @@ void CodeGen::genFuncletEpilog()
         }
     }
 
+    // TODO-PAC: emit autiasp
+    GetEmitter()->emitIns(INS_autiaz);
+   //compiler->unwindPacSignLR();
+
     inst_RV(INS_ret, REG_LR, TYP_I_IMPL);
     compiler->unwindReturn(REG_LR);
 

src/coreclr/jit/codegenarmarch.cpp

@@ -4744,6 +4744,10 @@ void CodeGen::genPushCalleeSavedRegisters()
     }
 #endif // DEBUG
 
+    // Sign LR as part of Pointer Authentication (PAC) support
+    GetEmitter()->emitIns(INS_paciaz);
+    compiler->unwindPacSignLR();
+
     // The frameType number is arbitrary, is defined below, and corresponds to one of the frame styles we
     // generate based on various sizes.
     int frameType = 0;

src/coreclr/jit/compiler.h

@@ -8949,6 +8949,7 @@ class Compiler
     void unwindSaveRegPair(regNumber reg1, regNumber reg2, int offset);           // stp reg1, reg2, [sp, #offset]
     void unwindSaveRegPairPreindexed(regNumber reg1, regNumber reg2, int offset); // stp reg1, reg2, [sp, #offset]!
     void unwindSaveNext();                                                        // unwind code: save_next
+    void unwindPacSignLR();                                                       // unwind code: pac_sign_lr
     void unwindReturn(regNumber reg);                                             // ret lr
 #endif                                                                            // defined(TARGET_ARM64)
 

src/coreclr/jit/unwindarm64.cpp

@@ -635,6 +635,31 @@ void Compiler::unwindSaveNext()
     pu->AddCode(0xE6);
 }
 
+void Compiler::unwindPacSignLR()
+{
+#if defined(FEATURE_CFI_SUPPORT)
+    if (generateCFIUnwindCodes())
+    {
+        FuncInfoDsc*   func     = funCurrentFunc();
+        UNATIVE_OFFSET cbProlog = 0;
+        if (compGeneratingProlog)
+        {
+            cbProlog = unwindGetCurrentOffset(func);
+        }
+
+        // DW_CFA_GNU_window_save 0x2D
+        createCfiCode(func, cbProlog, CFI_DEF_CFA_REGISTER, DWARF_REG_ILLEGAL);
+
+        return;
+    }
+#endif // FEATURE_CFI_SUPPORT
+
+     assert(compGeneratingProlog);
+
+    // pac_sign_lr: 11111100: sign the return address in lr with pacibsp
+    funCurrentFunc()->uwi.AddCode(0xFC);
+}
+
 void Compiler::unwindReturn(regNumber reg)
 {
     // Nothing to do; we will always have at least one trailing "end" opcode in our padding.
@@ -1081,6 +1106,12 @@ void DumpUnwindInfo(Compiler*         comp,
 
             printf("    %02X          save_next\n", b1);
         }
+        else if (b1 == 0xFC)
+        {
+            // pac_sign_lr: 11111100 : sign the return address in lr with pacibsp.
+
+            printf("    %02X          pac_sign_lr\n", b1);
+        }
         else
         {
             // Unknown / reserved unwind code

src/coreclr/unwinder/arm64/unwinder.cpp

@@ -258,7 +258,7 @@ do {
 #if !defined(DEBUGGER_STRIP_PAC)
 
 // NOTE: Pointer authentication is not used by .NET, so the implementation does nothing
-#define STRIP_PAC(Params, pointer)
+#define STRIP_PAC(pointer) *pointer &= 0x0000FFFFFFFFFFFF
 
 #endif
 
@@ -2335,15 +2335,15 @@ Return Value:
         }
 
         //
-        // pac (11111100): function has pointer authentication 
+        // pac (11111100): function has pointer authentication
         //
 
         else if (CurCode == 0xfc) {
             if (AccumulatedSaveNexts != 0) {
                 return STATUS_UNWIND_INVALID_SEQUENCE;
             }
 
-            STRIP_PAC(UnwindParams, &ContextRecord->Lr);
+            STRIP_PAC(&ContextRecord->Lr);
 
             //
             // TODO: Implement support for UnwindFlags RTL_VIRTUAL_UNWIND2_VALIDATE_PAC.