Protect against stack overflow caused by deep recursive calls

* PPTC version bump

* Also reset call depth when not using the unmanaged dispatch loop

* Increment call depth on function start rather than before call

src/ARMeilleure/Instructions/InstEmitException.cs

@@ -19,7 +19,7 @@ namespace ARMeilleure.Instructions
 
             context.LoadFromContext();
 
-            context.Return(Const(op.Address));
+            InstEmitFlowHelper.EmitReturn(context, Const(op.Address));
         }
 
         public static void Svc(ArmEmitterContext context)
@@ -49,7 +49,7 @@ namespace ARMeilleure.Instructions
 
             context.LoadFromContext();
 
-            context.Return(Const(op.Address));
+            InstEmitFlowHelper.EmitReturn(context, Const(op.Address));
         }
     }
 }

src/ARMeilleure/Instructions/InstEmitException32.cs

@@ -33,7 +33,7 @@ namespace ARMeilleure.Instructions
 
             context.LoadFromContext();
 
-            context.Return(Const(context.CurrOp.Address));
+            InstEmitFlowHelper.EmitReturn(context, Const(context.CurrOp.Address));
         }
     }
 }

src/ARMeilleure/Instructions/InstEmitFlow.cs

@@ -66,7 +66,7 @@ namespace ARMeilleure.Instructions
         {
             OpCodeBReg op = (OpCodeBReg)context.CurrOp;
 
-            context.Return(GetIntOrZR(context, op.Rn));
+            EmitReturn(context, GetIntOrZR(context, op.Rn));
         }
 
         public static void Tbnz(ArmEmitterContext context) => EmitTb(context, onNotZero: true);

src/ARMeilleure/Instructions/InstEmitFlowHelper.cs

@@ -12,6 +12,10 @@ namespace ARMeilleure.Instructions
 {
     static class InstEmitFlowHelper
     {
+        // How many calls we can have in our call stack before we give up and return to the dispatcher.
+        // This prevents stack overflows caused by deep recursive calls.
+        private const int MaxCallDepth = 200;
+
         public static void EmitCondBranch(ArmEmitterContext context, Operand target, Condition cond)
         {
             if (cond != Condition.Al)
@@ -163,12 +167,7 @@ namespace ARMeilleure.Instructions
         {
             if (isReturn)
             {
-                if (target.Type == OperandType.I32)
-                {
-                    target = context.ZeroExtend32(OperandType.I64, target);
-                }
-
-                context.Return(target);
+                EmitReturn(context, target);
             }
             else
             {
@@ -176,6 +175,19 @@ namespace ARMeilleure.Instructions
             }
         }
 
+        public static void EmitReturn(ArmEmitterContext context, Operand target)
+        {
+            Operand nativeContext = context.LoadArgument(OperandType.I64, 0);
+            DecreaseCallDepth(context, nativeContext);
+
+            if (target.Type == OperandType.I32)
+            {
+                target = context.ZeroExtend32(OperandType.I64, target);
+            }
+
+            context.Return(target);
+        }
+
         private static void EmitTableBranch(ArmEmitterContext context, Operand guestAddress, bool isJump)
         {
             context.StoreToContext();
@@ -238,6 +250,8 @@ namespace ARMeilleure.Instructions
 
             if (isJump)
             {
+                DecreaseCallDepth(context, nativeContext);
+
                 context.Tailcall(hostAddress, nativeContext);
             }
             else
@@ -259,8 +273,42 @@ namespace ARMeilleure.Instructions
                 Operand lblContinue = context.GetLabel(nextAddr.Value);
                 context.BranchIf(lblContinue, returnAddress, nextAddr, Comparison.Equal, BasicBlockFrequency.Cold);
 
+                DecreaseCallDepth(context, nativeContext);
+
                 context.Return(returnAddress);
             }
         }
+
+        public static void EmitCallDepthCheckAndIncrement(EmitterContext context, Operand guestAddress)
+        {
+            if (!Optimizations.EnableDeepCallRecursionProtection)
+            {
+                return;
+            }
+
+            Operand nativeContext = context.LoadArgument(OperandType.I64, 0);
+            Operand callDepthAddr = context.Add(nativeContext, Const((ulong)NativeContext.GetCallDepthOffset()));
+            Operand currentCallDepth = context.Load(OperandType.I32, callDepthAddr);
+            Operand lblDoCall = Label();
+
+            context.BranchIf(lblDoCall, currentCallDepth, Const(MaxCallDepth), Comparison.LessUI);
+            context.Store(callDepthAddr, context.Subtract(currentCallDepth, Const(1)));
+            context.Return(guestAddress);
+
+            context.MarkLabel(lblDoCall);
+            context.Store(callDepthAddr, context.Add(currentCallDepth, Const(1)));
+        }
+
+        private static void DecreaseCallDepth(EmitterContext context, Operand nativeContext)
+        {
+            if (!Optimizations.EnableDeepCallRecursionProtection)
+            {
+                return;
+            }
+
+            Operand callDepthAddr = context.Add(nativeContext, Const((ulong)NativeContext.GetCallDepthOffset()));
+            Operand currentCallDepth = context.Load(OperandType.I32, callDepthAddr);
+            context.Store(callDepthAddr, context.Subtract(currentCallDepth, Const(1)));
+        }
     }
 }