[interp] Fix pinvokes with HandleRef (#55404)

The m2n wrapper marshals HandleRef structs from a vtype to intptr. The MonoMethod for a pinvoke method stores the unmarshalled signature. When locating the args on the stack during the pinvoke call we need to use the marshalled signature instead (which is saved in the code stream for the calli opcode)

src/mono/mono/mini/interp/interp.c

@@ -1173,12 +1173,16 @@ compute_arg_offset (MonoMethodSignature *sig, int index, int prev_offset)
 }
 
 static guint32*
-initialize_arg_offsets (InterpMethod *imethod)
+initialize_arg_offsets (InterpMethod *imethod, MonoMethodSignature *csig)
 {
 	if (imethod->arg_offsets)
 		return imethod->arg_offsets;
 
-	MonoMethodSignature *sig = mono_method_signature_internal (imethod->method);
+	// For pinvokes, csig represents the real signature with marshalled args. If an explicit
+	// marshalled signature was not provided, we use the managed signature of the method.
+	MonoMethodSignature *sig = csig;
+	if (!sig)
+		sig = mono_method_signature_internal (imethod->method);
 	int arg_count = sig->hasthis + sig->param_count;
 	g_assert (arg_count);
 	guint32 *arg_offsets = (guint32*) g_malloc ((sig->hasthis + sig->param_count) * sizeof (int));
@@ -1201,13 +1205,13 @@ initialize_arg_offsets (InterpMethod *imethod)
 }
 
 static guint32
-get_arg_offset_fast (InterpMethod *imethod, int index)
+get_arg_offset_fast (InterpMethod *imethod, MonoMethodSignature *sig, int index)
 {
 	guint32 *arg_offsets = imethod->arg_offsets;
 	if (arg_offsets)
 		return arg_offsets [index];
 
-	arg_offsets = initialize_arg_offsets (imethod);
+	arg_offsets = initialize_arg_offsets (imethod, sig);
 	g_assert (arg_offsets);
 	return arg_offsets [index];
 }
@@ -1216,7 +1220,7 @@ static guint32
 get_arg_offset (InterpMethod *imethod, MonoMethodSignature *sig, int index)
 {
 	if (imethod) {
-		return get_arg_offset_fast (imethod, index);
+		return get_arg_offset_fast (imethod, sig, index);
 	} else {
 		g_assert (!sig->hasthis);
 		return compute_arg_offset (sig, index, -1);
@@ -2385,7 +2389,7 @@ do_jit_call (ThreadContext *context, stackval *ret_sp, stackval *sp, InterpFrame
 	if (cinfo->ret_mt != -1)
 		args [pindex ++] = ret_sp;
 	for (int i = 0; i < rmethod->param_count; ++i) {
-		stackval *sval = STACK_ADD_BYTES (sp, get_arg_offset_fast (rmethod, stack_index + i));
+		stackval *sval = STACK_ADD_BYTES (sp, get_arg_offset_fast (rmethod, NULL, stack_index + i));
 		if (cinfo->arginfo [i] == JIT_ARG_BYVAL)
 			args [pindex ++] = sval->data.p;
 		else
@@ -7199,7 +7203,7 @@ interp_frame_get_arg (MonoInterpFrameHandle frame, int pos)
 
 	g_assert (iframe->imethod);
 
-	return (char*)iframe->stack + get_arg_offset_fast (iframe->imethod, pos + iframe->imethod->hasthis);
+	return (char*)iframe->stack + get_arg_offset_fast (iframe->imethod, NULL, pos + iframe->imethod->hasthis);
 }
 
 static gpointer