Handle invokedynamic in packetinstructions

This isn't a very good implementation, but it's enough to get 1.16.2-pre3 working.

burger/toppings/packetinstructions.py

@@ -35,6 +35,7 @@
 from jawa.transforms import simple_swap
 
 from .topping import Topping
+from burger.util import stringify_invokedynamic
 
 class PacketInstructionsTopping(Topping):
     """Provides the instructions used to construct network packets."""
@@ -390,6 +391,9 @@ def operations(classloader, classname, classes, verbose, args=None,
                                                         args=_PIT.join(arguments)))
                                 break
 
+            elif mnemonic == "invokedynamic":
+                stack.append(stringify_invokedynamic(stack.pop(), instruction, cf))
+
             # Conditional statements and loops
             elif mnemonic.startswith("if"):
                 if "icmp" in mnemonic or "acmp" in mnemonic:

burger/util.py

@@ -27,6 +27,27 @@ def class_from_invokedynamic(ins, cf):
     # from the constructor.
     return methodhandle.reference.class_.name.value
 
+def stringify_invokedynamic(obj, ins, cf):
+    """
+    Converts an invokedynamic instruction into a string.
+
+    This is a rather limited implementation for now, only handling obj::method.
+    """
+    const = cf.constants[ins.operands[0].value] # Hack due to packetinstructions not expanding constants
+    bootstrap = cf.bootstrap_methods[const.method_attr_index]
+    method = cf.constants.get(bootstrap.method_ref)
+    # Make sure this is a reference to LambdaMetafactory
+    assert method.reference_kind == 6 # REF_invokeStatic
+    assert method.reference.class_.name == "java/lang/invoke/LambdaMetafactory"
+    assert method.reference.name_and_type.name == "metafactory"
+    assert len(bootstrap.bootstrap_args) == 3 # Num arguments
+    # Actual implementation.
+    methodhandle = cf.constants.get(bootstrap.bootstrap_args[1])
+    if methodhandle.reference_kind == 7: # REF_invokeSpecial
+        return "%s::%s" % (obj, methodhandle.reference.name_and_type.name.value)
+    else:
+        raise Exception("Unhandled reference_kind %d" % methodhandle.reference_kind)
+
 def try_eval_lambda(ins, args, cf):
     """
     Attempts to call a lambda function that returns a constant value.