panda arch: special case retval from aarch64

Author: lacraig2

panda/python/core/pandare/arch.py

@@ -250,7 +250,11 @@ def get_retval(self, cpu, convention='default'):
         rv = self.get_reg(cpu, reg)
 
         if convention == 'syscall':
-            rv = self.panda.from_unsigned_guest(rv)
+            bits = None
+            if self.panda.arch_name == "aarch64":
+                if cpu.env_ptr.aarch64 == 0:
+                    bits = 32
+            rv = self.panda.from_unsigned_guest(rv, bits=bits)
         return rv
 
 

panda/python/core/pandare/panda.py

@@ -1057,7 +1057,7 @@ def to_unsigned_guest(self, x):
         else:
             raise ValueError("Unsupported number of bits")
 
-    def from_unsigned_guest(self, x):
+    def from_unsigned_guest(self, x, bits=None):
         '''
         Convert an unsigned int32/unsigned int64 from the guest
         (depending on guest bit-size) to a (signed) python int
@@ -1068,8 +1068,10 @@ def from_unsigned_guest(self, x):
         Returns:
             int: Python integer representing x as a signed value
         '''
-        if x >= 2**(self.bits-1): # If highest bit is set, it's negative
-            return (x - 2**self.bits)
+        if bits is None:
+            bits = self.bits
+        if x >= 2**(bits-1): # If highest bit is set, it's negative
+            return (x - 2**bits)
         else: # Else it's positive
             return x