jbremer / pyasm2 Goto Github PK

When referencing an address with a segment, e.g. in the following snippet.

mov(eax, dword[fs:eax])

Then, because the python index limit for 32bit versions is MAX_INT which is 1<<31, we have to store the memory address temporarily in a global dictionary, with a random key. The key, an integer, is passed along in __getitem__ so that the MemoryAddress object (e.g. byte, dword, ..) can read the memory address from the global dictionary (and delete it from the dictionary afterwards.)
After the object has been passed, all is well.

Seems there are several problems when I'm trying to assemble xchg instructions, here is an example :

>>> '%s' % xchg(esi, esp)
Traceback (most recent call last):
  File "stdin", line 1, in module
  File "D:\TODO\pyasm2.py", line 755, in __str__
    ret += self.modrm(modrm_reg, modrm_rm)
  File "D:\TODO\pyasm2.py", line 512, in modrm
    reg = op1.index
AttributeError: 'NoneType' object has no attribute 'index'

The problem seems to be there only if I assemble xchg instruction with the opcode \x87 or \x86.

Whenever I implement a loop, I get the above error. I fail to figure out why it happens.
It didn't matter which type of label, they all produced the same result. It doesn't matter
what code i have before or after. As soon as I put in a Label I get the above error.

The tests provided all worked flawlessly.

I'm running windows 7 64bit, using 32bit Python 2.7.12.

Oh, I should add that I used parts of pyacc to create executable memory,
which has no issues running the code created by pyasm2. That works completely,
yet as soon as I include a label it gives me the error.

Any ideas? I know, asking is a stretch, but I don't know yet what to do.
Or maybe do you know a way to actually execute the code?

Because there doesn't seem to be one, so I had to come up with this ...

This code works:

mov(eax, [ebx+0x4])

>>> mov eax, [ebx+0x4]

But this one outputs an error:

mov(eax, [ebx*4+0x4])

>>> <repr(<pyasm2.x86.mov at 0x7f59dd3af320>) failed: AttributeError: 'int' object has no attribute 'value'>

It appears to be related to the disp attribute.

Proposed patch:

--- x86.py.bak  2016-10-14 01:06:35.613063043 +0200
+++ x86.py  2016-10-14 01:04:42.665010353 +0200
@@ -283,7 +283,7 @@
             q = str(self.reg2) if self.mult == 1 else \
                 str(self.reg2) + '*' + str(self.mult)
             s += q if not len(s) else '+' + q
-        if self.disp.value:
+        if self.disp:
             if self.disp >= 0:
                 q = '0x%x' % int(self.disp)
             else: