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 Forums >>  Brainstorms - General  >>  Pydasm: Determining Indirect vs Direct Register Access

Topic created on: March 23, 2007 12:25 CDT by apridgen .

I am using pydasm, and I am trying to determine when a register is being accessed indirectly or indirectly.  What are the flag values that differentiate a normal access and an indirect register access.

mov eax, 0x0
mov [eax], 0x0

Also, what would be the flags for byte,word, and dword accesses.  I really appreciate any help.  When I looked through the pydasm help section, nothing really jumped out at me.


Thanks in advance.

  ero     March 26, 2007 02:17.27 CDT
The operand object (op1, op2, op3 inside the instruction object) has a "type" attribute that can have the following values:

OPERAND_TYPE_NONE, OPERAND_TYPE_MEMORY, OPERAND_TYPE_REGISTER, OPERAND_TYPE_IMMEDIATE

In your case, "eax" will be OPERAND_TYPE_REGISTER, and "[eax]" OPERAND_TYPE_MEMORY.

The README.TXT inside the top libdasm directory has good documentation explaining all these (and all structure members have identical counterparts in pydasm).

As for the sizes, iirc, it depends on whether you disassemble in 16 or 32 bits, then you'd have to check for address-size override and operand-size override prefixes. The instructions also have different opcode to indicate size.

  apridgen   March 26, 2007 03:50.00 CDT
ero, thanks.

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