I use 'objdump' on linux in a variety of binaries and it returns their assembly. The commands that I receive is 'real' commands or pseudo-command? I have read that there are some commands which are a combination of other commands and they are called pseudo-commands. Is it true? If yes, how can I get only 'real' commands from a executable?
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On current x86- or ARM-based systems running Linux, the disassembled instructions will be real instructions.
Pseudo-operations are a convenience used when creating software, such as short sequences of instructions that are commonly used together, or instructions that are implemented in less-than-obvious ways.
For example, the instruction
mov eax, #0
which puts zero into register EAX, might be possible to implement in fewer bytes, and/or less time, as:
xor eax, eax
That exclusive-ORs register EAX with itself, which will always produce zero. An assembler thus might convert the easy-to-understand instruction into the smaller or faster form.
John Dallman
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