Strange behaviour in assembly language program

[Sergey 'DoubleF' Zaharchenko]

On Wed, 3 Mar 2004 06:23:28 +0000
Daniela <dgw at liwest.at> probably wrote:

> In this situation, I can only use a single-byte instruction to push 4 bytes, 
> everything else costs me too much space. The only one I know of, is PUSHA, 
> but it pushes too many bytes.

Quoting from dev-handbook:

> But assembly language programmers like to shave off cycles. The above
> example requires a call/ret combination. We can eliminate it by
> pushing an extra dword:
> 
> open:
>     push    dword mode
>     push    dword flags
>     push    dword path
>     mov eax, 5
>     push    eax     ; Or any other dword
>     int 80h
>     add esp, byte 16
> 
> The 5 that we have placed in EAX identifies the kernel function, in
> this case open.

The last time I wrote `push ebp \n mov ebp, esp' the push took 1
byte :). `push <your_favorite_reg>' will work, as the kernel doesn't
really care for the value of the dword.

-- 
DoubleF
"I'd love to go out with you, but I have to floss my cat."
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