align with 00h bytes?

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Jibz

Joined: 11 May 2004
Posts: 3
Location: Denmark

Jibz 11 May 2004, 10:18

I am working with in-memory dialog templates, and need to be able to align with 00h bytes instead of the default 90h bytes. The format is MS COFF.

I have tried writing a macro for doing this in a number of ways, but keep on getting errors. Could somebody please enlighten me as to how to do this?

11 May 2004, 10:18

decard

Joined: 11 Sep 2003
Posts: 1092
Location: Poland

decard 11 May 2004, 10:49

try something like this:

Code:

macro zero_align value { times ((value-1)-($+value-1) mod value) db 0 }

11 May 2004, 10:49

Jibz

Joined: 11 May 2004
Posts: 3
Location: Denmark

Jibz 11 May 2004, 11:05

Code:

format MS COFF

macro zero_align value { times ((value-1)-($+value-1) mod value) db 0 }

section '.text' code readable executable

    nop

zero_align 4

    nop

gives me

Code:

flat assembler  version 1.52
altest.asm [9]:
zero_align 4
altest.asm [3] zero_align [0]:
macro zero_align value { times ((value-1)-($+value-1) mod value) db 0 }
error: invalid expression.

Using RVA $ instead gives the same error ..

11 May 2004, 11:05

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8367
Location: Kraków, Poland

Tomasz Grysztar 11 May 2004, 11:48

Code:

macro align value,fill
{
  if fill eq
   align value
  else
   local ..size
   virtual
     @@: align value
     ..size = $-@b
   end virtual
   times ..size db fill
  end if
}

align 4,0
; or:
align 4,?

11 May 2004, 11:48

Jibz

Joined: 11 May 2004
Posts: 3
Location: Denmark

Jibz 11 May 2004, 11:57

Thanks a lot, that did the job Smile

11 May 2004, 11:57

hopcode

Joined: 04 Mar 2008
Posts: 563
Location: Germany

hopcode 03 Jan 2009, 11:49

Hallo all,
My solution (not fully tested) was already posted ?

Code:

macro @align val,fill { 
  times((($+val-1)and not (val-1))-$) db fill
}
;usage:
@align 4,0

does it work ?

03 Jan 2009, 11:49

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20517
Location: In your JS exploiting you and your system

revolution 03 Jan 2009, 12:00

hopcode wrote:

does it work ?

Only if val is a power of two.

03 Jan 2009, 12:00

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