Re: Searching for string problems

["Richard B. Johnson" <root@chaos.analogic.com>]

On Wed, 23 Apr 2003, Andrew Kirilenko wrote:

> Hello!
>
> > If you need to search the whole BIOS for that string, you need to
> > set up an outer loop using an unused register which starts at
> > the offset of the BIOS and increments by one byte everytime
> > you can't find the string. This value gets put into %di, instead
> > of the absolute number specified above.
> >
> > Like:
> >
> > scan:	movw	%cs, %ax
> > 	movw	%ax, %ds
> > 	movw	%ax, %es
> > 	movw	$where_in_BIOS_to_start, %bx
> > 	cld
> > 1:	movw	$cl_id_str, %si		# Offset of search string
> > 	movw	$cl_id_end, %cx		# Offset of string end + 1
> > 	subw	%si, %cx		# String length
> > 	decw	%cx			# Don't look for the \0
> > 	movw	%bx, %di		# ES:DI = where to look
> > 	repz	cmpsb			# Loop while the same
> > 	jz	found			# Found the string
> > 	incb	%bx			# Next starting offset
> > 	cmpb	$_BIOS_END, %bx		# Check for limit
> > 	jb	1b			# Continue
> > never_found_anywhere:
> >
> > found:
>
> I've written something similar to this before - and it wont' work, so I've
> reimplemented it. The problem is, that I don't know how to set ES properly. I
> only know, that BIOS data (and code) is located in 0xe000..0xf000 (real
> address).
>

Yeah. So. I set ES and DS to be exactly where CS is. This means that
if your &!)(^$&_ code executes it will work. So, instead of trying
it, you just blindly ignore it and state that it won't work.

Bullshit. I do this for a living and I gave you some valuable time
which you rejected out-of-hand. Have fun.


Cheers,
Dick Johnson
Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.