From:	Nate Eldredge <neldredge AT hmc DOT edu>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Bug in __dpmi_simulate_real_mode_procedure_retf_stack
Date:	20 Jan 2000 12:43:46 -0800
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Eli Zaretskii <eliz AT is DOT elta DOT co DOT il> writes:

> On Wed, 19 Jan 2000, Nigel Pattinson wrote:
> 
> > 	/* Set up %esi, %edi to copy data to the PM stack. */
> > 	subl	%ecx, %esp
> > 	movl	%esp, %edi
> > 	movl	ARG3, %esi
> > 
> > 	/* Copy the data. */
> > 	cld
> > 	rep
> > 	movsw
> > 
> > Since the size of the parameters (in ecx) is in 16-bit words, it looks
> > to me like the line
> > 
> > 	subl	%ecx, %esp
> > 
> > only reserves half the required amount of stack space.
> 
> But the copy of the data to the stack (see above) *also* uses words:
> it copies with "rep movsw".  So it moves ECX words to the stack, and
> that's exactly the amount of storage reserved there by subl.
> 
> So where exactly is the problem here?

Hmm... it is indeed copying %ecx words, but it's only reserving %ecx
*bytes*.  So it looks like it really is wrong.

Easiest fix is just to subl twice.
-- 

Nate Eldredge
neldredge AT hmc DOT edu

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