On Thu, 25 Apr 2002, Andrew Gallatin wrote:
>
> Kenneth Culver writes:
> > > I just looked at the NetBSD code & like linux, they use a macro which
> > > individually pushes the registers onto the stack rather than using
> > > pushal (which I assume is the same as what intel calls PUSHAD in their
> > > x86 instruction set ref. manual).
> > >
> > > NetBSD stopped using pushal in 1994 in rev 1.85 of their
> > > arch/i386/i386/locore.s in a commit helpfully documented
> > > "Don't use pusha and popa."
> > >
> > > Does anybody know why the other OSes push the registers individually,
> > > rather than using pushal? Could our using pushal be causing Kenneth's
> > > ebp to get lost, or is this just a red herring?
> > >
> > > Thanks,
> > >
> > > Drew
> > >
> > >
> > >
> > according to the intel docs, pushad (or what I'm assuming is pushal in our
> > case) pushes eax, ecx, edx, ebx then pushes some temporary value (the
> > original esp I think) then pushes ebp, esi, and edi:
> >
> > this is from the documentation for pushad
> >
> > IF OperandSize = 32 (* PUSHAD instruction *)
> > THEN
> > Temp (ESP);
> > Push(EAX);
> > Push(ECX);
> > Push(EDX);
> > Push(EBX);
> > Push(Temp);
> > Push(EBP);
> > Push(ESI);
> > Push(EDI);
> >
> > so could this be the problem?
> >
> > Ken
>
> I don't think so. The temp its pushing is the stack pointer. If you
> look at the layout of the trap frame, then you'll see tf_isp comes
> between tf_ebp & tf_ebx. I assume tf_isp is the stack pointer, so
> that should be OK..
>
> Drew
>
>
>
hrmm, well then it looks like pushal should be doing the right thing...
but I thought though that esp was the stack pointer... it's pushing the
original stack pointer onto isp, and then pushing ebp... I don't see why
this would screw anything up...
Ken
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