Re: year old problem

H. Peter Anvin (hpa@transmeta.com)
16 Nov 1999 00:23:00 GMT

Followup to: <19991116004726.A3036@fred.muc.de>
By author: Andi Kleen <ak@muc.de>
In newsgroup: linux.dev.kernel
>
> On Mon, Nov 15, 1999 at 11:36:31PM +0100, Eric Pouech wrote:
> > well, it seems to me that the code in __switch_to (loaddebug macro) *restores*
> > the DBi registers (from the tss in memory to the i386) while switching to 'next'
> > process
> >
> > my issue is that the i386 value of DR6 (status => which debug registers
> > which (may) have triggered a trap) are never (I should say no longer)
> > stored in tss as they used to be (and therefore never accessible with ptrace)
> >
> > in 2.0.x series, they were stored in tss while entering the TRAP handler
> > and it's no longer the case.
>
> Point taken. It seems to be a bug.
> For DR0-DR3/DR7 it doesn't make sense to save them all the time (because they
> can be set by ptrace, even by the program), but DR4-6 should be saved.
>

There is no DR4 and DR5.

-=hpa

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."


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