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Re: [Dailydave] We have met the enemy, and the enemy is ... you.

From: Michael Spath (michael.spathgmail.com)
Date: Fri Apr 14 2006 - 13:01:01 CDT

On 4/14/06, jnf <jnfnosec.net> wrote:

> INTO generates int 4, the first 32 interrupt vector numbers
> are reserved by intel, so it doesn't vary per OS.

INTO generates a #GP instead of int 4 when the DPL of the gate
descriptor is lower than the CPL. And since this DPL value is
stored in the IDT, it is under OS control. This dependency does
not exist for BOUND.

> I fail to really understand why we do not make use of certain
> features of the underlying hardware that would solve a lot
> of these problems.

For x86 I guess it's the same reason why hardware task switching
is not used : it's slower (BOUND) or does not do exactly what we
want (INTO).

regards,
--spath