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Date: Wed, 30 Jun 2010 21:04:08 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
       Alexandre Julliard <julliard@winehq.org>,
       "H . Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>,
       Prasad <prasad@linux.vnet.ibm.com>,
       "2 . 6 . 33 . x 2 . 6 . 34 . x" <stable@kernel.org>
Subject: Re: [GIT PULL] x86 breakpoint regression fix
Message-ID: <20100630190405.GB5243@nowhere>
References: <1277906559-10624-1-git-send-regression-fweisbec@gmail.com> <alpine.LFD.2.00.1006301535480.13070@eddie.linux-mips.org>
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On Wed, Jun 30, 2010 at 03:40:51PM +0100, Maciej W. Rozycki wrote:
> On Wed, 30 Jun 2010, Frederic Weisbecker wrote:
> 
> >     - icebp/int01 trap. This instruction (0xf1) is undocumented and
> >       generates an int 1 exception. Unlike single step through TF
> >       flag, it doesn't set the single step origin of the exception
> >       in dr6.
> 
>  Not quite completely undocumented, but a bit obscure indeed.  GDB calls 
> this instruction ICEBP and some Intel sources -- INT1.  It's been around 
> for a while (at least since 80286) and is mostly used by in-circuit 
> emulators (hence the name GDB uses).


Right, in fact it was quite easy to find any documentation about it, it's
just officially undocumented.