linux-kernel - Re: [GIT PULL] x86 breakpoint regression fix

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Message-ID: <20100630190405.GB5243@nowhere>
Date:	Wed, 30 Jun 2010 21:04:08 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	"Maciej W. Rozycki" <macro@...ux-mips.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Alexandre Julliard <julliard@...ehq.org>,
	"H . Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Prasad <prasad@...ux.vnet.ibm.com>,
	"2 . 6 . 33 . x 2 . 6 . 34 . x" <stable@...nel.org>
Subject: Re: [GIT PULL] x86 breakpoint regression fix

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.

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