linux-kernel - Re: can't we kill DIE_GPF ? (Was: x86/traps: cleanup DO

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Date:	Tue, 13 May 2014 19:11:48 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: can't we kill DIE_GPF ? (Was: x86/traps: cleanup DO_ERROR*()
	to prepare for uprobes fixes)

On 05/13, Masami Hiramatsu wrote:
>
> (2014/05/09 23:07), Oleg Nesterov wrote:
> > On 05/08, Oleg Nesterov wrote:
> >>
> >> For example, after this series
> >> we can convert math_error() into the "normal" DO_ERROR() user, and most probably
> >> we can do the same with do_general_protection().
> >
> > As for do_general_protection(), the problem is DIE_GPF.
> >
> > Masami, could you explain why it is needed ? kprobe_exceptions_notify()
> > is the only user, can't it use DIE_TRAP and check trapnr = X86_TRAP_GP ?
>
> Actually, this may be only for something which will happen on
> single-stepping out-of-line. And yes, I can move it onto the DIE_TRAP :)
>
> >
> > And if it can, probably we can do notify_die() at the start like other
> > DO_ERROR() functions do ?
>
> Agreed, it seems OK to me. (and seems better, since we can handle GPF
> before changing task->thread struct)
>
> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Great, thanks!

I'll resend this patch with the changelog and other changes.

Oleg.

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