linux-kernel - Re: [RFC 3/8] Kernel/uprobe: Define arch_uprobe_exception_notify as _

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Message-ID: <20150102174314.GA6761@redhat.com>
Date:	Fri, 2 Jan 2015 18:43:14 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Pratyush Anand <panand@...hat.com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	tixy@...aro.org, ananth@...ibm.com, sandeepa.prabhu@...aro.org,
	catalin.marinas@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, anil.s.keshavamurthy@...el.com,
	masami.hiramatsu.pt@...achi.com, wcohen@...hat.com
Subject: Re: [RFC 3/8] Kernel/uprobe: Define arch_uprobe_exception_notify
	as __weak

On 12/31, Pratyush Anand wrote:
>
> Both ARM and ARM64 handle uprobe exceptions through their own hooks.So
> nothing to be done in arch_uprobe_exception_notify except to return
> NOTIFY_DONE. Implement this as weak default function and remove
> definition from arm arch code.
>
> Signed-off-by: Pratyush Anand <panand@...hat.com>
> ---
>  arch/arm/kernel/uprobes.c |  6 ------
>  kernel/events/uprobes.c   | 18 ++++++++++++++++++
>  2 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/kernel/uprobes.c b/arch/arm/kernel/uprobes.c
> index 56adf9c1fde0..0f3663ca82fc 100644
> --- a/arch/arm/kernel/uprobes.c
> +++ b/arch/arm/kernel/uprobes.c
> @@ -178,12 +178,6 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>  	instruction_pointer_set(regs, utask->vaddr);
>  }
>
> -int arch_uprobe_exception_notify(struct notifier_block *self,
> -				 unsigned long val, void *data)
> -{
> -	return NOTIFY_DONE;
> -}

I agree, this is ugly. But I disagree with this change.

I think we should simply kill uprobe_exception_nb and unexport
arch_uprobe_exception_notify on x86/powerpc, and in fact I was going to do
this a long ago.

I'll send the patch later. Until then please add the dummy arch_uprobe_exception_notify()
like arch/arm does, to make the generic code happy.

Oleg.

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