linux-kernel - Re: [PATCH v2 02/13] uprobes: allow ignoring of probe hits

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Message-ID: <5265F4EB.2060803@linaro.org>
Date:	Mon, 21 Oct 2013 23:45:47 -0400
From:	David Long <dave.long@...aro.org>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	linux-arm-kernel@...ts.infradead.org, Rabin Vincent <rabin@....in>,
	"Jon Medhurst (Tixy)" <tixy@...aro.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 02/13] uprobes: allow ignoring of probe hits

On 10/19/13 13:02, Oleg Nesterov wrote:
> On 10/15, David Long wrote:
>>
>> @@ -1732,9 +1732,6 @@ static void handle_swbp(struct pt_regs *regs)
>>   		return;
>>   	}
>>
>> -	/* change it in advance for ->handler() and restart */
>> -	instruction_pointer_set(regs, bp_vaddr);
>> -
>
> Well, this looks obviously wrong. This SET_IP() has the comment ;)
>
> Note also that with this breaks __skip_sstep() on x86.
>
> Oleg.
>

Yes, and there's a missing weak stub function in there too.  It was a 
surprise to me that declaring an external as weak means that it quietly 
ignores the fact there is no definition for it at link time, and makes 
it zero.  I think there may be some similar land mines elsewhere in the 
kernel, unrelated to these changes or uprobes in general.

I have an updated version to go out with the v3 patches.  It is working 
with v3.12-rc6 on x86 and ARM, to the extent I'm able to test it.

-dl

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