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

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Date:	Tue, 22 Oct 2013 07:25:51 -0400 (EDT)
From:	Oleg Nesterov <onestero@...hat.com>
To:	David Long <dave.long@...aro.org>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	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

Sorry for top-posting/formatting,

Do you mean arch_uprobe_skip_sstep() ?

Yes, this __weak is wrong, already fixed in my tree. See
http://marc.info/?l=linux-mips&m=138132052022388&w=2

----- Original Message -----
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
Sent: Tuesday, 22 October, 2013 5:45:47 AM
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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