Message-ID: <555F5FE3.8060702@linaro.org>
Date: Fri, 22 May 2015 12:57:07 -0400
From: David Long <dave.long@linaro.org>
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To: Catalin Marinas <catalin.marinas@arm.com>,
        William Cohen <wcohen@redhat.com>
CC: "Jon Medhurst (Tixy)" <tixy@linaro.org>,
        Steve Capper <steve.capper@linaro.org>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Will Deacon <will.deacon@arm.com>, linux-kernel@vger.kernel.org,
        Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        sandeepa.s.prabhu@gmail.com, Russell King <linux@arm.linux.org.uk>,
        davem@davemloft.net, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v6 3/6] arm64: Kprobes with single stepping support
References: <1429561187-3661-1-git-send-email-dave.long@linaro.org> <1429561187-3661-4-git-send-email-dave.long@linaro.org> <20150520163946.GC29424@e104818-lin.cambridge.arm.com> <555D62BD.5040403@linaro.org> <20150522110007.GV29424@e104818-lin.cambridge.arm.com> <555F5011.90808@redhat.com> <20150522165428.GC29424@e104818-lin.cambridge.arm.com>
In-Reply-To: <20150522165428.GC29424@e104818-lin.cambridge.arm.com>
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On 05/22/15 12:54, Catalin Marinas wrote:
> On Fri, May 22, 2015 at 11:49:37AM -0400, William Cohen wrote:
>> On 05/22/2015 07:00 AM, Catalin Marinas wrote:
>>> Any plans to post an updated version with the "unexpected single-step
>>> error" fixed?
>>
>> The only place this issue with the "unexpected single-step error" has
>> been observed is with the arm64 kretporbe handler code calling kprobed
>> functions.  Experiments with kprobed functions being called in the
>> kprobe handlers showed that situation was handled appropriately.
>>
>> There is proposed fix to address the issue with the trampoline, the
>> attached patch.  This is modeled after the way that the x86 handles
>> the kretprobe.  The trampoline directly save and restores the
>> registers and uses a normal call to the kretprobe handler.  It
>> operates similarly to what you are suggesting above, but just for the
>> special case of the kretprobes.
>
> Thanks. I guess David will post a v7 series with this patch included and
> other comments addressed.
>
> BTW, I'll be on holiday for a week, back on the 1st of June. Hopefully
> this series gets some more reviews by then ;)
>

Yes, the v7 patch is in the works, with Will Cohen's trampoline fixes as 
well as your feedback.

-fl


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