Re: [PATCH v6 3/6] arm64: Kprobes with single stepping support

From: Catalin Marinas <catalin.marinas@arm.com>
To: William Cohen <wcohen@redhat.com>
Cc: David Long <dave.long@linaro.org>,
	"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
Date: Fri, 22 May 2015 17:54:29 +0100	[thread overview]
Message-ID: <20150522165428.GC29424@e104818-lin.cambridge.arm.com> (raw)
In-Reply-To: <555F5011.90808@redhat.com>

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 ;)

-- 
Catalin