linux-kernel - Re: [PATCH v15 04/10] arm64: Kprobes with single stepping support

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Date:	Wed, 10 Aug 2016 16:41:58 -0400
From:	David Long <dave.long@...aro.org>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Daniel Thompson <daniel.thompson@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Petr Mladek <pmladek@...e.com>,
	Zi Shen Lim <zlim.lnx@...il.com>,
	Will Deacon <will.deacon@....com>,
	sparclinux <sparclinux@...r.kernel.org>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	yalin wang <yalin.wang2010@...il.com>,
	Li Bin <huawei.libin@...wei.com>,
	Jisheng Zhang <jszhang@...vell.com>,
	John Blackwood <john.blackwood@...r.com>,
	Pratyush Anand <panand@...hat.com>,
	Huang Shijie <shijie.huang@....com>,
	Dave P Martin <Dave.Martin@....com>,
	Yang Shi <yang.shi@...aro.org>,
	Vladimir Murzin <Vladimir.Murzin@....com>,
	Steve Capper <steve.capper@...aro.org>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Mark Brown <broonie@...nel.org>,
	Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
	William Cohen <wcohen@...hat.com>,
	Alex Bennée <alex.bennee@...aro.org>,
	Adam Buchbinder <adam.buchbinder@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org, James Morse <james.morse@....com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robin Murphy <robin.murphy@....com>,
	Jens Wiklander <jens.wiklander@...aro.org>,
	Christoffer Dall <christoffer.dall@...aro.org>
Subject: Re: [PATCH v15 04/10] arm64: Kprobes with single stepping support

On 08/09/2016 01:23 PM, Catalin Marinas wrote:
> On Mon, Aug 08, 2016 at 10:29:05AM -0400, David Long wrote:
>> On 08/08/2016 07:13 AM, Daniel Thompson wrote:
>>> On 04/08/16 05:47, David Long wrote:
>>> >From b451caa1adaf1d03e08a44b5dad3fca31cebd97a Mon Sep 17 00:00:00 2001
>>>> From: "David A. Long" <dave.long@...aro.org>
>>>> Date: Thu, 4 Aug 2016 00:35:33 -0400
>>>> Subject: [PATCH] arm64: Remove stack duplicating code from jprobes
>>>>
>>>> Because the arm64 calling standard allows stacked function arguments
>>>> to be
>>>> anywhere in the stack frame, do not attempt to duplicate the stack
>>>> frame for
>>>> jprobes handler functions.
>>>>
>>>> Signed-off-by: David A. Long <dave.long@...aro.org>
>>>> ---
>>>> Documentation/kprobes.txt          |  7 +++++++
>>>> arch/arm64/include/asm/kprobes.h   |  2 --
>>>> arch/arm64/kernel/probes/kprobes.c | 31 +++++--------------------------
>>>> 3 files changed, 12 insertions(+), 28 deletions(-)
>>>>
>>>> diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
>>>> index 1f9b3e2..bd01839 100644
>>>> --- a/Documentation/kprobes.txt
>>>> +++ b/Documentation/kprobes.txt
>>>> @@ -103,6 +103,13 @@ Note that the probed function's args may be
>>>> passed on the stack
>>>> or in registers.  The jprobe will work in either case, so long as the
>>>> handler's prototype matches that of the probed function.
>>>>
>>>> +Note that in some architectures (e.g.: arm64) the stack copy is not
>>>
>>> Could sparc64 be added to this list?
>>>
>>>    For the sparc folks who are new to the thread, we've previously
>>>    established that the sparc64 ABI passes large structures by
>>>    allocating them from the caller's stack frame and passing a pointer
>>>    to the stack frame (i.e. arguments may not be at top of the stack).
>>>    We also noticed that sparc code does not save/restore anything from
>>>    the stack.
>>
>> I was reluctant to do that in the context of late changes to v4.8 for arm64
>> but now that any changes for this are going in as a new patch it would
>> indeed be useful to get involvement from sparc maintainers.
>
> I'm happy to take the arm64 patch for 4.8 as it's mainly a clean-up.
> Whether you can mention sparc64 as well, it depends on the sparc
> maintainers. You can either cc them or send the series as two patches,
> one for documentation and the other for arm64.
>

I didn't think that was going to be possible after v4.8-rc1.  I have 
separated the documentation and code changes.  I will send out the new 
code-only patch (otherwise unchanged in content) momentarily.

Thanks,
-dl