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

From: Catalin Marinas <catalin.marinas@arm.com>
To: David Long <dave.long@linaro.org>
Cc: "Daniel Thompson" <daniel.thompson@linaro.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Petr Mladek" <pmladek@suse.com>,
	"Zi Shen Lim" <zlim.lnx@gmail.com>,
	"Will Deacon" <will.deacon@arm.com>,
	sparclinux <sparclinux@vger.kernel.org>,
	"Andrey Ryabinin" <ryabinin.a.a@gmail.com>,
	"yalin wang" <yalin.wang2010@gmail.com>,
	"Li Bin" <huawei.libin@huawei.com>,
	"Jisheng Zhang" <jszhang@marvell.com>,
	"John Blackwood" <john.blackwood@ccur.com>,
	"Pratyush Anand" <panand@redhat.com>,
	"Huang Shijie" <shijie.huang@arm.com>,
	"Dave P Martin" <Dave.Martin@arm.com>,
	"Yang Shi" <yang.shi@linaro.org>,
	"Vladimir Murzin" <Vladimir.Murzin@arm.com>,
	"Steve Capper" <steve.capper@linaro.org>,
	"Suzuki K Poulose" <suzuki.poulose@arm.com>,
	"Marc Zyngier" <marc.zyngier@arm.com>,
	"Mark Brown" <broonie@kernel.org>,
	"Sandeepa Prabhu" <sandeepa.s.prabhu@gmail.com>,
	"William Cohen" <wcohen@redhat.com>,
	"Alex Bennée" <alex.bennee@linaro.org>,
	"Adam Buchbinder" <adam.buchbinder@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	linux-kernel@vger.kernel.org, "James Morse" <james.morse@arm.com>,
	"Masami Hiramatsu" <mhiramat@kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Robin Murphy" <robin.murphy@arm.com>,
	"Jens Wiklander" <jens.wiklander@linaro.org>,
	"Christoffer Dall" <christoffer.dall@linaro.org>
Subject: Re: [PATCH v15 04/10] arm64: Kprobes with single stepping support
Date: Tue, 9 Aug 2016 18:23:08 +0100	[thread overview]
Message-ID: <20160809172308.GD15447@e104818-lin.cambridge.arm.com> (raw)
In-Reply-To: <57A89731.20709@linaro.org>

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@linaro.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@linaro.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.

-- 
Catalin