linux-kernel - Re: [PATCH RFC v2 0/6] ARM64: Add kernel probes(Kprobes) support

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Date:	Mon, 21 Oct 2013 09:47:21 +0530
From:	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-kernel@...r.kernel.org, Patch Tracking <patches@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Steve Capper <steve.capper@...aro.org>,
	Nicolas Pitre <nico@...aro.org>, srikar@...ux.vnet.ibm.com,
	Steven Rostedt <rostedt@...dmis.org>,
	Deepak Saxena <dsaxena@...aro.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Vijaya Kumar K <Vijaya.Kumar@...iumnetworks.com>
Subject: Re: [PATCH RFC v2 0/6] ARM64: Add kernel probes(Kprobes) support

On 18 October 2013 14:02, Masami Hiramatsu
<masami.hiramatsu.pt@...achi.com> wrote:
> (2013/10/17 20:17), Sandeepa Prabhu wrote:
>> This patchset adds support for kernel probes(kprobes), jump probes(jprobes)
>> and return probes(kretprobes) support for ARM64.
>>
>> Kprobes mechanism make use of software breakpoint and single stepping
>> support available in ARM v8 kernel.
>>
>
> Thank you! This looks much better for me now. ;)
>
>> This patchset make use of (and dependant upon) dynamic kernel patching
>> feature published in patch series: https://lkml.org/lkml/2013/10/15/891
>>
>> changes: v1 -> v2
>>  1. Implemented review comments on v1
>>  2. Debug montior hooks implementation is changed to use rwlocks
>>     instead of rcu and spinlock.
>
> Eventually, we'd better reconsider using rcu there, or prohibit probing
> readlock related functions. For the first step, this will be good.
Okay, can be done while optimizing kprobes right, since systemtap/ktap
is yet to be verified on this patchset,
so can expect more scope for optimizing the paths for performance.
>
>>  3. Enabled recursing in kprobes handler for kprobes re-enter support.
>>  4. Re-split the patchset to seperate single-stepping, simulation and
>>     kretprobes features.
>>  5. instruction simulation is made independent of 'struct kprobes'
>>  6. Added 'Linaro Copyright' statements in new added files.
>>  7. Used arm64 instead of aarch64 in file names and comments.
>>
>> Tested on ARM v8 fast model with sample modules from: samples/kprobes/
>>
>> Sandeepa Prabhu (6):
>>   arm64: support single-step and breakpoint handler hooks
>>   arm64: Kprobes with single stepping support
>>   arm64: Kprobes instruction simulation support
>>   arm64: Add kernel return probes support(kretprobes)
>>   arm64: Enable kprobes support for arm64 platform
>>   kprobes: Add cases for arm and arm64 in sample module
>>
>>  arch/arm64/Kconfig                      |   2 +
>>  arch/arm64/configs/defconfig            |  20 +-
>>  arch/arm64/include/asm/debug-monitors.h |  21 +
>>  arch/arm64/include/asm/kprobes.h        |  60 +++
>>  arch/arm64/include/asm/probes.h         |  50 +++
>>  arch/arm64/include/asm/ptrace.h         |   6 +
>>  arch/arm64/kernel/Makefile              |   2 +
>>  arch/arm64/kernel/condn-helpers.c       | 120 ++++++
>>  arch/arm64/kernel/debug-monitors.c      |  86 +++-
>>  arch/arm64/kernel/entry.S               |   2 +
>
>
>>  arch/arm64/kernel/kprobes-arm64.c       | 313 +++++++++++++++
>>  arch/arm64/kernel/kprobes-arm64.h       |  30 ++
>
> One comment, this name looks a bit wired. Since it seems that these are
> for instruction decoding, can we merge it with probe-decode.h and
> rename it as probe-decode.{h,c}? When we implement uprobes, we still
> can expand it (add the decoding table for uprobes in the probe-decode.c).
probe-decode.c looks fine, as uprobes decode table can be added in
same place. -TODO for the next version.

>
>>  arch/arm64/kernel/kprobes.c             | 682 ++++++++++++++++++++++++++++++++
>>  arch/arm64/kernel/kprobes.h             |  30 ++
>>  arch/arm64/kernel/probes-decode.h       | 110 ++++++
>>  arch/arm64/kernel/simulate-insn.c       | 184 +++++++++
>>  arch/arm64/kernel/simulate-insn.h       |  33 ++
>>  arch/arm64/kernel/vmlinux.lds.S         |   1 +
>>  samples/kprobes/kprobe_example.c        |  16 +
>>  19 files changed, 1756 insertions(+), 12 deletions(-)
>
> BTW, is there any public git repository which has this series?
Yes, uploaded on linaro git:
https://git.linaro.org/gitweb?p=people/sandeepa.prabhu/linux-aarch64.git;a=shortlog;h=refs/heads/arm64-kprobes-v2

>
> Thank you again!
>
> --
> Masami HIRAMATSU
> IT Management Research Dept. Linux Technology Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: masami.hiramatsu.pt@...achi.com
>
>
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