Re: [RFC PATCH 0/5] livepatch: add support on arm64

From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Li Bin <huawei.libin@huawei.com>,
	rostedt@goodmis.org, mingo@kernel.org, jpoimboe@redhat.com,
	sjenning@redhat.com, jkosina@suse.cz, vojtech@suse.cz,
	catalin.marinas@arm.com, will.deacon@arm.com
Cc: live-patching@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, lizefan@huawei.com,
	felix.yang@huawei.com, guohanjun@huawei.com, xiexiuqi@huawei.com,
	takahiro.akashi@linaro.org, David Long <dave.long@linaro.org>
Subject: Re: [RFC PATCH 0/5] livepatch: add support on arm64
Date: Sat, 30 May 2015 09:01:22 +0900	[thread overview]
Message-ID: <5568FDD2.2040005@hitachi.com> (raw)
In-Reply-To: <1432792265-24076-1-git-send-email-huawei.libin@huawei.com>

On 2015/05/28 14:51, Li Bin wrote:
> This patchset propose a method for gcc -mfentry feature(profile
> before prologue) implementation for arm64, and propose the livepatch
> implementation for arm64 based on this feature.
> The gcc implementation about this feature will be post to the gcc 
> community soon.
> 
> With this -mfentry feature, the entry of each function like:
> 
> foo:
>     mov x9, x30 
>     bl __fentry__
>     mov x30, x9
>     [prologue]
>     ... 
> 
> The x9 is a callee corruptible register, and the __fentry__ function
> is responsible to protect all registers, so it can be used to protect
> the x30. And the added two instructions which is register mov operation
> have ralatively small impact on performance.

Hm, this implementation looks good to me :)
This also enables us to KPROBES_ON_FTRACE too.

Thanks,

> 
> This patchset has been tested on arm64 platform.
> 
> Li Bin (4):
>   livepatch: ftrace: arm64: Add support for DYNAMIC_FTRACE_WITH_REGS
>   livepatch: ftrace: add ftrace_function_stub_ip function
>   livepatch: ftrace: arm64: Add support for -mfentry on arm64
>   livepatch: arm64: add support for livepatch on arm64
> 
> Xie XiuQi (1):
>   livepatch: arm64: support relocation in a module
> 
>  arch/arm64/Kconfig                 |    5 +
>  arch/arm64/include/asm/ftrace.h    |    9 +
>  arch/arm64/include/asm/livepatch.h |   45 +++++
>  arch/arm64/kernel/Makefile         |    1 +
>  arch/arm64/kernel/arm64ksyms.c     |    4 +
>  arch/arm64/kernel/entry-ftrace.S   |  154 +++++++++++++++-
>  arch/arm64/kernel/ftrace.c         |   28 +++-
>  arch/arm64/kernel/livepatch.c      |   41 ++++
>  arch/arm64/kernel/module.c         |  355 ++++++++++++++++++------------------
>  include/linux/ftrace.h             |    1 +
>  kernel/livepatch/core.c            |   17 ++-
>  kernel/trace/ftrace.c              |   32 ++++
>  scripts/recordmcount.pl            |    2 +-
>  13 files changed, 508 insertions(+), 186 deletions(-)
>  create mode 100644 arch/arm64/include/asm/livepatch.h
>  create mode 100644 arch/arm64/kernel/livepatch.c
> 
> --
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-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@hitachi.com