Re: [PATCH] reduce the time of finding symbols for module

From: Ruslan Bilovol <rbilovol@cisco.com>
To: Torsten Duwe <duwe@suse.de>, Ruslan Bilovol <ruslan.bilovol@gmail.com>
Cc: Li Bin <huawei.libin@huawei.com>, Jessica Yu <jeyu@redhat.com>,
	Miroslav Benes <mbenes@suse.cz>,
	zhouchengming <zhouchengming1@huawei.com>,
	live-patching@vger.kernel.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	jpoimboe@redhat.com, jikos@kernel.org, pmladek@suse.com,
	Zefan Li <lizefan@huawei.com>, Hanjun Guo <guohanjun@huawei.com>
Subject: Re: [PATCH] reduce the time of finding symbols for module
Date: Tue, 17 Oct 2017 15:44:21 +0300	[thread overview]
Message-ID: <da67dde1-19ba-f1d0-db2b-6e874cf591b0@cisco.com> (raw)
In-Reply-To: <20171013131841.en3yuwtl3wedei5t@suse.de>

Hi,

On 10/13/2017 04:18 PM, Torsten Duwe wrote:
> On Fri, Oct 13, 2017 at 03:54:46PM +0300, Ruslan Bilovol wrote:
>> Hi Li,
>>
>> On Wed, Mar 29, 2017 at 4:50 AM, Li Bin <huawei.libin@huawei.com> wrote:
>>> Hi,
>> [snip]
>>>
>>> Yeah, from 2014, we started to work on livepatch support on aarch64, and
>>> in May 2015, we pushed the solution to the livepatch community[1] and gcc
>>> community (mfentry feature on aarch64)[2]. And then, there were an another
>>> gcc solution from linaro [3], which proposes to implement a new option
>>> -fprolog-pad=N that generate a pad of N nops at the beginning of each
>>> function, and AFAIK, Torsten Duwe from SUSE is still discussing this method
>>> with gcc community.
>>>
>>> At this stage, we are validating the livepatch support on aarch64 based on
>>> aarch64 mfentry feature. When the community has a clear plan, we are happy
>>> to make adaptation and contribute our related work to the community, including
>>> the kpatch-build support :-)
>>>
>>> [1] livepatch: add support on arm64
>>> https://lkml.org/lkml/2015/5/28/54
>>> [2] [AArch64] support -mfentry feature for arm64
>>> https://gcc.gnu.org/ml/gcc-patches/2016-03/msg00756.html
>>> [3] Kernel livepatching support in GCC
>>> https://gcc.gnu.org/ml/gcc/2015-05/msg00267.html
>>> [4] arm64: ftrace with regs for livepatch support
>>> http://lists.infradead.org/pipermail/linux-arm-kernel/2016-January/401352.html
>>>
>>
>> Since there is already -fpatchable-function-entry option committed by Torsten
>> to gcc on 25 Jul [1], have you restarted your activities with AArch64 livepatch
>> support?
>> If yes, I'm interested in testing of that feature/patches on our hardware
> 
> I also have the coresponding kernel patch(es) here. IIRC I already sent
> tham to LKML. I'll re-send them once there are more gcc's with -fpatchable-function-entry
> support out there.

Do you mean "[PATCH v3 0/2] arm64 live patching" [1] series?

I'm going to play with them and see how it works.

Another question: have you tested livepatching on Big Endian systems?

[1] https://lwn.net/Articles/697050

Thanks,
Ruslan