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

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Date:   Tue, 17 Oct 2017 15:44:21 +0300
From:   Ruslan Bilovol <rbilovol@...co.com>
To:     Torsten Duwe <duwe@...e.de>,
        Ruslan Bilovol <ruslan.bilovol@...il.com>
Cc:     Li Bin <huawei.libin@...wei.com>, Jessica Yu <jeyu@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>,
        zhouchengming <zhouchengming1@...wei.com>,
        live-patching@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        jpoimboe@...hat.com, jikos@...nel.org, pmladek@...e.com,
        Zefan Li <lizefan@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>
Subject: Re: [PATCH] reduce the time of finding symbols for module

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@...wei.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