linux-kernel - Re: [RFC PATCH v3 00/22] arm64: livepatch: Use ORC for dynamic frame pointer validation

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Date:   Mon, 6 Mar 2023 10:58:18 -0600
From:   "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
To:     Petr Mladek <pmladek@...e.com>,
        "Tomohiro Misono (Fujitsu)" <misono.tomohiro@...itsu.com>
Cc:     "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "chenzhongjin@...wei.com" <chenzhongjin@...wei.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "Keiya Nobuta (Fujitsu)" <nobuta.keiya@...itsu.com>,
        "sjitindarsingh@...il.com" <sjitindarsingh@...il.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will@...nel.org" <will@...nel.org>,
        "jamorris@...ux.microsoft.com" <jamorris@...ux.microsoft.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 00/22] arm64: livepatch: Use ORC for dynamic frame
 pointer validation



On 3/2/23 10:23, Petr Mladek wrote:
> On Wed 2023-03-01 03:12:08, Tomohiro Misono (Fujitsu) wrote:
>> <snip>
>>> Testing
>>> =======
>>>
>>> - I have run all of the livepatch selftests successfully. I have written a
>>>   couple of extra selftests myself which I will be posting separately
>> Hi,
>>
>> What test configuration/environment you are using for test?
>> When I tried kselftest with fedora based config on VM, I got errors
>> because livepatch transition won't finish until signal is sent
>> (i.e. it takes 15s for every transition).
>>
>> [excerpt from test result]
>>   ```
>>   $ sudo ./test-livepatch.sh
>>   TEST: basic function patching ... not ok
>>   
>>   --- expected
>>   +++ result
>>   @@ -2,11 +2,13 @@
>>    livepatch: enabling patch 'test_klp_livepatch'
>>    livepatch: 'test_klp_livepatch': initializing patching transition
>>    livepatch: 'test_klp_livepatch': starting patching transition
>>   +livepatch: signaling remaining tasks
>>    livepatch: 'test_klp_livepatch': completing patching transition
>>   ```
> 
> It might be interesting to see what process is blocking the
> transition. The transition state is visible in
> /proc/<pid>/patch_state.
> 
> The transition is blocked when a process is in KLP_UNPATCHED state.
> It is defined in include/linux/livepatch.h:
> 
> #define KLP_UNPATCHED	 0
> 
> Well, the timing against the transition is important. The following
> might help to see the blocking processes:
> 
> $> modprobe livepatch-sample ; \
>    sleep 1; \
>    for proc_path in \
>        `grep "\-1"  /proc/*/patch_state | cut -d '/'  -f-3` ; \
>    do \
>        cat $proc_path/comm ; \
>        cat $proc_path/stack ; \
>        echo ===  ; \
>    done
> 
> After this the livepatch has to be manualy disabled and removed
> 
> $> echo 0 >/sys/kernel/livepatch/livepatch_sample/enabled
> $> rmmod livepatch_sample
> 
> Best Regards,
> Petr

Thanks for the suggestion. I will try to reproduce the problem and look at what process(es) are holding up
the livepatch.

Madhavan