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

From: Petr Mladek <pmladek@suse.com>
To: "Tomohiro Misono (Fujitsu)" <misono.tomohiro@fujitsu.com>
Cc: "'madvenka@linux.microsoft.com'" <madvenka@linux.microsoft.com>,
	"jpoimboe@redhat.com" <jpoimboe@redhat.com>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"chenzhongjin@huawei.com" <chenzhongjin@huawei.com>,
	"mark.rutland@arm.com" <mark.rutland@arm.com>,
	"broonie@kernel.org" <broonie@kernel.org>,
	"Keiya Nobuta (Fujitsu)" <nobuta.keiya@fujitsu.com>,
	"sjitindarsingh@gmail.com" <sjitindarsingh@gmail.com>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	"will@kernel.org" <will@kernel.org>,
	"jamorris@linux.microsoft.com" <jamorris@linux.microsoft.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"live-patching@vger.kernel.org" <live-patching@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v3 00/22] arm64: livepatch: Use ORC for dynamic frame pointer validation
Date: Thu, 2 Mar 2023 17:23:18 +0100	[thread overview]
Message-ID: <ZADNdp5U+lP10Oqo@alley> (raw)
In-Reply-To: <TYCPR01MB69938E7E2E14697FCF166155E5AD9@TYCPR01MB6993.jpnprd01.prod.outlook.com>

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

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