linux-kernel - Re: [PATCH v10 00/10] livepatch: Atomic replace feature

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Date:   Mon, 26 Mar 2018 12:56:10 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Joe Lawrence <joe.lawrence@...hat.com>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Jason Baron <jbaron@...mai.com>, Jessica Yu <jeyu@...nel.org>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 00/10] livepatch: Atomic replace feature

On Mon 2018-03-12 14:57:04, Joe Lawrence wrote:
> Hi Petr,
> 
> These are the callback tests that I hacked up into a livepatch
> kselftest.  (Basically I copied a bunch of the sample modules and
> verified the expected dmesg output as I had listed in in the
> Documentation/livepatch/callbacks.txt file.)  The script is still a
> little rough and maybe this isn't the direction we want to go for proper
> kselftests, but perhaps it saves you some time/sanity for verifying this
> patchset.



> Hope this helps,
> 
> -- Joe
> 
> -- >8 -- >8 -- >8 -- >8 --
> 
> >From 0364430c53e12e21923bed20cb651374b4cf9ba9 Mon Sep 17 00:00:00 2001
> From: Joe Lawrence <joe.lawrence@...hat.com>
> Date: Tue, 6 Mar 2018 17:32:25 -0500
> Subject: WIP - livepatch kselftest
> 
> CONFIG_TEST_LIVEPATCH=m
> % make -C tools/testing/selftests TARGETS=livepatch run_tests
> 
> Signed-off-by: Joe Lawrence <joe.lawrence@...hat.com>
> ---
>  lib/Kconfig.debug                                |  11 +
>  lib/Makefile                                     |   9 +
>  lib/test_klp_callbacks_busy.c                    |  58 ++
>  lib/test_klp_callbacks_demo.c                    | 205 +++++++
>  lib/test_klp_callbacks_demo2.c                   | 149 +++++
>  lib/test_klp_callbacks_mod.c                     |  39 ++

I would suggest to put it into lib/livepatch/ subdirectory. I hope
that we will add more tests in the long term.


> diff --git a/tools/testing/selftests/livepatch/livepatch-test b/tools/testing/selftests/livepatch/livepatch-test
> new file mode 100755
> index 000000000000..798317bf69f6
> --- /dev/null
> +++ b/tools/testing/selftests/livepatch/livepatch-test

s/livepatch-test/livepatch-test.sh/  ?

It seems to be common to add .sh suffix for bash script names.


> @@ -0,0 +1,658 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (C) 2018 Joe Lawrence <joe.lawrence@...hat.com>
> +
> +MAX_RETRIES=30
> +RETRY_INTERVAL=2	# seconds
> +BETWEEN_TESTS=20	# seconds

These 20 seconds kept me in a tense (waiting for the final result)
for a very long time ;-) Is there any particular reason for such
a long delay?

I wonder if we need a delay at all or if let's say 2 seconds might
be enough.


> +echo -n "TEST1 ... "
> +dmesg -C
> +
> +load_mod $MOD_TARGET
> +load_mod $MOD_LIVEPATCH
> +wait_for_transition $MOD_LIVEPATCH
> +disable_lp $MOD_LIVEPATCH
> +unload_mod $MOD_LIVEPATCH
> +unload_mod $MOD_TARGET
> +
> +check_result "% modprobe $MOD_TARGET
> +$MOD_TARGET: livepatch_callbacks_mod_init
> +% modprobe $MOD_LIVEPATCH
> +livepatch: enabling patch '$MOD_LIVEPATCH'
> +livepatch: '$MOD_LIVEPATCH': initializing patching transition
> +$MOD_LIVEPATCH: pre_patch_callback: $MOD_TARGET -> [MODULE_STATE_LIVE] Normal state
> +$MOD_LIVEPATCH: pre_patch_callback: vmlinux
> +livepatch: '$MOD_LIVEPATCH': starting patching transition
> +livepatch: '$MOD_LIVEPATCH': completing patching transition
> +$MOD_LIVEPATCH: post_patch_callback: $MOD_TARGET -> [MODULE_STATE_LIVE] Normal state
> +$MOD_LIVEPATCH: post_patch_callback: vmlinux
> +livepatch: '$MOD_LIVEPATCH': patching complete
> +% echo 0 > /sys/kernel/livepatch/$MOD_LIVEPATCH/enabled
> +livepatch: '$MOD_LIVEPATCH': initializing unpatching transition
> +$MOD_LIVEPATCH: pre_unpatch_callback: $MOD_TARGET -> [MODULE_STATE_LIVE] Normal state
> +$MOD_LIVEPATCH: pre_unpatch_callback: vmlinux
> +livepatch: '$MOD_LIVEPATCH': starting unpatching transition
> +livepatch: '$MOD_LIVEPATCH': completing unpatching transition
> +$MOD_LIVEPATCH: post_unpatch_callback: $MOD_TARGET -> [MODULE_STATE_LIVE] Normal state
> +$MOD_LIVEPATCH: post_unpatch_callback: vmlinux
> +livepatch: '$MOD_LIVEPATCH': unpatching complete
> +% rmmod $MOD_LIVEPATCH
> +% rmmod $MOD_TARGET
> +$MOD_TARGET: livepatch_callbacks_mod_exit"

I was a bit surprised when seeing this way of checking results.
But on the other hand, it looks pretty effective, especially for
the callbacks. And the 3rd look, any patched function might write
something into the log when called.

I like it. Let's see how it works in the long term. But I am rather
positive.

Thanks a lot for working on it.

Best Regards,
Petr