Date: Fri, 31 May 2024 18:06:48 -0300
From: Marcos Paulo de Souza <mpdesouza@...e.com>
To: Joe Lawrence <joe.lawrence@...hat.com>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>, Jiri Kosina <jikos@...nel.org>, 
 Miroslav Benes <mbenes@...e.cz>, Petr Mladek <pmladek@...e.com>, Shuah Khan
 <shuah@...nel.org>,  live-patching@...r.kernel.org,
 linux-kselftest@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] selftests: livepatch: Test atomic replace against
 multiple modules

On Fri, 2024-05-31 at 15:44 -0400, Joe Lawrence wrote:
> On Sat, May 25, 2024 at 11:34:08AM -0300, Marcos Paulo de Souza
> wrote:
> > Adapt the current test-livepatch.sh script to account the number of
> > applied livepatches and ensure that an atomic replace livepatch
> > disables
> > all previously applied livepatches.
> > 
> > Signed-off-by: Marcos Paulo de Souza <mpdesouza@...e.com>
> > ---
> > Changes since v1:
> > * Added checks in the existing test-livepatch.sh instead of
> > creating a
> >   new test file. (Joe)
> > * Fixed issues reported by ShellCheck (Joe)
> > ---
> >  .../testing/selftests/livepatch/test-livepatch.sh  | 46
> > ++++++++++++++++++++--
> >  1 file changed, 42 insertions(+), 4 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/livepatch/test-livepatch.sh
> > b/tools/testing/selftests/livepatch/test-livepatch.sh
> > index e3455a6b1158..d85405d18e54 100755
> > --- a/tools/testing/selftests/livepatch/test-livepatch.sh
> > +++ b/tools/testing/selftests/livepatch/test-livepatch.sh
> > @@ -107,9 +107,12 @@ livepatch: '$MOD_LIVEPATCH': unpatching
> > complete
> >  
> >  # - load a livepatch that modifies the output from /proc/cmdline
> > and
> >  #   verify correct behavior
> > -# - load an atomic replace livepatch and verify that only the
> > second is active
> > -# - remove the first livepatch and verify that the atomic replace
> > livepatch
> > -#   is still active
> > +# - load two addtional livepatches and check the number of
> > livepatch modules
> > +#   applied
> > +# - load an atomic replace livepatch and check that the other
> > three modules were
> > +#   disabled
> > +# - remove all livepatches besides the atomic replace one and
> > verify that the
> > +#   atomic replace livepatch is still active
> >  # - remove the atomic replace livepatch and verify that none are
> > active
> >  
> >  start_test "atomic replace livepatch"
> > @@ -119,12 +122,31 @@ load_lp $MOD_LIVEPATCH
> >  grep 'live patched' /proc/cmdline > /dev/kmsg
> >  grep 'live patched' /proc/meminfo > /dev/kmsg
> >  
> > +for mod in test_klp_syscall test_klp_callbacks_demo; do
> 
> Slightly nitpicky here, but the tests were originally written with
> the
> livepatch module names via variables like $MOD_LIVEPATCH.  Would
> using
> $MOD_LIVEPATCH{1,2,3} help indicate that their specifics aren't
> really
> interesting, that we just need 3 of them?

Makes sense. I thought about it when I was changing the code, but I
didn't want to change it too much, so it was the result. But that makes
sense to have the modules better named.

> 
> > +	load_lp $mod
> > +done
> > +
> > +mods=(/sys/kernel/livepatch/*)
> > +nmods=${#mods[@]}
> > +if [ "$nmods" -ne 3 ]; then
> > +	die "Expecting three modules listed, found $nmods"
> > +fi
> > +
> 
> I was going to suggest that we might protect against a situation
> where
> other livepatch modules were active, that a simple count wouldn't be
> sufficient.  But then I thought about this test, atomic replace!
> Anything previously loaded is going to be pushed aside anyway.
> 
> So maybe (in another patch or set) it would be worth enhancing
> functions.sh :: start_test() do a quick sanity check to see that the
> initial conditions are safe?  That might also prevent some collateral
> damage when test A fails and leaves the world a strange place for
> tests
> B, C, etc.

We have been discussing about start/end functions that would check for
leftover modules... maybe should be a good think to implement soon as
we land more tests.

> 
> >  load_lp $MOD_REPLACE replace=1
> >  
> >  grep 'live patched' /proc/cmdline > /dev/kmsg
> >  grep 'live patched' /proc/meminfo > /dev/kmsg
> >  
> > -unload_lp $MOD_LIVEPATCH
> > +mods=(/sys/kernel/livepatch/*)
> > +nmods=${#mods[@]}
> > +if [ "$nmods" -ne 1 ]; then
> > +	die "Expecting only one moduled listed, found $nmods"
> > +fi
> > +
> > +# These modules were disabled by the atomic replace
> > +for mod in test_klp_callbacks_demo test_klp_syscall
> > $MOD_LIVEPATCH; do
> > +	unload_lp "$mod"
> > +done
> >  
> >  grep 'live patched' /proc/cmdline > /dev/kmsg
> >  grep 'live patched' /proc/meminfo > /dev/kmsg
> > @@ -142,6 +164,20 @@ livepatch: '$MOD_LIVEPATCH': starting patching
> > transition
> >  livepatch: '$MOD_LIVEPATCH': completing patching transition
> >  livepatch: '$MOD_LIVEPATCH': patching complete
> >  $MOD_LIVEPATCH: this has been live patched
> > +% insmod test_modules/test_klp_syscall.ko
> 
> Similar minor nit here, too.  If we think copy/pasting all the
> $MOD_FOO
> is annoying, I am fine with leaving this as is.  I don't have a
> strong
> opinion other than following some convention.
> 
> With that, I'm happy to ack as-is or with variable names.

Thanks Joe! I think that is Petr's call, either way I can rework this
patch, or send additional ones to adjust the tests.

> 
> Acked-by: Joe Lawrence <joe.lawrence@...hat.com>
> 
> --
> Joe
> 

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