linux-kernel - Re: [PATCH PATCH 2/2] selftests: livepatch: test if ftrace can trace a livepatched function

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Message-ID: <alpine.LSU.2.21.2503171006260.4236@pobox.suse.cz>
Date: Mon, 17 Mar 2025 10:07:58 +0100 (CET)
From: Miroslav Benes <mbenes@...e.cz>
To: Filipe Xavier <felipeaggger@...il.com>
cc: Josh Poimboeuf <jpoimboe@...nel.org>, Jiri Kosina <jikos@...nel.org>, 
    Petr Mladek <pmladek@...e.com>, Joe Lawrence <joe.lawrence@...hat.com>, 
    Shuah Khan <shuah@...nel.org>, Marcos Paulo de Souza <mpdesouza@...e.com>, 
    live-patching@...r.kernel.org, linux-kselftest@...r.kernel.org, 
    linux-kernel@...r.kernel.org, felipe_life@...e.com
Subject: Re: [PATCH PATCH 2/2] selftests: livepatch: test if ftrace can trace
 a livepatched function

On Fri, 14 Mar 2025, Filipe Xavier wrote:

> On 3/14/25 10:14 AM, Miroslav Benes wrote:
> 
> > Hi,
> >
> >> +start_test "trace livepatched function and check that the live patch
> >> remains in effect"
> >> +
> >> +FUNCTION_NAME="livepatch_cmdline_proc_show"
> >> +
> >> +load_lp $MOD_LIVEPATCH
> >> +trace_function "$FUNCTION_NAME"
> > trace_funtion() calls cleanup_ftrace() to prepare the test. Ok.
> >
> >> +if [[ "$(cat /proc/cmdline)" == "$MOD_LIVEPATCH: this has been live
> >> patched" ]] ; then
> >> +	log "livepatch: ok"
> >> +fi
> >> +
> >> +check_traced_function "$FUNCTION_NAME"
> >> +
> >> +cleanup_tracing
> > Here, I suppose, cleanup_tracing() is called to clean up after the check
> > above so that nothing stays and more tests can be added later. Right?
> > Would it make sense then to call cleanup_tracing() in
> > check_traced_function()? I think it would less error prone.
> > If needed, check_traced_function() can always be upgraded so that it
> > checks for more traced functions.
> 
> In cases where we need to check two or more functions with
> check_traced_function,
> 
> if there is cleanup_tracing, it will not be possible, make sense?
> 
> e.g: function1 call -> function2 call -> function3.

I meant... check_traced_function() (or check_traced_functions() in this 
case) can have multiple arguments. You would loop over them inside and 
then clean up. Or did I misunderstood?

Miroslav