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

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Message-ID: <6d9b9394-690b-49a3-b8df-7ef510c96c00@gmail.com>
Date: Fri, 14 Mar 2025 16:00:19 -0300
From: Filipe Xavier <felipeaggger@...il.com>
To: Miroslav Benes <mbenes@...e.cz>
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 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.

>
> Miroslav