Re: [PATCH v2] selftests: livepatch: test if ftrace can trace a livepatched function

[Joe Lawrence <joe.lawrence@redhat.com>]

On 1/14/25 12:18, Marcos Paulo de Souza wrote:
> On Sat, 2025-01-11 at 15:42 -0300, Filipe Xavier wrote:
>> This new test makes sure that ftrace can trace a
>> function that was introduced by a livepatch.
>>
>> Signed-off-by: Filipe Xavier <felipeaggger@gmail.com>
> 
> Thanks for the new test Filipe!
> 
> I have some nits below, but these don't need to be addressed for the
> test to be merged. Either way,
> 
> Reviewed-by: Marcos Paulo de Souza <mpdesouza@suse.com>
> Tested-by: Marcos Paulo de Souza <mpdesouza@suse.com>
> 
> 
> 
>> ---
>> Changes in v2:
>> - functions.sh: added reset tracing on push and pop_config.
>> - test-ftrace.sh: enabled tracing_on before test init.
>> - nitpick: added double quotations on filenames and fixed some
>> wording. 
>> - Link to v1:
>> https://lore.kernel.org/r/20250102-ftrace-selftest-livepatch-v1-1-84880baefc1b@gmail.com
>> ---
>>  tools/testing/selftests/livepatch/functions.sh   | 14 ++++++++++
>>  tools/testing/selftests/livepatch/test-ftrace.sh | 33
>> ++++++++++++++++++++++++
>>  2 files changed, 47 insertions(+)
>>
>> diff --git a/tools/testing/selftests/livepatch/functions.sh
>> b/tools/testing/selftests/livepatch/functions.sh
>> index
>> e5d06fb402335d85959bafe099087effc6ddce12..e6c13514002dae5f8d7461f90b8
>> 241ab43024ea4 100644
>> --- a/tools/testing/selftests/livepatch/functions.sh
>> +++ b/tools/testing/selftests/livepatch/functions.sh
>> @@ -62,6 +62,9 @@ function push_config() {
>>  			awk -F'[: ]' '{print "file " $1 " line " $2
>> " " $4}')
>>  	FTRACE_ENABLED=$(sysctl --values kernel.ftrace_enabled)
>>  	KPROBE_ENABLED=$(cat "$SYSFS_KPROBES_DIR/enabled")
>> +	TRACING_ON=$(cat "$SYSFS_DEBUG_DIR/tracing/tracing_on")
>> +	CURRENT_TRACER=$(cat
>> "$SYSFS_DEBUG_DIR/tracing/current_tracer")
>> +	FTRACE_FILTER=$(cat
>> "$SYSFS_DEBUG_DIR/tracing/set_ftrace_filter")
>>  }
>>  
>>  function pop_config() {
>> @@ -74,6 +77,17 @@ function pop_config() {
>>  	if [[ -n "$KPROBE_ENABLED" ]]; then
>>  		echo "$KPROBE_ENABLED" >
>> "$SYSFS_KPROBES_DIR/enabled"
>>  	fi
>> +	if [[ -n "$TRACING_ON" ]]; then
>> +		echo "$TRACING_ON" >
>> "$SYSFS_DEBUG_DIR/tracing/tracing_on"
>> +	fi
>> +	if [[ -n "$CURRENT_TRACER" ]]; then
>> +		echo "$CURRENT_TRACER" >
>> "$SYSFS_DEBUG_DIR/tracing/current_tracer"
>> +	fi
>> +	if [[ "$FTRACE_FILTER" == *"#"* ]]; then
>> +		echo > "$SYSFS_DEBUG_DIR/tracing/set_ftrace_filter"
>> +	elif [[ -n "$FTRACE_FILTER" ]]; then
>> +		echo "$FTRACE_FILTER" >
>> "$SYSFS_DEBUG_DIR/tracing/set_ftrace_filter"
>> +	fi
>>  }
> 
> I believe that this could be a separate patch, since this is new
> functionality that's being added to functions.sh, and not exactly
> related to the new test.
> 
>>  
>>  function set_dynamic_debug() {
>> diff --git a/tools/testing/selftests/livepatch/test-ftrace.sh
>> b/tools/testing/selftests/livepatch/test-ftrace.sh
>> index
>> fe14f248913acbec46fb6c0fec38a2fc84209d39..66af5d726c52e48e5177804e182
>> b4ff31784d5ac 100755
>> --- a/tools/testing/selftests/livepatch/test-ftrace.sh
>> +++ b/tools/testing/selftests/livepatch/test-ftrace.sh
>> @@ -61,4 +61,37 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
>>  % rmmod $MOD_LIVEPATCH"
>>  
>>  
>> +# - verify livepatch can load
>> +# - check if traces have a patched function
>> +# - unload livepatch and reset trace
>> +
>> +start_test "trace livepatched function and check that the live patch
>> remains in effect"
>> +
>> +TRACE_FILE="$SYSFS_DEBUG_DIR/tracing/trace"
>> +FUNCTION_NAME="livepatch_cmdline_proc_show"
>> +
>> +load_lp $MOD_LIVEPATCH
>> +
>> +echo 1 > "$SYSFS_DEBUG_DIR/tracing/tracing_on"
>> +echo $FUNCTION_NAME > "$SYSFS_DEBUG_DIR/tracing/set_ftrace_filter"
>> +echo "function" > "$SYSFS_DEBUG_DIR/tracing/current_tracer"
>> +echo "" > "$TRACE_FILE"
>> +
>> +if [[ "$(cat /proc/cmdline)" != "$MOD_LIVEPATCH: this has been live
>> patched" ]] ; then
>> +	echo -e "FAIL\n\n"
>> +	die "livepatch kselftest(s) failed"
>> +fi
>> +
>> +grep -q $FUNCTION_NAME "$TRACE_FILE"
>> +FOUND=$?
>> +
>> +disable_lp $MOD_LIVEPATCH
>> +unload_lp $MOD_LIVEPATCH
>> +
>> +if [ "$FOUND" -eq 1 ]; then
>> +	echo -e "FAIL\n\n"
>> +	die "livepatch kselftest(s) failed"
>> +fi
>> +
>> +
>>  exit 0
> 
> The test works, and that's very cool. But when running locally, I find
> the if we miss check_result call it doesn't add a newline after the
> "ok":
> 
> ...
> # timeout set to 0                                                    
> # selftests: livepatch: test-ftrace.sh                                
> # TEST: livepatch interaction with ftrace_enabled sysctl ... ok       
> # TEST: trace livepatched function and check that the live patch
> remains in effect ... ok 5 selftests: livepatch: test-ftrace.sh       
> # timeout set to 0                                                    
> # selftests: livepatch: test-sysfs.sh  
> ...
> 
> If the check_result below is added the output if sane again:
> 
> ...
> # selftests: livepatch: test-ftrace.sh
> # TEST: livepatch interaction with ftrace_enabled sysctl ... ok
> # TEST: trace livepatched function and check that the live patch
> remains in effect ... ok
> ok 5 selftests: livepatch: test-ftrace.sh
> ...
> 
> I checked and this would be the only one test without using
> check_result, so maybe we should add this either way? I'm not sure what
> you guys think about it.
> 
> 
> diff --git a/tools/testing/selftests/livepatch/test-ftrace.sh
> b/tools/testing/selftests/livepatch/test-ftrace.sh
> index 66af5d726c52..135c0fb17a98 100755
> --- a/tools/testing/selftests/livepatch/test-ftrace.sh
> +++ b/tools/testing/selftests/livepatch/test-ftrace.sh
> @@ -93,5 +93,18 @@ if [ "$FOUND" -eq 1 ]; then
>  	die "livepatch kselftest(s) failed"
>  fi
>  
> +check_result "% insmod test_modules/$MOD_LIVEPATCH.ko
> +livepatch: enabling patch '$MOD_LIVEPATCH'
> +livepatch: '$MOD_LIVEPATCH': initializing patching transition
> +livepatch: '$MOD_LIVEPATCH': starting patching transition
> +livepatch: '$MOD_LIVEPATCH': completing patching transition
> +livepatch: '$MOD_LIVEPATCH': patching complete
> +% echo 0 > $SYSFS_KLP_DIR/$MOD_LIVEPATCH/enabled
> +livepatch: '$MOD_LIVEPATCH': initializing unpatching transition
> +livepatch: '$MOD_LIVEPATCH': starting unpatching transition
> +livepatch: '$MOD_LIVEPATCH': completing unpatching transition
> +livepatch: '$MOD_LIVEPATCH': unpatching complete
> +% rmmod $MOD_LIVEPATCH"
> +
>  

Ah good catch, I noticed the newline, too, but didn't notice that the
test wasn't using check_result().  For consistency, let's make that
change before merging.

Thanks,

-- 
Joe