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

[Marcos Paulo de Souza <mpdesouza@suse.com>]

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"
+
 
 exit 0

> 
> ---
> base-commit: fc033cf25e612e840e545f8d5ad2edd6ba613ed5
> change-id: 20250101-ftrace-selftest-livepatch-161fb77dbed8
> 
> Best regards,