selftests: livepatch: test if ftrace can trace a livepatched function

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>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20250324-ftrace-sftest-livepatch-v3-2-d9d7cc386c75@gmail.com
Signed-off-by: Petr Mladek <pmladek@suse.com>

tools/testing/selftests/livepatch/test-ftrace.sh

@@ -61,4 +61,38 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 % rmmod $MOD_LIVEPATCH"
 
 
+# - verify livepatch can load
+# - check if traces have a patched function
+# - reset trace and unload livepatch
+
+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"
+
+if [[ "$(cat /proc/cmdline)" == "$MOD_LIVEPATCH: this has been live patched" ]] ; then
+	log "livepatch: ok"
+fi
+
+check_traced_functions "$FUNCTION_NAME"
+
+disable_lp $MOD_LIVEPATCH
+unload_lp $MOD_LIVEPATCH
+
+check_result "% insmod test_modules/$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
+livepatch: ok
+% 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