tracing: Add __string_len() example

There's no example code that uses __string_len(), and since the sample
code is used for testing the event logic, add a use case.

Link: https://lore.kernel.org/linux-trace-kernel/20240223152827.5f9f78e2@gandalf.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h
index f2d2d56ce8e2e40d9822f660f7e55ba5e6ea2030..2dfaf7fc7bfa32c6e620805920c20c81bd39514f 100644 (file)
--- a/samples/trace_events/trace-events-sample.h
+++ b/samples/trace_events/trace-events-sample.h
@@ -303,6 +303,7 @@ TRACE_EVENT(foo_bar,
                __bitmask(      cpus,   num_possible_cpus()     )
                __cpumask(      cpum                            )
                __vstring(      vstr,   fmt,    va              )
+               __string_len(   lstr,   foo,    bar / 2 < strlen(foo) ? bar / 2 : strlen(foo) )
        ),
 
        TP_fast_assign(
@@ -311,12 +312,13 @@ TRACE_EVENT(foo_bar,
                memcpy(__get_dynamic_array(list), lst,
                       __length_of(lst) * sizeof(int));
                __assign_str(str, string);
+               __assign_str(lstr, foo);
                __assign_vstr(vstr, fmt, va);
                __assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus());
                __assign_cpumask(cpum, cpumask_bits(mask));
        ),
 
-       TP_printk("foo %s %d %s %s %s %s (%s) (%s) %s", __entry->foo, __entry->bar,
+       TP_printk("foo %s %d %s %s %s %s %s (%s) (%s) %s", __entry->foo, __entry->bar,
 
 /*
  * Notice here the use of some helper functions. This includes:
@@ -360,7 +362,8 @@ TRACE_EVENT(foo_bar,
                  __print_array(__get_dynamic_array(list),
                                __get_dynamic_array_len(list) / sizeof(int),
                                sizeof(int)),
-                 __get_str(str), __get_bitmask(cpus), __get_cpumask(cpum),
+                 __get_str(str), __get_str(lstr),
+                 __get_bitmask(cpus), __get_cpumask(cpum),
                  __get_str(vstr))
 );