NAME

       tracefs_event_systems, tracefs_system_events, tracefs_iterate_raw_events - Work with trace systems and
       events.

SYNOPSIS

       #include <tracefs.h>

       char **tracefs_event_systems(const char *tracing_dir);
       char **tracefs_system_events(const char *tracing_dir, const char *system);
       int tracefs_event_enable(struct tracefs_instance *instance, const char *system, const char *event);
       int tracefs_event_disable(struct tracefs_instance *instance, const char *system, const char *event);
       int tracefs_iterate_raw_events(struct tep_handle *tep, struct tracefs_instance *instance, cpu_set_t *cpus, int cpu_size, int (*callback)(struct tep_event *, struct tep_record *, int, void *), void *callback_context);

DESCRIPTION

       Trace systems and events related APIs.

       The tracefs_event_systems() function returns array of strings with the names of all registered trace
       systems, located in the given tracing_dir directory. This could be NULL or the location of the tracefs
       mount point for the trace systems of the local machine, or it may be a path to a copy of the tracefs
       directory from another machine. The last entry in the array is a NULL pointer. The array must be freed
       with tracefs_list_free() API.

       The tracefs_system_events() function returns array of strings with the names of all registered trace
       events for given trace system specified by system, located in the given tracing_dir directory. This could
       be NULL or the location of the tracefs mount point for the trace systems of the local machine, or it may
       be a path to a copy of the tracefs directory from another machine. The last entry in the array as a NULL
       pointer. The array must be freed with tracefs_list_free() API.

       The tracefs_event_enable() function enables a given event based on the system and event passed in for the
       given instance. If instance is NULL, then the top level tracing directory is used. If system and event
       are both NULL, then all events are enabled for the instance. If event is NULL then all events within the
       system are enabled. If system is NULL, then all systems are searched and any event within a system that
       matches event is enabled. Both system and event may be regular expressions as defined by regex(3).

       The tracefs_event_disable() function disables the events that match the system and event parameters for
       the given instance. What events are disable follow the same rules as tracefs_event_enable() for matching
       events. That is, if instance is NULL, then the top level tracing directory is used. If both system and
       event are NULL then all events are disabled for the given instance, and so on.

       The tracefs_iterate_raw_events() function will read the tracefs raw data buffers and call the specified
       callback function for every event it encounters. Events are iterated in sorted order: oldest first. An
       initialized tep handler is required (See tracefs_local_events(3)). If instance is NULL, then the toplevel
       tracefs buffer is used, otherwise the buffer for the corresponding instance is read. To filter only on a
       subset of CPUs, cpus and cpu_size may be set to only call callback with events that occurred on the CPUs
       specified, otherwise if cpus is NULL then the callback function will be called for all events, and
       cpu_size is ignored. The callback function will be called with the following parameters: A pointer to a
       struct tep_event that corresponds to the type of event the record is; The record representing the event;
       The CPU that the event occurred on; and a pointer to user specified callback_context. If the callback
       returns non-zero, the iteration stops.

RETURN VALUE

       The tracefs_event_systems() and _tracefs_system_events() functions return an array of strings. The last
       element in that array is a NULL pointer. The array must be freed with tracefs_list_free() API. In case of
       an error, NULL is returned.

       Both tracefs_event_enable() and tracefs_event_disable() return 0 if they found any matching events (Note
       it does not check the previous status of the event. If tracefs_event_enable() finds an event that is
       already enabled, and there are no other errors, then it will return 0). If an error occurs, even if other
       events were found, it will return -1 and errno will be set. If no errors occur, but no events are found
       that match the system and event parameters, then -1 is returned and errno is not set.

       The tracefs_iterate_raw_events() function returns -1 in case of an error or 0 otherwise.

EXAMPLE

           #include <tracefs.h>

           char **systems = tracefs_event_systems(NULL);

                   if (systems) {
                           int i = 0;
                           /* Got registered trace systems from the top trace instance */
                           while (systems[i]) {
                                   char **events = tracefs_system_events(NULL, systems[i]);
                                   if (events) {
                                           /* Got registered events in system[i] from the top trace instance */
                                           int j = 0;

                                           while (events[j]) {
                                                   /* Got event[j] in system[i] from the top trace instance */
                                                   j++;
                                           }
                                           tracefs_list_free(events);
                                   }
                                   i++;
                           }
                           tracefs_list_free(systems);
                   }
           ....
           static int records_walk(struct tep_event *tep, struct tep_record *record, int cpu, void *context)
           {
                   /* Got recorded event on cpu */
                   return 0;
           }
           ...
           struct tep_event *tep = tracefs_local_events(NULL);

                   if (!tep) {
                           /* Failed to initialise tep handler with local events */
                           ...
                   }

                   errno = 0;
                   ret = tracefs_event_enable(NULL, "sched", NULL);
                   if (ret < 0 && !errno)
                           printf("Could not find 'sched' events\n");
                   tracefs_event_enable(NULL, "irq", "irq_handler_\(enter\|exit\)");

                   if (tracefs_iterate_raw_events(tep, NULL, NULL, 0, records_walk, NULL) < 0) {
                           /* Error walking through the recorded raw events */
                   }

                   /* Disable all events */
                   tracefs_event_disable(NULL, NULL, NULL);
                   tep_free(tep);

FILES

           tracefs.h
                   Header file to include in order to have access to the library APIs.
           -ltracefs
                   Linker switch to add when building a program that uses the library.

SEE ALSO

       libtracefs(3), libtraceevent(3), trace-cmd(1)

AUTHOR

           Steven Rostedt <rostedt@goodmis.org[1]>
           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>

REPORTING BUGS

       Report bugs to <linux-trace-devel@vger.kernel.org[3]>

LICENSE

       libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES

       https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

COPYING

       Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public
       License (GPL).

NOTES

        1. rostedt@goodmis.org
           mailto:rostedt@goodmis.org

        2. tz.stoyanov@gmail.com
           mailto:tz.stoyanov@gmail.com

        3. linux-trace-devel@vger.kernel.org
           mailto:linux-trace-devel@vger.kernel.org

libtracefs 1.2.5                                   08/29/2021                                      LIBTRACEFS(3)