libtracefs(3)

# libtracefs(3) Manual Page

## NAME

libtracefs - Linux kernel trace file system library

## SYNOPSIS

    #include <tracefs.h>

    Locations of tracing files and directories:
            char *tracefs_get_tracing_file(const char *name);
            void tracefs_put_tracing_file(char *name);
            const char *tracefs_tracing_dir(void);
            const char *tracefs_debug_dir(void);
            int tracefs_set_tracing_dir(char *tracing_dir)
            int tracefs_tracing_dir_is_mounted(bool mount, const char **path);

    Trace instances:
            struct tracefs_instance *tracefs_instance_create(const char *name);
            int tracefs_instance_destroy(struct tracefs_instance *instance);
            struct tracefs_instance *tracefs_instance_alloc(const char *tracing_dir, const char *name);
            void tracefs_instance_free(struct tracefs_instance *instance);
            char **tracefs_instances(const char *regex);
            void tracefs_instance_clear(struct tracefs_instance *instance);
            void tracefs_instance_reset(struct tracefs_instance *instance);
            bool tracefs_instance_is_new(struct tracefs_instance *instance);
            bool tracefs_file_exists(struct tracefs_instance *instance, char *name);
            bool tracefs_dir_exists(struct tracefs_instance *instance, char *name);
            char *tracefs_instance_get_file(struct tracefs_instance *instance, const char *file);
            char *tracefs_instance_get_dir(struct tracefs_instance *instance);
            int tracefs_instance_file_open(struct tracefs_instance *instance, const char *file, int mode);
            int tracefs_instance_file_write(struct tracefs_instance *instance, const char *file, const char *str);
            int tracefs_instance_file_write_number(struct tracefs_instance *instance, const char *file, size_t val);
            int tracefs_instance_file_append(struct tracefs_instance *instance, const char *file, const char *str);
            int tracefs_instance_file_clear(struct tracefs_instance *instance, const char *file);
            char *tracefs_instance_file_read(struct tracefs_instance *instance, const char *file, int *psize);
            int tracefs_instance_file_read_number(struct tracefs_instance *instance, const char *file, long long int *res);
            const char *tracefs_instance_get_name(struct tracefs_instance *instance);
            const char *tracefs_instance_get_trace_dir(struct tracefs_instance *instance);
            int tracefs_instances_walk(int (*callback)(const char *, void *), void *context);
            bool tracefs_instance_exists(const char *name);
            int tracefs_instance_set_affinity(struct tracefs_instance *instance, const char *cpu_str);
            int tracefs_instance_set_affinity_set(struct tracefs_instance *instance, cpu_set_t *set, size_t set_size);
            int tracefs_instance_set_affinity_raw(struct tracefs_instance *instance, const char *mask);
            char *tracefs_instance_get_affinity(struct tracefs_instance *instance);
            int tracefs_instance_get_affinity_set(struct tracefs_instance *instance, cpu_set_t *set, size_t set_size);
            char *tracefs_instance_get_affinity_raw(struct tracefs_instance *instance);
            size_t tracefs_instance_get_buffer_size(struct tracefs_instance *instance, int cpu);
            int tracefs_instance_set_buffer_size(struct tracefs_instance *instance, size_t size, int cpu);
            int tracefs_instance_get_buffer_percent(struct tracefs_instance *instance);
            int tracefs_instance_set_buffer_percent(struct tracefs_instance *instance, int val);

    Trace events:
            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);
            enum tracefs_enable_state tracefs_event_is_enabled(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);
            void tracefs_iterate_stop(struct tracefs_instance *instance);
            int tracefs_follow_event(struct tep_handle *tep, struct tracefs_instance *instance,
                                      const char *system, const char *event_name,
                                      int (*callback)(struct tep_event *,
                                                      struct tep_record *,
                                                      int, void *),
                                      void *callback_data);
            int tracefs_follow_missed_events(struct tracefs_instance *instance,
                                      int (*callback)(struct tep_event *,
                                                      struct tep_record *,
                                                      int, void *),
                                      void *callback_data);
            int tracefs_follow_event_clear(struct tracefs_instance *instance,
                              const char *system, const char *event_name);
            int tracefs_follow_missed_events_clear(struct tracefs_instance *instance);
            struct tep_handle *tracefs_local_events(const char *tracing_dir);
            struct tep_handle *tracefs_local_events_system(const char *tracing_dir, const char * const *sys_names);
            int tracefs_fill_local_events(const char *tracing_dir, struct tep_handle *tep, int *parsing_failures);
            int tracefs_load_cmdlines(const char *tracing_dir, struct tep_handle *tep);
            int tracefs_load_headers(const char *tracing_dir, struct tep_handle *tep);
            char *tracefs_event_get_file(struct tracefs_instance *instance, const char *system, const char *event,
                                 const char *file);
            char *tracefs_event_file_read(struct tracefs_instance *instance, const char *system, const char *event,
                                  const char *file, int *psize);
            int tracefs_event_file_write(struct tracefs_instance *instance, const char *system, const char *event,
                                 const char *file, const char *str);
            int tracefs_event_file_append(struct tracefs_instance *instance, const char *system, const char *event,
                                  const char *file, const char *str);
            int tracefs_event_file_clear(struct tracefs_instance *instance, const char *system, const char *event,
                                 const char *file);
            bool tracefs_event_file_exists(struct tracefs_instance *instance, const char *system, const char *event,
                                   const char *file);

    Snapshot buffer:
            int tracefs_snapshot_snap(struct tracefs_instance *instance);
            int tracefs_snapshot_clear(struct tracefs_instance *instance);
            int tracefs_snapshot_free(struct tracefs_instance *instance);
            int tracefs_iterate_snapshot_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);
            struct tracefs_cpu *tracefs_cpu_snapshot_open(struct tracefs_instance *instance,
                                                 int cpu, bool nonblock);

    Event filters:
            int tracefs_filter_string_append(struct tep_event *event, char **filter,
                                             struct tracefs_filter type, const char *field,
                                             enum tracefs_synth_compare compare, const char *val);
            int tracefs_filter_string_verify(struct tep_event *event, const char *filter, char **err);
            int tracefs_event_filter_apply(struct tracefs_instance *instance, struct tep_event *event, const char *filter);
            int tracefs_event_filter_clear(struct tracefs_instance *instance, struct tep_event *event);

    Function filters:
            int tracefs_function_filter(struct tracefs_instance *instance, const char *filter, const char *module, int flags);
            int tracefs_function_notrace(struct tracefs_instance *instance, const char *filter, const char *module, int flags);
            int tracefs_filter_functions(const char *filter, const char *module, char ***list);

    PID filters:
            int tracefs_filter_pid_function(struct tracefs_instance *instance, int pid,
                                    bool reset, bool notrace);
            int tracefs_filter_pid_function_clear(struct tracefs_instance *instance, bool notrace);
            int tracefs_filter_pid_events(struct tracefs_instance *instance, int pid,
                                    bool reset, bool notrace);
            int tracefs_filter_pid_events_clear(struct tracefs_instance *instance, bool notrace);

    Trace helper functions:
            void tracefs_list_free(char **list);
            char **tracefs_list_add(char *list, const char *string);
            int *tracefs_list_size(char **list);
            char *tracefs_get_clock(struct tracefs_instance *instance);
            int tracefs_trace_is_on(struct tracefs_instance *instance);
            int tracefs_trace_on(struct tracefs_instance *instance);
            int tracefs_trace_off(struct tracefs_instance *instance);
            int tracefs_trace_on_get_fd(struct tracefs_instance *instance);
            int tracefs_trace_on_fd(int fd);
            int tracefs_trace_off_fd(int fd);

    Trace stream:
            ssize_t tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, int flags);
            ssize_t tracefs_trace_pipe_print(struct tracefs_instance *instance, int flags);
            void tracefs_trace_pipe_stop(struct tracefs_instance *instance);

    Memory mapping the ring buffer:
            bool tracefs_cpu_is_mapped(struct tracefs_cpu *tcpu);
            bool tracefs_mapped_is_supported(void);
            int tracefs_cpu_map(struct tracefs_cpu *tcpu);
            void tracefs_cpu_unmap(struct tracefs_cpu *tcpu);
            struct tracefs_cpu *tracefs_cpu_open_mapped(struct tracefs_instance *instance,
                                                    int cpu, bool nonblock);

    Trace options:
            const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
            bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
            const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
            bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
            bool tracefs_option_mask_is_set(const struct tracefs_options_mask options, enum tracefs_option_id id);
            int *tracefs_option_enable(struct tracefs_instance *instance, enum tracefs_option_id id);
            int tracefs_option_disable(struct tracefs_instance *instance, enum tracefs_option_id id);
            const char *tracefs_option_name(enum tracefs_option_id id);
            enum tracefs_option_id tracefs_option_id(const char *name);

    Ftrace tracers:
            char **tracefs_tracers(const char *tracing_dir);
            char ** tracefs_instance_tracers(struct tracefs_instance *instance);
            bool tracefs_tracer_available(const char *tracing_dir, const char *tracer);
            int tracefs_tracer_set(struct tracefs_instance *instance, enum tracefs_tracers tracer);
            int tracefs_tracer_set(struct tracefs_instance *instance, enum tracefs_tracers tracer, const char *name);
            int tracefs_tracer_clear(struct tracefs_instance *instance);

    Writing data in the trace buffer:
            int tracefs_print_init(struct tracefs_instance *instance);
            int tracefs_printf(struct tracefs_instance *instance, const char *fmt, …);
            int tracefs_vprintf(struct tracefs_instance *instance, const char *fmt, va_list ap);
            void tracefs_print_close(struct tracefs_instance *instance);
            int tracefs_binary_init(struct tracefs_instance *instance);
            int tracefs_binary_write(struct tracefs_instance *instance, void *data, int len);
            void tracefs_binary_close(struct tracefs_instance *instance);

    Control library logs:
            int tracefs_set_loglevel(enum tep_loglevel level);

    Read the ring buffer statistics:
            struct tracefs_buffer_stat *tracefs_instance_get_stat(struct tracefs_instance *instance, int cpu);
            void tracefs_instance_put_stat(struct tracefs_buffer_stat *tstat);
            ssize_t tracefs_buffer_stat_entries(struct tracefs_buffer_stat *tstat);
            ssize_t tracefs_buffer_stat_overrun(struct tracefs_buffer_stat *tstat);
            ssize_t tracefs_buffer_stat_commit_overrun(struct tracefs_buffer_stat *tstat);
            ssize_t tracefs_buffer_stat_bytes(struct tracefs_buffer_stat *tstat);
            long long tracefs_buffer_stat_event_timestamp(struct tracefs_buffer_stat *tstat);
            long long tracefs_buffer_stat_timestamp(struct tracefs_buffer_stat *tstat);
            ssize_t tracefs_buffer_stat_dropped_events(struct tracefs_buffer_stat *tstat);
            ssize_t tracefs_buffer_stat_read_events(struct tracefs_buffer_stat *tstat);

    Dynamic event generic APIs:
            struct tracefs_dynevent;
            enum tracefs_dynevent_type;
            int tracefs_dynevent_create(struct tracefs_dynevent *devent);
            int tracefs_dynevent_destroy(struct tracefs_dynevent *devent, bool force);
            int tracefs_dynevent_destroy_all(unsigned int types, bool force);
            void tracefs_dynevent_free(struct tracefs_dynevent *devent);
            void tracefs_dynevent_list_free(struct tracefs_dynevent **events);
            struct tracefs_dynevent *tracefs_dynevent_get(enum tracefs_dynevent_type type, const char *system, const char *event);
            struct tracefs_dynevent **tracefs_dynevent_get_all(unsigned int types, const char *system);
            enum tracefs_dynevent_type tracefs_dynevent_info(struct tracefs_dynevent *dynevent, char **system, char **event, char **prefix, char **addr, char **format);
            struct tep_event *tracefs_dynevent_get_event(struct tep_handle *tep, struct tracefs_dynevent *dynevent);

    Even probes (eprobes):
            struct tracefs_dynevent * tracefs_eprobe_alloc(const char *system, const char *event, const char *target_system, const char *target_event, const char *fetchargs);

    Uprobes, Kprobes and Kretprobes:
            struct tracefs_dynevent * tracefs_kprobe_alloc(const char *system, const char *event, const char *addr, const char *format);
            struct tracefs_dynevent * tracefs_kretprobe_alloc(const char *system, const char *event, const char *addr, const char *format, unsigned int max);
            int tracefs_kprobe_raw(const char *system, const char *event, const char *addr, const char *format);
            int tracefs_kretprobe_raw(const char *system, const char *event, const char *addr, const char *format);
            tracefs_uprobe_alloc(const char *system, const char *event,
                         const char *file, unsigned long long offset, const char *fetchargs)
            tracefs_uretprobe_alloc(const char *system, const char *event,
                         const char *file, unsigned long long offset, const char *fetchargs);
            int tracefs_kprobe_destroy(const char *system, const char *event,
                               const char *addr, const char *format, bool force);

    Synthetic events:
            struct tracefs_synth *tracefs_sql(struct tep_handle *tep, const char *name,
                                            const char *sql_buffer, char **err);
            struct tracefs_synth *tracefs_synth_alloc(struct tep_handle *tep,
                                                     const char *name,
                                                     const char *start_system,
                                                     const char *start_event,
                                                     const char *end_system,
                                                     const char *end_event,
                                                     const char *start_match_field,
                                                     const char *end_match_field,
                                                     const char *match_name);
            int tracefs_synth_add_match_field(struct tracefs_synth *synth,
                                              const char *start_match_field,
                                              const char *end_match_field,
                                              const char *name);
            int tracefs_synth_add_compare_field(struct tracefs_synth *synth,
                                                const char *start_compare_field,
                                                const char *end_compare_field,
                                                enum tracefs_synth_calc calc,
                                                const char *name);
            int tracefs_synth_add_start_field(struct tracefs_synth *synth,
                                              const char *start_field,
                                              const char *name);
            int tracefs_synth_add_end_field(struct tracefs_synth *synth,
                                            const char *end_field,
                                            const char *name);
            int tracefs_synth_append_start_filter(struct tracefs_synth *synth,
                                                  struct tracefs_filter type,
                                                  const char *field,
                                                  enum tracefs_synth_compare compare,
                                                  const char *val);
            int tracefs_synth_append_end_filter(struct tracefs_synth *synth,
                                                struct tracefs_filter type,
                                                const char *field,
                                                enum tracefs_synth_compare compare,
                                                const char *val);
            void tracefs_synth_free(struct tracefs_synth *synth);
            int tracefs_synth_create(struct tracefs_synth *synth);
            int tracefs_synth_destroy(struct tracefs_synth *synth);
            int tracefs_synth_set_instance(struct tracefs_synth *synth, struct tracefs_instance *instance);
            int tracefs_synth_echo_cmd(struct trace_seq *seq, struct tracefs_synth *synth);
            bool tracefs_synth_complete(struct tracefs_synth *synth);
            struct tracefs_hist *tracefs_synth_get_start_hist(struct tracefs_synth *synth);
            int tracefs_synth_trace(struct tracefs_synth *synth,
                                    enum tracefs_synth_handler type, const char *var);
            int tracefs_synth_snapshot(struct tracefs_synth *synth,
                                       enum tracefs_synth_handler type, const char *var);
            int tracefs_synth_save(struct tracefs_synth *synth,
                                   enum tracefs_synth_handler type, const char *var,
                                   char **save_fields);
            const char *tracefs_synth_get_name(struct tracefs_synth *synth);
            int tracefs_synth_raw_fmt(struct trace_seq *seq, struct tracefs_synth *synth);
            const char *tracefs_synth_show_event(struct tracefs_synth *synth);
            const char *tracefs_synth_show_start_hist(struct tracefs_synth *synth);
            const char *tracefs_synth_show_end_hist(struct tracefs_synth *synth);
            struct tep_event *tracefs_synth_get_event(struct tep_handle *tep, struct tracefs_synth *synth);

    Ftrace errors reporting:
            char *tracefs_error_last(struct tracefs_instance *instance);
            char *tracefs_error_all(struct tracefs_instance *instance);
            int tracefs_error_clear(struct tracefs_instance *instance);

    Histograms:
            struct tracefs_hist *tracefs_hist_alloc(struct tracefs_tep * tep,
                                    const char *system, const char *event,
                                    const char *key, enum tracefs_hist_key_type type);
            struct tracefs_hist *tracefs_hist_alloc_2d(struct tracefs_tep * tep,
                                    const char *system, const char *event,
                                    const char *key1, enum tracefs_hist_key_type type1,
                                    const char *key2, enum tracefs_hist_key_type type2));
            struct tracefs_hist *tracefs_hist_alloc_nd(struct tracefs_tep * tep,
                                    const char *system, const char *event,
                                    struct tracefs_hist_axis *axes);
            struct tracefs_hist *tracefs_hist_alloc_nd_cnt(struct tep_handle *tep,
                                      const char *system, const char *event_name,
                                      struct tracefs_hist_axis_cnt *axes);
            void tracefs_hist_free(struct tracefs_hist *hist);
            int tracefs_hist_add_key(struct tracefs_hist *hist, const char *key,
                                     enum tracefs_hist_key_type type);
            int tracefs_hist_add_key_cnt(struct tracefs_hist *hist, const char *key,
                                     enum tracefs_hist_key_type type, int cnt);
            int tracefs_hist_add_value(struct tracefs_hist *hist, const char *value);
            int tracefs_hist_add_sort_key(struct tracefs_hist *hist,
                                          const char *sort_key);
            int tracefs_hist_set_sort_key(struct tracefs_hist *hist,
                                          const char *sort_key, …);
            int tracefs_hist_sort_key_direction(struct tracefs_hist *hist,
                                                const char *sort_key,
                                                enum tracefs_hist_sort_direction dir);
            int tracefs_hist_add_name(struct tracefs_hist *hist, const char *name);
            int tracefs_hist_append_filter(struct tracefs_hist *hist,
                                           enum tracefs_filter type,
                                           const char *field,
                                           enum tracefs_compare compare,
                                           const char *val);
            int tracefs_hist_echo_cmd(struct trace_seq *s, struct tracefs_instance *instance,
                                      struct tracefs_hist *hist,
                                      enum tracefs_hist_command command);
            int tracefs_hist_command(struct tracefs_instance *instance,
                                     struct tracefs_hist *hist,
                                     enum tracefs_hist_command command);
            const char *tracefs_hist_get_name(struct tracefs_hist *hist);
            const char *tracefs_hist_get_event(struct tracefs_hist *hist);
            const char *tracefs_hist_get_system(struct tracefs_hist *hist);
            int tracefs_hist_start(struct tracefs_instance *instance, struct tracefs_hist *hist);
            int tracefs_hist_destroy(struct tracefs_instance *instance, struct tracefs_hist *hist);
            int tracefs_hist_pause(struct tracefs_instance *instance, struct tracefs_hist *hist);
            int tracefs_hist_continue(struct tracefs_instance *instance, struct tracefs_hist *hist);
            int tracefs_hist_reset(struct tracefs_instance *instance, struct tracefs_hist *hist);

    Recording of trace_pipe_raw files:
            struct tracefs_cpu *tracefs_cpu_open(struct tracefs_instance *instance,
                                                 int cpu, bool nonblock);
            struct tracefs_cpu *tracefs_cpu_alloc_fd(int fd, int subbuf_size, bool nonblock);
            void tracefs_cpu_close(struct tracefs_cpu *tcpu);
            void tracefs_cpu_free_fd(struct tracefs_cpu *tcpu);
            int tracefs_cpu_read_size(struct tracefs_cpu *tcpu);
            int tracefs_cpu_read(struct tracefs_cpu *tcpu, void *buffer, bool nonblock);
            int tracefs_cpu_buffered_read(struct tracefs_cpu *tcpu, void *buffer, bool nonblock);
            int tracefs_cpu_write(struct tracefs_cpu *tcpu, int wfd, bool nonblock);
            int tracefs_cpu_stop(struct tracefs_cpu *tcpu);
            int tracefs_cpu_flush(struct tracefs_cpu *tcpu, void *buffer);
            int tracefs_cpu_flush_write(struct tracefs_cpu *tcpu, int wfd);
            int tracefs_cpu_pipe(struct tracefs_cpu *tcpu, int wfd, bool nonblock);
            struct kbuffer *tracefs_cpu_read_buf(struct tracefs_cpu *tcpu, bool nonblock);
            struct kbuffer *tracefs_cpu_buffered_read_buf(struct tracefs_cpu *tcpu, bool nonblock);
            struct kbuffer *tracefs_cpu_flush_buf(struct tracefs_cpu *tcpu);

    Helper functions for modifying the ring buffer sub-buffers:
            size_t tracefs_instance_get_subbuf_size(struct tracefs_instance *instance);
            int tracefs_instance_set_subbuf_size(struct tracefs_instance *instance, size_t size);

    Helper functions for guest tracing:
            char *tracefs_find_cid_pid(int cid);
            char *tracefs_instance_find_cid_pid(struct tracefs_instance *instance, int cid);
            int tracefs_time_conversion(int cpu, int *shift, int *multi, long long *offset);

## DESCRIPTION

The libtracefs(3) library provides APIs to access kernel trace file system.

## 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

libtraceevent(3), trace-cmd(1)

## AUTHOR

    Steven Rostedt <rostedt@goodmis.org>
    Tzvetomir Stoyanov <tz.stoyanov@gmail.com>

## REPORTING BUGS

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

## 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).