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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | COPYING | NOTES | COLOPHON |
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LIBTRACEFS(3) libtracefs Manual LIBTRACEFS(3)
tracefs_dynevent_create, tracefs_dynevent_destroy,
tracefs_dynevent_destroy_all, tracefs_dynevent_free,
tracefs_dynevent_list_free, tracefs_dynevent_get,
tracefs_dynevent_get_all, tracefs_dynevent_info,
tracefs_dynevent_get_event - Create, destroy, free and get
dynamic events.
#include <tracefs.h>
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);
The tracefs_dynevent_create() function creates dynamic event
devent in the system.
The tracefs_dynevent_destroy() function removes dynamic event
devent from the system. If force is true, the function will
attempt to disable all events in all trace instances, before
removing the dynamic event. The devent context is not freed, use
tracefs_dynevent_free() to free it.
The tracefs_dynevent_destroy_all() function removes all dynamic
events of given types from the system. The types parameter is a
type of specific dynamic event, or a bitmask of dynamic events
types tracefs_dynevent_type, that will be removed. If types is 0,
dynamic events from all types will be removed. If force is true,
the function will attempt to disable all events in all trace
instances, before removing the dynamic events.
The tracefs_dynevent_get() function allocates and returns a
single instance of a dynamic event that matches the given type,
system and event that is passed to it. NULL is returned if there
is no match. The returned event is what is found in the system,
and must be freed with tracefs_dynevent_free(). If system is
NULL, then the first event of any system of the given type that
has the name of event will be returned.
The tracefs_dynevent_get_all() function allocates and returns an
array of pointers to dynamic events of given types that exist in
the system. The last element of the array is a NULL pointer. The
array must be freed with tracefs_dynevent_list_free(). If there
are no events a NULL pointer is returned. The types parameter is
a type of specific dynamic event, or a bitmask of dynamic events
types tracefs_dynevent_type, that will be retrieved. If types is
0, dynamic events from all types will be retrieved.
The tracefs_dynevent_free() function frees a dynamic event
context devent.
The tracefs_dynevent_list_free() function frees an array of
pointers to dynamic event, returned by tracefs_dynevent_get_all()
API.
The tracefs_dynevent_info() function returns the type and
information of a given dynamic event dynevent. If any of the
system, event, prefix, addr or format arguments are not NULL,
then strings are allocated and returned back via these arguments.
The system and event holds the system and the name of the dynamic
event. If prefix is non NULL, then it will hold an allocated
string that holds the prefix portion of the dynamic event (the
content up to the ":", exluding it). If addr is non NULL, it will
hold the address or function that the dynamic event is attached
to, if relevant for this event type. If format is non NULL, it
will hold the format string of the dynamic event. Note, that the
content in group, event, prefix, addr, and format must be freed
with free(3) if they are set.
The tracefs_dynevent_get_event() function returns a tep event,
describing the given dynamic event. The API detects any newly
created or removed dynamic events. The returned pointer to tep
event is controlled by @tep and must not be freed.
tracefs_dynevent_create() returns 0 on success, or -1 on error.
If a parsing error occurs then tracefs_error_last(3) may be used
to retrieve the error message explaining the parsing issue.
tracefs_dynevent_destroy() and tracefs_dynevent_destroy_all()
return 0 on success, or -1 on error. If force is enabled, the
functions may fail on disabling the events.
tracefs_dynevent_get() function returns an allocated dynamic
event from the system that matches the type, system and event
given.
tracefs_dynevent_get_all() function returns allocated array of
pointers to dynamic events, or NULL in case of an error or in
case there are no events in the system. That array must be freed
by tracefs_dynevent_list_free().
tracefs_dynevent_info() returns the type of the given dynamic
event or TRACEFS_DYNEVENT_UNKNOWN on error. If system, event,
prefix, addr, or format are non NULL, they will contain allocated
strings that must be freed by free(3).
The tracefs_dynevent_get_event() function returns a pointer to a
tep event or NULL in case of an error or if the requested dynamic
event is missing. The returned pointer to tep event is controlled
by @tep and must not be freed.
The following errors are for all the above calls:
ENODEV dynamic events of requested type are not configured for
the running kernel.
ENOMEM Memory allocation error.
tracefs_dynevent_create() can fail with the following errors:
EINVAL Most likely a parsing error occurred (use
tracefs_error_last(3) to possibly see what that error was).
Other errors may also happen caused by internal system calls.
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <tracefs.h>
static struct tep_event *open_event;
static struct tep_format_field *file_field;
static struct tep_event *openret_event;
static struct tep_format_field *ret_field;
static int callback(struct tep_event *event, struct tep_record *record,
int cpu, void *data)
{
struct trace_seq seq;
trace_seq_init(&seq);
tep_print_event(event->tep, &seq, record, "%d-%s: ", TEP_PRINT_PID, TEP_PRINT_COMM);
if (event->id == open_event->id) {
trace_seq_puts(&seq, "open file='");
tep_print_field(&seq, record->data, file_field);
trace_seq_puts(&seq, "'\n");
} else if (event->id == openret_event->id) {
unsigned long long ret;
tep_read_number_field(ret_field, record->data, &ret);
trace_seq_printf(&seq, "open ret=%lld\n", ret);
} else {
goto out;
}
trace_seq_terminate(&seq);
trace_seq_do_printf(&seq);
out:
trace_seq_destroy(&seq);
return 0;
}
static pid_t run_exec(char **argv, char **env)
{
pid_t pid;
pid = fork();
if (pid)
return pid;
execve(argv[0], argv, env);
perror("exec");
exit(-1);
}
const char *mykprobe = "my_kprobes";
int main (int argc, char **argv, char **env)
{
struct tracefs_dynevent *kprobe, *kretprobe;
const char *sysnames[] = { mykprobe, NULL };
struct tracefs_instance *instance;
struct tep_handle *tep;
pid_t pid;
if (argc < 2) {
printf("usage: %s command\n", argv[0]);
exit(-1);
}
instance = tracefs_instance_create("exec_open");
if (!instance) {
perror("creating instance");
exit(-1);
}
tracefs_dynevent_destroy_all(TRACEFS_DYNEVENT_KPROBE | TRACEFS_DYNEVENT_KRETPROBE, true);
kprobe = tracefs_kprobe_alloc(mykprobe, "open", "do_sys_openat2",
"file=+0($arg2):ustring flags=+0($arg3):x64 mode=+8($arg3):x64\n");
kretprobe = tracefs_kretprobe_alloc(mykprobe, "openret", "do_sys_openat2", "ret=%ax", 0);
if (!kprobe || !kretprobe) {
perror("allocating dynamic events");
exit(-1);
}
if (tracefs_dynevent_create(kprobe) || tracefs_dynevent_create(kretprobe)){
char *err = tracefs_error_last(NULL);
perror("Failed to create kprobes:");
if (err && strlen(err))
fprintf(stderr, "%s\n", err);
exit(-1);
}
tep = tracefs_local_events_system(NULL, sysnames);
if (!tep) {
perror("reading events");
exit(-1);
}
open_event = tep_find_event_by_name(tep, mykprobe, "open");
file_field = tep_find_field(open_event, "file");
openret_event = tep_find_event_by_name(tep, mykprobe, "openret");
ret_field = tep_find_field(openret_event, "ret");
tracefs_event_enable(instance, mykprobe, NULL);
pid = run_exec(&argv[1], env);
/* Let the child start to run */
sched_yield();
do {
tracefs_load_cmdlines(NULL, tep);
tracefs_iterate_raw_events(tep, instance, NULL, 0, callback, NULL);
} while (waitpid(pid, NULL, WNOHANG) != pid);
/* Will disable the events */
tracefs_dynevent_destroy_all(TRACEFS_DYNEVENT_KPROBE | TRACEFS_DYNEVENT_KRETPROBE, true);
tracefs_dynevent_free(kprobe);
tracefs_dynevent_free(kretprobe);
tracefs_instance_destroy(instance);
tep_free(tep);
return 0;
}
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.
libtracefs(3), libtraceevent(3), trace-cmd(1)
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
Yordan Karadzhov <y.karadz@gmail.com[3]>
Report bugs to <linux-trace-devel@vger.kernel.org[4]>
libtracefs is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
Copyright (C) 2021 VMware, Inc. Free use of this software is
granted under the terms of the GNU Public License (GPL).
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
2. tz.stoyanov@gmail.com
mailto:tz.stoyanov@gmail.com
3. y.karadz@gmail.com
mailto:y.karadz@gmail.com
4. linux-trace-devel@vger.kernel.org
mailto:linux-trace-devel@vger.kernel.org
This page is part of the libtracefs (Linux kernel trace file
system library) project. Information about the project can be
found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report
for this manual page, see ⟨https://www.trace-cmd.org/⟩. This
page was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-05-17.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
libtracefs 1.7.0 12/22/2023 LIBTRACEFS(3)
Pages that refer to this page: tracefs_eprobe_alloc(3), tracefs_kprobe_alloc(3), tracefs_uprobe_alloc(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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