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|
libtracefs(3)
=============
NAME
----
tracefs_uprobe_alloc,tracefs_uretprobe_alloc - Allocate new user (return) probe
SYNOPSIS
--------
[verse]
--
*#include <tracefs.h>*
struct tracefs_dynevent pass:[*]
*tracefs_uprobe_alloc*(const char pass:[*]_system_, const char pass:[*]_event_,
const char pass:[*]_file_, unsigned long long _offset_, const char pass:[*]_fetchargs_)
struct tracefs_dynevent pass:[*]
*tracefs_uretprobe_alloc*(const char pass:[*]_system_, const char pass:[*]_event_,
const char pass:[*]_file_, unsigned long long _offset_, const char pass:[*]_fetchargs_)
--
DESCRIPTION
-----------
*tracefs_uprobe_alloc*() allocates a new uprobe context. It will be in the _system_ group
(or uprobes if _system_ is NULL) and with _event_ name. The uprobe will be attached to _offset_
within the _file_. The list of arguments, described in _fetchargs_, will be fetched with the uprobe.
The returned pointer to the user probe context must be freed with *tracefs_dynevent_free*().
The ubrobe is not configured in the system, tracefs_dynevent_* set of APIs can be used to configure
it.
The *tracefs_uretprobe_alloc*() behaves the same as *tracefs_uprobe_alloc*(), the only difference is
that it allocates context to user return probe (uretprobe).
RETURN VALUE
------------
The *tracefs_uprobe_alloc*() and *tracefs_uretprobe_alloc*() APIs return a pointer to an allocated
tracefs_dynevent structure, describing the user probe. This pointer must be freed with
*tracefs_dynevent_free*(3). Note, this only allocates a descriptor representing the uprobe. It does
not modify the running system. On error NULL is returned.
EXAMPLE
-------
[source,c]
--
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <tracefs.h>
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: %s",
TEP_PRINT_PID, TEP_PRINT_COMM, TEP_PRINT_NAME);
trace_seq_puts(&seq, "'\n");
trace_seq_terminate(&seq);
trace_seq_do_printf(&seq);
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 *myprobe = "my_urobes";
int main (int argc, char **argv, char **env)
{
struct tracefs_dynevent *uprobe, *uretprobe;
struct tep_handle *tep;
struct tracefs_instance *instance;
const char *sysnames[] = { myprobe, NULL };
long addr;
pid_t pid;
if (argc < 3) {
printf("usage: %s file_offset command\n", argv[0]);
exit(-1);
}
addr = strtol(argv[1], NULL, 0);
instance = tracefs_instance_create("exec_open");
if (!instance) {
perror("creating instance");
exit(-1);
}
tracefs_dynevent_destroy_all(TRACEFS_DYNEVENT_UPROBE|TRACEFS_DYNEVENT_URETPROBE, true);
uprobe = tracefs_uprobe_alloc(myprobe, "user_probe", argv[2], addr, NULL);
uretprobe = tracefs_uretprobe_alloc(myprobe, "user_retprobe", argv[2], addr, NULL);
if (!uprobe || !uretprobe) {
perror("allocating user probes");
exit(-1);
}
if (tracefs_dynevent_create(uprobe) ||
tracefs_dynevent_create(uretprobe)) {
perror("creating user probes");
exit(-1);
}
tep = tracefs_local_events_system(NULL, sysnames);
if (!tep) {
perror("reading events");
exit(-1);
}
tracefs_event_enable(instance, myprobe, "user_probe");
tracefs_event_enable(instance, myprobe, "user_retprobe");
pid = run_exec(&argv[2], 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);
/* disable and destroy the events */
tracefs_dynevent_destroy(uprobe, true);
tracefs_dynevent_destroy(uretprobe, true);
tracefs_dynevent_free(uprobe);
tracefs_dynevent_free(uretprobe);
tracefs_instance_destroy(instance);
return 0;
}
--
FILES
-----
[verse]
--
*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
------
[verse]
--
*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) 2022 VMware, Inc. Free use of this software is granted under
the terms of the GNU Public License (GPL).
|
