Man page - tracefs_uprobe_alloc(3)

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Manual

LIBTRACEFS

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
EXAMPLE
FILES
SEE ALSO
AUTHOR
REPORTING BUGS
LICENSE
RESOURCES
COPYING
NOTES

NAME

tracefs_uprobe_alloc, tracefs_uretprobe_alloc - Allocate new user (return) probe

SYNOPSIS

#include <tracefs.h>

struct tracefs_dynevent *
tracefs_uprobe_alloc (const char * system , const char * event ,
const char * file , unsigned long long offset , const char * fetchargs )
struct tracefs_dynevent *
tracefs_uretprobe_alloc (const char * system , const char * event ,
const char * file , unsigned long long offset , const char * 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

#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

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) 2022 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