190 lines
4.6 KiB
Plaintext
190 lines
4.6 KiB
Plaintext
libtracefs(3)
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=============
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NAME
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----
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tracefs_uprobe_alloc,tracefs_uretprobe_alloc - Allocate new user (return) probe
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SYNOPSIS
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--------
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[verse]
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--
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*#include <tracefs.h>*
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struct tracefs_dynevent pass:[*]
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*tracefs_uprobe_alloc*(const char pass:[*]_system_, const char pass:[*]_event_,
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const char pass:[*]_file_, unsigned long long _offset_, const char pass:[*]_fetchargs_)
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struct tracefs_dynevent pass:[*]
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*tracefs_uretprobe_alloc*(const char pass:[*]_system_, const char pass:[*]_event_,
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const char pass:[*]_file_, unsigned long long _offset_, const char pass:[*]_fetchargs_)
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--
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DESCRIPTION
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-----------
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*tracefs_uprobe_alloc*() allocates a new uprobe context. It will be in the _system_ group
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(or uprobes if _system_ is NULL) and with _event_ name. The uprobe will be attached to _offset_
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within the _file_. The list of arguments, described in _fetchargs_, will be fetched with the uprobe.
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The returned pointer to the user probe context must be freed with *tracefs_dynevent_free*().
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The ubrobe is not configured in the system, tracefs_dynevent_* set of APIs can be used to configure
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it.
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The *tracefs_uretprobe_alloc*() behaves the same as *tracefs_uprobe_alloc*(), the only difference is
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that it allocates context to user return probe (uretprobe).
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RETURN VALUE
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------------
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The *tracefs_uprobe_alloc*() and *tracefs_uretprobe_alloc*() APIs return a pointer to an allocated
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tracefs_dynevent structure, describing the user probe. This pointer must be freed with
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*tracefs_dynevent_free*(3). Note, this only allocates a descriptor representing the uprobe. It does
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not modify the running system. On error NULL is returned.
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EXAMPLE
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-------
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[source,c]
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--
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/wait.h>
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#include <tracefs.h>
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static int callback(struct tep_event *event, struct tep_record *record,
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int cpu, void *data)
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{
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struct trace_seq seq;
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trace_seq_init(&seq);
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tep_print_event(event->tep, &seq, record, "%d-%s: %s",
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TEP_PRINT_PID, TEP_PRINT_COMM, TEP_PRINT_NAME);
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trace_seq_puts(&seq, "'\n");
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trace_seq_terminate(&seq);
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trace_seq_do_printf(&seq);
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trace_seq_destroy(&seq);
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return 0;
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}
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static pid_t run_exec(char **argv, char **env)
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{
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pid_t pid;
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pid = fork();
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if (pid)
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return pid;
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execve(argv[0], argv, env);
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perror("exec");
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exit(-1);
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}
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const char *myprobe = "my_urobes";
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int main (int argc, char **argv, char **env)
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{
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struct tracefs_dynevent *uprobe, *uretprobe;
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struct tep_handle *tep;
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struct tracefs_instance *instance;
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const char *sysnames[] = { myprobe, NULL };
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long addr;
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pid_t pid;
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if (argc < 3) {
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printf("usage: %s file_offset command\n", argv[0]);
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exit(-1);
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}
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addr = strtol(argv[1], NULL, 0);
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instance = tracefs_instance_create("exec_open");
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if (!instance) {
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perror("creating instance");
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exit(-1);
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}
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tracefs_dynevent_destroy_all(TRACEFS_DYNEVENT_UPROBE|TRACEFS_DYNEVENT_URETPROBE, true);
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uprobe = tracefs_uprobe_alloc(myprobe, "user_probe", argv[2], addr, NULL);
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uretprobe = tracefs_uretprobe_alloc(myprobe, "user_retprobe", argv[2], addr, NULL);
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if (!uprobe || !uretprobe) {
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perror("allocating user probes");
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exit(-1);
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}
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if (tracefs_dynevent_create(uprobe) ||
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tracefs_dynevent_create(uretprobe)) {
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perror("creating user probes");
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exit(-1);
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}
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tep = tracefs_local_events_system(NULL, sysnames);
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if (!tep) {
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perror("reading events");
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exit(-1);
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}
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tracefs_event_enable(instance, myprobe, "user_probe");
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tracefs_event_enable(instance, myprobe, "user_retprobe");
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pid = run_exec(&argv[2], env);
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/* Let the child start to run */
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sched_yield();
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do {
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tracefs_load_cmdlines(NULL, tep);
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tracefs_iterate_raw_events(tep, instance, NULL, 0, callback, NULL);
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} while (waitpid(pid, NULL, WNOHANG) != pid);
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/* disable and destroy the events */
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tracefs_dynevent_destroy(uprobe, true);
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tracefs_dynevent_destroy(uretprobe, true);
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tracefs_dynevent_free(uprobe);
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tracefs_dynevent_free(uretprobe);
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tracefs_instance_destroy(instance);
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return 0;
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}
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--
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FILES
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-----
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[verse]
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--
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*tracefs.h*
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Header file to include in order to have access to the library APIs.
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*-ltracefs*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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*libtracefs*(3),
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*libtraceevent*(3),
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*trace-cmd*(1)
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtracefs is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
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COPYING
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-------
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Copyright \(C) 2022 VMware, Inc. Free use of this software is granted under
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the terms of the GNU Public License (GPL).
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