libtracefs(3) ============= NAME ---- tracefs_uprobe_alloc,tracefs_uretprobe_alloc - Allocate new user (return) probe SYNOPSIS -------- [verse] -- *#include * 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 #include #include #include 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* *Tzvetomir Stoyanov* -- REPORTING BUGS -------------- Report bugs to 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).