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Diffstat (limited to 'Documentation/libtracefs-uprobes.txt')
| -rw-r--r-- | Documentation/libtracefs-uprobes.txt | 189 |
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diff --git a/Documentation/libtracefs-uprobes.txt b/Documentation/libtracefs-uprobes.txt new file mode 100644 index 0000000..1ca80da --- /dev/null +++ b/Documentation/libtracefs-uprobes.txt @@ -0,0 +1,189 @@ +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). |