'\" t
.\"     Title: libtracefs
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 07/25/2024
.\"    Manual: libtracefs Manual
.\"    Source: libtracefs 1.8.1
.\"  Language: English
.\"
.TH "LIBTRACEFS" "3" "07/25/2024" "libtracefs 1\&.8\&.1" "libtracefs Manual"
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.\" * Define some portability stuff
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.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
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.\" * set default formatting
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.nh
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.\" * MAIN CONTENT STARTS HERE *
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.SH "NAME"
tracefs_uprobe_alloc, tracefs_uretprobe_alloc \- Allocate new user (return) probe
.SH "SYNOPSIS"
.sp
.nf
\fB#include <tracefs\&.h>\fR

struct tracefs_dynevent *
\fBtracefs_uprobe_alloc\fR(const char *\fIsystem\fR, const char *\fIevent\fR,
                     const char *\fIfile\fR, unsigned long long \fIoffset\fR, const char *\fIfetchargs\fR)
struct tracefs_dynevent *
\fBtracefs_uretprobe_alloc\fR(const char *\fIsystem\fR, const char *\fIevent\fR,
                     const char *\fIfile\fR, unsigned long long \fIoffset\fR, const char *\fIfetchargs\fR)
.fi
.SH "DESCRIPTION"
.sp
\fBtracefs_uprobe_alloc\fR() allocates a new uprobe context\&. It will be in the \fIsystem\fR group (or uprobes if \fIsystem\fR is NULL) and with \fIevent\fR name\&. The uprobe will be attached to \fIoffset\fR within the \fIfile\fR\&. The list of arguments, described in \fIfetchargs\fR, will be fetched with the uprobe\&. The returned pointer to the user probe context must be freed with \fBtracefs_dynevent_free\fR()\&. The ubrobe is not configured in the system, tracefs_dynevent_* set of APIs can be used to configure it\&.
.sp
The \fBtracefs_uretprobe_alloc\fR() behaves the same as \fBtracefs_uprobe_alloc\fR(), the only difference is that it allocates context to user return probe (uretprobe)\&.
.SH "RETURN VALUE"
.sp
The \fBtracefs_uprobe_alloc\fR() and \fBtracefs_uretprobe_alloc\fR() APIs return a pointer to an allocated tracefs_dynevent structure, describing the user probe\&. This pointer must be freed with \fBtracefs_dynevent_free\fR(3)\&. Note, this only allocates a descriptor representing the uprobe\&. It does not modify the running system\&. On error NULL is returned\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#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, "\*(Aq\en");

        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\en", 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;
}
.fi
.if n \{\
.RE
.\}
.SH "FILES"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBtracefs\&.h\fR
        Header file to include in order to have access to the library APIs\&.
\fB\-ltracefs\fR
        Linker switch to add when building a program that uses the library\&.
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBlibtracefs\fR(3), \fBlibtraceevent\fR(3), \fBtrace\-cmd\fR(1)
.SH "AUTHOR"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBSteven Rostedt\fR <\m[blue]\fBrostedt@goodmis\&.org\fR\m[]\&\s-2\u[1]\d\s+2>
\fBTzvetomir Stoyanov\fR <\m[blue]\fBtz\&.stoyanov@gmail\&.com\fR\m[]\&\s-2\u[2]\d\s+2>
.fi
.if n \{\
.RE
.\}
.SH "REPORTING BUGS"
.sp
Report bugs to <\m[blue]\fBlinux\-trace\-devel@vger\&.kernel\&.org\fR\m[]\&\s-2\u[3]\d\s+2>
.SH "LICENSE"
.sp
libtracefs is Free Software licensed under the GNU LGPL 2\&.1
.SH "RESOURCES"
.sp
\m[blue]\fBhttps://git\&.kernel\&.org/pub/scm/libs/libtrace/libtracefs\&.git/\fR\m[]
.SH "COPYING"
.sp
Copyright (C) 2022 VMware, Inc\&. Free use of this software is granted under the terms of the GNU Public License (GPL)\&.
.SH "NOTES"
.IP " 1." 4
rostedt@goodmis.org
.RS 4
\%mailto:rostedt@goodmis.org
.RE
.IP " 2." 4
tz.stoyanov@gmail.com
.RS 4
\%mailto:tz.stoyanov@gmail.com
.RE
.IP " 3." 4
linux-trace-devel@vger.kernel.org
.RS 4
\%mailto:linux-trace-devel@vger.kernel.org
.RE