dtrace-example.c

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at

 * http://www.apache.org/licenses/LICENSE-2.0

 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Copyright (c) 2015 by Delphix. All rights reserved.
 */

#include <dtrace.h>
#include <stdlib.h>
#include <string.h>

static const char *g_script =
"BEGIN\n"
"{\n"
"	trace(\"Hello, DTrace API!\");\n"
"	exit(0);\n"
"}\n";

static dtrace_hdl_t *g_dtp;

/*PRINTFLIKE1*/
static void
die(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	(void) vfprintf(stderr, fmt, ap);
	va_end(ap);

	exit(1);
}

/*PRINTFLIKE1*/
static void
ddie(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	(void) vfprintf(stderr, fmt, ap);
	if (fmt[strlen(fmt) - 1] != '\n') {
		(void) fprintf(stderr, ": %s\n",
		    dtrace_errmsg(g_dtp, dtrace_errno(g_dtp)));
	}
	va_end(ap);

	exit(1);
}

static int g_exit;

static int
chewrec(const dtrace_probedata_t *data, const dtrace_recdesc_t *rec, void *arg)
{
	if (rec == NULL)
		return (DTRACE_CONSUME_NEXT);

	switch (rec->dtrd_action) {
	case DTRACEACT_DIFEXPR:
		(void) printf("%s\n", data->dtpda_data);
		return (DTRACE_CONSUME_NEXT);
	case DTRACEACT_EXIT:
		g_exit = 1;
		return (DTRACE_CONSUME_NEXT);
	default:
		(void) printf("%d\n", rec->dtrd_action);
		return (DTRACE_CONSUME_NEXT);
	}

	return (DTRACE_CONSUME_THIS);
}

int
main(int argc, char **argv)
{
	int err;

	if ((g_dtp = dtrace_open(DTRACE_VERSION, 0, &err)) == NULL) {
		die("failed to initialize: %s\n",
		    dtrace_errmsg(NULL, err));
	}

	if (dtrace_setopt(g_dtp, "bufsize", "1k") == -1)
		ddie("failed to set 'bufsize'");

	dtrace_prog_t *prog;
	dtrace_proginfo_t info;

	if ((prog = dtrace_program_strcompile(g_dtp, g_script,
	    DTRACE_PROBESPEC_NAME, 0, 0, NULL)) == NULL) {
		die("failed to compile\n");
	}

	if (dtrace_program_exec(g_dtp, prog, &info) == -1)
		die("failed to enable probes\n");

	if (dtrace_go(g_dtp) != 0)
		ddie("failed to start");

	int done = 0;

	do {
		if (!g_exit && !done)
			dtrace_sleep(g_dtp);

		if (g_exit || done) {
			done = 1;
			if (dtrace_stop(g_dtp) == -1)
				ddie("failed to stop");
		}

		switch (dtrace_work(g_dtp, stdout, NULL, chewrec, NULL)) {
		case DTRACE_WORKSTATUS_DONE:
			done = 1;
			break;
		case DTRACE_WORKSTATUS_OKAY:
			break;
		default:
			die("processing aborted");
		}
	} while (!done);

	dtrace_close(g_dtp);

	return (0);
}