1#include <stdbool.h>
 2#include <stdio.h>
 3#include <unistd.h>
 4#include <errno.h>
 5#include <sys/types.h>
 6#include <sys/stat.h>
 7#include <fcntl.h>
 8#include <stdlib.h>
 9#include <signal.h>
10
11#define _SDT_HAS_SEMAPHORES 1
12#include "sdt.h"
13
14#define SEC(name) __attribute__((section(name), used))
15
16#define BUF_SIZE 256
17
18/* defined in urandom_read_aux.c */
19void urand_read_without_sema(int iter_num, int iter_cnt, int read_sz);
20/* these are coming from urandom_read_lib{1,2}.c */
21void urandlib_read_with_sema(int iter_num, int iter_cnt, int read_sz);
22void urandlib_read_without_sema(int iter_num, int iter_cnt, int read_sz);
23
24unsigned short urand_read_with_sema_semaphore SEC(".probes");
25
26static __attribute__((noinline))
27void urandom_read(int fd, int count)
28{
29	char buf[BUF_SIZE];
30	int i;
31
32	for (i = 0; i < count; ++i) {
33		read(fd, buf, BUF_SIZE);
34
35		/* trigger USDTs defined in executable itself */
36		urand_read_without_sema(i, count, BUF_SIZE);
37		STAP_PROBE3(urand, read_with_sema, i, count, BUF_SIZE);
38
39		/* trigger USDTs defined in shared lib */
40		urandlib_read_without_sema(i, count, BUF_SIZE);
41		urandlib_read_with_sema(i, count, BUF_SIZE);
42	}
43}
44
45static volatile bool parent_ready;
46
47static void handle_sigpipe(int sig)
48{
49	parent_ready = true;
50}
51
52int main(int argc, char *argv[])
53{
54	int fd = open("/dev/urandom", O_RDONLY);
55	int count = 4;
56	bool report_pid = false;
57
58	if (fd < 0)
59		return 1;
60
61	if (argc >= 2)
62		count = atoi(argv[1]);
63	if (argc >= 3) {
64		report_pid = true;
65		/* install SIGPIPE handler to catch when parent closes their
66		 * end of the pipe (on the other side of our stdout)
67		 */
68		signal(SIGPIPE, handle_sigpipe);
69	}
70
71	/* report PID and wait for parent process to send us "signal" by
72	 * closing stdout
73	 */
74	if (report_pid) {
75		while (!parent_ready) {
76			fprintf(stdout, "%d\n", getpid());
77			fflush(stdout);
78		}
79		/* at this point stdout is closed, parent process knows our
80		 * PID and is ready to trace us
81		 */
82	}
83
84	urandom_read(fd, count);
85
86	close(fd);
87	return 0;
88}