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 */
19 void urand_read_without_sema(int iter_num, int iter_cnt, int read_sz);
20 /* these are coming from urandom_read_lib{1,2}.c */
21 void urandlib_read_with_sema(int iter_num, int iter_cnt, int read_sz);
22 void urandlib_read_without_sema(int iter_num, int iter_cnt, int read_sz);
23
24 unsigned short urand_read_with_sema_semaphore SEC(".probes");
25
26 static __attribute__((noinline))
urandom_read(int fd,int count)27 void 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
45 static volatile bool parent_ready;
46
handle_sigpipe(int sig)47 static void handle_sigpipe(int sig)
48 {
49 parent_ready = true;
50 }
51
main(int argc,char * argv[])52 int 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 }
89