1 /*
2 * vdso_test.c: Sample code to test parse_vdso.c
3 * Copyright (c) 2014 Andy Lutomirski
4 * Subject to the GNU General Public License, version 2
5 *
6 * Compile with:
7 * gcc -std=gnu99 vdso_test.c parse_vdso.c
8 *
9 * Tested on x86, 32-bit and 64-bit. It may work on other architectures, too.
10 */
11
12 #include <stdint.h>
13 #include <elf.h>
14 #include <stdio.h>
15 #include <sys/auxv.h>
16 #include <sys/time.h>
17
18 extern void *vdso_sym(const char *version, const char *name);
19 extern void vdso_init_from_sysinfo_ehdr(uintptr_t base);
20 extern void vdso_init_from_auxv(void *auxv);
21
main(int argc,char ** argv)22 int main(int argc, char **argv)
23 {
24 unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR);
25 if (!sysinfo_ehdr) {
26 printf("AT_SYSINFO_EHDR is not present!\n");
27 return 0;
28 }
29
30 vdso_init_from_sysinfo_ehdr(getauxval(AT_SYSINFO_EHDR));
31
32 /* Find gettimeofday. */
33 typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
34 gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday");
35
36 if (!gtod) {
37 printf("Could not find __vdso_gettimeofday\n");
38 return 1;
39 }
40
41 struct timeval tv;
42 long ret = gtod(&tv, 0);
43
44 if (ret == 0) {
45 printf("The time is %lld.%06lld\n",
46 (long long)tv.tv_sec, (long long)tv.tv_usec);
47 } else {
48 printf("__vdso_gettimeofday failed\n");
49 }
50
51 return 0;
52 }
53