tools/testing/selftests/vDSO/vdso_test.c

   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
  22 /*
  23  * ARM64's vDSO exports its gettimeofday() implementation with a different
  24  * name and version from other architectures, so we need to handle it as
  25  * a special case.
  26  */
  27 #if defined(__aarch64__)
  28 const char *version = "LINUX_2.6.39";
  29 const char *name = "__kernel_gettimeofday";
  30 #else
  31 const char *version = "LINUX_2.6";
  32 const char *name = "__vdso_gettimeofday";
  33 #endif
  34
  35 int main(int argc, char **argv)
  36 {
  37         unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR);
  38         if (!sysinfo_ehdr) {
  39                 printf("AT_SYSINFO_EHDR is not present!\n");
  40                 return 0;
  41         }
  42
  43         vdso_init_from_sysinfo_ehdr(getauxval(AT_SYSINFO_EHDR));
  44
  45         /* Find gettimeofday. */
  46         typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
  47         gtod_t gtod = (gtod_t)vdso_sym(version, name);
  48
  49         if (!gtod) {
  50                 printf("Could not find %s\n", name);
  51                 return 1;
  52         }
  53
  54         struct timeval tv;
  55         long ret = gtod(&tv, 0);
  56
  57         if (ret == 0) {
  58                 printf("The time is %lld.%06lld\n",
  59                        (long long)tv.tv_sec, (long long)tv.tv_usec);
  60         } else {
  61                 printf("%s failed\n", name);
  62         }
  63
  64         return 0;
  65 }