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/*
* vdso_test.c: Sample code to test parse_vdso.c
* Copyright (c) 2014 Andy Lutomirski
* Subject to the GNU General Public License, version 2
*
* Compile with:
* gcc -std=gnu99 vdso_test.c parse_vdso.c
*
* Tested on x86, 32-bit and 64-bit. It may work on other architectures, too.
*/
#include <stdint.h>
#include <elf.h>
#include <stdio.h>
#include <sys/auxv.h>
#include <sys/time.h>
extern void *vdso_sym(const char *version, const char *name);
extern void vdso_init_from_sysinfo_ehdr(uintptr_t base);
extern void vdso_init_from_auxv(void *auxv);
/*
* ARM64's vDSO exports its gettimeofday() implementation with a different
* name and version from other architectures, so we need to handle it as
* a special case.
*/
#if defined(__aarch64__)
const char *version = "LINUX_2.6.39";
const char *name = "__kernel_gettimeofday";
#else
const char *version = "LINUX_2.6";
const char *name = "__vdso_gettimeofday";
#endif
int main(int argc, char **argv)
{
unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR);
if (!sysinfo_ehdr) {
printf("AT_SYSINFO_EHDR is not present!\n");
return 0;
}
vdso_init_from_sysinfo_ehdr(getauxval(AT_SYSINFO_EHDR));
/* Find gettimeofday. */
typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
gtod_t gtod = (gtod_t)vdso_sym(version, name);
if (!gtod) {
printf("Could not find %s\n", name);
return 1;
}
struct timeval tv;
long ret = gtod(&tv, 0);
if (ret == 0) {
printf("The time is %lld.%06lld\n",
(long long)tv.tv_sec, (long long)tv.tv_usec);
} else {
printf("%s failed\n", name);
}
return 0;
}
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