x86/vdso/doc: Make vDSO examples more portable

[linux-2.6-block.git] / Documentation / vDSO / vdso_test.c

diff --git a/Documentation/vDSO/vdso_test.c b/Documentation/vDSO/vdso_test.c
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+++ b/Documentation/vDSO/vdso_test.c
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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);
+
+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("LINUX_2.6", "__vdso_gettimeofday");
+
+       if (!gtod) {
+               printf("Could not find __vdso_gettimeofday\n");
+               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("__vdso_gettimeofday failed\n");
+       }
+
+       return 0;
+}