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authorAndy Lutomirski <luto@amacapital.net>2014-06-12 17:53:10 -0700
committerH. Peter Anvin <hpa@zytor.com>2014-06-12 19:01:24 -0700
commit4ebbefd6b93c34d6da0d950b1d2e0dcca2f1e6ef (patch)
tree5d94b4e1dd26d5c1a4ce2866486936333ca2e96f /Documentation/vDSO/vdso_test.c
parent6e8f21584a30ba6ce73cfef34f316d5bf3fadaab (diff)
x86/vdso/doc: Make vDSO examples more portable
This adds a new vdso_test.c that's written entirely in C. It also makes all of the vDSO examples work on 32-bit x86. Cc: Stefani Seibold <stefani@seibold.net> Signed-off-by: Andy Lutomirski <luto@amacapital.net> Link: http://lkml.kernel.org/r/62b701fc44b79f118ac2b2d64d19965fc5c291fb.1402620737.git.luto@amacapital.net Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'Documentation/vDSO/vdso_test.c')
-rw-r--r--Documentation/vDSO/vdso_test.c52
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/vDSO/vdso_test.c b/Documentation/vDSO/vdso_test.c
new file mode 100644
index 000000000000..8daeb7d7032c
--- /dev/null
+++ b/Documentation/vDSO/vdso_test.c
@@ -0,0 +1,52 @@
+/*
+ * 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;
+}