From e3eb49321c85e43fcc6842f3f57ee097b32555e4 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 23 Jul 2011 23:45:33 -0400
Subject: [PATCH] some preliminaries for vdso clock support

these changes also make it so clock_gettime(CLOCK_REALTIME, &ts) works
even on pre-2.6 kernels, emulated via the gettimeofday syscall. there
is no cost for the fallback check, as it falls under the error case
that already must be checked for storing the error code in errno, but
which would normally be hidden inside __syscall_ret.
---
 src/time/clock_gettime.c | 25 +++++++++++++++++++++++--
 src/time/gettimeofday.c  |  7 ++++++-
 src/time/time.c          | 10 ++++++----
 3 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/src/time/clock_gettime.c b/src/time/clock_gettime.c
index c345c46e..c27c9e9e 100644
--- a/src/time/clock_gettime.c
+++ b/src/time/clock_gettime.c
@@ -1,7 +1,28 @@
 #include <time.h>
+#include <errno.h>
+#include <stdint.h>
 #include "syscall.h"
+#include "libc.h"
 
-int clock_gettime(clockid_t clk, struct timespec *ts)
+int __vdso_clock_gettime(clockid_t, struct timespec *) __attribute__((weak));
+static int (*cgt)(clockid_t, struct timespec *) = __vdso_clock_gettime;
+
+int __clock_gettime(clockid_t clk, struct timespec *ts)
 {
-	return syscall(SYS_clock_gettime, clk, ts);
+	int r;
+	if (cgt) return cgt(clk, ts);
+	r = __syscall(SYS_clock_gettime, clk, ts);
+	if (!r) return r;
+	if (r == -ENOSYS) {
+		if (clk == CLOCK_REALTIME) {
+			__syscall(SYS_gettimeofday, clk, ts, 0);
+			ts->tv_nsec = (int)ts->tv_nsec * 1000;
+			return 0;
+		}
+		r = -EINVAL;
+	}
+	errno = -r;
+	return -1;
 }
+
+weak_alias(__clock_gettime, clock_gettime);
diff --git a/src/time/gettimeofday.c b/src/time/gettimeofday.c
index 2436e490..09afb70b 100644
--- a/src/time/gettimeofday.c
+++ b/src/time/gettimeofday.c
@@ -1,8 +1,13 @@
+#include <time.h>
 #include <sys/time.h>
 #include "syscall.h"
 
 int gettimeofday(struct timeval *tv, void *tz)
 {
-	__syscall(SYS_gettimeofday, tv, 0);
+	struct timespec ts;
+	if (!tv) return 0;
+	clock_gettime(CLOCK_REALTIME, &ts);
+	tv->tv_sec = ts.tv_sec;
+	tv->tv_usec = (int)ts.tv_nsec / 1000;
 	return 0;
 }
diff --git a/src/time/time.c b/src/time/time.c
index 05e075b9..22754850 100644
--- a/src/time/time.c
+++ b/src/time/time.c
@@ -2,10 +2,12 @@
 #include <sys/time.h>
 #include "syscall.h"
 
+int __clock_gettime(clockid_t, struct timespec *);
+
 time_t time(time_t *t)
 {
-	struct timeval tv;
-	__syscall(SYS_gettimeofday, &tv, 0);
-	if (t) *t = tv.tv_sec;
-	return tv.tv_sec;
+	struct timespec ts;
+	__clock_gettime(CLOCK_REALTIME, &ts);
+	if (t) *t = ts.tv_sec;
+	return ts.tv_sec;
 }
-- 
2.25.1