1 files changed, 39 insertions, 22 deletions

diff --git a/src/time/clock_gettime.c b/src/time/clock_gettime.c
index 1572de0e..24128804 100644
--- a/src/time/clock_gettime.c
+++ b/src/time/clock_gettime.c
@@ -5,37 +5,54 @@
 #include "libc.h"
 #include "atomic.h"
 
-static int sc_clock_gettime(clockid_t clk, struct timespec *ts)
+#ifdef VDSO_CGT_SYM
+
+void *__vdsosym(const char *, const char *);
+
+static void *volatile vdso_func;
+
+static int cgt_init(clockid_t clk, struct timespec *ts)
 {
-	int r = __syscall(SYS_clock_gettime, clk, ts);
-	if (!r) return r;
-	if (r == -ENOSYS) {
-		if (clk == CLOCK_REALTIME) {
-			__syscall(SYS_gettimeofday, ts, 0);
-			ts->tv_nsec = (int)ts->tv_nsec * 1000;
-			return 0;
-		}
-		r = -EINVAL;
-	}
-	errno = -r;
-	return -1;
+	void *p = __vdsosym(VDSO_CGT_VER, VDSO_CGT_SYM);
+	int (*f)(clockid_t, struct timespec *) =
+		(int (*)(clockid_t, struct timespec *))p;
+	a_cas_p(&vdso_func, (void *)cgt_init, p);
+	return f ? f(clk, ts) : -ENOSYS;
 }
 
-void *__vdsosym(const char *, const char *);
+static void *volatile vdso_func = (void *)cgt_init;
+
+#endif
 
 int __clock_gettime(clockid_t clk, struct timespec *ts)
 {
+	int r;
+
 #ifdef VDSO_CGT_SYM
-	static int (*volatile cgt)(clockid_t, struct timespec *);
-	if (!cgt) {
-		void *f = __vdsosym(VDSO_CGT_VER, VDSO_CGT_SYM);
-		if (!f) f = (void *)sc_clock_gettime;
-		a_cas_p(&cgt, 0, f);
+	int (*f)(clockid_t, struct timespec *) =
+		(int (*)(clockid_t, struct timespec *))vdso_func;
+	if (f) {
+		r = f(clk, ts);
+		if (!r) return r;
+		if (r == -EINVAL) return __syscall_ret(r);
+		/* Fall through on errors other than EINVAL. Some buggy
+		 * vdso implementations return ENOSYS for clocks they
+		 * can't handle, rather than making the syscall. This
+		 * also handles the case where cgt_init fails to find
+		 * a vdso function to use. */
 	}
-	return cgt(clk, ts);
-#else
-	return sc_clock_gettime(clk, ts);
 #endif
+
+	r = __syscall(SYS_clock_gettime, clk, ts);
+	if (r == -ENOSYS) {
+		if (clk == CLOCK_REALTIME) {
+			__syscall(SYS_gettimeofday, ts, 0);
+			ts->tv_nsec = (int)ts->tv_nsec * 1000;
+			return 0;
+		}
+		r = -EINVAL;
+	}
+	return __syscall_ret(r);
 }
 
 weak_alias(__clock_gettime, clock_gettime);