timerfd: add time64 syscall support, decouple 32-bit time_t

the changes here are semantically and structurally identical to those
made to timer_settime and timer_gettime for time64 support.

src/linux/timerfd.c

@@ -1,6 +1,9 @@
 #include <sys/timerfd.h>
+#include <errno.h>
 #include "syscall.h"
 
+#define IS32BIT(x) !((x)+0x80000000ULL>>32)
+
 int timerfd_create(int clockid, int flags)
 {
 	return syscall(SYS_timerfd_create, clockid, flags);
@@ -8,10 +11,49 @@ int timerfd_create(int clockid, int flags)
 
 int timerfd_settime(int fd, int flags, const struct itimerspec *new, struct itimerspec *old)
 {
+#ifdef SYS_timerfd_settime64
+	time_t is = new->it_interval.tv_sec, vs = new->it_value.tv_sec;
+	long ins = new->it_interval.tv_nsec, vns = new->it_value.tv_nsec;
+	int r = -ENOSYS;
+	if (SYS_timerfd_settime == SYS_timerfd_settime64
+	    || !IS32BIT(is) || !IS32BIT(vs) || (sizeof(time_t)>4 && old))
+		r = __syscall(SYS_timerfd_settime64, fd, flags,
+			((long long[]){is, ins, vs, vns}), old);
+	if (SYS_timerfd_settime == SYS_timerfd_settime64 || r!=-ENOSYS)
+		return __syscall_ret(r);
+	if (!IS32BIT(is) || !IS32BIT(vs))
+		return __syscall_ret(-ENOTSUP);
+	long old32[4];
+	r = __syscall(SYS_timerfd_settime, fd, flags,
+		((long[]){is, ins, vs, vns}), old32);
+	if (!r && old) {
+		old->it_interval.tv_sec = old32[0];
+		old->it_interval.tv_nsec = old32[1];
+		old->it_value.tv_sec = old32[2];
+		old->it_value.tv_nsec = old32[3];
+	}
+	return __syscall_ret(r);
+#endif
 	return syscall(SYS_timerfd_settime, fd, flags, new, old);
 }
 
 int timerfd_gettime(int fd, struct itimerspec *cur)
 {
+#ifdef SYS_timerfd_gettime64
+	int r = -ENOSYS;
+	if (sizeof(time_t) > 4)
+		r = __syscall(SYS_timerfd_gettime64, fd, cur);
+	if (SYS_timerfd_gettime == SYS_timerfd_gettime64 || r!=-ENOSYS)
+		return __syscall_ret(r);
+	long cur32[4];
+	r = __syscall(SYS_timerfd_gettime, fd, cur32);
+	if (!r) {
+		cur->it_interval.tv_sec = cur32[0];
+		cur->it_interval.tv_nsec = cur32[1];
+		cur->it_value.tv_sec = cur32[2];
+		cur->it_value.tv_nsec = cur32[3];
+	}
+	return __syscall_ret(r);
+#endif
 	return syscall(SYS_timerfd_gettime, fd, cur);
 }