pselect, ppoll: add time64 syscall support, decouple 32-bit time_t

time64 syscall is used only if it's the only one defined for the arch,
or if the requested timeout length does not fit in 32 bits. on current
32-bit archs where time_t is a 32-bit type, this makes it statically
unreachable.

on 64-bit archs, there are only superficial changes to the code after
preprocessing. both before and after these changes, these functions
copied their timeout arguments to avoid letting the kernel clobber the
caller's copies. now, the copying also serves to change the type from
userspace timespec to a pair of longs, which makes a difference only
in the 32-bit fallback case, not on 64-bit.

src/linux/ppoll.c

@@ -1,10 +1,26 @@
 #define _GNU_SOURCE
 #include <poll.h>
 #include <signal.h>
+#include <errno.h>
 #include "syscall.h"
 
+#define IS32BIT(x) !((x)+0x80000000ULL>>32)
+#define CLAMP(x) (int)(IS32BIT(x) ? (x) : 0x7fffffffU+((0ULL+(x))>>63))
+
 int ppoll(struct pollfd *fds, nfds_t n, const struct timespec *to, const sigset_t *mask)
 {
+	time_t s = to ? to->tv_sec : 0;
+	long ns = to ? to->tv_nsec : 0;
+#ifdef SYS_ppoll_time64
+	int r = -ENOSYS;
+	if (SYS_ppoll == SYS_ppoll_time64 || !IS32BIT(s))
+		r = __syscall_cp(SYS_ppoll_time64, fds, n,
+			to ? ((long long[]){s, ns}) : 0,
+			mask, _NSIG/8);
+	if (SYS_ppoll == SYS_ppoll_time64 || r != -ENOSYS)
+		return __syscall_ret(r);
+	s = CLAMP(s);
+#endif
 	return syscall_cp(SYS_ppoll, fds, n,
-		to ? (struct timespec []){*to} : 0, mask, _NSIG/8);
+		to ? ((long[]){s, ns}) : 0, mask, _NSIG/8);
 }

src/select/pselect.c

@@ -1,12 +1,26 @@
 #include <sys/select.h>
 #include <signal.h>
 #include <stdint.h>
+#include <errno.h>
 #include "syscall.h"
 
+#define IS32BIT(x) !((x)+0x80000000ULL>>32)
+#define CLAMP(x) (int)(IS32BIT(x) ? (x) : 0x7fffffffU+((0ULL+(x))>>63))
+
 int pselect(int n, fd_set *restrict rfds, fd_set *restrict wfds, fd_set *restrict efds, const struct timespec *restrict ts, const sigset_t *restrict mask)
 {
 	syscall_arg_t data[2] = { (uintptr_t)mask, _NSIG/8 };
-	struct timespec ts_tmp;
-	if (ts) ts_tmp = *ts;
-	return syscall_cp(SYS_pselect6, n, rfds, wfds, efds, ts ? &ts_tmp : 0, data);
+	time_t s = ts ? ts->tv_sec : 0;
+	long ns = ts ? ts->tv_nsec : 0;
+#ifdef SYS_pselect6_time64
+	int r = -ENOSYS;
+	if (SYS_pselect6 == SYS_pselect6_time64 || !IS32BIT(s))
+		r = __syscall_cp(SYS_pselect6_time64, n, rfds, wfds, efds,
+			ts ? ((long long[]){s, ns}) : 0, data);
+	if (SYS_pselect6 == SYS_pselect6_time64 || r!=-ENOSYS)
+		return __syscall_ret(r);
+	s = CLAMP(s);
+#endif
+	return syscall_cp(SYS_pselect6, n, rfds, wfds, efds,
+		ts ? ((long[]){s, ns}) : 0, data);
 }