[glibc/azanella/y2038] linux: Add ppoll time64 optimization

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e118ad3ca4f48502ed686fb6ee35c0eccdb21cea

commit e118ad3ca4f48502ed686fb6ee35c0eccdb21cea
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Fri Jul 10 13:50:56 2020 -0300

    linux: Add ppoll time64 optimization
    
    It avoid issues the __NR_ppoll_time64 syscall if the kernel does not
    support it.
    
    Checked on x86_64-linux-gnu and i686-linux-gnu (on 5.4 and on 4.15
    kernel).

Diff:
---
 sysdeps/unix/sysv/linux/ppoll.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/ppoll.c b/sysdeps/unix/sysv/linux/ppoll.c
index 079d56b5eb..c4e5b0e733 100644
--- a/sysdeps/unix/sysv/linux/ppoll.c
+++ b/sysdeps/unix/sysv/linux/ppoll.c
@@ -22,7 +22,7 @@
 #include <sys/poll.h>
 #include <sysdep-cancel.h>
 #include <kernel-features.h>
-
+#include <time64-support.h>
 
 int
 __ppoll64 (struct pollfd *fds, nfds_t nfds, const struct __timespec64 *timeout,
@@ -40,13 +40,20 @@ __ppoll64 (struct pollfd *fds, nfds_t nfds, const struct __timespec64 *timeout,
 #ifndef __NR_ppoll_time64
 # define __NR_ppoll_time64 __NR_ppoll
 #endif
-  int ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
+  int ret;
+
+  if (supports_time64 ())
+    {
+      ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
 			    __NSIG_BYTES);
 
-#ifdef __ASSUME_TIME64_SYSCALLS
-  if (ret >= 0 || errno != ENOSYS)
-    return ret;
+      if (ret == 0 || errno != ENOSYS)
+	return ret;
+
+      mark_time64_unsupported ();
+    }
 
+#ifndef __ASSUME_TIME64_SYSCALLS
   struct timespec ts32;
   if (timeout)
     {