[glibc] linux: Only use 64-bit syscall if required for ppoll

[glibc] linux: Only use 64-bit syscall if required for ppoll

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=ecf2661281c71a9752c7238ab93bc12b16cfff23

commit ecf2661281c71a9752c7238ab93bc12b16cfff23
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Tue Jun 15 15:41:00 2021 -0300

    linux: Only use 64-bit syscall if required for ppoll
    
    For !__ASSUME_TIME64_SYSCALLS there is no need to issue a 64-bit syscall
    if the provided timeout fits in a 32-bit one.  The 64-bit usage should
    be rare since the timeout is a relative one.  This also avoids the need
    to use supports_time64() (which breaks the usage case of live migration
    like CRIU or similar).
    
    Checked on i686-linux-gnu on a 4.15 kernel and on a 5.11 kernel
    (with and without --enable-kernel=5.1) and on x86_64-linux-gnu.
    
    Reviewed-by: Lukasz Majewski <lukma@denx.de>

Diff:
---
 sysdeps/unix/sysv/linux/Makefile    |  9 +++++++++
 sysdeps/unix/sysv/linux/ppoll.c     | 40 ++++++++++++++-----------------------
 sysdeps/unix/sysv/linux/tst-ppoll.c | 15 ++++++++++++++
 3 files changed, 39 insertions(+), 25 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 294c366e3b..c36ea0e494 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -137,6 +137,15 @@ tests-time64 += \
 
 CFLAGS-tst-sigcontext-get_pc.c = -fasynchronous-unwind-tables
 
+ifeq (yes,$(build-shared))
+librt = $(common-objpfx)rt/librt.so
+else
+librt = $(common-objpfx)rt/librt.a
+endif
+
+$(objpfx)tst-ppoll: $(librt)
+$(objpfx)tst-ppoll-time64: $(librt)
+
 # Generate the list of SYS_* macros for the system calls (__NR_*
 # macros).  The file syscall-names.list contains all possible system
 # call names, and the generated header file produces SYS_* macros for
diff --git a/sysdeps/unix/sysv/linux/ppoll.c b/sysdeps/unix/sysv/linux/ppoll.c
index 624f14f517..8ca133b1fa 100644
--- a/sysdeps/unix/sysv/linux/ppoll.c
+++ b/sysdeps/unix/sysv/linux/ppoll.c
@@ -21,9 +21,6 @@
 #include <time.h>
 #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,
@@ -38,40 +35,33 @@ __ppoll64 (struct pollfd *fds, nfds_t nfds, const struct __timespec64 *timeout,
       timeout = &tval;
     }
 
-  int ret;
-
-  if (supports_time64 ())
-    {
 #ifndef __NR_ppoll_time64
 # define __NR_ppoll_time64 __NR_ppoll
 #endif
+
+#ifdef __ASSUME_TIME64_SYSCALLS
+  return SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
+			 __NSIG_BYTES);
+#else
+  int ret;
+  bool need_time64 = timeout != NULL && !in_time_t_range (timeout->tv_sec);
+  if (need_time64)
+    {
       ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
 			    __NSIG_BYTES);
-
       if (ret == 0 || errno != ENOSYS)
 	return ret;
-
-      mark_time64_unsupported ();
+      __set_errno (EOVERFLOW);
+      return -1;
     }
 
-#ifndef __ASSUME_TIME64_SYSCALLS
   struct timespec ts32;
-  if (timeout)
-    {
-      if (! in_time_t_range (timeout->tv_sec))
-        {
-          __set_errno (EOVERFLOW);
-          return -1;
-        }
-
-      ts32 = valid_timespec64_to_timespec (*timeout);
-    }
+  if (timeout != NULL)
+    ts32 = valid_timespec64_to_timespec (*timeout);
 
-  ret = SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL, sigmask,
-			__NSIG_BYTES);
+  return SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL, sigmask,
+			 __NSIG_BYTES);
 #endif
-
-  return ret;
 }
 
 #if __TIMESIZE != 64
diff --git a/sysdeps/unix/sysv/linux/tst-ppoll.c b/sysdeps/unix/sysv/linux/tst-ppoll.c
index 9fe6ad07ce..e21e2fcc72 100644
--- a/sysdeps/unix/sysv/linux/tst-ppoll.c
+++ b/sysdeps/unix/sysv/linux/tst-ppoll.c
@@ -19,9 +19,11 @@
 #include <time.h>
 #include <poll.h>
 #include <errno.h>
+#include <intprops.h>
 #include <support/check.h>
 #include <support/xtime.h>
 #include <support/timespec.h>
+#include <support/support.h>
 #include <stdbool.h>
 
 static int test_ppoll_timeout (bool zero_tmo)
@@ -41,6 +43,16 @@ static int test_ppoll_timeout (bool zero_tmo)
   return 0;
 }
 
+static void
+test_ppoll_large_timeout (void)
+{
+  support_create_timer (0, 100000000, false, NULL);
+  struct timespec ts = { TYPE_MAXIMUM (time_t), 0 };
+  struct pollfd fds = { -1, 0, 0 };
+  TEST_COMPARE (ppoll (&fds, 1, &ts, 0), -1);
+  TEST_VERIFY (errno == EINTR || errno == EOVERFLOW);
+}
+
 static int
 do_test (void)
 {
@@ -50,6 +62,9 @@ do_test (void)
   /* Check if ppoll exits after specified timeout.  */
   test_ppoll_timeout (false);
 
+  /* Check if ppoll with large timeout.  */
+  test_ppoll_large_timeout ();
+
   return 0;
 }