x86: Remove vsyscall usage

This patch removes the vsyscall usage for x86_64 port.  As indicated
by kernel code comments [1], vsyscalls are a legacy ABI and its concept
is problematic:

- It interferes with ASLR.
- It's awkward to write code that lives in kernel addresses but is
  callable by userspace at fixed addresses.
- The whole concept is impossible for 32-bit compat userspace.
- UML cannot easily virtualize a vsyscall.

The VDSO is a better approach for such functionality.  Tested on i686,
x86_64, and x32.

	* sysdeps/unix/sysv/linux/i386/gettimeofday.c
	(__gettimeofday_syscall): Remove vsyscall fallback.
	* sysdeps/unix/sysv/linux/i386/time.c (__time_syscall): Likewise.
	* sysdeps/unix/sysv/linux/x86/gettimeofday.c (__gettimeofday_syscall):
	Add syscall fallback function.
	(gettimeofday_ifunc): Use __gettimeofday_syscall as fallback mechanism
	if vDSO is not present.
	* sysdeps/unix/sysv/linux/x86/time.c (__time_syscall): Add syscall
	fallback function.
	(time_ifunc): Use __time_syscall as fallback mechanism if vDSO is not
	present.
	* sysdeps/unix/sysv/linux/x86_64/gettimeofday.c: Remove file.
	* sysdeps/unix/sysv/linux/x86_64/time.c: Likewise.

[1] arch/x86/kernel/vsyscall_64.c

6 files changed, 20 insertions, 74 deletions

diff --git a/sysdeps/unix/sysv/linux/i386/gettimeofday.c b/sysdeps/unix/sysv/linux/i386/gettimeofday.c
index 3e00eb46aa..fdb0fabedb 100644
--- a/sysdeps/unix/sysv/linux/i386/gettimeofday.c
+++ b/sysdeps/unix/sysv/linux/i386/gettimeofday.c
@@ -20,16 +20,6 @@
 
 #ifdef SHARED
 
-# include <dl-vdso.h>
-# include <errno.h>
-
-/* If the vDSO is not available we fall back on the syscall.  */
-static int
-__gettimeofday_syscall (struct timeval *tv, struct timezone *tz)
-{
-  return INLINE_SYSCALL (gettimeofday, 2, tv, tz);
-}
-# define GETTIMEOFAY_FALLBACK (void*) (&__gettimeofday_syscall)
 # undef libc_ifunc_hidden_def
 # define libc_ifunc_hidden_def(name)  \
   libc_ifunc_hidden_def1 (__GI_##name, __gettimeofday_syscall)
diff --git a/sysdeps/unix/sysv/linux/i386/time.c b/sysdeps/unix/sysv/linux/i386/time.c
index e8a4e593e1..66b9a6c87a 100644
--- a/sysdeps/unix/sysv/linux/i386/time.c
+++ b/sysdeps/unix/sysv/linux/i386/time.c
@@ -18,17 +18,6 @@
 
 #ifdef SHARED
 
-# include <dl-vdso.h>
-# include <errno.h>
-
-/* If the vDSO is not available we fall back on the old vsyscall.  */
-static time_t
-__time_syscall (time_t *t)
-{
-  INTERNAL_SYSCALL_DECL (err);
-  return INTERNAL_SYSCALL (time, err, 1, t);
-}
-# define TIME_FALLBACK  (void*) &__time_syscall
 # undef libc_ifunc_hidden_def
 # define libc_ifunc_hidden_def(name)  \
   libc_ifunc_hidden_def1 (__GI_##name, __time_syscall)
diff --git a/sysdeps/unix/sysv/linux/x86/gettimeofday.c b/sysdeps/unix/sysv/linux/x86/gettimeofday.c
index c820fd767b..440cb0243a 100644
--- a/sysdeps/unix/sysv/linux/x86/gettimeofday.c
+++ b/sysdeps/unix/sysv/linux/x86/gettimeofday.c
@@ -21,6 +21,13 @@
 #ifdef SHARED
 
 # include <dl-vdso.h>
+# include <errno.h>
+
+static int
+__gettimeofday_syscall (struct timeval *tv, struct timezone *tz)
+{
+  return INLINE_SYSCALL (gettimeofday, 2, tv, tz);
+}
 
 void *gettimeofday_ifunc (void) __asm__ ("__gettimeofday");
 
@@ -29,9 +36,9 @@ gettimeofday_ifunc (void)
 {
   PREPARE_VERSION_KNOWN (linux26, LINUX_2_6);
 
-  /* If the vDSO is not available we fall back on the old vsyscall.  */
+  /* If the vDSO is not available we fall back to syscall.  */
   return (_dl_vdso_vsym ("__vdso_gettimeofday", &linux26)
-	  ?: GETTIMEOFAY_FALLBACK);
+	  ?: (void*) (&__gettimeofday_syscall));
 }
 asm (".type __gettimeofday, %gnu_indirect_function");
 
diff --git a/sysdeps/unix/sysv/linux/x86/time.c b/sysdeps/unix/sysv/linux/x86/time.c
index 1ab92489e5..ebf092ae12 100644
--- a/sysdeps/unix/sysv/linux/x86/time.c
+++ b/sysdeps/unix/sysv/linux/x86/time.c
@@ -21,6 +21,14 @@
 #ifdef SHARED
 
 #include <dl-vdso.h>
+#include <errno.h>
+
+static time_t
+__time_syscall (time_t *t)
+{
+  INTERNAL_SYSCALL_DECL (err);
+  return INTERNAL_SYSCALL (time, err, 1, t);
+}
 
 void *time_ifunc (void) __asm__ ("time");
 
@@ -29,7 +37,9 @@ time_ifunc (void)
 {
   PREPARE_VERSION_KNOWN (linux26, LINUX_2_6);
 
-  return _dl_vdso_vsym ("__vdso_time", &linux26) ?: TIME_FALLBACK;
+/* If the vDSO is not available we fall back on the syscall.  */
+  return _dl_vdso_vsym ("__vdso_time", &linux26)
+			?: (void*) &__time_syscall;
 }
 asm (".type time, %gnu_indirect_function");
 
diff --git a/sysdeps/unix/sysv/linux/x86_64/gettimeofday.c b/sysdeps/unix/sysv/linux/x86_64/gettimeofday.c
deleted file mode 100644
index daa14defb0..0000000000
--- a/sysdeps/unix/sysv/linux/x86_64/gettimeofday.c
+++ /dev/null
@@ -1,26 +0,0 @@
-/* Copyright (C) 2002-2015 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#include <sys/time.h>
-
-#ifdef SHARED
-/* If the vDSO is not available we fall back on the old vsyscall.  */
-# define VSYSCALL_ADDR_vgettimeofday	0xffffffffff600000ul
-# define GETTIMEOFAY_FALLBACK  (void*)VSYSCALL_ADDR_vgettimeofday
-#endif
-
-#include <sysdeps/unix/sysv/linux/x86/gettimeofday.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/time.c b/sysdeps/unix/sysv/linux/x86_64/time.c
deleted file mode 100644
index 6ceb819d82..0000000000
--- a/sysdeps/unix/sysv/linux/x86_64/time.c
+++ /dev/null
@@ -1,24 +0,0 @@
-/* Copyright (C) 2001-2015 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#ifdef SHARED
-/* If the vDSO is not available we fall back on the old vsyscall.  */
-#define VSYSCALL_ADDR_vtime	0xffffffffff600400
-#define TIME_FALLBACK           (void*)VSYSCALL_ADDR_vtime
-#endif
-
-#include <sysdeps/unix/sysv/linux/x86/time.c>