linux: Remove assembly umount2 implementation

Only alpha and ia64 do not support __NR_umount2 (defined as
__NR_umount), but recent kernel fixes (74cd2184833f for ia64, and
12b57c5c70f39 for alpha) add the required alias.

Checked with a build against all affected ABIs.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

sysdeps/unix/sysv/linux/ia64/syscalls.list

@@ -1,7 +1,5 @@
 # File name	Caller	Syscall name	# args	Strong name	Weak names
 
-umount2		-	umount		2	__umount2	umount2
-
 getpriority	-	getpriority	i:ii	__getpriority	getpriority
 
 # proper socket implementations:

sysdeps/unix/sysv/linux/include/sys/mount.h

@@ -0,0 +1,31 @@
+/* Internal declarations for sys/mount.h.
+   Copyright (C) 2020 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _INCLUDE_SYS_MOUNT_H
+#define _INCLUDE_SYS_MOUNT_H	1
+
+#include_next <sys/mount.h>
+
+# ifndef _ISOMAC
+
+extern __typeof (umount) __umount __THROW;
+extern __typeof (umount2) __umount2 __THROW;
+libc_hidden_proto (__umount2)
+
+# endif /* _ISOMAC */
+#endif /* sys/sysinfo.h */

sysdeps/unix/sysv/linux/umount.c

@@ -16,12 +16,10 @@
    License along with the GNU C Library.  If not, see
    <https://www.gnu.org/licenses/>.  */
 
-/* Since the generic Linux syscall ABI doesn't have an oldumount system call,
+#include <sys/mount.h>
-   do what the kernel does down here.  */
+#include <sysdep.h>
 
-extern long int __umount2 (const char *name, int flags);
+int
-
-long int
 __umount (const char *name)
 {
   return __umount2 (name, 0);

sysdeps/unix/sysv/linux/umount2.S

@@ -1,13 +0,0 @@
-/* umount system call with two parameters.  */
-
-#include <sysdep.h>
-#if defined __NR_oldumount || defined __NR_umount2
-#ifdef __NR_oldumount
-PSEUDO (__umount2, umount, 2)
-#else
-PSEUDO (__umount2, umount2, 2)
-#endif
-	ret
-PSEUDO_END(__umount2)
-weak_alias (__umount2, umount2)
-#endif

sysdeps/unix/sysv/linux/umount2.c

@@ -0,0 +1,29 @@
+/* Unmount filesystem.
+   Copyright (C) 2020 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/mount.h>
+#include <sysdep.h>
+
+int
+__umount2 (const char *special_file, int flags)
+{
+  return INLINE_SYSCALL_CALL (umount2, special_file, flags);
+}
+libc_hidden_def (__umount2)
+
+weak_alias (__umount2, umount2)