[v2] linux: Remove assembly umount2 implementation

  Changes from previous version:

  - Add a new umount2.c implementation and internal sys/mount.h
    header.

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.
---
 sysdeps/unix/sysv/linux/ia64/syscalls.list  |  2 --
 sysdeps/unix/sysv/linux/include/sys/mount.h | 31 +++++++++++++++++++++
 sysdeps/unix/sysv/linux/umount.c            |  8 ++----
 sysdeps/unix/sysv/linux/umount2.S           | 13 ---------
 sysdeps/unix/sysv/linux/umount2.c           | 29 +++++++++++++++++++
 5 files changed, 63 insertions(+), 20 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/include/sys/mount.h
 delete mode 100644 sysdeps/unix/sysv/linux/umount2.S
 create mode 100644 sysdeps/unix/sysv/linux/umount2.c
  

* Adhemerval Zanella via Libc-alpha:

> diff --git a/sysdeps/unix/sysv/linux/include/sys/mount.h b/sysdeps/unix/sysv/linux/include/sys/mount.h
> new file mode 100644
> index 0000000000..6f6122cca3
> --- /dev/null
> +++ b/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 */

I think we are inconsistent about the # indentation within header guards
under include/, so this is fine.

> diff --git a/sysdeps/unix/sysv/linux/umount.c b/sysdeps/unix/sysv/linux/umount.c
> index ab6a20f596..2a75760dfa 100644
> --- a/sysdeps/unix/sysv/linux/umount.c
> +++ b/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,
> -   do what the kernel does down here.  */
> +#include <sys/mount.h>
> +#include <sysdep.h>
>  
> -extern long int __umount2 (const char *name, int flags);
> -
> -long int
> +int
>  __umount (const char *name)
>  {
>    return __umount2 (name, 0);

The return type change is correct (and required by the newly added
prototype).

> diff --git a/sysdeps/unix/sysv/linux/umount2.c b/sysdeps/unix/sysv/linux/umount2.c
> new file mode 100644
> index 0000000000..a91fd50733
> --- /dev/null
> +++ b/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)

Looks good.

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

Thanks,
Florian