Re: [PATCH 07/12] aarch64: fix syscalls for BTI

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 05/07/2020 16:40, Adhemerval Zanella via Libc-alpha wrote:
> > +#include <sysdep.h>
> > +PSEUDO (__umount2, umount2, 2)
> > +	ret
> > +PSEUDO_END(__umount2)
> > +weak_alias (__umount2, umount2)
> > +END_FILE
> 
> I think it is better to adapt the linux umount2.S to a C file instead of
> adding another arch-specific implementation.  Only alpha and ia64 do
> not support __NR_umount2 (exported as __NR_umount), but recent kernel
> fixes (74cd2184833f for ia64, 12b57c5c70f39 for alpha) add the alias.
> So we can use __NR_umount without the need to check its definition:

yes i think this is a useful thing to do
(independently of aarch64 bti work).

doesn't the patch add new umount2 symbol on
ia64 and alpha though?

> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
> index 0326f92c40..62ac921e8f 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -54,7 +54,7 @@ CFLAGS-malloc.c += -DMORECORE_CLEARS=2
>  endif
>  
>  ifeq ($(subdir),misc)
> -sysdep_routines += adjtimex clone umount umount2 readahead sysctl \
> +sysdep_routines += adjtimex clone umount readahead sysctl \
>  		   setfsuid setfsgid epoll_pwait signalfd \
>  		   eventfd eventfd_read eventfd_write prlimit \
>  		   personality epoll_wait tee vmsplice splice \
> diff --git a/sysdeps/unix/sysv/linux/ia64/syscalls.list b/sysdeps/unix/sysv/linux/ia64/syscalls.list
> index 56f4138c43..bd39441d3c 100644
> --- a/sysdeps/unix/sysv/linux/ia64/syscalls.list
> +++ b/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:
> diff --git a/sysdeps/unix/sysv/linux/umount.c b/sysdeps/unix/sysv/linux/umount.c
> index ab6a20f596..cdc8759118 100644
> --- a/sysdeps/unix/sysv/linux/umount.c
> +++ b/sysdeps/unix/sysv/linux/umount.c
> @@ -16,12 +16,17 @@
>     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);
> +int
> +__umount2 (const char *special_file, int flags)
> +{
> +  return INLINE_SYSCALL_CALL (umount2, special_file, flags);
> +}
> +weak_alias (__umount2, umount2)
>  
> -long int
> +int
>  __umount (const char *name)
>  {
>    return __umount2 (name, 0);
> diff --git a/sysdeps/unix/sysv/linux/umount2.S b/sysdeps/unix/sysv/linux/umount2.S
> deleted file mode 100644
> index 92241bbf97..0000000000
> --- a/sysdeps/unix/sysv/linux/umount2.S
> +++ /dev/null
> @@ -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
> 
> 

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