Re: [PATCH 14/15] arch: add split IPC system calls where needed

Arnd Bergmann
2019-01-11T17:33:27Z

On Thu, Jan 10, 2019 at 9:33 PM Heiko Carstens
<heiko.carstens@de.ibm.com> wrote:
> On Thu, Jan 10, 2019 at 05:24:34PM +0100, Arnd Bergmann wrote:

> > diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
> > index 022fc099b628..428cf512a757 100644
> > --- a/arch/s390/kernel/syscalls/syscall.tbl
> > +++ b/arch/s390/kernel/syscalls/syscall.tbl
> > @@ -391,3 +391,15 @@
> > 381 common kexec_file_load sys_kexec_file_load compat_sys_kexec_file_load
> > 382 common io_pgetevents sys_io_pgetevents compat_sys_io_pgetevents
> > 383 common rseq sys_rseq compat_sys_rseq
> > +# room for arch specific syscalls
> > +392 64 semtimedop sys_semtimedop -
> > +393 common semget sys_semget sys_semget
> ...
> > +395 common shmget sys_shmget sys_shmget
> ...
> > +398 common shmdt sys_shmdt sys_shmdt
> > +399 common msgget sys_msgget sys_msgget
>
> These four need compat system call wrappers, unfortunately... (well,
> actually only shmget and shmdt require them, but let's add them for
> all four). See arch/s390/kernel/compat_wrapper.c
>
> I'm afraid this compat special handling will be even more annoying in
> the future, since s390 will be the only architecture which requires
> this special handling.
>
> _Maybe_ it would make sense to automatically generate a weak compat
> system call wrapper for s390 with the SYSCALL_DEFINE macros, but that
> probably won't work in all cases.

For some reason I was under the impression that s390 already did that.
However, it seems that x86 does, so I'll try to convert the x86 version
for s390, and see if I can get rid of all the wrappers that way.

It would certainly be safer to have the wrappers always present,
especially if we expect future system calls to be added to the
s390 table by whoever implements the syscall itself.

Arnd