Re: [PATCH v4 1/4] powerpc: make llseek 32bit-only.

[Arnd Bergmann]

On Thu, Aug 29, 2019 at 2:37 PM Michal SuchÃnek <msuchanek@xxxxxxx> wrote:
> On Thu, 29 Aug 2019 14:19:46 +0200 Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > On Thu, Aug 29, 2019 at 12:23 PM Michal Suchanek <msuchanek@xxxxxxx> wrote:
> > In particular, I don't see why you single out llseek here, but leave other
> > syscalls that are not needed on 64-bit machines such as pread64().
>
> Because llseek is not built in fs/ when building 64bit only causing a
> link error.
>
> I initially posted patch to build it always but it was pointed out it
> is not needed, and  the interface does not make sense on 64bit, and
> that platforms that don't have it on 64bit now don't want that useless
> code.

Ok, please put that into the changeset description then.

I looked at uses of __NR__llseek in debian code search and
found this one:

https://codesearch.debian.net/show?file=umview_0.8.2-1.2%2Fxmview%2Fum_mmap.c&line=328

It looks like this application will try to use llseek instead of lseek
when built against kernel headers that define __NR_llseek.

Changing the powerpc kernel not to provide that to user
space may break it unless the program gets recompiled against
the latest headers.

      Arnd