Re: Backport due to incorrect socket syscall definitions on s390x with Linux 4.3 headers.

[Khem Raj <raj.khem@gmail.com>]

On Thu, Feb 25, 2016 at 7:35 AM, Stefan Liebler <stli@linux.vnet.ibm.com> wrote:
> Hi,
>
> Beginning with Linux 4.3, the kernel headers contain direct system call
> numbers __NR_socket etc. on s390x. On older kernels, the socket-multiplexer
> syscall __NR_socketcall was used.
>
> To enable these new syscalls, the patch
> "S390: Call direct system calls for socket operations."
> (https://sourceware.org/git/?p=glibc.git;a=commit;h=016495b818cb61df7d0d10e6db54074271b3e3a5)
> was applied upstream.
> If glibc 2.23 is configured with --enable-kernel=4.3 and newer,
> the direct socket syscalls are used.
> For older kernels, the socket-multiplexer syscall is used.
>
> In glibc 2.22 and earlier, this patch is currently not applied.
> If you build glibc on an kernel < 4.3, the socket-multiplexer syscall is
> used. But if you build glibc on kernel >= 4.3, the direct
> socket-syscalls are used. If you install this glibc on an
> kernel < 4.3, all socket operations will fail.
> See "Bug 19682 - s390x: Incorrect syscall definitions cause breakage with
> Linux 4.3 headers" (https://sourceware.org/bugzilla/show_bug.cgi?id=19682)
> The configure switch --enable-kernel does not influence this behaviour on
> older glibc-releases.
>
> The solution is to remove the direct socket-syscalls in
> sysdeps/unix/sysv/linux/s390/s390-64/syscalls.list (see attached patch) on
> older glibc-releases as it was done by the upstream patch, too. These
> entries were never used on s390x, but the c-files in
> sysdeps/unix/sysv/linux/.
> After this removal, the behaviour of the socket functions are not changed
> compared to the original glibc release version and the
> socket-multiplexer-syscall is always used.
>
> Florian Weimer told me, that he already did this for Fedora 23 (glibc 2.22)
> and Fedora 22 (glibc 2.21).
> Thus, backporting this to glibc branch 2.22, and 2.21 would be the best for
> Fedora.
>
> Which other glibc-branches should be updated???
>
> Please give feedback.

S390 does not support OpenEmbedded/Yocto framework, however my opinion
is to back port it
to all glibc versions that are used in currently supported distro
versions, so may be distro maintainers
can voice which those versions are.

>
> Bye
> Stefan
>
> ---
> ChangeLog:
>
>         * sysdeps/unix/sysv/linux/s390/s390-64/syscalls.list:
>         Remove socketcall syscalls.