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

[Mike Frysinger <vapier at gentoo dot org>]

On 25 Feb 2016 16:35, Stefan Liebler wrote:
> 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???

i would say all branches at least back to glibc-2.20

the Gentoo s390 boxes are on linux-4.4 so it won't impact our releasing,
but would be good to have the releases themselves be OK on older :).
-mike

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