[PATCH-for-2.21-and-2.22] s390-64: remove socketcall syscalls

[Stefan Liebler]

On 12/31/2015 11:28 PM, Aurelien Jarno wrote:
> I have found some times to investigate. It seems there is no issue, my
> bad. I just discovered that on s390x, syscalls numbers above 256 are
> actually a a call to syscall 0 with the syscall number passed in
> register %r1. My version of strace was not aware of the new syscalls
> and presented them as syscall setup(). Sorry for the false alert.
>
That's correct svc does only support NR up to 255 directly.
For 256 and above %r1=NR and svc 0 is needed.
The svc 0 with setup r1 works for NR < 256, too.

> So it seems all is fine, but we still need the patch to use the
> socketcall interface until we can assume the direct socket syscalls are
> always available. I'll repost the patch on the libc-stable interface
> with the comment fixed, as I have been told in the meantimes it's a
> better list for discussing about already released versions.
On s390x the direct socket syscalls were introduced with kernel 4.3.
Before 4.3, the socket syscalls were always done with c-files in 
sysdeps/unix/sysv/linux/.
The entries in syscalls.list were never used on s390x.

The upstream behaviour activates the direct socket calls if 
__LINUX_KERNEL_VERSION >= 0x040300. Otherwise the 
socketcall-wrapper-syscall is used.

If glibc is build on a system with kernel >= 4.3 and the entries in 
syscalls.list, then those direct syscalls are generated
and those aren't available on kernels < 4.3.