[Bug 1562004] Re: S390: glibc does not use direct socket-syscalls, but the multiplexer-socket-syscall.

[Dimitri John Ledkov]

Hello,

4.3.0 minimal kernel ABI is too high for Ubuntu. And specifically for
the Ubuntu 16.04 LTS release.

Specifically this will prevent executing Ubuntu on foreign kernels. For
example it will be impossible to run Ubuntu buildd chroots on stable
Debian releases; it will be impossible to run Ubuntu docker containers
on e.g. IBM z/KVM distribution; this will prevent LXD from running on
multiple current stable host platforms. For these reasons, this request
is out of scope for 16.04 as it will limit availability and usability of
16.04 LTS. Minimal kernel ABIs are re-visited early each cycle, and take
into consideration wide variety of usecases, currently supported
hardware, and supported users both with Ubuntu alone and the wider Linux
community.

Regards,

Dimitri.

** Changed in: glibc (Ubuntu)
       Status: New => Won't Fix

** Changed in: glibc (Ubuntu)
    Milestone: None => ubuntu-16.04

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Title:
  S390: glibc does not use direct socket-syscalls, but the multiplexer-
  socket-syscall.

Status in glibc package in Ubuntu:
  Won't Fix

Bug description:
  == Comment: #0 - Stefan Liebler <STLI at de.ibm.com> - 2016-03-24 11:16:16 ==
  Hi,

  the glibc socket functions, like connect(), bind(), socket(), ... do currently use svc 102
  (multiplexer-socket-syscall: see /usr/include/s390x-linux-gnu/asm/unistd.h:
  #define __NR_socketcall         102)

  The direct socketsyscalls are also available for s390 since kernel 4.3:
  #define __NR_connect		362
  #define __NR_bind		361
  #define __NR_socket		359
  ...

  The kernel in my used ubuntu alpha is 4.4.0-15 and the glibc 2.23.
  This glibc release can use these direct socket-syscalls,
  if glibc is configured with "--enable-kernel=4.3.0".
  Or even better, use the kernel-level, which will be used in the first release for s390.

  
  Here is the kernel commit:
  "s390: wire up separate socketcalls system calls"
  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=977108f89c989b1eeb5c8d938e1e71913391eb5f

  and the glibc commit:
  "S390: Call direct system calls for socket operations."
  https://sourceware.org/git/?p=glibc.git;a=commit;h=016495b818cb61df7d0d10e6db54074271b3e3a5

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