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

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== Comment: #0 - Stefan Liebler <email address hidden> - 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

[Dimitri John Ledkov (xnox)]

Assigning to glibc maintainer

[Dimitri John Ledkov (xnox)]

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.

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------- Comment From <email address hidden> 2016-04-19 04:21 EDT-------
IBM: will set the new Target to Ubuntu 18.04 soon

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------- Comment From <email address hidden> 2016-07-04 09:11 EDT-------
Will be closed. Canonical will not implement this fix within 16.x nor in 18.x.