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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 instead. In glibc 2.22 and earlier, this patch is not applied. If you build glibc on a 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 a 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 (this 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. After talking to the distribution maintainers, the decision is to backport it to glibc 2.22, 2.21, 2.20 as done with this commit. Bye Stefan
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