Comment 7 for bug 339743

Fascinating. The problem is that pipe2() is not actually returning -1 and setting errno = ENOSYS like it should. Instead, it is returning 331, which is __NR_pipe2, and leaving errno == 0.

This affects every x86_64 kernel from v2.6.26 (8ab32bb) through v2.6.29-rc3, and was fixed by

commit c09249f8d1b84344eca882547afdbffee8c09d14
Author: Roland McGrath <email address hidden>
Date: Fri Feb 6 18:15:18 2009 -0800

    x86-64: fix int $0x80 -ENOSYS return

    One of my past fixes to this code introduced a different new bug.
    When using 32-bit "int $0x80" entry for a bogus syscall number,
    the return value is not correctly set to -ENOSYS. This only happens
    when neither syscall-audit nor syscall tracing is enabled (i.e., never
    seen if auditd ever started).

    The fix makes the int $0x80 path match the sysenter and syscall paths.

    Reported-by: Dmitry V. Levin <email address hidden>
    Signed-off-by: Roland McGrath <email address hidden>