CONFIG_OABI_COMPAT is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Allow old ABI binaries to run with this kernel (EXPERIMENTAL)

modulename: sys_oabi-compat.ko


Linux Kernel Configuration
└─>Kernel Features
└─>Allow old ABI binaries to run with this kernel (EXPERIMENTAL)
In linux kernel since version 2.6.16 (release Date: 2006-03-19)  
This option preserves the old syscall interface along with the
new (ARM EABI) one. It also provides a compatibility layer to
intercept syscalls that have structure arguments which layout
in memory differs between the legacy ABI and the new ARM EABI
(only for non "thumb" binaries). This option adds a tiny
overhead to all syscalls and produces a slightly larger kernel.

The seccomp filter system will not be available when this is
selected, since there is no way yet to sensibly distinguish
between calling conventions during filtering.

If you know you'll be using only pure EABI user space then you
can say N here. If this option is not selected and you attempt
to execute a legacy ABI binary then the result will be
UNPREDICTABLE (in fact it can be predicted that it won't work
at all). If in doubt say N.

source code: