IA32 Emulation

modulename: tls.ko

and/or

sys_ia32.ko

and/or

entry_64_compat.ko

and/or

syscall_32.ko

and/or

nosyscall.ko

and/or

ia32entry.ko

configname: CONFIG_IA32_EMULATION

Linux Kernel Configuration for x86
└─>Executable file formats / Emulations
└─>IA32 Emulation
In linux kernel since version 2.6.12  
Include code to run 32-bit programs under a 64-bit kernel. You should
likely turn this on, unless you're 100% sure that you don't have any
32-bit programs left.

source code:
arch/x86/kernel/tls.c

depends
CONFIG_X86_64

is selected by
CONFIG_COMPAT_32