root/headers/private/system/arch/x86_64/arch_config.h 
/*
 * Copyright 2012, Alex Smith, alex@alex-smith.me.uk.
 * Distributed under the terms of the MIT License.
 */
#ifndef _KERNEL_ARCH_x86_64_CONFIG_H
#define _KERNEL_ARCH_x86_64_CONFIG_H

#define FUNCTION_CALL_PARAMETER_ALIGNMENT_TYPE  unsigned long

#define STACK_GROWS_DOWNWARDS

//#define ATOMIC_FUNCS_ARE_SYSCALLS
//#define ATOMIC64_FUNCS_ARE_SYSCALLS

#endif /* _KERNEL_ARCH_x86_64_CONFIG_H */