_syscall#

ssize_t write(int fd, const void *buf, size_t count);

_syscall3(int , write, int, fd, const void *,buf, unsigned int, count); <-- 매크로

#define _syscall3(type, name, type1, arg1, type2, arg2, type3,arg3) \
type name(type1, arg1, type2, arg2, type3, arg3) \
{
long __res ; \
__asm__ volatile("int $0x80" \
: "=a" (__res) \
: "0" (__NR_##name) , "b", ((long)(arg1)) , "c" ((long)(arg2)), \
      "d" ((long))(arg3)) : "memory"); \
__syscall_return(type, __res); \
}