stack_end = (stack_start + 15) & -16;
stack_end = stack_end & -16;
__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...){  struct sigcontext *sc = &ucp->uc_mcontext;  extern void __start_context (ucontext_t *link, long gp, ...);  unsigned long stack_start, stack_end;  va_list ap;  long *rbs;  int i;  stack_start = (long) sc->sc_stack.ss_sp;  stack_end = (long) sc->sc_stack.ss_sp + sc->sc_stack.ss_size;  stack_start = (stack_start + 7) & -8;  stack_end = (stack_start + 15) & -16;  if (argc > 8)    {      fprintf (stderr, _("\makecontext: does not know how to handle more than 8 arguments\n"));      exit (-1);    }  /* set the entry point and global pointer: */  sc->sc_br[0] = ((struct fdesc *) &__start_context)->ip;  sc->sc_br[1] = ((struct fdesc *) func)->ip;  sc->sc_gr[1] = ((struct fdesc *) func)->gp;  /* set up the call frame: */  sc->sc_ar_pfs = ((sc->sc_ar_pfs & ~0x3fffffffffUL)		   | (argc + 2) | ((argc + 2) << 7));  rbs = (long *) stack_start;  PUSH((long) ucp->uc_link);  PUSH(((struct fdesc *) &__start_context)->gp);  va_start (ap, argc);  for (i = 0; i < argc; ++i)    PUSH(va_arg (ap, long));  va_end (ap);  /* set the memory and register stack pointers: */  sc->sc_ar_bsp = (long) rbs;  sc->sc_gr[12] = stack_end - 16;  /* clear the NaT bits for r1 and r12: */  sc->sc_nat &= ~((1 << 1) | (1 << 12));  sc->sc_ar_rnat = 0;}