TRACEREG_SZ
new_stack -= STACKFRAME_SZ + TRACEREG_SZ;
memset(new_stack, 0, STACKFRAME_SZ + TRACEREG_SZ);
memcpy(new_stack, (char *)regs - STACKFRAME_SZ, STACKFRAME_SZ + TRACEREG_SZ);
child_stack_sz = (STACKFRAME_SZ + TRACEREG_SZ);