THREAD_START_SP
((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1)
secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
#define GET_USERREG() ((struct pt_regs *)(THREAD_START_SP + (unsigned long)current_thread_info()) - 1)
(unsigned long)current_thread_info() + THREAD_START_SP - (addr))