static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
	struct stackframe frame;
	const register unsigned long current_sp asm ("sp");

	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);

	if (!tsk)
		tsk = current;

	if (regs) {
		frame.fp = regs->regs[29];
		frame.sp = regs->sp;
		frame.pc = regs->pc;
	} else if (tsk == current) {
		frame.fp = (unsigned long)__builtin_frame_address(0);
		frame.sp = current_sp;
		frame.pc = (unsigned long)dump_backtrace;
	} else {
		/*
		 * task blocked in __switch_to
		 */
		frame.fp = thread_saved_fp(tsk);
		frame.sp = thread_saved_sp(tsk);
		frame.pc = thread_saved_pc(tsk);
	}

	printk("Call trace:\n");
	while (1) {
		unsigned long where = frame.pc;
		int ret;

		ret = unwind_frame(&frame);
		if (ret < 0)
			break;
		dump_backtrace_entry(where, frame.sp);
	}
}

Unknown