kk Blog —— 通用基础

union thread_union {
	struct thread_info thread_info;
	unsigned long stack[THREAD_SIZE/sizeof(long)];
};

DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
DEFINE_PER_CPU(struct irq_stack *, softirq_stack);

struct irq_stack {
	u32                     stack[THREAD_SIZE/sizeof(u32)];
} __aligned(THREAD_SIZE);

bool handle_irq(unsigned irq, struct pt_regs *regs)
{
	struct irq_desc *desc;
	int overflow;

	overflow = check_stack_overflow();

	desc = irq_to_desc(irq);
	if (unlikely(!desc))
	return false;

	if (user_mode_vm(regs) || !execute_on_irq_stack(overflow, desc, irq)) {
		if (unlikely(overflow))
			print_stack_overflow();
		desc->handle_irq(irq, desc);
	}

	return true;
}

static inline int
execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
{
	struct irq_stack *curstk, *irqstk;
	u32 *isp, *prev_esp, arg1, arg2;

	curstk = (struct irq_stack *) current_stack();
	irqstk = __this_cpu_read(hardirq_stack);

	/*
	 * this is where we switch to the IRQ stack. However, if we are
	 * already using the IRQ stack (because we interrupted a hardirq
	 * handler) we can't do that and just have to keep using the
	 * current stack (which is the irq stack already after all)
	 */
	if (unlikely(curstk == irqstk))
	    return 0;

	isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));

	/* Save the next esp at the bottom of the stack */
	prev_esp = (u32 *)irqstk;
	*prev_esp = current_stack_pointer;

	if (unlikely(overflow))
	    call_on_stack(print_stack_overflow, isp);

	asm volatile("xchgl    %%ebx,%%esp    \n"
	         "call    *%%edi        \n"
	         "movl    %%ebx,%%esp    \n"
	         : "=a" (arg1), "=d" (arg2), "=b" (isp)
	         :  "0" (irq),   "1" (desc),  "2" (isp),
	        "D" (desc->handle_irq)
	         : "memory", "cc", "ecx");
	return 1;
}