text: #ifndef __ASM_IRQ_H
  #define __ASM_IRQ_H
  
  #define IRQ_STACK_SIZE			THREAD_SIZE
  #define IRQ_STACK_START_SP		THREAD_START_SP
  
  #ifndef __ASSEMBLER__
  
  #include <linux/percpu.h>
  
  #include <asm-generic/irq.h>
  #include <asm/thread_info.h>
  
  struct pt_regs;
  
  DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
  
  /*
   * The highest address on the stack, and the first to be used. Used to
   * find the dummy-stack frame put down by el?_irq() in entry.S, which
   * is structured as follows:
   *
   *       ------------
   *       |          |  <- irq_stack_ptr
   *   top ------------
   *       |   x19    | <- irq_stack_ptr - 0x08
   *       ------------
   *       |   x29    | <- irq_stack_ptr - 0x10
   *       ------------
   *
   * where x19 holds a copy of the task stack pointer where the struct pt_regs
   * from kernel_entry can be found.
   *
   */
  #define IRQ_STACK_PTR(cpu) ((unsigned long)per_cpu(irq_stack, cpu) + IRQ_STACK_START_SP)
  
  /*
   * The offset from irq_stack_ptr where entry.S will store the original
   * stack pointer. Used by unwind_frame() and dump_backtrace().
   */
  #define IRQ_STACK_TO_TASK_STACK(ptr) (*((unsigned long *)((ptr) - 0x08)))
  
  extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
  
  static inline int nr_legacy_irqs(void)
  {
  	return 0;
  }
  
  static inline bool on_irq_stack(unsigned long sp, int cpu)
  {
  	/* variable names the same as kernel/stacktrace.c */
  	unsigned long low = (unsigned long)per_cpu(irq_stack, cpu);
  	unsigned long high = low + IRQ_STACK_START_SP;
  
  	return (low <= sp && sp <= high);
  }
  
  #endif /* !__ASSEMBLER__ */
  #endif
  