irq-stack

  4 #ifdef CONFIG_KASAN
  5 #define KASAN_STACK_ORDER 1
  6 #else
  7 #define KASAN_STACK_ORDER 0
  8 #endif



 20 #define IRQ_STACK_ORDER (2 + KASAN_STACK_ORDER)
 21 #define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER)

PAGE_SIZE -- 1<<12 = 4096

>>> 4096<<2
16384 kB

324 union irq_stack_union {
325         char irq_stack[IRQ_STACK_SIZE]; //16 kB stack size
326         /*
327          * GCC hardcodes the stack canary as %gs:40.  Since the
328          * irq_stack is the object at %gs:0, we reserve the bottom
329          * 48 bytes of the irq stack for the canary.
330          */
331         struct {
332                 char gs_base[40];
333                 unsigned long stack_canary;
334         };
335 };



setup_percpu.c:244

244 #ifdef CONFIG_X86_64
245                 per_cpu(irq_stack_ptr, cpu) =
246                         per_cpu(irq_stack_union.irq_stack, cpu) +
247                         IRQ_STACK_SIZE - 64;

setup IRQ stack pointer on per-cpu variable.