kernel: add support for getting percpu variables that belong to other CPUs

kernel/percpu.c

@@ -24,7 +24,7 @@ extern kern_status_t init_per_cpu_areas(void)
 	return KERN_OK;
 }
 
-extern void *__percpu_get(void *var)
+extern void *__percpu_get(unsigned int cpu, void *var)
 {
 	uintptr_t pvar = (uintptr_t)var;
 	uintptr_t percpu_start = (uintptr_t)__percpu_start;
@@ -36,5 +36,5 @@ extern void *__percpu_get(void *var)
 
 	size_t var_offset = pvar - percpu_start;
 
-	return (char *)percpu_buffer + (this_cpu() * percpu_stride) + var_offset;
+	return (char *)percpu_buffer + (cpu * percpu_stride) + var_offset;
 }