1/*
 2 * Code for supporting irq vector tracepoints.
 3 *
 4 * Copyright (C) 2013 Seiji Aguchi <seiji.aguchi@hds.com>
 5 *
 6 */
 7#include <asm/hw_irq.h>
 8#include <asm/desc.h>
 9#include <linux/atomic.h>
10
11atomic_t trace_idt_ctr = ATOMIC_INIT(0);
12struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
13				(unsigned long) trace_idt_table };
14
15/* No need to be aligned, but done to keep all IDTs defined the same way. */
16gate_desc trace_idt_table[NR_VECTORS] __page_aligned_bss;
17
18static int trace_irq_vector_refcount;
19static DEFINE_MUTEX(irq_vector_mutex);
20
21static void set_trace_idt_ctr(int val)
22{
23	atomic_set(&trace_idt_ctr, val);
24	/* Ensure the trace_idt_ctr is set before sending IPI */
25	wmb();
26}
27
28static void switch_idt(void *arg)
29{
30	unsigned long flags;
31
32	local_irq_save(flags);
33	load_current_idt();
34	local_irq_restore(flags);
35}
36
37int trace_irq_vector_regfunc(void)
38{
39	mutex_lock(&irq_vector_mutex);
40	if (!trace_irq_vector_refcount) {
41		set_trace_idt_ctr(1);
42		smp_call_function(switch_idt, NULL, 0);
43		switch_idt(NULL);
44	}
45	trace_irq_vector_refcount++;
46	mutex_unlock(&irq_vector_mutex);
47	return 0;
48}
49
50void trace_irq_vector_unregfunc(void)
51{
52	mutex_lock(&irq_vector_mutex);
53	trace_irq_vector_refcount--;
54	if (!trace_irq_vector_refcount) {
55		set_trace_idt_ctr(0);
56		smp_call_function(switch_idt, NULL, 0);
57		switch_idt(NULL);
58	}
59	mutex_unlock(&irq_vector_mutex);
60}