int register_trapped_io()

in kernel/io_trapped.c [41:104]

• 51 lines of code
• 12 McCabe index (conditional complexity)

int register_trapped_io(struct trapped_io *tiop)
{
	struct resource *res;
	unsigned long len = 0, flags = 0;
	struct page *pages[TRAPPED_PAGES_MAX];
	int k, n;

	if (unlikely(trapped_io_disable))
		return 0;

	/* structure must be page aligned */
	if ((unsigned long)tiop & (PAGE_SIZE - 1))
		goto bad;

	for (k = 0; k < tiop->num_resources; k++) {
		res = tiop->resource + k;
		len += roundup(resource_size(res), PAGE_SIZE);
		flags |= res->flags;
	}

	/* support IORESOURCE_IO _or_ MEM, not both */
	if (hweight_long(flags) != 1)
		goto bad;

	n = len >> PAGE_SHIFT;

	if (n >= TRAPPED_PAGES_MAX)
		goto bad;

	for (k = 0; k < n; k++)
		pages[k] = virt_to_page(tiop);

	tiop->virt_base = vmap(pages, n, VM_MAP, PAGE_NONE);
	if (!tiop->virt_base)
		goto bad;

	len = 0;
	for (k = 0; k < tiop->num_resources; k++) {
		res = tiop->resource + k;
		pr_info("trapped io 0x%08lx overrides %s 0x%08lx\n",
		       (unsigned long)(tiop->virt_base + len),
		       res->flags & IORESOURCE_IO ? "io" : "mmio",
		       (unsigned long)res->start);
		len += roundup(resource_size(res), PAGE_SIZE);
	}

	tiop->magic = IO_TRAPPED_MAGIC;
	INIT_LIST_HEAD(&tiop->list);
	spin_lock_irq(&trapped_lock);
#ifdef CONFIG_HAS_IOPORT_MAP
	if (flags & IORESOURCE_IO)
		list_add(&tiop->list, &trapped_io);
#endif
#ifdef CONFIG_HAS_IOMEM
	if (flags & IORESOURCE_MEM)
		list_add(&tiop->list, &trapped_mem);
#endif
	spin_unlock_irq(&trapped_lock);

	return 0;
 bad:
	pr_warn("unable to install trapped io filter\n");
	return -1;
}