acpi: Disable ACPI table override if securelevel is set

From the kernel documentation (initrd_table_override.txt):

  If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible
  to override nearly any ACPI table provided by the BIOS with an
  instrumented, modified one.

When securelevel is set, the kernel should disallow any unauthenticated
changes to kernel space. ACPI tables contain code invoked by the kernel, so
do not allow ACPI tables to be overridden if securelevel is set.

Signed-off-by: Linn Crosetto <linn@hpe.com>
acpi_os_read_memory(acpi_physical_address phys_addr, u64 *value, u32 width)
{
	void __iomem *virt_addr;
	unsigned int size = width / 8;
	bool unmap = false;
	u64 dummy;

	rcu_read_lock();
	virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
	if (!virt_addr) {
		rcu_read_unlock();
		virt_addr = acpi_os_ioremap(phys_addr, size);
		if (!virt_addr)
			return AE_BAD_ADDRESS;
		unmap = true;
	}

	if (!value)
		value = &dummy;

	switch (width) {
	case 8:
		*(u8 *) value = readb(virt_addr);
		break;
	case 16:
		*(u16 *) value = readw(virt_addr);
		break;
	case 32:
		*(u32 *) value = readl(virt_addr);
		break;
	case 64:
		*(u64 *) value = readq(virt_addr);
		break;
	default:
		BUG();
	}

	if (unmap)
		iounmap(virt_addr);
	else
		rcu_read_unlock();

	return AE_OK;
}

acpi_os_read_memory(acpi_physical_address phys_addr, u64 *value, u32 width)
{
	void __iomem *virt_addr;
	unsigned int size = width / 8;
	bool unmap = false;
	u64 dummy;

	rcu_read_lock();
	virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
	if (!virt_addr) {
		rcu_read_unlock();
		virt_addr = acpi_os_ioremap(phys_addr, size);
		if (!virt_addr)
			return AE_BAD_ADDRESS;
		unmap = true;
	}

	if (!value)
		value = &dummy;

	switch (width) {
	case 8:
		*(u8 *) value = readb(virt_addr);
		break;
	case 16:
		*(u16 *) value = readw(virt_addr);
		break;
	case 32:
		*(u32 *) value = readl(virt_addr);
		break;
	case 64:
		*(u64 *) value = readq(virt_addr);
		break;
	default:
		BUG();
	}

	if (unmap)
		iounmap(virt_addr);
	else
		rcu_read_unlock();

	return AE_OK;
}
