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_status acpi_os_execute(acpi_execute_type type,
			    acpi_osd_exec_callback function, void *context)
{
	acpi_status status = AE_OK;
	struct acpi_os_dpc *dpc;
	struct workqueue_struct *queue;
	int ret;
	ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
			  "Scheduling function [%p(%p)] for deferred execution.\n",
			  function, context));

	if (type == OSL_DEBUGGER_MAIN_THREAD) {
		ret = acpi_debugger_create_thread(function, context);
		if (ret) {
			pr_err("Call to kthread_create() failed.\n");
			status = AE_ERROR;
		}
		goto out_thread;
	}

	/*
	 * Allocate/initialize DPC structure.  Note that this memory will be
	 * freed by the callee.  The kernel handles the work_struct list  in a
	 * way that allows us to also free its memory inside the callee.
	 * Because we may want to schedule several tasks with different
	 * parameters we can't use the approach some kernel code uses of
	 * having a static work_struct.
	 */

	dpc = kzalloc(sizeof(struct acpi_os_dpc), GFP_ATOMIC);
	if (!dpc)
		return AE_NO_MEMORY;

	dpc->function = function;
	dpc->context = context;

	/*
	 * To prevent lockdep from complaining unnecessarily, make sure that
	 * there is a different static lockdep key for each workqueue by using
	 * INIT_WORK() for each of them separately.
	 */
	if (type == OSL_NOTIFY_HANDLER) {
		queue = kacpi_notify_wq;
		INIT_WORK(&dpc->work, acpi_os_execute_deferred);
	} else if (type == OSL_GPE_HANDLER) {
		queue = kacpid_wq;
		INIT_WORK(&dpc->work, acpi_os_execute_deferred);
	} else {
		pr_err("Unsupported os_execute type %d.\n", type);
		status = AE_ERROR;
	}

	if (ACPI_FAILURE(status))
		goto err_workqueue;

	/*
	 * On some machines, a software-initiated SMI causes corruption unless
	 * the SMI runs on CPU 0.  An SMI can be initiated by any AML, but
	 * typically it's done in GPE-related methods that are run via
	 * workqueues, so we can avoid the known corruption cases by always
	 * queueing on CPU 0.
	 */
	ret = queue_work_on(0, queue, &dpc->work);
	if (!ret) {
		printk(KERN_ERR PREFIX
			  "Call to queue_work() failed.\n");
		status = AE_ERROR;
	}
err_workqueue:
	if (ACPI_FAILURE(status))
		kfree(dpc);
out_thread:
	return status;
}

acpi_status acpi_os_execute(acpi_execute_type type,
			    acpi_osd_exec_callback function, void *context)
{
	acpi_status status = AE_OK;
	struct acpi_os_dpc *dpc;
	struct workqueue_struct *queue;
	int ret;
	ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
			  "Scheduling function [%p(%p)] for deferred execution.\n",
			  function, context));

	if (type == OSL_DEBUGGER_MAIN_THREAD) {
		ret = acpi_debugger_create_thread(function, context);
		if (ret) {
			pr_err("Call to kthread_create() failed.\n");
			status = AE_ERROR;
		}
		goto out_thread;
	}

	/*
	 * Allocate/initialize DPC structure.  Note that this memory will be
	 * freed by the callee.  The kernel handles the work_struct list  in a
	 * way that allows us to also free its memory inside the callee.
	 * Because we may want to schedule several tasks with different
	 * parameters we can't use the approach some kernel code uses of
	 * having a static work_struct.
	 */

	dpc = kzalloc(sizeof(struct acpi_os_dpc), GFP_ATOMIC);
	if (!dpc)
		return AE_NO_MEMORY;

	dpc->function = function;
	dpc->context = context;

	/*
	 * To prevent lockdep from complaining unnecessarily, make sure that
	 * there is a different static lockdep key for each workqueue by using
	 * INIT_WORK() for each of them separately.
	 */
	if (type == OSL_NOTIFY_HANDLER) {
		queue = kacpi_notify_wq;
		INIT_WORK(&dpc->work, acpi_os_execute_deferred);
	} else if (type == OSL_GPE_HANDLER) {
		queue = kacpid_wq;
		INIT_WORK(&dpc->work, acpi_os_execute_deferred);
	} else {
		pr_err("Unsupported os_execute type %d.\n", type);
		status = AE_ERROR;
	}

	if (ACPI_FAILURE(status))
		goto err_workqueue;

	/*
	 * On some machines, a software-initiated SMI causes corruption unless
	 * the SMI runs on CPU 0.  An SMI can be initiated by any AML, but
	 * typically it's done in GPE-related methods that are run via
	 * workqueues, so we can avoid the known corruption cases by always
	 * queueing on CPU 0.
	 */
	ret = queue_work_on(0, queue, &dpc->work);
	if (!ret) {
		printk(KERN_ERR PREFIX
			  "Call to queue_work() failed.\n");
		status = AE_ERROR;
	}
err_workqueue:
	if (ACPI_FAILURE(status))
		kfree(dpc);
out_thread:
	return status;
}
