xen: add xenstored user-space device

This device is used by the user-space daemon that runs xenstore
(xenstored). It allows xenstored to map the xenstore memory page, and
reports the event channel xenstore is using.

Sponsored by: Citrix Systems R&D

dev/xen/xenstore/xenstored_dev.c:
 - Add the xenstored character device that's used to map the xenstore
   memory into user-space, and to report the event channel used by
   xenstore.

conf/files:
 - Add the device to the build process.

sys/conf/files

@@ -2640,6 +2640,7 @@ dev/xen/timer/timer.c		optional xen | xenhvm
 dev/xen/pvcpu/pvcpu.c		optional xen | xenhvm
 dev/xen/xenstore/xenstore.c	optional xen | xenhvm
 dev/xen/xenstore/xenstore_dev.c	optional xen | xenhvm
+dev/xen/xenstore/xenstored_dev.c	optional xen | xenhvm
 dev/xl/if_xl.c			optional xl pci
 dev/xl/xlphy.c			optional xl pci
 fs/autofs/autofs.c		optional autofs

sys/dev/xen/xenstore/xenstored_dev.c

@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2014 Roger Pau Monné <roger.pau@citrix.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/cdefs.h>
+#include <sys/errno.h>
+#include <sys/uio.h>
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/proc.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/conf.h>
+#include <sys/module.h>
+
+#include <xen/xen-os.h>
+
+#include <xen/hypervisor.h>
+#include <xen/xenstore/xenstorevar.h>
+#include <xen/xenstore/xenstore_internal.h>
+
+#include <vm/vm.h>
+#include <vm/pmap.h>
+
+#define XSD_READ_SIZE		20
+
+static int xsd_dev_read(struct cdev *dev, struct uio *uio, int ioflag);
+static int xsd_dev_mmap(struct cdev *dev, vm_ooffset_t offset,
+    vm_paddr_t *paddr, int nprot, vm_memattr_t *memattr);
+
+
+static struct cdevsw xsd_dev_cdevsw = {
+	.d_version = D_VERSION,
+	.d_read = xsd_dev_read,
+	.d_mmap = xsd_dev_mmap,
+	.d_name = "xsd_dev",
+};
+
+static int
+xsd_dev_read(struct cdev *dev, struct uio *uio, int ioflag)
+{
+	char evtchn[XSD_READ_SIZE];
+	int error, len;
+
+	len = snprintf(evtchn, sizeof(evtchn), "%u",
+	    HYPERVISOR_start_info->store_evtchn);
+	if (len < 0 || len > uio->uio_resid)
+		return (EINVAL);
+
+	error = uiomove(evtchn, len, uio);
+	if (error)
+		return (error);
+
+	return (0);
+}
+
+static int
+xsd_dev_mmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
+    int nprot, vm_memattr_t *memattr)
+{
+
+	if (offset != 0)
+		return (EINVAL);
+
+	*paddr = pmap_kextract((vm_offset_t)xen_store);
+
+	return (0);
+}
+
+/*------------------ Private Device Attachment Functions  --------------------*/
+/**
+ * \brief Identify instances of this device type in the system.
+ *
+ * \param driver  The driver performing this identify action.
+ * \param parent  The NewBus parent device for any devices this method adds.
+ */
+static void
+xsd_dev_identify(driver_t *driver __unused, device_t parent)
+{
+
+	if (!xen_pv_domain())
+		return;
+	if (HYPERVISOR_start_info->store_mfn != 0)
+		return;
+
+	/*
+	 * Only attach if xenstore is not available, because we are the
+	 * domain that's supposed to run it.
+	 */
+	BUS_ADD_CHILD(parent, 0, driver->name, 0);
+}
+
+/**
+ * \brief Probe for the existence of the Xenstored device
+ *
+ * \param dev  NewBus device_t for this instance.
+ *
+ * \return  Always returns 0 indicating success.
+ */
+static int 
+xsd_dev_probe(device_t dev)
+{
+
+	device_set_desc(dev, "Xenstored user-space device");
+	return (BUS_PROBE_NOWILDCARD);
+}
+
+/**
+ * \brief Attach the Xenstored device.
+ *
+ * \param dev  NewBus device_t for this instance.
+ *
+ * \return  On success, 0. Otherwise an errno value indicating the
+ *          type of failure.
+ */
+static int
+xsd_dev_attach(device_t dev)
+{
+	struct cdev *xsd_cdev;
+
+	xsd_cdev = make_dev(&xsd_dev_cdevsw, 0, UID_ROOT, GID_WHEEL, 0400,
+	    "xen/xenstored");
+	if (xsd_cdev == NULL)
+		return (EINVAL);
+
+	return (0);
+}
+
+/*-------------------- Private Device Attachment Data  -----------------------*/
+static device_method_t xsd_dev_methods[] = {
+	/* Device interface */
+	DEVMETHOD(device_identify,	xsd_dev_identify),
+	DEVMETHOD(device_probe,         xsd_dev_probe),
+	DEVMETHOD(device_attach,        xsd_dev_attach),
+
+	DEVMETHOD_END
+};
+
+DEFINE_CLASS_0(xsd_dev, xsd_dev_driver, xsd_dev_methods, 0);
+devclass_t xsd_dev_devclass;
+
+DRIVER_MODULE(xsd_dev, xenpv, xsd_dev_driver, xsd_dev_devclass,
+    NULL, NULL);