xen: add xenfs to allow usermode <-> Xen interaction

The xenfs filesystem exports various interfaces to usermode.  Initially
this exports a file to allow usermode to interact with xenbus/xenstore.

Traditionally this appeared in /proc/xen.  Rather than extending procfs,
this patch adds a backward-compat mountpoint on /proc/xen, and provides
a xenfs filesystem which can be mounted there.

Signed-off-by: Alex Zeffertt <alex.zeffertt@eu.citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 6 deletions

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index b2a03184a24..773d1cf2328 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -40,6 +40,7 @@
 #include <linux/ctype.h>
 #include <linux/fcntl.h>
 #include <linux/mm.h>
+#include <linux/proc_fs.h>
 #include <linux/notifier.h>
 #include <linux/kthread.h>
 #include <linux/mutex.h>
@@ -55,7 +56,10 @@
 #include "xenbus_comms.h"
 #include "xenbus_probe.h"
 
+
 int xen_store_evtchn;
+EXPORT_SYMBOL(xen_store_evtchn);
+
 struct xenstore_domain_interface *xen_store_interface;
 static unsigned long xen_store_mfn;
 
@@ -166,6 +170,9 @@ static int read_backend_details(struct xenbus_device *xendev)
         return read_otherend_details(xendev, "backend-id", "backend");
 }
 
+static struct device_attribute xenbus_dev_attrs[] = {
+        __ATTR_NULL
+};
 
 /* Bus type for frontend drivers. */
 static struct xen_bus_type xenbus_frontend = {
@@ -174,12 +181,13 @@ static struct xen_bus_type xenbus_frontend = {
         .get_bus_id = frontend_bus_id,
         .probe = xenbus_probe_frontend,
         .bus = {
-                .name     = "xen",
-                .match    = xenbus_match,
-                .uevent   = xenbus_uevent,
-                .probe    = xenbus_dev_probe,
-                .remove   = xenbus_dev_remove,
-                .shutdown = xenbus_dev_shutdown,
+                .name      = "xen",
+                .match     = xenbus_match,
+                .uevent    = xenbus_uevent,
+                .probe     = xenbus_dev_probe,
+                .remove    = xenbus_dev_remove,
+                .shutdown  = xenbus_dev_shutdown,
+                .dev_attrs = xenbus_dev_attrs,
         },
 };
 
@@ -852,6 +860,14 @@ static int __init xenbus_probe_init(void)
         if (!xen_initial_domain())
                 xenbus_probe(NULL);
 
+#ifdef CONFIG_XEN_COMPAT_XENFS
+        /*
+         * Create xenfs mountpoint in /proc for compatibility with
+         * utilities that expect to find "xenbus" under "/proc/xen".
+         */
+        proc_mkdir("xen", NULL);
+#endif
+
         return 0;
 
   out_unreg_back: