[PATCHv3] 1/3] libxc: prefer using privcmd character device

[Doug Goldstein <cardoe@cardoe.com>]

Prefer using the character device over the proc file if the character
device exists. This follows similar conversions of xenbus to avoid
issues with FMODE_ATOMIC_POS added in Linux 3.14 and newer.

CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
---
 tools/libxc/xc_linux_osdep.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/libxc/xc_linux_osdep.c b/tools/libxc/xc_linux_osdep.c
index 76c55ff..c3a3a14 100644
--- a/tools/libxc/xc_linux_osdep.c
+++ b/tools/libxc/xc_linux_osdep.c
@@ -46,7 +46,13 @@
 static xc_osdep_handle linux_privcmd_open(xc_interface *xch)
 {
     int flags, saved_errno;
-    int fd = open("/proc/xen/privcmd", O_RDWR);
+    int fd = open("/dev/xen/privcmd", O_RDWR); /* prefer this newer interface */
+
+    if ( fd == -1 && ( errno == ENOENT || errno == ENXIO || errno == ENODEV ))
+    {
+        /* Fallback to /proc/xen/privcmd */
+        fd = open("/proc/xen/privcmd", O_RDWR);
+    }
 
     if ( fd == -1 )
     {
-- 
2.4.10