arm: rate-limit logging from unimplemented PHYSDEVOP and HVMOP.

These are guest accessible and should therefore be rate-limited.
Moreover, include them only in debug builds.

This is CVE-2015-7813 / XSA-146.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/arm/hvm.c

@@ -57,7 +57,7 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
 
     default:
     {
-        printk("%s: Bad HVM op %ld.\n", __func__, op);
+        gdprintk(XENLOG_DEBUG, "HVMOP op=%lu: not implemented\n", op);
         rc = -ENOSYS;
         break;
     }

xen/arch/arm/physdev.c

@@ -8,12 +8,13 @@
 #include <xen/types.h>
 #include <xen/lib.h>
 #include <xen/errno.h>
+#include <xen/sched.h>
 #include <asm/hypercall.h>
 
 
 int do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 {
-    printk("%s %d cmd=%d: not implemented yet\n", __func__, __LINE__, cmd);
+    gdprintk(XENLOG_DEBUG, "PHYSDEVOP cmd=%d: not implemented\n", cmd);
     return -ENOSYS;
 }