[XEN] Change microcode_update function interface inside Xen.

Confine the knowledge that the buffer gets accessed without use of
proper guest handle accessors to a single file.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

2 files changed, 10 insertions, 5 deletions

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index 9c4b4d66f8..3dcac7d124 100644
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -455,7 +455,7 @@ out:
 	return error;
 }
 
-int microcode_update(void *buf, unsigned long len)
+int microcode_update(XEN_GUEST_HANDLE(void) buf, unsigned long len)
 {
 	int ret;
 
@@ -464,10 +464,15 @@ int microcode_update(void *buf, unsigned long len)
 		return -EINVAL;
 	}
 
+	if (len != (typeof(user_buffer_size))len) {
+		printk(KERN_ERR "microcode: too much data\n");
+		return -E2BIG;
+	}
+
 	mutex_lock(&microcode_mutex);
 
-	user_buffer = (void __user *) buf;
-	user_buffer_size = (int) len;
+	user_buffer = buf.p;
+	user_buffer_size = len;
 
 	ret = do_microcode_update();
 
diff --git a/xen/arch/x86/platform_hypercall.c b/xen/arch/x86/platform_hypercall.c
index 098c847112..1b886caab2 100644
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -104,8 +104,8 @@ long do_platform_op(XEN_GUEST_HANDLE(xen_platform_op_t) u_xenpf_op)
 
     case XENPF_microcode_update:
     {
-        extern int microcode_update(void *buf, unsigned long len);
-        ret = microcode_update(op->u.microcode.data.p,
+        extern int microcode_update(XEN_GUEST_HANDLE(void), unsigned long len);
+        ret = microcode_update(op->u.microcode.data,
                                op->u.microcode.length);
     }
     break;