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From: Blue Swirl <blauwirbel@gmail.com>
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Date: Thu, 11 Dec 2008 17:30:51 +0000
Subject: [Qemu-devel] [5978] Allow to register a callback with
	fw_cfg_add_callback()
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Revision: 5978
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5978
Author:   blueswir1
Date:     2008-12-11 17:30:50 +0000 (Thu, 11 Dec 2008)

Log Message:
-----------
Allow to register a callback with fw_cfg_add_callback()
fw_cfg_add_callback() checks if key has FW_CFG_WRITE_CHANNEL bit set
after masking the key with FW_CFG_ENTRY_MASK.

But as FW_CFG_ENTRY_MASK is ~(FW_CFG_WRITE_CHANNEL | FW_CFG_ARCH_LOCAL),
the bit is never set and function exits.

This patch corrects this by checking the bit before masking the value.

Signed-by-off: Laurent Vivier <Laurent.Vivier@bull.net>
Acked-by: Gleb Natapov <gleb@redhat.com>

Modified Paths:
--------------
    trunk/hw/fw_cfg.c

Modified: trunk/hw/fw_cfg.c
===================================================================
--- trunk/hw/fw_cfg.c	2008-12-11 17:29:00 UTC (rev 5977)
+++ trunk/hw/fw_cfg.c	2008-12-11 17:30:50 UTC (rev 5978)
@@ -240,10 +240,12 @@
     FWCfgState *s = opaque;
     int arch = !!(key & FW_CFG_ARCH_LOCAL);
 
+    if (!(key & FW_CFG_WRITE_CHANNEL))
+        return 0;
+
     key &= FW_CFG_ENTRY_MASK;
 
-    if (key >= FW_CFG_MAX_ENTRY || !(key & FW_CFG_WRITE_CHANNEL)
-        || len > 65535)
+    if (key >= FW_CFG_MAX_ENTRY || len > 65535)
         return 0;
 
     s->entries[arch][key].data = data;