[Xen-devel] [PATCH] x86/emulation: honor failure of in_longmode()

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

Failure of in_longmode() shouldn't be treated the same as the function
returning 'true'.

Besides that, the function should always return false on 32-bits,
eliminating the possibility for it failing there altogether.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- 2009-08-18.orig/xen/arch/x86/x86_emulate/x86_emulate.c      2009-08-18 
14:18:20.000000000 +0200
+++ 2009-08-18/xen/arch/x86/x86_emulate/x86_emulate.c   2009-08-24 
11:30:17.000000000 +0200
@@ -958,6 +958,7 @@ in_longmode(
     struct x86_emulate_ctxt *ctxt,
     struct x86_emulate_ops *ops)
 {
+#ifdef __x86_64__
     uint64_t efer;
 
     if (ops->read_msr == NULL)
@@ -965,6 +966,9 @@ in_longmode(
 
     ops->read_msr(MSR_EFER, &efer, ctxt);
     return !!(efer & EFER_LMA);
+#else
+    return 0;
+#endif
 }
 
 static int
@@ -3605,7 +3609,10 @@ x86_emulate(
         ss.attr.bytes = 0xc93; /* G+DB+P+S+Data */
 
 #ifdef __x86_64__
-        if ( in_longmode(ctxt, ops) )
+        rc = in_longmode(ctxt, ops);
+        if ( rc < 0 )
+            goto cannot_emulate;
+        if ( rc )
         {
             cs.attr.fields.db = 0;
             cs.attr.fields.l = 1;
@@ -3777,7 +3784,10 @@ x86_emulate(
         ss.limit = ~0u;  /* 4GB limit */
         ss.attr.bytes = 0xc93; /* G+DB+P+S+Data */
 
-        if ( in_longmode(ctxt, ops) )
+        rc = in_longmode(ctxt, ops);
+        if ( rc < 0 )
+            goto cannot_emulate;
+        if ( rc )
         {
             cs.attr.fields.db = 0;
             cs.attr.fields.l = 1;




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