[aandrejevic] 60944: [FAST486] Fix the Mod-Reg-R/M parser. EBP cannot be used as a SIB byte base, instead it's used to mark that the base is an immediate operand.

Author: aandrejevic
Date: Mon Nov 11 17:24:22 2013
New Revision: 60944

URL: http://svn.reactos.org/svn/reactos?rev=60944&view=rev
Log:
[FAST486]
Fix the Mod-Reg-R/M parser. EBP cannot be used as a SIB byte base,
instead it's used to mark that the base is an immediate operand.


Modified:
    branches/ntvdm/lib/fast486/common.inl

Modified: branches/ntvdm/lib/fast486/common.inl
URL:
http://svn.reactos.org/svn/reactos/branches/ntvdm/lib/fast486/common.inl?re…
==============================================================================
--- branches/ntvdm/lib/fast486/common.inl	[iso-8859-1] (original)
+++ branches/ntvdm/lib/fast486/common.inl	[iso-8859-1] Mon Nov 11 17:24:22 2013
@@ -719,7 +719,21 @@
             Index = (SibByte >> 3) & 0x07;
             if (Index != FAST486_REG_ESP) Index = State->GeneralRegs[Index].Long;
             else Index = 0;
-            Base = State->GeneralRegs[SibByte & 0x07].Long;
+
+            if ((SibByte & 0x07) != FAST486_REG_EBP)
+            {
+                /* Use the register a base */
+                Base = State->GeneralRegs[SibByte & 0x07].Long;
+            }
+            else
+            {
+                /* Fetch the base */
+                if (!Fast486FetchDword(State, &Base))
+                {
+                    /* Exception occurred */
+                    return FALSE;
+                }
+            }
 
             /* Calculate the address */
             ModRegRm->MemoryAddress = Base + Index * Scale;