From: Aleksandar Andrejevic <aandrejevic@reactos.org>
Date: Wed, 20 Nov 2013 14:21:47 +0000 (+0000)
Subject: [FAST486]
X-Git-Tag: backups/0.3.17@66124~1365^2~220
X-Git-Url: https://git.reactos.org/?p=reactos.git;a=commitdiff_plain;h=f90a1db2b70acc7d49e2eab956b90e7668b8a4fb

[FAST486]
The top half of EIP is cleared after a 16-bit jump.


svn path=/branches/ntvdm/; revision=61058
---

diff --git a/lib/fast486/opcodes.c b/lib/fast486/opcodes.c
index ac15525d8b5..b982996e967 100644
--- a/lib/fast486/opcodes.c
+++ b/lib/fast486/opcodes.c
@@ -606,10 +606,13 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeShortConditionalJmp)
 {
     BOOLEAN Jump = FALSE;
     CHAR Offset = 0;
+    BOOLEAN Size = State->SegmentRegs[FAST486_REG_CS].Size;
 
     /* Make sure this is the right instruction */
     ASSERT((Opcode & 0xF0) == 0x70);
 
+    TOGGLE_OPSIZE(Size);
+
     /* Fetch the offset */
     if (!Fast486FetchByte(State, (PUCHAR)&Offset))
     {
@@ -686,6 +689,12 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeShortConditionalJmp)
     {
         /* Move the instruction pointer */
         State->InstPtr.Long += Offset;
+
+        if (!Size)
+        {
+            /* Clear the top half of EIP */
+            State->InstPtr.Long &= 0xFFFF;
+        }
     }
 
     /* Return success */
@@ -1058,6 +1067,9 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeOut)
 FAST486_OPCODE_HANDLER(Fast486OpcodeShortJump)
 {
     CHAR Offset = 0;
+    BOOLEAN Size = State->SegmentRegs[FAST486_REG_CS].Size;
+
+    TOGGLE_OPSIZE(Size);
 
     /* Make sure this is the right instruction */
     ASSERT(Opcode == 0xEB);
@@ -1072,6 +1084,12 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeShortJump)
     /* Move the instruction pointer */
     State->InstPtr.Long += Offset;
 
+    if (!Size)
+    {
+        /* Clear the top half of EIP */
+        State->InstPtr.Long &= 0xFFFF;
+    }
+
     return TRUE;
 }
 
@@ -5087,7 +5105,10 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeJmp)
         }
 
         /* Move the instruction pointer */
-        State->InstPtr.LowWord += Offset;
+        State->InstPtr.Long += Offset;
+
+        /* Clear the top half of EIP */
+        State->InstPtr.Long &= 0xFFFF;
     }
 
     return TRUE;
@@ -5137,9 +5158,8 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeJmpAbs)
         return FALSE;
     }
 
-    /* Load new (E)IP */
-    if (Size) State->InstPtr.Long = Offset;
-    else State->InstPtr.LowWord = LOWORD(Offset);
+    /* Load new EIP */
+    State->InstPtr.Long = Offset;
 
     return TRUE;
 }
diff --git a/lib/fast486/opgroups.c b/lib/fast486/opgroups.c
index 9519aeb0eec..1c223e0994c 100644
--- a/lib/fast486/opgroups.c
+++ b/lib/fast486/opgroups.c
@@ -1539,6 +1539,9 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeGroupFF)
 
             /* Set the IP to the address */
             State->InstPtr.LowWord = Value;
+
+            /* Clear the top half of EIP */
+            State->InstPtr.Long &= 0xFFFF;
         }
         else if (ModRegRm.Register == 3)
         {
@@ -1588,6 +1591,8 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeGroupFF)
             /* Set the IP to the address */
             State->InstPtr.LowWord = Value;
 
+            /* Clear the top half of EIP */
+            State->InstPtr.Long &= 0xFFFF;
         }
         else if (ModRegRm.Register == 4)
         {
@@ -1627,6 +1632,9 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeGroupFF)
 
             /* Set the IP to the address */
             State->InstPtr.LowWord = Value;
+
+            /* Clear the top half of EIP */
+            State->InstPtr.Long &= 0xFFFF;
         }
         else if (ModRegRm.Register == 6)
         {