Improved linear address computation in bdshemu.

bdshemu/bdshemu.c

@@ -788,12 +788,6 @@ ShemuComputeLinearAddress(
 {
     uint64_t gla = 0;
 
-    // Memory operands usually have a segment.
-    if (Operand->Info.Memory.HasSeg)
-    {
-        gla += ShemuGetSegBase(Context, Operand->Info.Memory.Seg);
-    }
-
     if (Operand->Info.Memory.HasBase)
     {
         gla += ShemuGetGprValue(Context, Operand->Info.Memory.Base, Operand->Info.Memory.BaseSize, false);
@@ -857,11 +851,24 @@ ShemuComputeLinearAddress(
         gla &= 0xFFFFFFFF;
         break;
     case ND_ADDR_16:
-        gla &= 0xFFFFF;
+        gla &= 0xFFFF;
     default:
         break;
     }
 
+    // Memory operands usually have a segment. Note that we don't care about any segment checks, since we're most
+    // likely be provided with flat segments. If checks should be needed, dedicated callbacks should be added.
+    if (Operand->Info.Memory.HasSeg)
+    {
+        gla += ShemuGetSegBase(Context, Operand->Info.Memory.Seg);
+
+        if (Context->Mode != ND_CODE_64)
+        {
+            // Truncate to 32 bit outside 64 bit.
+            gla &= 0xFFFFFFFF;
+        }
+    }
+
     return gla;
 }
 

docs/source/index.rst

@@ -376,7 +376,7 @@ Determining if the instruction is a branch of any kind
    
    if (ix.RipAccess & ND_ACCESS_ANY_WRITE) // Instruction writes RIP.
    
-Computing the linear address of a memory operand
+Computing the virtual address of a memory operand
 ------------------------------------------------
 
 .. code-block:: c