----------------------------------------------------------------------
Patch name: patch.v8086-exception.lightcone
Author: LightCone
Date: Thu Aug  7 2003
Status: Proposed 

Detailed description:
This is a reformat of SF patch #704181 CPU interrupt function

Here is what the author wrote:
 Since the bug of bochs-2.0.win32 was found and
 corrected, it reports. cpu/exception.cpp of src : Within
 an interrupt() function, when present is the V8086 mode,
 a bug is in the portion which processes 386 (286)
 int/trap gate. From the V8086 mode, this portion is
 performed, when it is going to execute an int imm
 command. The portion in which push_32 () is called in
 the state of VM=1 is still a mistake. Although this
 push_32 () tends to write in to the stack of a protected
 mode, if it is still VM=1 of EFLAGS, the
 write_virtual_dword() function called out of push_32 () will
 take out a segment protection exception. After
 performing clear_VM() etc., it is necessary to make it
 call push_32 () correctly, since EFLAGS is saved locally.

Patch was created with:
  cvs diff -u
Apply patch to what version:
  cvs checked out on Thu Aug  7 2003
Instructions:
  To patch, go to main bochs directory.
  Type "patch -p0 < THIS_PATCH_FILE".
----------------------------------------------------------------------
Index: cpu/exception.cc
===================================================================
RCS file: /cvsroot/bochs/bochs/cpu/exception.cc,v
retrieving revision 1.33
diff -u -r1.33 exception.cc
--- cpu/exception.cc	26 Feb 2003 02:48:12 -0000	1.33
+++ cpu/exception.cc	7 Aug 2003 09:02:24 -0000
@@ -637,9 +637,23 @@
           // set RPL of CS to CPL
           load_cs(&cs_selector, &cs_descriptor, cs_descriptor.dpl);
           EIP = gate_dest_offset;
+          
+          // Modified by LightCone
+          Bit32u old_EFLAGS= read_eflags();
+          bx_bool bV8086Mode= v8086_mode();
+
+          // if INTERRUPT GATE set IF to 0
+          if ( !(gate_descriptor.type & 1) ) {// even is int-gate
+            BX_CPU_THIS_PTR clear_IF ();
+            }
+          BX_CPU_THIS_PTR clear_TF ();
+          BX_CPU_THIS_PTR clear_VM ();
+          BX_CPU_THIS_PTR clear_RF ();
+          BX_CPU_THIS_PTR clear_NT ();
+
 
           if (gate_descriptor.type>=14) { // 386 int/trap gate
-            if (v8086_mode()) {
+            if (bV8086Mode) {
               push_32(BX_CPU_THIS_PTR sregs[BX_SEG_REG_GS].selector.value);
               push_32(BX_CPU_THIS_PTR sregs[BX_SEG_REG_FS].selector.value);
               push_32(BX_CPU_THIS_PTR sregs[BX_SEG_REG_DS].selector.value);
@@ -653,46 +667,43 @@
               BX_CPU_THIS_PTR sregs[BX_SEG_REG_ES].cache.valid = 0;
               BX_CPU_THIS_PTR sregs[BX_SEG_REG_ES].selector.value = 0;
               }
+
             // push long pointer to old stack onto new stack
             push_32(old_SS);
             push_32(old_ESP);
 
             // push EFLAGS
-            push_32(read_eflags());
+            push_32(old_EFLAGS);
 
             // push long pointer to return address onto new stack
             push_32(old_CS);
             push_32(old_EIP);
 
-            if ( is_error_code )
+            if ( is_error_code ) {
               push_32(error_code);
+              }
             }
           else { // 286 int/trap gate
-            if (v8086_mode()) {
+            if (bV8086Mode) {
               BX_PANIC(("286 int/trap gate, VM"));
               }
+
             // push long pointer to old stack onto new stack
             push_16(old_SS);
             push_16(old_ESP); // ignores upper 16bits
 
             // push FLAGS
-            push_16(read_flags());
+            push_16((Bit16u)old_EFLAGS);
 
             // push return address onto new stack
             push_16(old_CS);
             push_16(old_EIP); // ignores upper 16bits
 
-            if ( is_error_code )
+            if ( is_error_code ) {
               push_16(error_code);
+              }
             }
 
-          // if INTERRUPT GATE set IF to 0
-          if ( !(gate_descriptor.type & 1) ) // even is int-gate
-            BX_CPU_THIS_PTR clear_IF ();
-          BX_CPU_THIS_PTR clear_TF ();
-          BX_CPU_THIS_PTR clear_VM ();
-          BX_CPU_THIS_PTR clear_RF ();
-          BX_CPU_THIS_PTR clear_NT ();
           return;
           }