From 68805961dc4ca2ce98ef213dfd9a6f8148e3dd17 Mon Sep 17 00:00:00 2001
From: Bart Oldeman <bart@dosemu.org>
Date: Thu, 28 Aug 2003 20:25:09 +0000
Subject: [PATCH] Don't disable a20 for "exit" int21/ah=4c

git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@654 6ac86273-5f31-0410-b378-82cca8765d1b
---
 kernel/procsupt.asm | 10 +++++++---
 kernel/proto.h      |  2 +-
 kernel/task.c       |  4 ++--
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/kernel/procsupt.asm b/kernel/procsupt.asm
index ecf25b7..01fedc4 100644
--- a/kernel/procsupt.asm
+++ b/kernel/procsupt.asm
@@ -45,8 +45,7 @@ segment HMA_TEXT
 ;
 ;       Special call for switching processes
 ;
-;       void exec_user(irp)
-;       iregs far *irp;
+;       void exec_user(iregs far *irp, int disable_a20)
 ;
                 global  _exec_user
 _exec_user:
@@ -60,15 +59,20 @@ _exec_user:
                 pop     ax		      ; return address (unused)
 
                 pop     ax		      ; irp (user ss:sp)
-                pop	dx 
+                pop	dx
+		pop	cx		      ; disable A20?
                 cli
                 mov     ss,dx
                 mov     sp,ax                   ; set-up user stack
                 sti
 ;
+		or	cx,cx
                 POP$ALL
+		jz      do_iret
                 extern _ExecUserDisableA20
                 jmp far _ExecUserDisableA20
+do_iret:
+		iret
 
 segment _LOWTEXT
 
diff --git a/kernel/proto.h b/kernel/proto.h
index 0c99ff0..d2b2c09 100644
--- a/kernel/proto.h
+++ b/kernel/proto.h
@@ -373,7 +373,7 @@ UWORD get_machine_name(BYTE FAR * netname);
 VOID set_machine_name(BYTE FAR * netname, UWORD name_num);
 
 /* procsupt.asm */
-VOID ASMCFUNC exec_user(iregs FAR * irp);
+VOID ASMCFUNC exec_user(iregs FAR * irp, int disable_a20);
 
 /* new by TE */
 
diff --git a/kernel/task.c b/kernel/task.c
index 3c3f6c7..9fb30fd 100644
--- a/kernel/task.c
+++ b/kernel/task.c
@@ -314,7 +314,7 @@ int load_transfer(UWORD ds, exec_blk *exp, UWORD fcbcode, COUNT mode)
     
     if (InDOS)
       --InDOS;
-    exec_user(irp);
+    exec_user(irp, 1);
     
     /* We should never be here          
        fatal("KERNEL RETURNED!!!");                    */
@@ -528,7 +528,7 @@ VOID return_user(void)
 
   if (InDOS)
     --InDOS;
-  exec_user((iregs FAR *) q->ps_stack);
+  exec_user((iregs FAR *) q->ps_stack, 0);
 }
 
 COUNT DosExeLoader(BYTE FAR * namep, exec_blk * exp, COUNT mode, COUNT fd)