From ae28f874021d92f0abd37113a56dcec89b570777 Mon Sep 17 00:00:00 2001
From: EkeEke <ekeeke31@gmail.com>
Date: Thu, 21 Jun 2018 00:28:57 +0200
Subject: [PATCH] [Core/MS] improved region detection (fixes BIOS support with
 Japanese games)

---
 core/cart_hw/sms_cart.c | 19 +++++++++++++++----
 core/cart_hw/sms_cart.h |  2 +-
 core/loadrom.c          |  4 ++--
 core/loadrom.h          |  2 +-
 4 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/core/cart_hw/sms_cart.c b/core/cart_hw/sms_cart.c
index cc4fd22..296d568 100644
--- a/core/cart_hw/sms_cart.c
+++ b/core/cart_hw/sms_cart.c
@@ -2,7 +2,7 @@
  *  Genesis Plus
  *  SG-1000, Master System & Game Gear cartridge hardware support
  *
- *  Copyright (C) 2007-2017  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2007-2018  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met:
@@ -718,10 +718,21 @@ int sms_cart_region_detect(void)
   while(i--);
 
   /* Mark-III hardware */
-  if (system_hw == SYSTEM_MARKIII)
+  if (config.system == SYSTEM_MARKIII)
   {
-    /* Japan */
-    return REGION_JAPAN_NTSC;
+    /* Japan only */
+    region_code = REGION_JAPAN_NTSC;
+  }
+
+  /* Master System / Game Gear ROM file */
+  if (system_hw >= SYSTEM_SMS)
+  {
+    /* missing header or valid header with Japan region code */
+    if (!rominfo.country[0] || !memcmp(rominfo.country,"SMS Japan",9) || !memcmp(rominfo.country,"GG Japan",8))
+    {
+      /* assume Japan region (fixes BIOS support) */
+      return REGION_JAPAN_NTSC;
+    }
   }
 
   /* default region */
diff --git a/core/cart_hw/sms_cart.h b/core/cart_hw/sms_cart.h
index 88aa5d7..6657926 100644
--- a/core/cart_hw/sms_cart.h
+++ b/core/cart_hw/sms_cart.h
@@ -2,7 +2,7 @@
  *  Genesis Plus
  *  SG-1000, Master System & Game Gear cartridge hardware support
  *
- *  Copyright (C) 2007-2017  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2007-2018  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met:
diff --git a/core/loadrom.c b/core/loadrom.c
index c9e3b0d..a02d7e0 100644
--- a/core/loadrom.c
+++ b/core/loadrom.c
@@ -3,7 +3,7 @@
  *  ROM Loading Support
  *
  *  Copyright (C) 1998-2003  Charles Mac Donald (original code)
- *  Copyright (C) 2007-2017  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2007-2018  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met:
@@ -311,7 +311,7 @@ void getrominfo(char *romheader)
     }
 
     /* if found, get infos from header */
-    if (offset)
+    if ((offset > 0) && (offset < cart.romsize))
     {
       /* checksum */
       rominfo.checksum = romheader[offset + 0x0a] | (romheader[offset + 0x0b] << 8);
diff --git a/core/loadrom.h b/core/loadrom.h
index 5809a76..e921c22 100644
--- a/core/loadrom.h
+++ b/core/loadrom.h
@@ -3,7 +3,7 @@
  *  ROM Loading Support
  *
  *  Copyright (C) 1998-2003  Charles Mac Donald (original code)
- *  Copyright (C) 2007-2017  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2007-2018  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met: