From 1bb536c383b297207aa74faeb34e5d1741cc2fd4 Mon Sep 17 00:00:00 2001
From: Kenneth J Davis <PerditionC@gmail.com>
Date: Sun, 8 Aug 2021 14:37:07 -0400
Subject: [PATCH] LONG SEEK actually use lower 32 bits of 64 bit value (not 16
 bits)

---
 hdr/portab.h      | 7 +++++++
 kernel/inthndlr.c | 5 +++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/hdr/portab.h b/hdr/portab.h
index a364d25..b1764c8 100644
--- a/hdr/portab.h
+++ b/hdr/portab.h
@@ -317,6 +317,13 @@ typedef signed long LONG;
 #define LONG long
 #endif
 
+#if USHRT_MAX == 0xFFFF
+# define loword(v) ((unsigned short)(v))
+#else
+# define loword(v) (0xFFFF & (unsigned)(v))
+#endif
+#define hiword(v) loword ((v) >> 16u)
+
 #define MK_UWORD(hib,lob) (((UWORD)(hib) <<  8u) | (UBYTE)(lob))
 #define MK_ULONG(hiw,low) (((ULONG)(hiw) << 16u) | (UWORD)(low))
 
diff --git a/kernel/inthndlr.c b/kernel/inthndlr.c
index 49beeee..5f5668e 100644
--- a/kernel/inthndlr.c
+++ b/kernel/inthndlr.c
@@ -2207,11 +2207,12 @@ VOID ASMCFUNC int2F_12_handler(struct int2f12regs FAR *pr)
     case 0x42:                 /* 64-bit move file pointer */
     {
       /* r.(DS:DX) points to 64-bit file position instead of r.(CX:DX) being 32-bit file position */
-      UWORD FAR *filepos = MK_FP(r.DS, r.DX);
+      UDWORD FAR *filepos = MK_FP(r.DS, r.DX);
       if (*(filepos+1) != 0) /* we currently only handle lower 32 bits, upper 32 bits must be 0 */
         goto error_invalid;
       r.BP = (UWORD)r.CL;
-      r.CX = *filepos;
+      r.CX = hiword(*filepos);
+      r.DX = loword(*filepos);
       /* fall through to 32-bit move file pointer (0x28) */
     }
     case 0x28:                 /* move file pointer */