From cd88561aea212798e12dd2ddb5aac3d6599cbece Mon Sep 17 00:00:00 2001
From: Richard Burgess <>
Date: Mon, 5 Dec 1994 11:35:32 +0000
Subject: [PATCH] autocommit for file dated 1994-12-05 11:35:32

---
 ossource/mosgdt.asm | 70 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 ossource/mosgdt.asm

diff --git a/ossource/mosgdt.asm b/ossource/mosgdt.asm
new file mode 100644
index 0000000..3cb257c
--- /dev/null
+++ b/ossource/mosgdt.asm
@@ -0,0 +1,70 @@
+;   MMURTL Operating System Source Code
+;   Copyright 1991,1992,1993,1994 Richard A. Burgess
+;   ALL RIGHTS RESERVED
+;   Version 1,0
+.DATA
+.INCLUDE MOSEDF.INC
+
+;=============================================================================
+;
+; All the static GDT descriptors below are defined as shown on page
+; 2-5 of the 80386 System Software Writer's Guide.
+; Comments next	to each of the entries mean:
+;
+; Limit - 00:15 DW A WORD (16 bits) with LSW of the Linear Segment Limit
+; Base  - 00:15 DW A WORD (16 bits) with LSW of the Linear Segment Base
+; Base  - 16:23 DB A BYTE (8 bits) with MSB of the Linear Segment Base
+; ProtType      DB P/DPL/1/CRA or EWA/ Protection, Type, etc...
+; GranSizeLim   DB Granularity/Size for code/
+; Base  - 24:31 DB A BYTE (8 bits) with MSB of the Linear Segment base
+;
+;=============================================================================
+;Sel 00h
+PUBLIC GDT	DD 2 DUP (0h)		;The first desc is always null
+
+;Sel 08
+OSCodeDesc	DW 0FFFFh			; Limit 15-0 (4Gb)
+			DW 0000h			; Base  15-0
+			DB 00h				; Base  23-16	;10000h
+			DB 10011010b		; P(1) DPL(00) 1 1 C(0) R(1) A(0)
+			DB 11001111b		; G(1) D(1) 0 0 Limit[19-16]
+			DB 00h				; Base  31-24
+
+;Sel 10h  - This the OS and User Data descriptor.
+
+DataDesc	DW 0FFFFh			;Limit (bits 0:15) at linear 00K
+			DW 0000h			;base (bits 15:0)
+			DB 00h				;base (bits 23:16)
+			DB 10010010b		;P(1) DPL(00) 1 0 E(0) W(1) A(0)
+			DB 11001111b		;G(1), B(1) 0 0 limit[19-16)
+			DB 00h				;Base at 0 (bits 31:24)
+
+;Sel 18h - This is the user's code descriptor.
+
+CodeDesc	DW 0FFFFh			; Limit 15-0 (0FFFFh)
+			DW 0000h			; Base  15-0
+			DB 00h				; Base  23-16
+			DB 10011010b		; P(1)-DPL(00)-1-1-C(0)-R(1)-A(0)
+			DB 11001111b		; G(1) D(1) 0 0 Limit[19-16]
+			DB 00h				; Base  31-24
+
+;Save these for the future...
+
+OSXtra0Desc	DD 0, 0		;Sel 20h
+OSXtra1Desc	DD 0, 0		;Sel 28h
+OSXtra2Desc	DD 0, 0		;Sel 30h
+OSXtra3Desc	DD 0, 0		;Sel 38h
+
+;WARNING: The rgCall Descriptors must never be moved from this location
+;	  in the GDT. They describe system entry points that will become
+;	  PUBLIC for external programs.	The first PUBLIC call gate is
+;	  selector 40h.
+
+;Sel 40
+
+PUBLIC rgCallDesc	DD (nCallGates*2) DUP (0)	;Call Gates
+
+PUBLIC rgTSSDesc	DD (nTSS*2) DUP (0) 		;Task descriptors
+
+
+;--------- END OF MODULE ------------------------------
-- 
2.40.0