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/*
* Mach Operating System
* Copyright (c) 1991,1990 Carnegie Mellon University
* Copyright (c) 1991 IBM Corporation
* Copyright (c) 1994 The University of Utah and
* the Computer Systems Laboratory (CSL).
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation,
* and that the name IBM not be used in advertising or publicity
* pertaining to distribution of the software without specific, written
* prior permission.
*
* CARNEGIE MELLON, IBM, AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON, IBM, AND CSL DISCLAIM ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
#ifndef _I386_GDT_
#define _I386_GDT_
#include <oskit/x86/base_gdt.h>
/* The layout of the GDT is as follows. Each four entries fill one cache line.
We need to match the oskit layout if we call into any oskit code that uses
the literal selectors. I don't think we do, except for base_gdt_load
itself. So we make sure the oskit's KERNEL_CS and KERNEL_DS selectors work
ok, but reuse the other base_gdt slots differently. It's presumed a Good
Thing to have all the commonly-used kernel-mode descriptors on one cache
line and all the user-mode descriptors on another single cache line.
idx sel what oskit base_gdt usage
0 0x00 reserved (null selector)
1 0x08 initial TSS oskit BASE_TSS
2 0x10 initial kernel code oskit KERNEL_CS
3 0x18 initial kernel data oskit KERNEL_DS
4 0x20 KERNEL_CS oskit KERNEL_16_CS
5 0x28 KERNEL_DS oskit KERNEL_16_CS
6 0x30 KERNEL_TSS oskit LINEAR_CS
7 0x38 KERNEL_LDT oskit LINEAR_DS
8 0x43 user-mode code oskit USER_CS
9 0x4b user-mode code oskit USER_DS
10 0x50 i386_set_gdt #1
11 0x58 i386_set_gdt #2
12 0x60 USER_LDT
13 0x68
14 0x70 FPE_CS
15 0x78 USER_FPREGS
For more, can no longer use oskit base_gdt defn since GDTSZ is 16 entries.
*/
#define BASE_KERNEL_CS 0x10 /* <oskit/x86/base_gdt.h> value of KERNEL_CS */
#define BASE_KERNEL_DS 0x18 /* <oskit/x86/base_gdt.h> value of KERNEL_DS */
#undef KERNEL_CS
#undef KERNEL_DS
#define KERNEL_CS 0x20
#define KERNEL_DS 0x28
#define KERNEL_TSS 0x30
#define KERNEL_LDT 0x38
#undef USER_CS
#undef USER_DS
#define USER_LDT 0x60
#define FPE_CS 0x70
#define USER_FPREGS 0x78
#define USER_GDT 0x50
#define USER_GDT_SLOTS 2
#define gdt base_gdt
/* Fill a segment descriptor in the GDT. */
#define fill_gdt_descriptor(segment, base, limit, access, sizebits) \
fill_descriptor(&gdt[segment/8], base, limit, access, sizebits)
#endif /* _I386_GDT_ */
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