2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1989, 1990 William F. Jolitz
5 * Copyright (c) 1990 The Regents of the University of California.
8 * This code is derived from software contributed to Berkeley by
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12 * modification, are permitted provided that the following conditions
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35 * from: @(#)segments.h 7.1 (Berkeley) 5/9/91
39 #ifndef _MACHINE_SEGMENTS_H_
40 #define _MACHINE_SEGMENTS_H_
43 * 386 Segmentation Data Structures and definitions
44 * William F. Jolitz (william@ernie.berkeley.edu) 6/20/1989
47 #include <x86/segments.h>
50 * Software definitions are in this convenient format,
51 * which are translated into inconvenient segment descriptors
52 * when needed to be used by the 386 hardware
55 struct soft_segment_descriptor {
56 unsigned ssd_base ; /* segment base address */
57 unsigned ssd_limit ; /* segment extent */
58 unsigned ssd_type:5 ; /* segment type */
59 unsigned ssd_dpl:2 ; /* segment descriptor priority level */
60 unsigned ssd_p:1 ; /* segment descriptor present */
61 unsigned ssd_xx:4 ; /* unused */
62 unsigned ssd_xx1:2 ; /* unused */
63 unsigned ssd_def32:1 ; /* default 32 vs 16 bit size */
64 unsigned ssd_gran:1 ; /* limit granularity (byte/page units)*/
68 * region descriptors, used to load gdt/idt tables before segments yet exist.
70 struct region_descriptor {
71 unsigned rd_limit:16; /* segment extent */
72 unsigned rd_base:32 __packed; /* base address */
76 * Segment Protection Exception code bits
79 #define SEGEX_EXT 0x01 /* recursive or externally induced */
80 #define SEGEX_IDT 0x02 /* interrupt descriptor table */
81 #define SEGEX_TI 0x04 /* local descriptor table */
82 /* other bits are affected descriptor index */
83 #define SEGEX_IDX(s) (((s)>>3)&0x1fff)
86 extern int _default_ldt;
87 extern union descriptor *gdt;
88 extern union descriptor *ldt;
89 extern struct soft_segment_descriptor gdt_segs[];
90 extern struct gate_descriptor *idt;
92 void lgdt(struct region_descriptor *rdp);
93 void sdtossd(struct segment_descriptor *sdp,
94 struct soft_segment_descriptor *ssdp);
95 void ssdtosd(struct soft_segment_descriptor *ssdp,
96 struct segment_descriptor *sdp);
99 #endif /* !_MACHINE_SEGMENTS_H_ */