sys/i386/include/segments.h

/*-
 * Copyright (c) 1989, 1990 William F. Jolitz
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * William Jolitz.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from: @(#)segments.h    7.1 (Berkeley) 5/9/91
 *      $Id$
 */

/*
 * 386 Segmentation Data Structures and definitions
 *      William F. Jolitz (william@ernie.berkeley.edu) 6/20/1989
 */

/*
 * Selectors
 */

#define ISPL(s) ((s)&3)         /* what is the priority level of a selector */
#define SEL_KPL 0               /* kernel priority level */
#define SEL_UPL 3               /* user priority level */
#define ISLDT(s)        ((s)&SEL_LDT)   /* is it local or global */
#define SEL_LDT 4               /* local descriptor table */
#define IDXSEL(s)       (((s)>>3) & 0x1fff)             /* index of selector */
#define LSEL(s,r)       (((s)<<3) | SEL_LDT | r)        /* a local selector */
#define GSEL(s,r)       (((s)<<3) | r)                  /* a global selector */

/*
 * Memory and System segment descriptors
 */
struct  segment_descriptor      {
        unsigned sd_lolimit:16 ;        /* segment extent (lsb) */
        unsigned sd_lobase:24 ;         /* segment base address (lsb) */
        unsigned sd_type:5 ;            /* segment type */
        unsigned sd_dpl:2 ;             /* segment descriptor priority level */
        unsigned sd_p:1 ;               /* segment descriptor present */
        unsigned sd_hilimit:4 ;         /* segment extent (msb) */
        unsigned sd_xx:2 ;              /* unused */
        unsigned sd_def32:1 ;           /* default 32 vs 16 bit size */
        unsigned sd_gran:1 ;            /* limit granularity (byte/page units)*/
        unsigned sd_hibase:8 ;          /* segment base address  (msb) */
} ;

/*
 * Gate descriptors (e.g. indirect descriptors)
 */
struct  gate_descriptor {
        unsigned gd_looffset:16 ;       /* gate offset (lsb) */
        unsigned gd_selector:16 ;       /* gate segment selector */
        unsigned gd_stkcpy:5 ;          /* number of stack wds to cpy */
        unsigned gd_xx:3 ;              /* unused */
        unsigned gd_type:5 ;            /* segment type */
        unsigned gd_dpl:2 ;             /* segment descriptor priority level */
        unsigned gd_p:1 ;               /* segment descriptor present */
        unsigned gd_hioffset:16 ;       /* gate offset (msb) */
} ;

/*
 * Generic descriptor
 */
union   descriptor      {
        struct  segment_descriptor sd;
        struct  gate_descriptor gd;
};

        /* system segments and gate types */
#define SDT_SYSNULL      0      /* system null */
#define SDT_SYS286TSS    1      /* system 286 TSS available */
#define SDT_SYSLDT       2      /* system local descriptor table */
#define SDT_SYS286BSY    3      /* system 286 TSS busy */
#define SDT_SYS286CGT    4      /* system 286 call gate */
#define SDT_SYSTASKGT    5      /* system task gate */
#define SDT_SYS286IGT    6      /* system 286 interrupt gate */
#define SDT_SYS286TGT    7      /* system 286 trap gate */
#define SDT_SYSNULL2     8      /* system null again */
#define SDT_SYS386TSS    9      /* system 386 TSS available */
#define SDT_SYSNULL3    10      /* system null again */
#define SDT_SYS386BSY   11      /* system 386 TSS busy */
#define SDT_SYS386CGT   12      /* system 386 call gate */
#define SDT_SYSNULL4    13      /* system null again */
#define SDT_SYS386IGT   14      /* system 386 interrupt gate */
#define SDT_SYS386TGT   15      /* system 386 trap gate */

        /* memory segment types */
#define SDT_MEMRO       16      /* memory read only */
#define SDT_MEMROA      17      /* memory read only accessed */
#define SDT_MEMRW       18      /* memory read write */
#define SDT_MEMRWA      19      /* memory read write accessed */
#define SDT_MEMROD      20      /* memory read only expand dwn limit */
#define SDT_MEMRODA     21      /* memory read only expand dwn limit accessed */
#define SDT_MEMRWD      22      /* memory read write expand dwn limit */
#define SDT_MEMRWDA     23      /* memory read write expand dwn limit acessed */
#define SDT_MEME        24      /* memory execute only */
#define SDT_MEMEA       25      /* memory execute only accessed */
#define SDT_MEMER       26      /* memory execute read */
#define SDT_MEMERA      27      /* memory execute read accessed */
#define SDT_MEMEC       28      /* memory execute only conforming */
#define SDT_MEMEAC      29      /* memory execute only accessed conforming */
#define SDT_MEMERC      30      /* memory execute read conforming */
#define SDT_MEMERAC     31      /* memory execute read accessed conforming */

/* is memory segment descriptor pointer ? */
#define ISMEMSDP(s)     ((s->d_type) >= SDT_MEMRO && (s->d_type) <= SDT_MEMERAC)

/* is 286 gate descriptor pointer ? */
#define IS286GDP(s)     (((s->d_type) >= SDT_SYS286CGT \
                                 && (s->d_type) < SDT_SYS286TGT))

/* is 386 gate descriptor pointer ? */
#define IS386GDP(s)     (((s->d_type) >= SDT_SYS386CGT \
                                && (s->d_type) < SDT_SYS386TGT))

/* is gate descriptor pointer ? */
#define ISGDP(s)        (IS286GDP(s) || IS386GDP(s))

/* is segment descriptor pointer ? */
#define ISSDP(s)        (ISMEMSDP(s) || !ISGDP(s))

/* is system segment descriptor pointer ? */
#define ISSYSSDP(s)     (!ISMEMSDP(s) && !ISGDP(s))

/*
 * Software definitions are in this convenient format,
 * which are translated into inconvenient segment descriptors
 * when needed to be used by the 386 hardware
 */

struct  soft_segment_descriptor {
        unsigned ssd_base ;             /* segment base address  */
        unsigned ssd_limit ;            /* segment extent */
        unsigned ssd_type:5 ;           /* segment type */
        unsigned ssd_dpl:2 ;            /* segment descriptor priority level */
        unsigned ssd_p:1 ;              /* segment descriptor present */
        unsigned ssd_xx:4 ;             /* unused */
        unsigned ssd_xx1:2 ;            /* unused */
        unsigned ssd_def32:1 ;          /* default 32 vs 16 bit size */
        unsigned ssd_gran:1 ;           /* limit granularity (byte/page units)*/
};

extern ssdtosd() ;      /* to decode a ssd */
extern sdtossd() ;      /* to encode a sd */

/*
 * region descriptors, used to load gdt/idt tables before segments yet exist.
 */
struct region_descriptor {
        unsigned rd_limit:16;           /* segment extent */
        unsigned rd_base:32;            /* base address  */
};

/*
 * Segment Protection Exception code bits
 */

#define SEGEX_EXT       0x01    /* recursive or externally induced */
#define SEGEX_IDT       0x02    /* interrupt descriptor table */
#define SEGEX_TI        0x04    /* local descriptor table */
                                /* other bits are affected descriptor index */
#define SEGEX_IDX(s)    ((s)>>3)&0x1fff)

/*
 * Size of IDT table
 */

#define NIDT    256
#define NRSVIDT 32              /* reserved entries for cpu exceptions */