FreeBSD/Linux Kernel Cross Reference
sys/amd64/include/segments.h

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * 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. 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
     * $FreeBSD$
     */
    
    #ifdef __i386__
    #include <i386/segments.h>
    #else /* !__i386__ */
    
    #ifndef _MACHINE_SEGMENTS_H_
    #define _MACHINE_SEGMENTS_H_
    
    /*
     * AMD64 Segmentation Data Structures and definitions
     */
    
    #include <x86/segments.h>
    
    /*
     * System segment descriptors (128 bit wide)
     */
    struct  system_segment_descriptor {
            u_int64_t sd_lolimit:16;        /* segment extent (lsb) */
            u_int64_t sd_lobase:24;         /* segment base address (lsb) */
            u_int64_t sd_type:5;            /* segment type */
            u_int64_t sd_dpl:2;             /* segment descriptor priority level */
            u_int64_t sd_p:1;               /* segment descriptor present */
            u_int64_t sd_hilimit:4;         /* segment extent (msb) */
            u_int64_t sd_xx0:3;             /* unused */
            u_int64_t sd_gran:1;            /* limit granularity (byte/page units)*/
            u_int64_t sd_hibase:40 __packed;/* segment base address  (msb) */
            u_int64_t sd_xx1:8;
            u_int64_t sd_mbz:5;             /* MUST be zero */
            u_int64_t sd_xx2:19;
    } __packed;
    
    /*
     * 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 long ssd_base;         /* segment base address  */
            unsigned long ssd_limit;        /* segment extent */
            unsigned long ssd_type:5;       /* segment type */
            unsigned long ssd_dpl:2;        /* segment descriptor priority level */
            unsigned long ssd_p:1;          /* segment descriptor present */
            unsigned long ssd_long:1;       /* long mode (for %cs) */
            unsigned long ssd_def32:1;      /* default 32 vs 16 bit size */
            unsigned long ssd_gran:1;       /* limit granularity (byte/page units)*/
    } __packed;
    
    /*
     * region descriptors, used to load gdt/idt tables before segments yet exist.
     */
    struct region_descriptor {
            uint64_t rd_limit:16;           /* segment extent */
            uint64_t rd_base:64 __packed;   /* base address  */
    } __packed;
    
    #ifdef _KERNEL
    extern struct soft_segment_descriptor gdt_segs[];
    extern struct gate_descriptor *idt;
    extern struct region_descriptor r_idt;
    
   void    lgdt(struct region_descriptor *rdp);
   void    sdtossd(struct user_segment_descriptor *sdp,
               struct soft_segment_descriptor *ssdp);
   void    ssdtosd(struct soft_segment_descriptor *ssdp,
               struct user_segment_descriptor *sdp);
   void    ssdtosyssd(struct soft_segment_descriptor *ssdp,
               struct system_segment_descriptor *sdp);
   void    update_gdt_gsbase(struct thread *td, uint32_t base);
   void    update_gdt_fsbase(struct thread *td, uint32_t base);
   #endif /* _KERNEL */
   
   #endif /* !_MACHINE_SEGMENTS_H_ */
   
   #endif /* __i386__ */

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