kernel/gdt.h

   1 /*
   2  *    Copyright (c) 2008 Joshua Phillips. All rights reserved.
   3  *
   4  *  Redistribution and use in source and binary forms, with or without
   5  *  modification, are permitted provided that the following conditions are
   6  *  met:
   7  *
   8  *    1. Redistributions of source code must retain the above copyright
   9  *       notice, this list of conditions and the following disclaimer.
  10  *    2. Redistributions in binary form must reproduce the above copyright
  11  *       notice, this list of conditions and the following disclaimer in
  12  *       the documentation and/or other materials provided with the
  13  *       distribution.
  14  *
  15  *  THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
  16  *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  18  *  DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  19  *  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  *  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  21  *  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  22  *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
  23  *  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  24  *  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
  25  *  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28
  29 #ifndef GDT_H
  30 #define GDT_H
  31
  32 #include "stdint.h"
  33
  34 // Segment selectors - these correspond to entries
  35 // in the GDT (in gdt.c)
  36 #define SEG_DPL0_CODE 0x08 // Kernel-level code
  37 #define SEG_DPL0_DATA 0x10 // Kernel-level data
  38 #define SEG_DPL3_CODE 0x1B // User-level code
  39 #define SEG_DPL3_DATA 0x23 // User-level data
  40 #define SEG_DPL3_TSS  0x2B // User-level TSS
  41
  42 // The structure of the Task State Segment
  43 struct tss {
  44     uint16_t prev, res0;
  45     uint32_t esp0;
  46     uint16_t ss0, res1;
  47     uint32_t esp1;
  48     uint16_t ss1, res2;
  49     uint32_t esp2;
  50     uint16_t ss2, res3;
  51     uint32_t cr3, eip, eflags, eax, ecx, edx, ebx, esp, ebp, esi, edi;
  52     uint16_t es, res4, cs, res5, ss, res6, ds, res7, fs, res8, gs, res9;
  53     uint16_t ldt, res10, debug_trap, iomap_base;
  54 };
  55
  56 // Main initialization function for the GDT
  57 void gdt_init(void **p_gdt);
  58
  59 #endif