kernel2/gdt.c

   1 /*
   2     meinOS - A unix-like x86 microkernel operating system
   3     Copyright (C) 2008  Janosch Gräf <janosch.graef@gmx.net>
   4
   5     This program is free software: you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation, either version 3 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License
  16     along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19 #include <gdt.h>
  20 #include <malloc.h>
  21 #include <string.h>
  22 #include <debug.h>
  23
  24 void gdt_reloadsregs() {
  25   /*const selector_t csel = {
  26     .index = 1,
  27     .ti = 0,
  28     .priv = PRIV_KERNEL
  29   };*/
  30   const selector_t dsel = {
  31     .index = 2,
  32     .ti = 0,
  33     .priv = PRIV_KERNEL
  34   };
  35   /*asm("mov %0,%%ds;"
  36       "ljmp %1,$gdt_reloadregs_fi;"
  37       "gdt_reloadregs_fi:"
  38       ::"r"((uint16_t)16),"i"((uint16_t)8));*/
  39
  40   asm("ljmpl $0x08, $1f;"
  41       "1:"
  42       "mov %0, %%ds;"
  43       "mov %0, %%es;"
  44       "mov %0, %%fs;"
  45       "mov %0, %%gs;"
  46       "mov %0, %%ss;"
  47       ::"r"(dsel):"eax");
  48   return;
  49 }
  50
  51 /**
  52  * Initializes GDT
  53  *  @return 0=Success; -1=Failure
  54  */
  55 int gdt_init() {
  56   //gdt = calloc(GDT_MAXDESC,sizeof(gdtdesc_t));
  57   memset(gdt,0,GDT_MAXDESC*sizeof(gdtdesc_t));
  58
  59   // Ring 0
  60   gdt_set_descriptor(1,0x000FFFFF,0x00000000,GDT_SEGMENT|GDT_PRESENT|GDT_CODESEG,PRIV_KERNEL);
  61   gdt_set_descriptor(2,0x000FFFFF,0x00000000,GDT_SEGMENT|GDT_PRESENT|GDT_DATASEG,PRIV_KERNEL);
  62
  63   // Ring 3
  64   gdt_set_descriptor(3,0x000FFFFF,0x00000000,GDT_SEGMENT|GDT_PRESENT|GDT_CODESEG,PRIV_USER);
  65   gdt_set_descriptor(4,0x000FFFFF,0x00000000,GDT_SEGMENT|GDT_PRESENT|GDT_DATASEG,PRIV_USER);
  66
  67   gdtsel_t selector = {
  68     .size = GDT_MAXDESC*sizeof(gdtdesc_t)-1,
  69     .offset = (uint32_t)&gdt
  70   };
  71   asm("lgdt (%0)"::"r"(&selector));
  72   gdt_reloadsregs();
  73
  74   return 0;
  75 }
  76
  77 void gdt_set_descriptor(int segment,size_t size,void *vdbase,int access,priv_t priv) {
  78   uint32_t base = (uint32_t)vdbase;
  79   gdt[segment].size0_15 = size&0xFFFF;
  80   gdt[segment].flags = ((size>>16)&0x0F)|0xC0;
  81   gdt[segment].base0_15 = base&0xFFFF;
  82   gdt[segment].base16_23 = (base>>16)&0xFF;
  83   gdt[segment].base24_31 = ((base>>24)&0xFF);
  84   gdt[segment].access = access|((priv&3)<<5);
  85 }