kernel2/tss.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 <tss.h>
  20 #include <cpu.h>
  21 #include <gdt.h>
  22 #include <string.h>
  23 #include <stddef.h>
  24 #include <stdint.h>
  25 #include <debug.h>
  26 #include <procm.h>
  27
  28 /**
  29  * Initializes TSS
  30  *  @return 0=Success; -1=Failure
  31  */
  32 int tss_init() {
  33   cpu_t *cpu = cpu_this;
  34
  35   // create TSS
  36   tss_t *tss = malloc(sizeof(tss_t));
  37   if (tss==NULL) return -1;
  38   memset(tss,0,sizeof(tss_t));
  39   tss->ss0 = IDX2SEL(2,PRIV_KERNEL);
  40   tss->esp0 = (uint32_t)(cpu->stack+cpu->stacksize-4)+sizeof(struct vm86_segmentregs);
  41   tss->iopb_offset = offsetof(tss_t,iopb);
  42   cpu->tss = tss;
  43
  44   // create TSS descriptor
  45   int index = GDT_TSSDESC+cpu_getid();
  46   gdt_set_descriptor(index,sizeof(tss_t)-1,tss,GDT_PRESENT|GDT_TSS,PRIV_USER);
  47   gdt[index].flags &= 0x0F;
  48
  49   // load TSS descriptor
  50   selector_t selector = {
  51     .index = index,
  52     .ti = 0,
  53     .priv = PRIV_KERNEL
  54   };
  55   asm("ltr %0"::"a"(selector));
  56
  57   return 0;
  58 }