kernel/arch/x86_64/idt.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2007  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   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
  20 #include <system.h>
  21 #include <build.h>
  22 #include <arch/io.h>
  23 #include <string.h>
  24
  25 /* Defines an IDT entry */
  26 struct idt_entry
  27 {
  28         unsigned short base_lo;
  29         unsigned short sel;
  30         unsigned char always0;
  31         unsigned char flags;
  32         unsigned short base_hi;
  33 } __attribute__((packed));
  34
  35 struct idt_ptr
  36 {
  37         unsigned short limit;
  38         unsigned int base;
  39 } __attribute__((packed));
  40
  41 /* Declare an IDT of 256 entries. Although we will only use the
  42 *  first 32 entries in this tutorial, the rest exists as a bit
  43 *  of a trap. If any undefined IDT entry is hit, it normally
  44 *  will cause an "Unhandled Interrupt" exception. Any descriptor
  45 *  for which the 'presence' bit is cleared (0) will generate an
  46 *  "Unhandled Interrupt" exception */
  47 struct idt_entry idt[256];
  48 struct idt_ptr idtp;
  49
  50 /* This exists in 'start.asm', and is used to load our IDT */
  51 extern void idt_load();
  52
  53 #define set_intr_gate(n,addr) \
  54         _set_gate(&idt[n],14,0,addr)
  55
  56 #define set_trap_gate(n,addr) \
  57         _set_gate(&idt[n],15,0,addr)
  58
  59 #define set_system_gate(n,addr) \
  60         _set_gate(&idt[n],15,3,addr)
  61
  62 /* Use this function to set an entry in the IDT. Alot simpler
  63 *  than twiddling with the GDT ;) */
  64 void idt_set_gate(unsigned char num, unsigned long base, unsigned short sel, unsigned char flags)
  65 {
  66         /* The interrupt routine's base address */
  67         idt[num].base_lo = (base & 0xFFFF);
  68         idt[num].base_hi = (base >> 16) & 0xFFFF;
  69
  70         /* The segment or 'selector' that this IDT entry will use
  71         *  is set here, along with any access flags */
  72         idt[num].sel = sel;
  73         idt[num].always0 = 0;
  74         idt[num].flags = flags;
  75 }
  76
  77 extern int system_call (void);
  78
  79 /* Installs the IDT */
  80 unsigned int idt_install ()
  81 {
  82         /* Sets the special IDT pointer up, just like in 'gdt.c' */
  83         idtp.limit = (sizeof (struct idt_entry) * 256) - 1;
  84         idtp.base = &idt;
  85
  86         /* Clear out the entire IDT, initializing it to zeros */
  87         memset(&idt, 0, sizeof(struct idt_entry) * 256);
  88
  89         /* Add any new ISRs to the IDT here using idt_set_gate */
  90
  91         /* Points the processor's internal register to the new IDT */
  92         idt_load ();
  93
  94         set_system_gate (0x80, &system_call);
  95
  96         return 1;
  97 }