root/kernel/idt.c

/* */

DEFINITIONS

1. set_idt_entry
2. idt_init

   1 /*
   2  * fiwix/kernel/idt.c
   3  *
   4  * Copyright 2018-2021, Jordi Sanfeliu. All rights reserved.
   5  * Distributed under the terms of the Fiwix License.
   6  */
   7 
   8 #include <fiwix/asm.h>
   9 #include <fiwix/types.h>
  10 #include <fiwix/segments.h>
  11 #include <fiwix/string.h>
  12 
  13 struct gate_desc idt[NR_IDT_ENTRIES];
  14 
  15 struct desc_r idtr = {
  16         sizeof(idt) - 1,
  17         (unsigned int)idt
  18 };
  19 
  20 static void *except_handlers[] = {
  21         &except0, &except1, &except2, &except3, &except4, &except5, &except6, &except7,
  22         &except8, &except9, &except10, &except11, &except12, &except13, &except14, &except15,
  23         &except16, &except17, &except18, &except19, &except20, &except21, &except22, &except23,
  24         &except24, &except25, &except26, &except27, &except28, &except29, &except30, &except31
  25 };
  26 
  27 static void *irq_handlers[] = {
  28         &irq0, &irq1, &irq2, &irq3, &irq4, &irq5, &irq6, &irq7,
  29         &irq8, &irq9, &irq10, &irq11, &irq12, &irq13, &irq14, &irq15
  30 };
  31 
  32 static void set_idt_entry(int num, __off_t handler, unsigned int flags)
  33 {
  34         idt[num].gd_looffset = handler & 0x0000FFFF;
  35         idt[num].gd_selector = KERNEL_CS;
  36         idt[num].gd_flags = flags << 8;
  37         idt[num].gd_hioffset = handler >> 16;
  38 }
  39 
  40 void idt_init(void)
  41 {
  42         int n;
  43 
  44         memset_b(idt, NULL, sizeof(idt));
  45         for(n = 0; n < NR_IDT_ENTRIES; n++) {
  46                 if(n < 0x20) {
  47                         set_idt_entry(n, (__off_t)except_handlers[n], SD_32TRAPGATE | SD_PRESENT);
  48                         continue;
  49                 }
  50                 if(n < 0x30) {
  51                         set_idt_entry(n, (__off_t)irq_handlers[n - 0x20], SD_32INTRGATE | SD_PRESENT);
  52                         continue;
  53                 }
  54                 set_idt_entry(n, (__off_t)&unknown_irq, SD_32INTRGATE | SD_PRESENT);
  55         }
  56 
  57         set_idt_entry(0x80, (__off_t)&syscall, SD_32TRAPGATE | SD_DPL3 | SD_PRESENT);
  58 
  59         load_idt((unsigned int)&idtr);
  60 }

/* */