63 lines
1.7 KiB
C
63 lines
1.7 KiB
C
#include <system.h>
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/* Defines an IDT entry */
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struct idt_entry
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{
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unsigned short base_lo;
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unsigned short sel;
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unsigned char always0;
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unsigned char flags;
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unsigned short base_hi;
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} __attribute__((packed));
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struct idt_ptr
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{
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unsigned short limit;
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unsigned int base;
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} __attribute__((packed));
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/* Declare an IDT of 256 entries. Although we will only use the
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* first 32 entries in this tutorial, the rest exists as a bit
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* of a trap. If any undefined IDT entry is hit, it normally
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* will cause an "Unhandled Interrupt" exception. Any descriptor
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* for which the 'presence' bit is cleared (0) will generate an
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* "Unhandled Interrupt" exception */
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struct idt_entry idt[256];
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struct idt_ptr idtp;
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/* This exists in 'start.asm', and is used to load our IDT */
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extern void idt_load();
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/* Use this function to set an entry in the IDT. Alot simpler
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* than twiddling with the GDT ;) */
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void idt_set_gate(unsigned char num, unsigned long base, unsigned short sel, unsigned char flags)
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{
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/* The interrupt routine's base address */
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idt[num].base_lo = (base & 0xFFFF);
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idt[num].base_hi = (base >> 16) & 0xFFFF;
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/* The segment or 'selector' that this IDT entry will use
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* is set here, along with any access flags */
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idt[num].sel = sel;
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idt[num].always0 = 0;
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idt[num].flags = flags;
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}
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/* Installs the IDT */
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void idt_install()
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{
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/* Sets the special IDT pointer up, just like in 'gdt.c' */
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idtp.limit = (sizeof (struct idt_entry) * 256) - 1;
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idtp.base = &idt;
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/* Clear out the entire IDT, initializing it to zeros */
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memset(&idt, 0, sizeof(struct idt_entry) * 256);
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/* Add any new ISRs to the IDT here using idt_set_gate */
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/* Points the processor's internal register to the new IDT */
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idt_load();
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}
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