52 lines
1.5 KiB
C
52 lines
1.5 KiB
C
#include "idt.h"
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#include <stdint.h>
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/* Segment selectors */
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#define KERNEL_CS 0x08
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/* How every interrupt gate (handler) is defined */
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typedef struct {
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uint16_t low_offset; /* Lower 16 bits of handler function address */
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uint16_t sel; /* Kernel segment selector */
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uint8_t always0;
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/* First byte
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* Bit 7: "Interrupt is present"
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* Bits 6-5: Privilege level of caller (0=kernel..3=user)
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* Bit 4: Set to 0 for interrupt gates
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* Bits 3-0: bits 1110 = decimal 14 = "32 bit interrupt gate" */
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uint8_t flags;
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uint16_t high_offset; /* Higher 16 bits of handler function address */
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} __attribute__((packed)) idt_gate_t ;
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/* A pointer to the array of interrupt handlers.
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* Assembly instruction 'lidt' will read it */
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typedef struct {
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uint16_t limit;
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uint32_t base;
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} __attribute__((packed)) idt_register_t;
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#define IDT_ENTRIES 256
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static idt_gate_t idt[IDT_ENTRIES];
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static idt_register_t idt_reg;
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#define low_16(address) (uint16_t)((address) & 0xFFFF)
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#define high_16(address) (uint16_t)(((address) >> 16) & 0xFFFF)
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void idt_set_gate(int n,uint32_t handler) {
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idt[n].low_offset=low_16(handler);
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idt[n].sel=KERNEL_CS;
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idt[n].always0=0;
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idt[n].flags=0xEE;
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idt[n].high_offset=high_16(handler);
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}
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void load_idt() {
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idt_reg.base=(uint32_t) &idt;
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idt_reg.limit=IDT_ENTRIES * sizeof(idt_gate_t) - 1;
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/* Don't make the mistake of loading &idt -- always load &idt_reg */
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asm volatile("lidtl (%0)":: "r" (&idt_reg));
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}
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