cfenollosa_os-tutorial/21-shell/cpu/idt.h
2015-03-20 19:20:44 +01:00

40 lines
1011 B
C

#ifndef IDT_H
#define IDT_H
#include "types.h"
/* Segment selectors */
#define KERNEL_CS 0x08
/* How every interrupt gate (handler) is defined */
typedef struct {
u16 low_offset; /* Lower 16 bits of handler function address */
u16 sel; /* Kernel segment selector */
u8 always0;
/* First byte
* Bit 7: "Interrupt is present"
* Bits 6-5: Privilege level of caller (0=kernel..3=user)
* Bit 4: Set to 0 for interrupt gates
* Bits 3-0: bits 1110 = decimal 14 = "32 bit interrupt gate" */
u8 flags;
u16 high_offset; /* Higher 16 bits of handler function address */
} __attribute__((packed)) idt_gate_t ;
/* A pointer to the array of interrupt handlers.
* Assembly instruction 'lidt' will read it */
typedef struct {
u16 limit;
u32 base;
} __attribute__((packed)) idt_register_t;
#define IDT_ENTRIES 256
idt_gate_t idt[IDT_ENTRIES];
idt_register_t idt_reg;
/* Functions implemented in idt.c */
void set_idt_gate(int n, u32 handler);
void set_idt();
#endif