115 lines
3.3 KiB
C
115 lines
3.3 KiB
C
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//
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// descriptor_tables.h - Defines the interface for initialising the GDT and IDT.
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// Also defines needed structures.
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// Based on code from Bran's kernel development tutorials.
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// Rewritten for JamesM's kernel development tutorials.
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//
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#include "common.h"
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#include <stdint.h>
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// Initialisation function is publicly accessible.
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void init_descriptor_tables();
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// This structure contains the value of one GDT entry.
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// We use the attribute 'packed' to tell GCC not to change
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// any of the alignment in the structure.
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struct gdt_entry_struct
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{
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uint16_t limit_low; // The lower 16 bits of the limit.
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uint16_t base_low; // The lower 16 bits of the base.
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uint8_t base_middle; // The next 8 bits of the base.
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uint8_t access; // Access flags, determine what ring this segment can be used in.
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uint8_t granularity;
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uint8_t base_high; // The last 8 bits of the base.
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} __attribute__((packed));
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typedef struct gdt_entry_struct gdt_entry_t;
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// This struct describes a GDT pointer. It points to the start of
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// our array of GDT entries, and is in the format required by the
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// lgdt instruction.
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struct gdt_ptr_struct
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{
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uint16_t limit; // The upper 16 bits of all selector limits.
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uint32_t base; // The address of the first gdt_entry_t struct.
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} __attribute__((packed));
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typedef struct gdt_ptr_struct gdt_ptr_t;
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// A struct describing an interrupt gate.
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struct idt_entry_struct
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{
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uint16_t base_lo; // The lower 16 bits of the address to jump to when this interrupt fires.
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uint16_t sel; // Kernel segment selector.
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uint8_t always0; // This must always be zero.
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uint8_t flags; // More flags. See documentation.
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uint16_t base_hi; // The upper 16 bits of the address to jump to.
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} __attribute__((packed));
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typedef struct idt_entry_struct idt_entry_t;
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// A struct describing a pointer to an array of interrupt handlers.
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// This is in a format suitable for giving to 'lidt'.
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struct idt_ptr_struct
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{
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uint16_t limit;
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uint32_t base; // The address of the first element in our idt_entry_t array.
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} __attribute__((packed));
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typedef struct idt_ptr_struct idt_ptr_t;
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// These extern directives let us access the addresses of our ASM ISR handlers.
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extern void isr0 ();
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extern void isr1 ();
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extern void isr2 ();
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extern void isr3 ();
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extern void isr4 ();
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extern void isr5 ();
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extern void isr6 ();
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extern void isr7 ();
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extern void isr8 ();
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extern void isr9 ();
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extern void isr10();
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extern void isr11();
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extern void isr12();
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extern void isr13();
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extern void isr14();
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extern void isr15();
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extern void isr16();
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extern void isr17();
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extern void isr18();
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extern void isr19();
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extern void isr20();
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extern void isr21();
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extern void isr22();
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extern void isr23();
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extern void isr24();
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extern void isr25();
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extern void isr26();
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extern void isr27();
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extern void isr28();
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extern void isr29();
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extern void isr30();
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extern void isr31();
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extern void irq0();
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extern void irq1();
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extern void irq2();
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extern void irq3();
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extern void irq4();
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extern void irq5();
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extern void irq6();
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extern void irq7();
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extern void irq8();
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extern void irq9();
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extern void irq10();
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extern void irq11();
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extern void irq12();
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extern void irq13();
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extern void irq14();
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extern void irq15();
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