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descriptor_tables.h
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descriptor_tables.h
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#include <common.h>
// Initialisation function is publicly accessible.
void init_descriptor_tables();
// This structure contains the value of one GDT entry.
// We use the attribute 'packed' to tell GCC not to change
// any of the alignment in the structure.
struct gdt_entry_struct
{
u16int limit_low; // The lower 16 bits of the limit.
u16int base_low; // The lower 16 bits of the base.
u8int base_middle; // The next 8 bits of the base.
u8int access; // Access flags, determine what ring this segment can be used in.
u8int granularity;
u8int base_high; // The last 8 bits of the base.
} __attribute__((packed));
typedef struct gdt_entry_struct gdt_entry_t;
// This struct describes a GDT pointer. It points to the start of
// our array of GDT entries, and is in the format required by the
// lgdt instruction.
struct gdt_ptr_struct
{
u16int limit; // The upper 16 bits of all selector limits.
u32int base; // The address of the first gdt_entry_t struct.
} __attribute__((packed));
typedef struct gdt_ptr_struct gdt_ptr_t;
// A struct describing an interrupt gate.
struct idt_entry_struct
{
u16int base_lo; // The lower 16 bits of the address to jump to when this interrupt fires.
u16int sel; // Kernel segment selector.
u8int always0; // This must always be zero.
u8int flags; // More flags. See documentation.
u16int base_hi; // The upper 16 bits of the address to jump to.
} __attribute__((packed));
typedef struct idt_entry_struct idt_entry_t;
// A struct describing a pointer to an array of interrupt handlers.
// This is in a format suitable for giving to 'lidt'.
struct idt_ptr_struct
{
u16int limit;
u32int base; // The address of the first element in our idt_entry_t array.
} __attribute__((packed));
typedef struct idt_ptr_struct idt_ptr_t;
// These extern directives let us access the addresses of our ASM ISR handlers.
extern void isr0 ();
extern void isr1 ();
extern void isr2 ();
extern void isr3 ();
extern void isr4 ();
extern void isr5 ();
extern void isr6 ();
extern void isr7 ();
extern void isr8 ();
extern void isr9 ();
extern void isr10();
extern void isr11();
extern void isr12();
extern void isr13();
extern void isr14();
extern void isr15();
extern void isr16();
extern void isr17();
extern void isr18();
extern void isr19();
extern void isr20();
extern void isr21();
extern void isr22();
extern void isr23();
extern void isr24();
extern void isr25();
extern void isr26();
extern void isr27();
extern void isr28();
extern void isr29();
extern void isr30();
extern void isr31();
extern void irq0 ();
extern void irq1 ();
extern void irq2 ();
extern void irq3 ();
extern void irq4 ();
extern void irq5 ();
extern void irq6 ();
extern void irq7 ();
extern void irq8 ();
extern void irq9 ();
extern void irq10();
extern void irq11();
extern void irq12();
extern void irq13();
extern void irq14();
extern void irq15();