77 lines
1.4 KiB
C
77 lines
1.4 KiB
C
#ifndef GDT_H
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#define GDT_H
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#include "types.h"
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#define GDT_MAX_ENTRIES 8
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// Access byte
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#define GDT_AC 1 // Access bit
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#define GDT_RW 1 << 1 // Read/Write bit
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#define GDT_DC 1 << 2 // Direction bit/Conforming bit
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#define GDT_EXEC 1 << 3 // Executable bit
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#define GDT_S 1 << 4 // Descriptor type
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#define GDT_PRVL_0 0 // Privilege (from 0 to 3)
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#define GDT_PRVL_1 1 << 5
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#define GDT_PRVL_2 2 << 5
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#define GDT_PRVL_3 3 << 5
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#define GDT_PR 1 << 7 // Present Bit
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// Flags
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#define GDT_SZ 1 << 2 // Size bit
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#define GDT_GR 1 << 3 // Granularity bit
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typedef struct GDT_ENTRY {
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u32 base;
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u32 limit;
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u8 flags;
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u8 access;
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} GDT_ENTRY;
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struct GDT_REGISTER {
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u16 limit;
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u32 base;
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} __attribute__((packed));
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typedef struct GDT_TSS {
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u16 previous_task,previous_task_unused;
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u32 esp0;
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u16 ss0, ss0_unused;
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u32 esp1;
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u16 ss1, ss1_unused;
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u32 esp2;
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u16 ss2, ss2_unused;
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u32 cr3;
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u32 eip;
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u32 eflags;
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u32 eax;
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u32 ecx;
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u32 edx;
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u32 ebx;
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u32 esp;
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u32 ebp;
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u32 esi;
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u32 edi;
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u16 es, es_reserved;
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u16 cs, cs_reserved;
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u16 ss, ss_reserved;
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u16 ds, ds_reserved;
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u16 fs, fs_reserved;
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u16 gs, gs_reserved;
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u16 ldtss, ldtss_reserved;
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u16 t_reserved, io_map;
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} __attribute__((packed)) GDT_TSS;
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/**
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* Copy GDT in memory
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*/
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void gdt_memcpy();
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/**
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* Write a GDT entry at address addr
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*/
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void gdt_write_entry(GDT_ENTRY entry, u32 id);
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int gdt_user_ds_base();
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#endif
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