39 lines
1.2 KiB
C
39 lines
1.2 KiB
C
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/******************************************************************
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* gdt.h - GLOBAL DESCRIPTOR TABLE *
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* Contains structures and function declarations for GDT *
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******************************************************************/
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#ifndef __GDT_H
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#define __GDT_H
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/* Defines a GDT entry. We say packed, because it prevents the
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* compiler from doing things that it thinks is best: Prevent
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* compiler "optimization" by packing */
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struct gdt_entry
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{
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unsigned short limit_low;
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unsigned short base_low;
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unsigned char base_middle;
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unsigned char access;
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unsigned char granularity;
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unsigned char base_high;
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} __attribute__((packed));
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/* Special pointer which includes the limit: The max bytes
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* taken up by the GDT, minus 1. Again, this NEEDS to be packed */
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struct gdt_ptr
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{
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unsigned short limit;
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unsigned int base;
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} __attribute__((packed));
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/* This will be a function in start.asm. We use this to properly
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* reload the new segment registers */
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extern void i86_gdt_flush();
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extern void i86_gdt_set_gate(int num, unsigned long base, unsigned long limit, unsigned char access, unsigned char gran);
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extern struct gdt_entry* i86_gdt_get_gate(int num);
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extern void i86_gdt_install();
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#endif
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