51 lines
1.3 KiB
C
51 lines
1.3 KiB
C
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#include "gdt.h"
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#include "../Helpers/types.h"
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#include "../Helpers/memory.h"
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//Declare global vars
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GdtDescriptorStruct GDT_DESCRIPTORS[4];
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GdtPointerStruct GDT_POINTER;
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//Adapt parameter to the gdt descriptor structure
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void gdt_initGdtDesc(u32 base, u32 limit, u8 access, u8 flags, GdtDescriptorStruct *Descriptor){
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Descriptor->limit1 = limit & 0xFFFF;
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Descriptor->base1 = base & 0xFFFF;
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Descriptor->base2 = (base & 0xFF0000) >> 16;
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Descriptor->access = access;
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Descriptor->limit2 = (limit & 0xF0000 ) >> 16;
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Descriptor->flags = flags & 0xFF;
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Descriptor->base3 = (base & 0xFF000000) >> 24;
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}
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//Copy the gdt into mémory and load it
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void gdt_loadGdt(){
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//Init default segment
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gdt_initGdtDesc(0x0,0x0,0x0,0x0, &GDT_DESCRIPTORS[0]);
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//Init code segment
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gdt_initGdtDesc(0x0,0xFFFFF,0x9A,0x0D, &GDT_DESCRIPTORS[1]);
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//Init data segment
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gdt_initGdtDesc(0x0,0xFFFFF,0x92,0x0D, &GDT_DESCRIPTORS[2]);
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//Init stack segment
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gdt_initGdtDesc(0x00B00000,0x00000500,0x96,0x0D, &GDT_DESCRIPTORS[3]);
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//Init GDT Pointer
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GDT_POINTER.size=4*sizeof(GDT_DESCRIPTORS);
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GDT_POINTER.segment=0x00007E00;
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//Copy Gdt into memory and init registers
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memcpy((u32)GDT_DESCRIPTORS, (u32)GDT_POINTER.segment, (u32)GDT_POINTER.size);
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//Load the GDT
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__asm__("lgdtl (%0);"
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:
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:"r"(&GDT_POINTER)
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);
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}
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