51 lines
1.4 KiB
C++
51 lines
1.4 KiB
C++
#include "gdt.h"
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#include <kernel/kernio.h>
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#include <lib/std/memory.h>
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struct SegmentDescriptor_t {
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uint16_t limit_0;
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uint16_t base_0;
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uint8_t base_1;
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uint8_t access;
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uint8_t limit_1:4;
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uint8_t flags:4;
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uint8_t base_2;
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} __attribute__((packed));
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SegmentDescriptor_t _GDT[256];
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void lgdt(void* GDT, uint16_t size) {
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struct {
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uint16_t size;
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void* GDT;
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} __attribute__((packed)) GDTR = { size, GDT };
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asm ( "lgdt %0" : : "m"(GDTR) );
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}
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void initGDT() {
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memset(&_GDT, 0, sizeof(_GDT));
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// Leave 0 blank for null segment
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// Code Base 0 limit 32 Access EXEC + RW
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setGDT(1, 0x00000000, 0xFFFFFFFF, GDT_ACCESS_PRESENT | GDT_ACCESS_EXEC | GDT_ACCESS_RW, GDT_FLAG_GR_PAGE | GDT_FLAG_SZ_32B);
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// Data Base 0 Limit 32 Access RW
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setGDT(2, 0x00000000, 0xFFFFFFFF, GDT_ACCESS_PRESENT | GDT_ACCESS_RW, GDT_FLAG_GR_PAGE | GDT_FLAG_SZ_32B);
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lgdt(&_GDT, sizeof(_GDT));
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SEGMENTS_RELOAD();
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}
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void setGDT(uint32_t index, uint32_t baseAddr, uint32_t limitAddr, uint8_t accessLvl, uint8_t flags) {
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if (index > 256) return;
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_GDT[index].base_0 = (baseAddr >> 0) & 0xFFFF;
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_GDT[index].base_1 = (baseAddr >> 16) & 0xFF;
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_GDT[index].base_2 = (baseAddr>> 24) & 0xFF;
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_GDT[index].limit_0 = (limitAddr >> 0) & 0xFFFF;
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_GDT[index].limit_1 = (limitAddr >> 16) & 0x0F;
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_GDT[index].access = accessLvl;
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_GDT[index].flags = flags & 0x0F;
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}
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