63 lines
1.5 KiB
C
63 lines
1.5 KiB
C
#include <stdio.h>
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#include <gdt.h>
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#include <drivers/gdt_ec.h>
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#define GDT_ENTRIES 5
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uint64_t gdt[GDT_ENTRIES];
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struct {
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uint16_t limit;
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uint32_t base;
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} __attribute__((packed)) gp;
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extern void gdt_flush(uint32_t);
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void gdt_install(bool prnt_gdt)
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{
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if (prnt_gdt)
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{
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printf("<===== GDT =====>\n");
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}
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create_descriptor(0, 0, 0, 0, prnt_gdt); /* Null */
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create_descriptor(1, 0, 0x000FFFFF, GDT_CODE_PL0, prnt_gdt); /* Kernel code */
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create_descriptor(2, 0, 0x000FFFFF, GDT_DATA_PL0, prnt_gdt); /* Kernel data */
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create_descriptor(3, 0, 0x000FFFFF, GDT_CODE_PL3, prnt_gdt); /* User code */
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create_descriptor(4, 0, 0x000FFFFF, GDT_DATA_PL3, prnt_gdt); /* User data */
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if (prnt_gdt)
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{
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printf("<===== GDT =====>\n");
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}
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gp.limit = sizeof(gdt) - 1;
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gp.base = (uint32_t)&gdt;
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gdt_flush((uint32_t)&gp);
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}
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void create_descriptor(int index, uint32_t base, uint32_t limit, uint16_t flag, bool prnt_gdt)
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{
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uint64_t descriptor;
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descriptor = limit & 0x000F0000; /* limit bits 19:16 */
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descriptor |= (flag << 8) & 0x00F0FF00; /* flags and access */
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descriptor |= (base >> 16) & 0x000000FF; /* base bits 23:16 */
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descriptor |= base & 0xFF000000; /* base bits 31:24 */
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descriptor <<= 32;
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descriptor |= ((uint64_t)base << 16); /* base bits 15:0 */
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descriptor |= (limit & 0x0000FFFF); /* limit bits 15:0 */
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gdt[index] = descriptor;
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if (prnt_gdt)
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{
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printf("GDT[%d] = 0x%llX\n", index, descriptor);
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}
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}
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