44 lines
1023 B
C++
44 lines
1023 B
C++
#include <kernel/GDT.h>
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#include <kernel/kmalloc.h>
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struct GDTR
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{
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uint16_t size;
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void* address;
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} __attribute__((packed));
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static GDTR s_gdtr;
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static SegmentDesriptor* s_gdt;
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extern "C" void load_gdt(void* gdt_ptr);
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void write_gdt_entry_raw(uint8_t segment, uint32_t low, uint32_t high)
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{
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uint8_t index = segment >> 3;
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s_gdt[index].low = low;
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s_gdt[index].high = high;
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}
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void write_gdt_entry(uint8_t segment, SegmentDesriptor descriptor)
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{
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write_gdt_entry_raw(segment, descriptor.low, descriptor.high);
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}
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void gdt_initialize()
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{
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constexpr uint8_t GDT_SIZE = 5;
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s_gdt = new SegmentDesriptor[GDT_SIZE];
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s_gdtr.address = s_gdt;
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s_gdtr.size = GDT_SIZE * 8 - 1;
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write_gdt_entry(0x00, { 0, 0x00000, 0x00, 0x0 }); // null
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write_gdt_entry(0x08, { 0, 0xFFFFF, 0x9A, 0xC }); // kernel code
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write_gdt_entry(0x10, { 0, 0xFFFFF, 0x92, 0xC }); // kernel data
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write_gdt_entry(0x18, { 0, 0xFFFFF, 0xFA, 0xC }); // user code
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write_gdt_entry(0x20, { 0, 0xFFFFF, 0xF2, 0xC }); // user data
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load_gdt(&s_gdtr);
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}
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