70 lines
1.8 KiB
C++
70 lines
1.8 KiB
C++
#include <kernel/GDT.h>
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#include <kernel/Processor.h>
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#include <string.h>
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namespace Kernel
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{
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GDT* GDT::create([[maybe_unused]] void* processor)
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{
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auto* gdt = new GDT();
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ASSERT(gdt);
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#if ARCH(x86_64)
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constexpr uint8_t code_flags = 0xA;
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constexpr uint8_t data_flags = 0xC;
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#elif ARCH(i686)
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constexpr uint8_t code_flags = 0xC;
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constexpr uint8_t data_flags = 0xC;
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#endif
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gdt->write_entry(0x00, 0x00000000, 0x00000, 0x00, 0x0); // null
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gdt->write_entry(0x08, 0x00000000, 0xFFFFF, 0x9A, code_flags); // kernel code
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gdt->write_entry(0x10, 0x00000000, 0xFFFFF, 0x92, data_flags); // kernel data
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gdt->write_entry(0x18, 0x00000000, 0xFFFFF, 0xFA, code_flags); // user code
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gdt->write_entry(0x20, 0x00000000, 0xFFFFF, 0xF2, data_flags); // user data
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#if ARCH(i686)
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gdt->write_entry(0x28, reinterpret_cast<uint32_t>(processor), sizeof(Processor), 0x92, 0x4); // processor data
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#endif
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gdt->write_tss();
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return gdt;
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}
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void GDT::write_entry(uint8_t offset, uint32_t base, uint32_t limit, uint8_t access, uint8_t flags)
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{
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ASSERT(offset % sizeof(SegmentDescriptor) == 0);
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uint8_t idx = offset / sizeof(SegmentDescriptor);
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auto& desc = m_gdt[idx];
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desc.base1 = (base >> 0) & 0xFFFF;
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desc.base2 = (base >> 16) & 0xFF;
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desc.base3 = (base >> 24) & 0xFF;
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desc.limit1 = (limit >> 0) & 0xFFFF;
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desc.limit2 = (limit >> 16) & 0x0F;
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desc.access = access & 0xFF;
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desc.flags = flags & 0x0F;
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}
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void GDT::write_tss()
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{
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memset(&m_tss, 0x00, sizeof(TaskStateSegment));
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m_tss.iopb = sizeof(TaskStateSegment);
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uintptr_t base = reinterpret_cast<uintptr_t>(&m_tss);
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write_entry(m_tss_offset, (uint32_t)base, sizeof(TaskStateSegment), 0x89, 0x0);
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#if ARCH(x86_64)
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auto& desc = m_gdt[(m_tss_offset + 8) / sizeof(SegmentDescriptor)];
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desc.low = base >> 32;
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desc.high = 0;
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#endif
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}
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}
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