Kernel: Initialize GDT in kernel code
We dont use the boot GDT only while booting
This commit is contained in:
Bananymous
142
kernel/arch/i386/GDT.cpp
Normal file
142
kernel/arch/i386/GDT.cpp
Normal file
@@ -0,0 +1,142 @@
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#include <BAN/Assert.h>
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#include <kernel/GDT.h>
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#include <string.h>
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extern "C" uintptr_t g_boot_stack_top[0];
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namespace Kernel::GDT
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{
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struct TaskStateSegment
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{
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uint16_t link;
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uint16_t reserved1;
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uint32_t esp0;
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uint16_t ss0;
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uint16_t reserved2;
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uint32_t esp1;
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uint16_t ss1;
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uint16_t reserved3;
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uint32_t esp2;
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uint16_t ss2;
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uint16_t reserved4;
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uint32_t cr3;
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uint32_t eip;
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uint32_t eflags;
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uint32_t eax;
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uint32_t ecx;
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uint32_t edx;
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uint32_t ebx;
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uint32_t esp;
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uint32_t ebp;
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uint32_t esi;
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uint32_t edi;
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uint16_t es;
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uint16_t reserved5;
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uint16_t cs;
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uint16_t reserved6;
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uint16_t ss;
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uint16_t reserved7;
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uint16_t ds;
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uint16_t reserved8;
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uint16_t fs;
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uint16_t reserved9;
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uint16_t gs;
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uint16_t reserved10;
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uint16_t ldtr;
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uint16_t reserved11;
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uint16_t reserved12;
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uint16_t iopb;
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uint32_t ssp;
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} __attribute__((packed));
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union SegmentDescriptor
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{
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struct
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{
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uint16_t limit1;
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uint16_t base1;
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uint8_t base2;
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uint8_t access;
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uint8_t limit2 : 4;
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uint8_t flags : 4;
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uint8_t base3;
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} __attribute__((packed));
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struct
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{
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uint32_t low;
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uint32_t high;
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} __attribute__((packed));
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} __attribute__((packed));
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struct GDTR
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{
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uint16_t size;
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uint32_t address;
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} __attribute__((packed));
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static TaskStateSegment* s_tss = nullptr;
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static SegmentDescriptor* s_gdt = nullptr;
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static GDTR s_gdtr;
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static void 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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SegmentDescriptor& desc = *(SegmentDescriptor*)((uintptr_t)s_gdt + offset);
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desc.base1 = base;
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desc.base2 = base >> 16;
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desc.base3 = base >> 24;
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desc.limit1 = limit;
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desc.limit2 = limit >> 16;
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desc.access = access;
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desc.flags = flags;
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}
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static void write_tss(uint8_t offset)
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{
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s_tss = new TaskStateSegment();
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ASSERT(s_tss);
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memset(s_tss, 0x00, sizeof(TaskStateSegment));
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s_tss->ss0 = 0x10;
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s_tss->esp0 = (uintptr_t)g_boot_stack_top;
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write_entry(offset, (uint32_t)s_tss, sizeof(TaskStateSegment), 0x89, 0x0);
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}
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static void flush_gdt()
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{
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asm volatile("lgdt %0" :: "m"(s_gdtr));
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}
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extern "C" void flush_tss(uint16_t offset)
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{
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asm volatile("ltr %0" :: "m"(offset));
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}
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void initialize()
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{
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constexpr uint32_t descriptor_count = 6;
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s_gdt = new SegmentDescriptor[descriptor_count];
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ASSERT(s_gdt);
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s_gdtr.address = (uint64_t)s_gdt;
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s_gdtr.size = descriptor_count * sizeof(SegmentDescriptor) - 1;
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write_entry(0x00, 0x00000000, 0x00000, 0x00, 0x0); // null
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write_entry(0x08, 0x00000000, 0xFFFFF, 0x9A, 0xC); // kernel code
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write_entry(0x10, 0x00000000, 0xFFFFF, 0x92, 0xC); // kernel data
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write_entry(0x18, 0x00000000, 0xFFFFF, 0xFA, 0xC); // user code
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write_entry(0x20, 0x00000000, 0xFFFFF, 0xF2, 0xC); // user data
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write_tss(0x28);
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flush_gdt();
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flush_tss(0x28);
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}
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}
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@@ -20,37 +20,27 @@
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.long 32
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.section .bss, "aw", @nobits
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# Create stack
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stack_bottom:
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.skip 16384
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stack_top:
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.global g_kernel_cmdline
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g_kernel_cmdline:
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.skip 4096
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# Create stack
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.global g_boot_stack_bottom
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g_boot_stack_bottom:
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.skip 16384
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.global g_boot_stack_top
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g_boot_stack_top:
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.global g_gdtr
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g_gdtr:
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.skip 2 + 4
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.global g_gdt
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g_gdt:
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.skip 5 * 8
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# 0 MiB -> 1 MiB: bootloader stuff
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# 1 MiB -> 2 MiB: kernel
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# 2 MiB -> 3 MiB: kmalloc
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# 3 MiB -> 4 Mib: kmalloc_fixed
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.align 32
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boot_page_directory_pointer_table:
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.skip 4 * 8
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.align 4096
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boot_page_directory1:
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.skip 512 * 8
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# Reserve memory for paging structures,
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# we will identity map first 4 MiB
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# 0 MiB -> 1 MiB: bootloader stuff
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# 1 MiB -> 2 MiB: kernel
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# 2 MiB -> 3 MiB: kmalloc
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# 3 MiB -> 4 Mib: kmalloc_eternal
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.align 32
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boot_page_directory_pointer_table:
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.skip 4 * 8
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.align 4096
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boot_page_directory1:
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.skip 512 * 8
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.section .text, "a"
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.global g_kernel_cmdline
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g_kernel_cmdline:
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.skip 4096
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.global g_multiboot_info
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g_multiboot_info:
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@@ -59,6 +49,16 @@ g_multiboot_info:
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g_multiboot_magic:
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.skip 4
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.section .text, "a"
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boot_gdt:
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.quad 0x0000000000000000 # null
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.quad 0x00CF9A000000FFFF # kernel code
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.quad 0x00CF92000000FFFF # kernel data
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boot_gdtr:
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.short . - boot_gdt - 1
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.long boot_gdt
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has_cpuid:
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pushfl
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pushfl
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@@ -140,18 +140,7 @@ initialize_paging:
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ret
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initialize_gdt:
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# setup gdt
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movw $(5 * 8 - 1), g_gdtr
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movl $(g_gdt), g_gdtr + 2
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movl $(0x0000FFFF), g_gdt + 0x08
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movl $(0x00CF9A00), g_gdt + 0x08 + 4
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movl $(0x0000FFFF), g_gdt + 0x10
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movl $(0x00CF9200), g_gdt + 0x10 + 4
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movl $(0x0000FFFF), g_gdt + 0x18
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movl $(0x00CFFA00), g_gdt + 0x18 + 4
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movl $(0x0000FFFF), g_gdt + 0x20
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movl $(0x00CFF200), g_gdt + 0x20 + 4
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lgdt g_gdtr
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lgdt boot_gdtr
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# flush gdt
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movw $0x10, %ax
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@@ -164,12 +153,11 @@ initialize_gdt:
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flush:
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ret
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.global _start
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.type _start, @function
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_start:
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# Initialize stack and multiboot info
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movl $stack_top, %esp
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movl $g_boot_stack_top, %esp
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movl %eax, g_multiboot_magic
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movl %ebx, g_multiboot_info
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@@ -7,6 +7,7 @@ ELF_FORMAT=elf32-i386
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KERNEL_ARCH_OBJS= \
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$(ARCHDIR)/boot.o \
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$(ARCHDIR)/GDT.o \
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$(ARCHDIR)/IDT.o \
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$(ARCHDIR)/MMU.o \
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$(ARCHDIR)/SpinLock.o \
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