forked from Bananymous/banan-os
Kernel: move GDT initialization to boot.S
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Bananymous
parent
aac7595a47
commit
491610db2c
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@ -1,113 +0,0 @@
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#include <kernel/GDT.h>
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#include <stdint.h>
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namespace GDT
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{
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union SegmentDesriptor
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{
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struct
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{
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uint16_t limit_lo;
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uint16_t base_lo;
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uint8_t base_hi1;
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uint8_t type : 4;
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uint8_t system : 1;
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uint8_t DPL : 2;
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uint8_t present : 1;
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uint8_t limit_hi : 4;
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uint8_t flags : 4;
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uint8_t base_hi2;
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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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SegmentDesriptor() : low(0), high(0) {}
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SegmentDesriptor(uint32_t base, uint32_t limit, uint8_t access, uint8_t _flags)
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: low(0), high(0)
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{
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set_base(base);
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set_limit(limit);
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high |= ((uint16_t)access) << 8;
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flags = _flags;
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}
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void set_base(uint32_t base)
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{
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base_lo = base & 0xFFFF;
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base_hi1 = (base >> 16) & 0x00FF;
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base_hi2 = (base >> 24) & 0x00FF;
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}
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void set_limit(uint32_t limit)
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{
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limit_lo = limit & 0xFFFF;
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limit_hi = (limit >> 16) & 0x00FF;
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}
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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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void* address;
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} __attribute__((packed));
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static GDTR s_gdtr;
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static SegmentDesriptor s_gdt[5];
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extern "C" void load_gdt(void* gdt_ptr);
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asm(
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".global load_gdt;"
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"load_gdt:"
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"movl 4(%esp),%eax;"
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"lgdt (%eax);"
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"movw $0x10, %ax;"
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"movw %ax, %ds;"
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"movw %ax, %es;"
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"movw %ax, %fs;"
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"movw %ax, %gs;"
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"movw %ax, %ss;"
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"jmp $0x08,$flush;"
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"flush:"
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"ret;"
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);
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void write_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_entry(uint8_t segment, SegmentDesriptor descriptor)
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{
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write_entry_raw(segment, descriptor.low, descriptor.high);
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}
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void initialize()
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{
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s_gdtr.address = s_gdt;
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s_gdtr.size = sizeof(s_gdt) - 1;
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write_entry(0x00, { 0, 0x00000, 0x00, 0x0 }); // null
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write_entry(0x08, { 0, 0xFFFFF, 0x9A, 0xC }); // kernel code
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write_entry(0x10, { 0, 0xFFFFF, 0x92, 0xC }); // kernel data
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write_entry(0x18, { 0, 0xFFFFF, 0xFA, 0xC }); // user code
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write_entry(0x20, { 0, 0xFFFFF, 0xF2, 0xC }); // user data
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load_gdt(&s_gdtr);
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}
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}
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@ -29,6 +29,13 @@
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g_kernel_cmdline:
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.skip 4096
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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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# Reserve memory for paging structures,
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# we will identity map first 4 MiB
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@ -110,19 +117,7 @@ enable_sse:
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movl %eax, %cr4
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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 %eax, g_multiboot_magic
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movl %ebx, g_multiboot_info
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# Copy kernel command line to known location
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call copy_kernel_commandline
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call check_requirements
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call enable_sse
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initialize_paging:
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# identity map first 4 MiB
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movl $(0x00000000 + 0x83), boot_page_directory1 + 0
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movl $(0x00200000 + 0x83), boot_page_directory1 + 8
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@ -142,14 +137,55 @@ _start:
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orl $0x80000000, %ecx
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movl %ecx, %cr0
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# call global constuctors
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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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# flush gdt
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movw $0x10, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %fs
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movw %ax, %gs
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movw %ax, %ss
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jmp $0x08, $flush
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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 $stack_top, %esp
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movl %eax, g_multiboot_magic
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movl %ebx, g_multiboot_info
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call copy_kernel_commandline
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call check_requirements
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call enable_sse
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call initialize_paging
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call initialize_gdt
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call _init
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# call to the kernel itself (clear ebp for stacktrace)
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xorl %ebp, %ebp
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call kernel_main
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# call global destructors
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call _fini
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system_halt:
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@ -7,7 +7,6 @@ KERNEL_ARCH_OBJS= \
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$(ARCHDIR)/APIC.o \
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$(ARCHDIR)/boot.o \
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$(ARCHDIR)/CPUID.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)/Panic.o \
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@ -1,8 +1,44 @@
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#pragma once
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#include <stdint.h>
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namespace GDT
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{
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void initialize();
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union SegmentDesriptor
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{
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struct
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{
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uint16_t limit_lo;
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uint16_t base_lo;
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uint8_t base_hi1;
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uint8_t type : 4;
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uint8_t system : 1;
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uint8_t DPL : 2;
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uint8_t present : 1;
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uint8_t limit_hi : 4;
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uint8_t flags : 4;
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uint8_t base_hi2;
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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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void* address;
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} __attribute__((packed));
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extern "C" GDTR g_gdtr[];
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extern "C" SegmentDesriptor g_gdt[];
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}
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@ -70,8 +70,6 @@ extern "C" void kernel_main()
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kmalloc_initialize();
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dprintln("kmalloc initialized");
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GDT::initialize();
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dprintln("GDT initialized");
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IDT::initialize();
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dprintln("IDT initialized");
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