forked from Bananymous/banan-os
Changed back to lower half kernel, since im dump.
I dont see the benefit of higher half (and could not get multiboot info)
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Bananymous
parent
9e933a5ec5
commit
d289916bc0
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@ -6,109 +6,34 @@
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.set MB_CHECKSUM, -(MB_MAGIC + MB_FLAGS) #checksum of above, to prove we are multiboot
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# Multiboot header
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.section .multiboot.data, "aw"
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.section .multiboot
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.align 4
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.long MB_MAGIC
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.long MB_FLAGS
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.long MB_CHECKSUM
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# Create stack
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.section .bootstrap_stack, "aw", @nobits
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.section .bss
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stack_bottom:
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.skip 16384 # 16 KiB
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stack_top:
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# Preallocate pages
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.section .bss, "aw", @nobits
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.align 4096
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boot_page_directory:
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.skip 4096
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boot_page_table1:
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.skip 4096
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# Kernel entrypoint
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.section .multiboot.text, "a"
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.section .text
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.global _start
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.type _start, @function
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_start:
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# Physical address of boot_page_table1
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movl $(boot_page_table1 - 0xC0000000), %edi
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movl $stack_top, %esp
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# First address to map is 0
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movl $0, %esi
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pushl %eax
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pushl %ebx
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# Map 1023 pages, 1024th will be VGA memory
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movl $1023, %ecx
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call _init
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1:
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# Only map the kernel
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cmpl $_kernel_start, %esi
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jl 2f
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cmpl $(_kernel_end - 0xC0000000), %esi
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jge 3f
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# Map physical address as "present, writable"
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# Note that this maps .text and .rodata as writable. Mind security and map them as non-writable.
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movl %esi, %edx
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orl $0x003, %edx
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movl %edx, (%edi)
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2:
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# Size of page is 4096 bytes
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addl $4096, %esi
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# Size of entry in boot_page_table1 is 4 bytes
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addl $4, %edi
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# Loop to next entry if we haven't finished
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loop 1b
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3:
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# Map VGA memory to 0xC03FF000 as "present, writable"
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movl $(0x000B8000 | 0x003), boot_page_table1 - 0xC0000000 + 1023 * 4
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# The page table is used at both page directory entry 0 (virtually from 0x0
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# to 0x3FFFFF) (thus identity mapping the kernel) and page directory entry
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# 768 (virtually from 0xC0000000 to 0xC03FFFFF) (thus mapping it in the
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# higher half). The kernel is identity mapped because enabling paging does
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# not change the next instruction, which continues to be physical. The CPU
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# would instead page fault if there was no identity mapping.
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# Map the page table to virtual addresses 0x00000000 and 0xC0000000
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movl $(boot_page_table1 - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 0
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movl $(boot_page_table1 - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 768 * 4
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# Set cr3 to the address of the boot_page_directory
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movl $(boot_page_directory - 0xC0000000), %ecx
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movl %ecx, %cr3
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# Enable paging and the write-protect bit
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movl %cr0, %ecx
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orl $0x80010000, %ecx
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movl %ecx, %cr0
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# Jump to higher half with an absolute jump
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lea 4f, %ecx
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jmp *%ecx
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.section .text
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4:
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# Now paging is fully set up and enabled
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# Unmap the identity mapping since it is not unnecessary
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movl $0, boot_page_directory + 0
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# Reload crc3 to force a TLB flush for the changes to take effect
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movl %cr3, %ecx
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movl %ecx, %cr3
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# Setup stack
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mov $stack_top, %esp
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# Call into C code
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call kernel_main
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# Hang if kernel_main returns
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cli
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1: hlt
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1:
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hlt
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jmp 1b
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.size _start, . - _start
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@ -2,37 +2,24 @@ ENTRY(_start)
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SECTIONS
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{
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. = 0x00100000;
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. = 1M;
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_kernel_start = .;
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.multiboot.data : {
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*(.multiboot.data)
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}
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.multiboot.text : {
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*(.multiboot.text)
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}
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. += 0xC0000000;
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.text ALIGN(4K) : AT(ADDR(.text) - 0xC0000000)
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.text BLOCK(4K) : ALIGN(4K)
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{
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*(.multiboot)
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*(.text)
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}
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.rodata ALIGN(4K) : AT(ADDR(.rodata) - 0xC0000000)
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.rodata BLOCK(4K) : ALIGN(4K)
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{
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*(.rodata)
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}
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.data ALIGN(4K) : AT(ADDR(.data) - 0xC0000000)
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.data BLOCK(4K) : ALIGN(4K)
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{
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*(.data)
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}
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.bss ALIGN(4K) : AT(ADDR(.bss) - 0xC0000000)
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.bss BLOCK(4K) : ALIGN(4K)
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{
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*(COMMON)
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*(.bss)
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*(.bootstrap_stack)
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}
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_kernel_end = .;
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}
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@ -7,7 +7,7 @@
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static constexpr size_t VGA_WIDTH = 80;
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static constexpr size_t VGA_HEIGHT = 25;
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static uint16_t* const VGA_MEMORY = (uint16_t*)0xC03FF000;
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static uint16_t* const VGA_MEMORY = (uint16_t*)0xB8000;
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static size_t terminal_row;
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static size_t terminal_col;
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@ -3,11 +3,8 @@
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#include <stddef.h>
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#include <sys/cdefs.h>
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__BEGIN_DECLS
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void terminal_initialize();
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void terminal_putchar(char c);
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void terminal_write(const char* data, size_t size);
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void terminal_writestring(const char* data);
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__END_DECLS
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@ -1,21 +1,60 @@
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#include <kernel/GDT.h>
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#include <kernel/kmalloc.h>
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#include <kernel/panic.h>
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#include <kernel/tty.h>
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#include <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include <stdlib.h>
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#define DISABLE_INTERRUPTS() asm volatile("cli")
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#define ENABLE_INTERRUPTS() asm volatile("sti")
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// https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Boot-information-format
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struct multiboot_info_t
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{
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uint32_t flags;
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uint32_t mem_lower;
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uint32_t mem_upper;
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uint32_t boot_device;
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uint32_t cmdline;
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uint32_t mods_count;
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uint32_t mods_addr;
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uint32_t syms[4];
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uint32_t mmap_length;
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uint32_t mmap_addr;
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uint32_t drives_length;
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uint32_t drives_addr;
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uint32_t config_table;
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uint32_t boot_loader_name;
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uint32_t apm_table;
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uint32_t vbe_control_info;
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uint32_t vbe_mode_info;
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uint16_t vbe_mode;
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uint16_t vbe_interface_seg;
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uint16_t vbe_interface_off;
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uint16_t vbe_interface_len;
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uint8_t framebuffer[22];
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#if 1
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uint8_t color_info[6];
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#endif
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} __attribute__((packed));
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extern "C"
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void kernel_main()
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void kernel_main(multiboot_info_t* mbi, uint32_t magic)
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{
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asm volatile("cli");
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DISABLE_INTERRUPTS();
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terminal_initialize();
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if (magic != 0x2BADB002)
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Kernel::panic("Invalid magic in multiboot");
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if (mbi->flags & 0b00100000)
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{
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printf("mmap_length: %d\n", mbi->mmap_length);
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printf("mmap_addr: %p\n", mbi->mmap_addr);
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}
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printf("Hello from the kernel!\n");
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printf("%p\n", kernel_main);
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int a = 10;
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printf("%p\n", &a);
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}
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