298 lines
5.0 KiB
ArmAsm
298 lines
5.0 KiB
ArmAsm
.code16
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main:
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ljmp $0x0,$entry
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entry:
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/* Set up initial segments */
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xor %ax, %ax
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mov %ax, %ds
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mov %ax, %ss
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/* Don't lose dl */
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mov %dl, boot_disk
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/* Initialize stack to just below us */
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mov $0x7c00, %ax
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mov %ax, %sp
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/* Prepare to switch to unreal mode */
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cli
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push %ds
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push %es
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/* Enable A20 */
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in $0x92, %al
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or $2, %al
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out %al, $0x92
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/* Switch to unreal mode */
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lgdtw gdtr
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mov %cr0, %eax
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or $1, %al
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mov %eax, %cr0
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jmp pmode
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pmode:
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mov $0x10, %bx
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mov %bx, %ds
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mov %bx, %es
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and $0xfe, %al
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mov %eax, %cr0
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jmp unrealmode
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unrealmode:
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pop %es
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pop %ds
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/* Clear the screen */
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mov $0, %al
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movl $3840, %ecx
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movl $0xb8000, %edi
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addr32 rep stosb
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/* Check if we can actually go to long mode on this */
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mov $0x80000001, %eax
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cpuid
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and $0x20000000, %edx
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jnz can_long
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movl $str_Need_long, %esi
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movl $str_Need_long_end - str_Need_long, %ecx
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movl $0xb8000, %edi
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addr32 rep movsb
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jmp _oh_no
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can_long:
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/* Print "Loading..." */
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movl $str_Loading, %esi
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movl $str_Loading_end - str_Loading, %ecx
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movl $0xb8000, %edi
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addr32 rep movsb
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/* Use BIOS disk reads to locate the kernel and ramdisk
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* and load them around the 2MB mark (by loading them
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* in smaller chunks and copying those up thanks to
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* our unreal mode %ds) */
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/* Ask for drive params */
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mov $0x48, %ah
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mov boot_disk, %dl
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mov $drive_params, %si
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int $0x13
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/* Are we a CD? Do we need to load more of ourselves? */
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mov drive_params_bps, %ax
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cmp $0x800, %ax
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je boot_from_cd
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movl $str_Bad, %esi
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movl $str_Bad_end - str_Bad, %ecx
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movl $0xb8000, %edi
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addr32 rep movsb
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_oh_no:
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jmp _oh_no
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.extern _bss_start
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/* To load from the CD, we have 2048 byte sectors */
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boot_from_cd:
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movl $0x4000000, %ebx
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movl $0x0, dap_lba_low /* Sector 10h generally has our primary boot descriptor */
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movw $_bss_start, dap_buffer /* Load into root_data */
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/* Load one sector */
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load_one:
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mov $0x42, %ah /* Extended read */
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mov boot_disk, %dl /* Using our boot disk */
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mov $dap, %si /* From the DAP below */
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int $0x13
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cmp $0, %ah
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jnz done
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/* Move the sector up */
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movl $_bss_start, %esi
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movl %ebx, %edi
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xor %ecx, %ecx
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movw drive_params_bps, %cx
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addr32 rep movsb
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/* Increment */
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movl dap_lba_low, %ecx
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add $1, %ecx
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movl %ecx, dap_lba_low
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xor %ecx, %ecx
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movw drive_params_bps, %cx
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add %ecx, %ebx
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/* Update spinner */
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movl ind_Spinny, %ecx
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inc %ecx
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and $0x3FF, %ecx
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movl %ecx, ind_Spinny
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shr $8, %ecx
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movb str_Spinny(%ecx), %ah
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mov $str_Loading_end - str_Loading - 2 + 0xb8000, %ecx
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movb %ah, (%ecx)
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jmp load_one
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done:
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/* The entire CD is now in memory at 64MiB, hopefully. */
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/* Collect information on lower memory. */
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mov $0x500, %ax
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mov %ax, %es
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clc
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int $0x12
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mov %ax, lower_mem
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/* Collect information on upper memory. */
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mov $0x0, %di
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call do_e820
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jc hang
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/* Actually switch to protected mode. */
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mov %cr0, %eax
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or $1, %eax
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mov %eax, %cr0
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mov $0x10, %ax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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mov %ax, %ss
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cli
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.global bios_main
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ljmp $0x08,$bios_main
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hang:
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jmp hang
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do_e820:
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xor %ebx, %ebx
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xor %bp, %bp
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mov $0x534D4150, %edx
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mov $0xe820, %eax
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movl $0x1,%es:20(%di)
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mov $24, %ecx
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int $0x15
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jb do_e820.failed
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mov $0x534D4150, %edx
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cmp %edx, %eax
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jne do_e820.failed
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test %ebx, %ebx
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je do_e820.failed
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jmp do_e820.jmpin
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do_e820.e820lp:
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mov $0xe820, %eax
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movl $0x1,%es:20(%di)
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mov $24, %ecx
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int $0x15
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jb do_e820.e820f
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mov $0x534D4150, %edx
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do_e820.jmpin:
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jcxz do_e820.skipent
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cmp $20, %cl
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jbe do_e820.notext
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testb $0x1, %es:20(%di)
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je do_e820.skipent
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do_e820.notext:
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mov %es:8(%di), %ecx
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or %es:12(%di), %ecx
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jz do_e820.skipent
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inc %bp
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add $24, %di
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do_e820.skipent:
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test %ebx, %ebx
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jne do_e820.e820lp
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do_e820.e820f:
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mov %bp, mmap_ent
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clc
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ret
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do_e820.failed:
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stc
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ret
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.align 8
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gdtr:
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.word gdt_end - gdt_base - 1
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.long gdt_base
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gdt_base:
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.quad 0
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.word 0xFFFF
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.word 0
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.byte 0
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.byte 0x9a
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.byte 0xcf
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.byte 0
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.word 0xffff
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.word 0
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.byte 0
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.byte 0x92
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.byte 0xcf
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.byte 0
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gdt_end:
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.global boot_disk
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boot_disk:
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.byte 0
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.global mmap_ent
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mmap_ent:
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.byte 0
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.byte 0
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.global lower_mem
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lower_mem:
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.byte 0
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.byte 0
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.align 4
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.global dap
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dap:
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.byte 16
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.byte 0 /* always 0 */
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.global dap_sectors
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dap_sectors:
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.word 1
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.global dap_buffer
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dap_buffer:
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.long 0x0
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dap_lba_low:
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.long 0
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dap_lba_high:
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.long 0
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.align 4
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drive_params:
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.word 0x1A
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.word 0 /* flags */
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.long 0 /* cylinders */
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.long 0 /* heads */
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.long 0 /* sectors */
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.quad 0 /* total sectors */
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.global drive_params_bps
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drive_params_bps:
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.word 0 /* bytes per sector */
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str_Bad:
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.byte 'B',7,'a',7,'d',7,' ',7,'d',7,'i',7,'s',7,'k',7
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str_Bad_end:
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str_Loading:
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.byte 'L',7,'o',7,'a',7,'d',7,'i',7,'n',7,'g',7,'.',7,'.',7,'.',7,' ',7,' ',7
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str_Loading_end:
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str_Need_long:
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.byte 'T',7,'o',7,'a',7,'r',7,'u',7,'O',7,'S',7,' ',7,'2',7,' ',7,'r',7,'e',7,'q',7,'u',7,'i',7,'r',7,'e',7,'s',7,' ',7,'a',7,' ',7,'6',7,'4',7,'-',7,'b',7,'i',7,'t',7,' ',7,'p',7,'r',7,'o',7,'c',7,'e',7,'s',7,'s',7,'o',7,'r',7
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str_Need_long_end:
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str_Spinny:
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.byte '|','/','-','\\'
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ind_Spinny:
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.long 0
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