small changes, part 2, rewriting bootloader partially, giving up on this branch
This commit is contained in:
parent
e520b52cd5
commit
a947a7a143
5 changed files with 212 additions and 298 deletions
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@ -1,20 +1,17 @@
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0x0000 - 0x03ff : interrupt vector table
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0x0400 - 0x04ff : bios data area
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0x0500 - 0x05ff : structure pointers
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0x00 : fat
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0x04 : root directory
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0x08 : kernel
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0x0c : file handle array
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0x10 : process array
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0x0600 - 0x1fff : not assigned
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0x2000 - 0x3fff : memory map
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for each word : 1 page
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0x0000 = free
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0x0001 = unavailable
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0x0002 = kernel
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other = process number
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0x4000 - 0x6fff : not assigned
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0x0500 - 0x05ff : global info
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0x00 dword : fat pointer
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0x04 dword : root directory pointer
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0x08 word : usable memory from 0 to 1MiB in kiB
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0x0a word : usable memory from 1MiB to 16MiB in kiB
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0x0c dword : bootloader:
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lower word: low memory usage by bootloader in kiB,
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upper word: kernel image length in kiB
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kernel:
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file handle array pointer
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0x10 dword : process array pointer
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0x14 word : usable memory from 16MiB up in 64s of kiB
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0x0600 - 0x6fff : not assigned
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0x7000 - 0x7bff : bootloader scratch
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0x7000 : memory map bios buffer
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0x7c00 - 0x7fff : bootloader
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9
makefile
9
makefile
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@ -9,8 +9,13 @@ floppy: bootloader fs
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bootloader: obj
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nasm src/bootloader.asm -o obj/bootloader.bin
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kernel: fs
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gcc src/kernel/*.c -o out/fs/kernel.sys -ffreestanding -nostdlib -m32 -T src/kernel/link.ld
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kernel: obj fs
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gcc src/kernel/*.c -o obj/kernel.elf -ffreestanding -nostdlib -m32 -fno-asynchronous-unwind-tables
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ld obj/kernel.elf -o obj/kernel-stripped.elf -T src/kernel/link.ld -s --orphan-handling=discard -m elf_i386
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objcopy obj/kernel-stripped.elf out/fs/kernel.sys -O binary
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clean:
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rm -r obj out
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fs: out
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mkdir -p out/fs
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@ -15,275 +15,245 @@
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;TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE
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;USE OR PERFORMANCE OF THIS SOFTWARE.
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pointers:
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.fat equ 0x0500
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.root_dir equ 0x0504
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.kernel equ 0x0508
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kload equ 0x0010_0000
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fat_header:
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.oem_name equ 0x7c03;mkfs.fat - ignored
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.bytes_per_sector equ 0x7c0b;0x0200 - assumed
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.sectors_per_cluster equ 0x7c0d;0x01 - assumed
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global_info:;0x0500 - 0x05ff (0x0515)
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.fat equ 0x0500;dword - pointer
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.root_dir equ 0x0504;dword - pointer
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.low_mem equ 0x0508;word - usable memory from 0 to 1MiB in kiB
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.mid_mem equ 0x050a;word - usable memory from 1MiB to 16MiB in kiB
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.mem_used equ 0x050c;word - used memory from 0 to 1MiB in kiB
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.kernel_s equ 0x050e;word - kernel image length in kiB
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;dword - kernel use
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.high_mem equ 0x0514;word - usable memory from 16MiB up in 64s of kiB
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fat_header:;0x7c03 - 0x7c3d
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.oem_name equ 0x7c03;mkfs.fat -
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.bytes_per_sector equ 0x7c0b;0x0200 -
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.sectors_per_cluster equ 0x7c0d;0x01 -
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.reserved_sectors equ 0x7c0e;0x0002 - handled
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.n_fats equ 0x7c10;0x01 - assumed
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.n_fats equ 0x7c10;0x01 -
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.root_dir_entries equ 0x7c11; -
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.n_sectors equ 0x7c13;0x0b40 -
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.media_type equ 0x7c15; -
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.sectors_per_fat equ 0x7c16; - handled
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.sectors_per_track equ 0x7c18;0x0012 -
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.sides equ 0x7c1a;0x0002 -
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.hidden_sectors equ 0x7c1c;0x0000_0000 - assumed, top half used as scratch for sector number of cluster 0
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.long_sectors equ 0x7c20;0x0000_0000 - assumed
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.drive_number equ 0x7c24; - ignored, used as scratch
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.flags equ 0x7c25; - ignored
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.signature equ 0x7c26;0x29 - halts on other values
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.id equ 0x7c27; - ignored
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.label equ 0x7c2b;PORTLAND OS - assumed
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.fs_type equ 0x7c36;FAT12 - assumed
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.hidden_sectors equ 0x7c1c;0x0000_0000 -
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.long_sectors equ 0x7c20;0x0000_0000 -
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.drive_number equ 0x7c24; - ignored, used as scratch for real drive number
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.flags equ 0x7c25; -
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.signature equ 0x7c26;0x29 - errors on other values
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.id equ 0x7c27; -
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.label equ 0x7c2b;PORTLAND OS -
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.fs_type equ 0x7c36;FAT12 - errors on other values
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error_codes:
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.bad_fat_header equ 0o000
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.insufficient_memory equ 0o001
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.no_kernel equ 0o002
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.kernel_too_big equ 0o003
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org 0x7c3e
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bits 16
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;Enable A20 line
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in al, 0x92
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or al, 0x02
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out 0x92, al
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;Load second sector of bootloader
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mov ah, 0x42
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mov si, dap
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int 0x13
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;Check FAT signature
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test byte [fat_header.signature], 0x29
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jne bad_fat_header
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test word [fat_header.fs_type], 0x4146;FA
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jne bad_fat_header
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test word [fat_header.fs_type + 2], 0x3154;T1
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jne bad_fat_header
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test word [fat_header.fs_type + 4], 0x2032;2
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jne bad_fat_header
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test word [fat_header.fs_type + 6], 0x2020;
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jne bad_fat_header
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;Store boot drive ID for later
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mov byte [fat_header.drive_number], dl
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memory:
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mov bx, 0x2010
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mov eax, 0x0001_0001
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.clear:
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mov dword [bx], eax
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add bx, 4
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test bx, 0x4000
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jne .clear
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;Get available low memory
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int 0x12
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mov word [global_info.low_mem], ax
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mov word [global_info.mem_used], 0x0020
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xor ax, ax
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mov es, ax
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mov si, 0x7000
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xor ebx, ebx
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.loop:
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mov eax, 0x0000_e820
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mov ecx, 24
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mov edx, 0x534d_4150
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;Get available mid and high memory
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xor dx, dx
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mov ax, 0xe801
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int 0x15
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jc .done
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test cl, 24
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jne .not_24
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test byte [0x7014], 0x01
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jz .loop
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.not_24:
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test dword [0x7010], 1
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jne .loop
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test byte [0x7003], 0
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jne .loop
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test dword [0x7004], 0
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jne .loop
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test dword [0x700c], 0
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je .check_lower
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mov dword [0x7008], 0xffff_ffff
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.check_lower:
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test dword [0x7008], 0
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je .loop
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mov edx, ebx
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mov ebx, dword [0x7000]
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mov eax, ebx
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add eax, dword [0x7008]
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jnc .pagify
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mov eax, 0xffff_ffff
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.pagify:
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dec ebx
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shr ebx, 12
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inc ebx
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shr eax, 12
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dec eax
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test eax, 0xffff_f000
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jz .maxed
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mov eax, 0x0000_0fff
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.maxed:
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inc eax
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test eax, ebx
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je .next
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shl ebx, 1
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or ebx, 0x2000
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shl eax, 1
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add eax, 0x2000
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mov ecx, eax
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xor ax, ax
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.free_loop:
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mov word [ebx], ax
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add ebx, 2
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test ebx, ecx
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jne .free_loop
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.next:
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mov ebx, edx
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jmp .loop
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.done:
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mov dword [0x2000], 0x0002_0002
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mov dword [0x2004], 0x0002_0002
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mov dword [0x2008], 0x0002_0002
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mov dword [0x200c], 0x0002_0002
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test byte [fat_header.signature], 0x29
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jne halt
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test dx, dx
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jnz .got
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mov cx, ax
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mov dx, bx
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.got:
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mov word [global_info.mid_mem], cx
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mov word [global_info.high_mem], dx
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;Load FAT
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mov ax, word [fat_header.reserved_sectors]
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mov word [dap.start], ax
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xor eax, eax
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mov ax, word [fat_header.sectors_per_fat]
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xor ecx, ecx
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mov cx, word [fat_header.reserved_sectors]
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call allocate_and_load
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mov dword [pointers.fat], ebx
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call load_low
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mov dword [global_info.fat], ebx
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load_root:
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;Load root directory
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mov ax, word [fat_header.sectors_per_fat]
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xor dh, dh
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mov dl, word [fat_header.n_fats]
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mul dx
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add ax, [fat_header.reserved_sectors]
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jnc .no_inc
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inc dx
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.no_inc:
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mov word [dap.start], ax
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mov word [dap.start + 2], dx
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mov ax, word [fat_header.root_dir_entries]
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dec ax
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shr ax, 4
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inc ax
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call load_low
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mov dword [global_info.root_dir], ebx
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;Calculate end of root directory
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xor ecx, ecx
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mov cx, word [fat_header.reserved_sectors]
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add cx, word [fat_header.sectors_per_fat]
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jnc .no_carry
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or ecx, 0x0001_0000
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.no_carry:
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call allocate_and_load
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mov dword [pointers.root_dir], ebx
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xor edx, edx
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mov dx, word [fat_header.root_dir_entries]
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shl edx, 5
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add edx, ebx
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mov cx, word [fat_header.root_dir_entries]
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shl ecx, 5
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add ecx, ebx
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jc insufficient_memory
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find_kernel:
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mov eax, 0x6e_72_65_6b;kern
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mov ecx, 0x20_20_6c_65;el
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mov ebx, dword [pointers.root_dir]
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mov eax, 0x6e72_656b;kern
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mov edx, 0x2020_6c65;el
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.loop:
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;Check name
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test dword [ebx], eax
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jne .next
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test dword [ebx + 4], ecx
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test dword [ebx + 4], edx
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jne .next
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test word [ebx + 8], 0x79_73;sy
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test word [ebx + 8], 0x7973;sy
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jne .next
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test byte [ebx + 10], 0x73;s
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je .found
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.next:
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;Next record
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add ebx, 32
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test ebx, edx
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test ebx, ecx
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jne .loop
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jmp halt
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;Got to end of directory
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mov dl, error_codes.no_kernel
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jmp error
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;ebx is pointer to entry
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;word [ebx + 26] is first cluster
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;dword [ebx + 28] is size
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.found:
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mov byte [allocate_and_load.load], 0xc3;ret
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;Save size for later
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mov eax, dword [ebx + 28]
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shr eax, 10
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test eax, 0x003f_0000
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jz .store_size
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mov dl, error_codes.kernel_too_big
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jmp error
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.store_size:
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mov word [global_info.kernel_s], ax
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mov eax, dword [ebx + 0x1c]
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dec eax
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shr eax, 9
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inc eax
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;Save sector number for later
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mov cx, [ebx + 26]
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test eax, 0xffff_0000
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jnz halt
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push word [ebx + 0x1a]
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call allocate_and_load
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mov dword [pointers.kernel], ebx
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mov ax, word [fat_header.root_dir_entries]
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dec ax
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shr ax, 4
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dec ax
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add ax, word [fat_header.reserved_sectors]
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jc halt
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add ax, word [fat_header.sectors_per_fat]
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jc halt
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mov word [fat_header.hidden_sectors + 2], ax
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;find 1kiB buffer
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mov ax, 2
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mov byte [load_low.ret_with_segment], 0xc3;ret
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call load_low
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shl ebx, 4
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load_kernel:
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mov word [dap.length], 0x0001
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mov word [dap.offset], bx
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xor bx, bx
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shr ebx, 4
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jmp .over_sig
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times $$ + 0x01fe - $ db 0
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dw 0xaa55
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load_low:
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;ax in : number of sectors
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;qword [dap.start] in : starting sector
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.over_sig:
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test ebx, 0xffff_0000
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jnz halt
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;Store length in DAP
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mov word [dap.length], ax
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;Calculate kiB used
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dec ax
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shr ax, 1
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inc ax
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mov dx, ax
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add ax, word [global_info.mem_usage]
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;Fail if not enough is available
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jc insufficient_memory
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cmp ax, word [global_info.low_mem]
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jg insufficient_memory
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;Check if address will fit in DAP
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test ah, ah
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jnz insufficient_memory
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;Commit usage
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mov word [global_info.low_mem_usage], ax
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;Put address into DAP
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xor ebx, ebx
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mov bh, al
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shr bx, 2
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mov word [dap.segment], bx
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mov word [dap.offset], 0x0000
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.ret_with_segment:
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xor edx, edx
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pop dx
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mov word [dap.start + 2], 0x0000
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mov ah, 0x42
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;Load from disk
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mov si, dap
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.loop:
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mov cx, dx
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add cx, word [fat_header.hidden_sectors + 2]
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jc halt
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mov word [dap.start], cx
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mov ah, 0x42
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int 0x13
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shl ebx, 4
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ret
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mov ebx, dword [pointers.fat]
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add ebx, edx
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add ebx, edx
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add ebx, edx
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bad_fat_header:
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mov dl, error_codes.bad_fat_header
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jmp error
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xor edx, edx
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mov dx, word [ebx + 1]
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shl edx, 8
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mov dl, byte [ebx]
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insufficient_memory:
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mov dl, error_codes.insufficient_memory
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jmp error
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add word [dap.segment], 0x0020
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jc halt
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mov ecx, edx
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and ecx, 0x0ff8
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test ecx, 0x0ff8
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jne .loop
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mov ebx, dword [pointers.kernel]
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;TODO
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error:
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;Print error code (in octal)
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mov ax, 0xb800
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mov ds, ax
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mov word [0], 0x0f72;E
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mov ax, 0x0f00
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mov al, dl
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and al, 0x07
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or al, 0x30
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mov word [6], ax;bottom digit
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shr dl, 3
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mov al, dl
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and al, 0x07
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or al, 0x30
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mov word [4], ax;middle digit
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shr dl, 3
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mov al, dl
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or al, 0x30
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mov word [2], ax;top digit
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cli
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lgdt [gdt]
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mov eax, cr0
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or al, 0x01
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mov cr0, eax
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jmp 0x08:kernel_start;get start from file header
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.halt:
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hlt
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jmp .halt
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gdt:
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dw 0x28
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|
|
@ -299,69 +269,9 @@ dw 0x0010
|
|||
.length dw 0x0001
|
||||
.offset dw 0x7e00
|
||||
.segment dw 0x0000
|
||||
.start dd 0x0000_0001
|
||||
.start_h dd 0x0000_0000
|
||||
.start dq 0x0000_0000_0000_0001
|
||||
|
||||
;ecx = sector
|
||||
;ax = sector count
|
||||
;bx out = address of start
|
||||
allocate_and_load:
|
||||
mov word [dap.length], ax
|
||||
mov dword [dap.start], ecx
|
||||
|
||||
dec ax
|
||||
shr ax, 3
|
||||
inc ax
|
||||
|
||||
mov bx, 0x200e
|
||||
xor cx, cx
|
||||
mov dx, 0x2200
|
||||
|
||||
.loop:
|
||||
add bx, 2
|
||||
test bx, dx
|
||||
je halt
|
||||
|
||||
test word [bx], 0x0000
|
||||
je .eq
|
||||
|
||||
xor cx, cx
|
||||
jmp .loop
|
||||
|
||||
.eq:
|
||||
inc cx
|
||||
test cx, ax
|
||||
jne .loop
|
||||
|
||||
dec ax
|
||||
shl ax, 1
|
||||
sub bx, ax
|
||||
mov dx, bx
|
||||
|
||||
mov ax, 0x0002
|
||||
.mark_loop:
|
||||
mov word [bx], ax
|
||||
loop .mark_loop
|
||||
|
||||
mov bx, dx
|
||||
and ebx, 0x0000_dfff
|
||||
shl ebx, 12
|
||||
|
||||
.load:
|
||||
mov eax, ebx
|
||||
mov word [dap.offset], ax
|
||||
shr eax, 4
|
||||
and ax, 0xf000
|
||||
mov word [dap.segment], ax
|
||||
|
||||
mov ah, 0x42
|
||||
mov si, dap
|
||||
int 0x13
|
||||
|
||||
ret
|
||||
|
||||
halt:
|
||||
cli
|
||||
.hlt:
|
||||
hlt
|
||||
jmp .hlt
|
||||
memory_usage:
|
||||
.low dw ;word - used memory from 0 to 1MiB in kiB
|
||||
.mid dw 0x0000;word - used memory from 1MiB to 16MiB in kiB
|
||||
.high dw 0x0000;word - used memory from 16MiB up in 64s of kiB
|
||||
|
|
@ -1,11 +1,13 @@
|
|||
OUTPUT_FORMAT(binary)
|
||||
MEMORY {
|
||||
kload : ORIGIN = 0x01000000, LENGTH = 0x01000000
|
||||
}
|
||||
|
||||
SECTIONS {
|
||||
. = 0x01000000;
|
||||
.text : {
|
||||
main = .;
|
||||
_start = .;
|
||||
*(.text)
|
||||
}
|
||||
.rodata : { *(.rodata) }
|
||||
.data : { *(.data) }
|
||||
.bss : { *(.bss) }
|
||||
} >kload
|
||||
.rodata : { *(.rodata) } >kload
|
||||
.data : { *(.data) *(.bss) } >kload
|
||||
}
|
||||
|
|
@ -23,7 +23,7 @@ OF THIS SOFTWARE.
|
|||
#include "proc.h"
|
||||
#include "misc.h"
|
||||
|
||||
void main(void) {
|
||||
void _start(void) {
|
||||
*(uint16_t *)0x0000200e = 0x0000;
|
||||
|
||||
*(uint32_t *)0x0000050c = (uint32_t)allocate_pages(16 * sizeof(struct file_handle_info), 2);
|
||||
|
|
|
|||
Reference in a new issue