181 lines
3.9 KiB
PHP
181 lines
3.9 KiB
PHP
ATTR_READ_ONLY = 0x01
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ATTR_HIDDEN = 0x02
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ATTR_SYSTEM = 0x04
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ATTR_VOLUME_ID = 0x08
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ATTR_DIRECTORY = 0x10
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ATTR_ARCHIVE = 0x20
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struc fat_entry
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{
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.name db 8 dup ?
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.ext db 3 dup ?
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.attrs db ?
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.reserved dw ?
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.creation_time dw ?
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.creation_date dw ?
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.access_date dw ?
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.reserved2 dw ?
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.mod_time dw ?
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.mod_date dw ?
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.start dw ?
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.size dd ?
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}
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virtual at di
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fat_entry fat_entry
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end virtual
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; CHS to LBA
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; LBA = (C * HPC + H) * SPT + (S - 1)
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;;; Read sectors from disk to buffer
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;;;
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;;; @param AX LBA starting sector
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;;; @param CX sector count
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;;; @param ES:BX buffer
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;;;
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disk_read_sectors:
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; https://en.wikipedia.org/wiki/Logical_block_addressing
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; convert LBA to CHS
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; HPC = Head per Cluster
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; SPT = Sector per Track
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; S = (LBA % SPT) + 1
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push ax
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push bx
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push cx
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xor dx, dx
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div word [sectors_per_track]
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inc dx
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mov [S], dx
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; H = (LBA / SPT) % HPC
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; C = LBA / (HPC * SPT)
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xor dx, dx
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div word [heads_per_cylinder]
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mov [C], ax
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mov [H], dx
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; read sectors
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mov ah, 0x2
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mov al, 0x1
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mov ch, byte [C]
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mov cl, byte [S]
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mov dh, byte [H]
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mov dl, [drive_number]
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int 0x13
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jc @f
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pop cx
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pop bx
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pop ax
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add bx, word [bytes_per_sector]
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inc ax
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loop disk_read_sectors
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ret
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@@:
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mov si, msg_error_sector
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call bios_print
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ret
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C dw 0x00
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H dw 0x00
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S dw 0x00
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fat_load_root:
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mov ax, DISK_BUFFER/0x10
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mov es, ax
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; load root directory
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mov ax, [sectors_per_FAT]
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xor cx, cx
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mov cl, [FAT_count]
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mul cx
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add ax, [reserved_sectors]
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push ax
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mov bx, [bytes_per_sector]
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mov cl, 0x5
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shr bx, cl
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mov ax, [root_dir_entries]
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xor dx, dx
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div bx
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mov cx, ax
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pop ax
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mov [data_start], ax
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add [data_start], cx
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xor bx, bx
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call disk_read_sectors
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ret
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;; @param SI filename to search
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fat_search_root:
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mov cx, [root_dir_entries]
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mov di, 0x0
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@@:
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push si
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push cx
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mov cx, 0xB ; name(8) + ext(3)
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push di
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rep cmpsb
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pop di
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pop cx
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pop si
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je .file_found
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add di, 0x20
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loop @b
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; set carry if not found
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stc
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ret
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.file_found:
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mov ax, [es:fat_entry.start]
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clc
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ret
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;;; @param AX cluster
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;;; @param ES:BX buffer
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fat_load_binary:
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push ax
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sub ax, 0x2
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xor cx, cx
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mov cl, [sectors_per_cluster]
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mul cx
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add ax, [data_start]
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xor cx, cx
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mov cl, [sectors_per_cluster]
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call disk_read_sectors
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pop ax
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mov cx, ax
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mov dx, ax
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shr dx, 0x1
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add cx, dx
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push bx
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mov bx, DISK_BUFFER
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add bx, cx
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mov dx, [bx]
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pop bx
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test ax, 0x1
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jnz .odd_cluster
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.even_cluster:
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and dx, 0xFFF
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jmp .end
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.odd_cluster:
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shr dx, 0x4
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.end:
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mov ax, dx
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cmp dx, 0xFF0
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jb fat_load_binary
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ret
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msg_error_sector db "ERROR: reading sector", CR, LF, 0
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data_start dw 0x0 |