; filesystem access unit ; Access Address ; Method Type Target Start ; -------- -------- ----------- ----------- ; Level 0: IO-Ports Physical HD c=0:h=0:s=1 ; Level 1: Level0 Logical HD s=0 ; Level 2: Level1 Logical Partition s=0 ; Level 3: Level2 Logical FAT,Cluster cluster=2 ;MIN_SECT_PER_CLUST equ 8 ; 4k MIN MAX_SECT_PER_CLUST equ 128 ; 64k MAX direntry_name equ (byte ptr 00h) ; directory entry direntry_ext equ (byte ptr 08h) direntry_attr equ (byte ptr 0Bh) direntry_time equ (word ptr 16h) direntry_cluster equ (word ptr 1Ah) direntry_size equ (dword ptr 1Ch) char_DELETED equ 0E5h ; some constants char_NOFILE equ 0 fa_readonly equ 00000001b ; file attributes fa_hidden equ 00000010b fa_system equ 00000100b fa_volumeid equ 00001000b fa_directory equ 00010000b fa_archive equ 00100000b ROOT equ 0 ; root dir cluster EOF equ -1 ; EOF cluster ; --------------------------------------------------------------------------- level0_getcmdport: mov dx, 1F7h ; master test level0_drive, 10b jz __1 mov dx, 177h ; slave __1: ret level0_calcdrive: xor al, al ; primary/secondary bt word ptr level0_drive, 0 rcl al, 5 or al, 10100000b ret level0_init: call level0_getcmdport __1: in al, dx ; busy test al, 00000001b jnz __error test al, 10000000b jnz __1 dec dx ; drive # call level0_calcdrive out dx, al inc dx ; ready xor cx, cx __2: dec cx jz __error in al, dx test al, 00000001b jnz __error test al, 01000000b jz __2 mov al, 0ECh ; indentify drive out dx, al __3: in al, dx ; data test al, 00000001b jnz __error test al, 00001000b jz __3 sub dl, 7 ; read lea di, level0_driveinfo mov cx, 256/2 rep insw clc ret __error: stc ret level0_read: call io_mask call level0_rw jc __error mov al, 20h ; read out dx, al mov si, level0_count les di, level0_ptr __3: in al, dx ; data test al, 00000001b jnz __error test al, 00001000b jz __3 sub dl, 7 mov cx, 512/2 ; read rep insw add dl, 7 dec si jnz __3 push cs pop es call io_unmask clc ret __error: call io_unmask stc ret level0_write: call io_mask call level0_rw jc __error mov al, 30h ; write out dx, al mov di, level0_count les si, level0_ptr __3: in al, dx ; ready? test al, 00000001b jnz __error test al, 00001000b jz __3 sub dl, 7 mov cx, 512/2 ; write seges rep outsw add dl, 7 dec di jnz __3 push cs pop es call io_unmask clc ret __error: call io_unmask stc ret io_mask: in al, 21h mov level0_port21, al in al, 0A1h mov level0_portA1, al mov al, 0FFh out 21h, al out 0A1h, al ret io_unmask: mov al, level0_port21 out 21h, al mov al, level0_portA1 out 0A1h, al ret level0_rw: call level0_getcmdport __1: in al, dx test al, 00000001b jnz __error test al, 10000000b jnz __1 sub dl, 5 ; sector count mov al, byte ptr level0_count out dx, al inc dx ; sector mov al, byte ptr level0_sector out dx, al inc dx ; cylinder - lo mov ax, level0_cylinder out dx, al inc dx ; cylinder - hi mov al, ah out dx, al inc dx ; drive # call level0_calcdrive or al, byte ptr level0_head out dx, al inc dx ; ready __2: in al, dx test al, 00000001b jnz __error test al, 01000000b jz __2 clc ret __error: stc ret ; --------------------------------------------------------------------------- level1_read: call level1_rw call level0_read ret level1_write: call level1_rw call level0_write ret level1_rw: push level1_ptr pop level0_ptr mov ax, level1_count mov level0_count, ax mov eax, level1_sector cdq movzx ecx, level0_max_sector div ecx inc dx mov level0_sector, dx xor edx, edx movzx ecx, level0_max_head div ecx mov level0_head, dx mov level0_cylinder, ax ret ; --------------------------------------------------------------------------- level2_init: mov level2_drivecount, 0 lea di, level2_drivestart xor ebp, ebp call level2_recscan clc ret level2_recscan: call __read cmp level2_mbr.word ptr 512-2, 0AA55h jne __exit lea si, level2_mbr + 512 - 2 - 64 mov cx, 4 __scan_ptable: push cx push si mov al, [si].byte ptr 4 ; cmp al, 1 ; fat12 ; je __found_drive cmp al, 4 ; fat16 je __found_drive cmp al, 6 ; bigdos je __found_drive cmp al, 5 ; extended je __found_ext __scan_next: pop si pop cx cmp level2_drivecount, 26 jae __exit add si, 16 loop __scan_ptable __exit: ret __read: pushad mov level1_sector, ebp mov level1_count, 1 mov level1_ptr.o, offset level2_mbr mov level1_ptr.s, cs call level1_read popad ret __found_drive: mov eax, [si].dword ptr 8 add eax, ebp ; scan drives to avoid recursive extended pusha lea di, level2_drivestart mov cx, level2_drivecount repnz scasd popa jz __scan_next inc level2_drivecount stosd jmp __scan_next __found_ext: push ebp add ebp, [si].dword ptr 8 call level2_recscan pop ebp call __read jmp __scan_next level2_initdrive: mov bx, level2_drive shl bx, 2 push level2_drivestart[bx] pop level2_basesector ret level2_read: call level2_rw call level1_read ret level2_write: call level2_rw call level1_write ret level2_rw: push level2_ptr pop level1_ptr mov eax, level2_sector add eax, level2_basesector mov level1_sector, eax push level2_count pop level1_count ret ; --------------------------------------------------------------------------- level3_init: mov level2_sector, 0 mov level2_count, 1 mov level2_ptr.o, offset level3_boot mov level2_ptr.s, cs call level2_read jc __error lea bx, level3_boot cmp [bx].word ptr 512-2, 0AA55h jne __error lea si, [bx].byte ptr 36h lea di, FAT16_ID mov cx, 8 rep cmpsb je __FAT16 jmp __error __FAT16: movzx eax, [bx].word ptr 0Eh mov level3_reserved, eax xor eax, eax mov al, [bx].byte ptr 0Dh mov level3_sectpercluster, eax ; cmp eax, MIN_SECT_PER_CLUST ; jb __error cmp eax, MAX_SECT_PER_CLUST ja __error mov al, [bx].byte ptr 10h mov level3_fatcopies, eax mov ax, [bx].word ptr 11h mov level3_rootdirentries, eax shl eax, 5 add eax, 511 shr eax, 9 mov level3_rootdirsectors, eax cmp eax, MAX_SECT_PER_CLUST ja __error movzx eax, [bx].word ptr 16h mov level3_sectperfat, eax mov eax, level3_sectperfat imul eax, level3_fatcopies add eax, level3_reserved mov level3_rootstart, eax add eax, level3_rootdirsectors mov level3_datastart, eax movzx eax, [bx].word ptr 13h or ax, ax jnz __1 mov eax, [bx].dword ptr 20h __1: mov level3_totalsectors, eax sub eax, level3_datastart xor edx, edx mov ecx, level3_sectpercluster div ecx mov level3_totalclusters, eax mov level3_cachesector, -1 clc ret __error: stc ret ; input: bx=cluster ; output: ax=value level3_cluster_get: call level3_read_fat_sector push bx call level3_calcfat_LO mov ax, word ptr level3_cache[bx] pop bx ret ; input: bx=cluster ; ax=value level3_cluster_set: call level3_read_fat_sector push bx call level3_calcfat_LO mov word ptr level3_cache[bx], ax pop bx call level3_write_fat_sector ret level3_calcfat_HI: movzx eax, bx ; fat sector # shr eax, 8 ret level3_calcfat_LO: and bx, 255 shl bx, 1 ret ; input: ebx=cluster # level3_read_fat_sector: pushad call level3_calcfat_HI add eax, level3_reserved ; partition sector # cmp level3_cachesector, eax je __skip mov level3_cachesector, eax mov level2_sector, eax mov level2_count, 1 mov level2_ptr.o, offset level3_cache mov level2_ptr.s, cs call level2_read __skip: popad ret level3_write_fat_sector:pushad call level3_calcfat_HI add eax, level3_reserved ; partition sector # mov level2_sector, eax mov level2_count, 1 mov level2_ptr.o, offset level3_cache mov level2_ptr.s, cs mov ecx, level3_fatcopies __1: pushad call level2_write popad mov eax, level3_sectperfat add level2_sector, eax loop __1 popad ret level3_read: pushad call level3_calc call level2_read popad ret level3_write: pushad call level3_calc call level2_write popad ret level3_calc: push level3_ptr pop level2_ptr cmp level3_cluster, ROOT je __root movzx eax, level3_count imul eax, level3_sectpercluster mov level2_count, ax movzx eax, level3_cluster sub eax, 2 xor edx, edx mov ecx, level3_sectpercluster mul ecx add eax, level3_datastart mov level2_sector, eax ret __root: mov eax, level3_rootdirsectors mov level2_count, ax mov eax, level3_rootstart mov level2_sector, eax ret ; --------------------------------------------------------------------------- FAT16_ID db 'FAT16 ' ; ---------------------------------------------------------------------------