mirror of https://github.com/FDOS/kernel.git
Enable LBA booting for FAT16 and workaround for floppies where DL is not
passed. git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@397 6ac86273-5f31-0410-b378-82cca8765d1b
This commit is contained in:
Bart Oldeman
parent
11be0d22e4
commit
cbad615e0b
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@ -178,15 +178,21 @@ Entry: jmp short real_start
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; ENTRY
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;-----------------------------------------------------------------------
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real_start: cli
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cld
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real_start: cli
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cld
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xor ax, ax
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mov ss, ax ; initialize stack
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mov ss, ax ; initialize stack
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mov ds, ax
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mov bp, 0x7c00
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lea sp, [bp-0x20]
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sti
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int 0x13 ; reset drive
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mov bp, 0x7c00
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lea sp, [bp-0x20]
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sti
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cmp byte [drive], 0xff ; BIOS bug ??
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jne dont_use_dl
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mov [drive], dl ; BIOS passes drive number in DL
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; a reset should not be needed here
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dont_use_dl:
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; int 0x13 ; reset drive
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; int 0x12 ; get memory available in AX
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; mov ax, 0x01e0
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; mov cl, 6 ; move boot sector to higher memory
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@ -203,10 +209,9 @@ real_start: cli
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cont: mov ds, ax
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mov ss, ax
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mov [drive], dl ; BIOS passes drive number in DL
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call print
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db "Loading FreeDOS ",0
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db "FreeDOS",0
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%ifdef CALCPARAMS
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GETDRIVEPARMS
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@ -337,7 +342,8 @@ finished: ; Mark end of FAT chain with 0, so we have a single
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pop ds
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call print
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db " KERNEL",0
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db " Kernel",0 ; "KERNEL"
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; loadFile: Loads the file into memory, one cluster at a time.
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@ -403,6 +409,64 @@ readDisk: push si
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read_next: push dx
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push ax
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;******************** LBA_READ *******************************
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; check for LBA support
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push bx
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mov ah,041h ;
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mov bx,055aah ;
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mov dl, [drive]
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int 0x13
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jc read_normal_BIOS
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sub bx,0aa55h
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jne read_normal_BIOS
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shr cx,1 ; CX must have 1 bit set
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jnc read_normal_BIOS
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; OK, drive seems to support LBA addressing
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lea si,[LBA_DISK_PARAMETER_BLOCK]
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; setup LBA disk block
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mov [si+12],bx
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mov [si+14],bx
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pop bx
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pop ax
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pop dx
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push dx
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push ax
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mov [si+ 8],ax
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mov [si+10],dx
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mov [si+4],bx
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mov [si+6],es
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mov ah,042h
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jmp short do_int13_read
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LBA_DISK_PARAMETER_BLOCK:
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db 10h ; constant size of block
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db 0
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dw 1 ; 1 sector read
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; and overflow into code !!!
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read_normal_BIOS:
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pop bx
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pop ax
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pop dx
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push dx
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push ax
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;******************** END OF LBA_READ ************************
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;
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; translate sector number to BIOS parameters
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;
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@ -480,14 +544,18 @@ ax_min_2: push ax
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pop ax
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%else
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mov ax, 0x0201
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do_int13_read:
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mov dl, [drive]
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int 0x13
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%endif
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read_finished:
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jnc read_ok ; jump if no error
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xor ah, ah ; else, reset floppy
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int 0x13
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pop ax
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pop dx ; and...
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read_next_chained:
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jmp short read_next ; read the same sector again
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read_ok:
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@ -512,10 +580,10 @@ no_incr_es: pop ax
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sub di,si ; if there is anything left to read,
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jg read_next ; continue
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%else
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add ax, 1
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add ax, byte 1
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adc dx, byte 0 ; DX:AX = next sector to read
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dec di ; if there is anything left to read,
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jnz read_next ; continue
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jnz read_next_chained ; continue
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%endif
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clc
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@ -622,6 +622,9 @@ VOID put_boot(COUNT drive, BYTE * bsFile, BOOL both)
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temp = bs32->sysFatSecMask + 1;
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for (bs32->sysFatSecShift = 0; temp != 1;
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bs32->sysFatSecShift++, temp >>= 1) ;
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/* use fixed drive for A:, B: and DL otherwise */
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bs32->bsDriveNumber = drive < 2 ? 0 : 0xff;
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}
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#ifdef DEBUG
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if (fs == 32)
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@ -656,6 +659,9 @@ VOID put_boot(COUNT drive, BYTE * bsFile, BOOL both)
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/* sector data starts on */
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temp = temp + bs->sysRootDirSecs;
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bs->sysDataStart = temp;
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/* use fixed BIOS drive 0 for A:, B: and DL otherwise */
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bs32->bsDriveNumber = drive < 2 ? 0 : 0xff;
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}
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#ifdef DEBUG
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