diff options
| -rw-r--r-- | ldlinux.asm | 227 |
1 files changed, 120 insertions, 107 deletions
diff --git a/ldlinux.asm b/ldlinux.asm index a8048119..02521e91 100644 --- a/ldlinux.asm +++ b/ldlinux.asm @@ -311,7 +311,6 @@ not_harddisk: ; sti - ; ; Do we have EBIOS (EDD)? ; @@ -328,7 +327,8 @@ eddcheck: ; ; We have EDD support... ; - mov byte [getlinsec.jmp+1],getlinsec_ebios-(getlinsec.jmp+2) + ; 0xEB = short jump + mov word [getlinsec_cbios],((getlinsec_ebios-(getlinsec_cbios+2)) << 8) + 0xeb .noedd: ; @@ -341,48 +341,13 @@ eddcheck: call getonesec ; Some modicum of integrity checking - cmp dword [ldlinux_magic],LDLINUX_MAGIC - jne kaboom - cmp dword [ldlinux_magic+4],HEXDATE + cmp dword [ldlinux_magic+4],LDLINUX_MAGIC^HEXDATE jne kaboom ; Go for it... jmp ldlinux_ent ; -; kaboom: write a message and bail out. -; -disk_error: -kaboom: - xor si,si - mov ss,si - mov sp,StackBuf-4 ; Reset stack - mov ds,si ; Reset data segment - pop dword [fdctab] ; Restore FDC table -.patch: mov si,bailmsg - call writestr ; Returns with AL = 0 - cbw ; AH <- 0 - int 16h ; Wait for keypress - int 19h ; And try once more to boot... -.norge: jmp short .norge ; If int 19h returned; this is the end - -; -; -; writestr: write a null-terminated string to the console -; This assumes we're on page 0. This is only used for early -; messages, so it should be OK. -; -writestr: -.loop: lodsb - and al,al - jz .return - mov ah,0Eh ; Write to screen as TTY - mov bx,0007h ; Attribute - int 10h - jmp short .loop -.return: ret - -; ; getonesec: get one disk sector ; getonesec: @@ -407,69 +372,9 @@ getonesec: ; getlinsec: add eax,[bsHidden] ; Add partition offset -.jmp: jmp strict short getlinsec_cbios ; This is patched - -; -; getlinsec_ebios: -; -; getlinsec implementation for EBIOS (EDD) -; -getlinsec_ebios: -.loop: - push bp ; Sectors left - call maxtrans ; Enforce maximum transfer size - movzx ecx,bp ; Sectors we are about to read - mov bp,retry_count -.retry: - - ; Form DAPA on stack - push dword 0 - push eax - push es - push cx - push bp - push word 16 - mov si,sp - mov dl,[DriveNumber] - mov ah,42h ; Extended Read - push ds - push ss - pop ds ; DS <- SS - pushad - int 13h - popad - pop ds - lea sp,[si+16] ; Remove DAPA - pop bp - jc .error - - add eax,ecx ; Advance sector pointer - sub bp,cx ; Sectors left - shl cx,SECTOR_SHIFT ; 512-byte sectors - add bx,cx ; Advance buffer pointer - and bp,bp - jnz .loop - - ret - -.error: - ; Some systems seem to get "stuck" in an error state when - ; using EBIOS. Doesn't happen when using CBIOS, which is - ; good, since some other systems get timeout failures - ; waiting for the floppy disk to spin up. - - pushad ; Try resetting the device - xor ax,ax - int 13h - popad - dec bp - jnz .retry - - shr word [MaxTransfer],1 ; Reduce the transfer size - jnz .loop - - jmp disk_error + xor edx,edx ; Zero-extend LBA (eventually allow 64 bits) + ; Fall through. In the case of EBIOS, we patch over the first instruction. ; ; getlinsec_cbios: ; @@ -477,6 +382,7 @@ getlinsec_ebios: ; getlinsec_cbios: .loop: + push edx push eax push bp push bx @@ -487,13 +393,14 @@ getlinsec_cbios: ; Dividing by sectors to get (track,sector): we may have ; up to 2^18 tracks, so we need to use 32-bit arithmetric. ; - xor edx,edx ; Zero-extend LBA to 64 bits div esi xor cx,cx xchg cx,dx ; CX <- sector index (0-based) ; EDX <- 0 ; eax = track # div edi ; Convert track to head/cyl + + ; We should test this, but it doesn't fit... ; cmp eax,1023 ; ja .error @@ -529,12 +436,13 @@ getlinsec_cbios: popad jc .error .resume: - movzx ecx,al - shl ax,9 ; Convert sectors in AL to bytes in AX + movzx ecx,al ; ECX <- sectors transferred + shl ax,SECTOR_SHIFT ; Convert sectors in AL to bytes in AX pop bx add bx,ax pop bp pop eax + pop edx add eax,ecx sub bp,cx jnz .loop @@ -546,11 +454,99 @@ getlinsec_cbios: xor ax,ax ; Sectors transferred <- 0 shr word [MaxTransfer],1 - jnz .resume - + jnz .error jmp disk_error ; +; getlinsec_ebios: +; +; getlinsec implementation for EBIOS (EDD) +; +getlinsec_ebios: +.loop: + push bp ; Sectors left +.retry2: + call maxtrans ; Enforce maximum transfer size + movzx edi,bp ; Sectors we are about to read + mov cx,retry_count +.retry: + + ; Form DAPA on stack + push edx + push eax + push es + push bx + push di + push word 16 + mov si,sp + mov dl,[DriveNumber] + mov ah,42h ; Extended Read + push ds + push ss + pop ds ; DS <- SS + pushad + int 13h + popad + pop ds + lea sp,[si+16] ; Remove DAPA + jc .error + pop bp + add eax,edi ; Advance sector pointer + sub bp,di ; Sectors left + shl di,SECTOR_SHIFT ; 512-byte sectors + add bx,di ; Advance buffer pointer + and bp,bp + jnz .loop + + ret + +.error: + ; Some systems seem to get "stuck" in an error state when + ; using EBIOS. Doesn't happen when using CBIOS, which is + ; good, since some other systems get timeout failures + ; waiting for the floppy disk to spin up. + + pushad ; Try resetting the device + xor ax,ax + int 13h + popad + loop .retry ; CX-- and jump if not zero + + shr word [MaxTransfer],1 ; Reduce the transfer size + jnz .retry2 + + ; Fall back to CBIOS here? + + ; Fall through to disk_error + +; +; kaboom: write a message and bail out. +; +disk_error: +kaboom: + xor si,si + mov ss,si + mov sp,StackBuf-4 ; Reset stack + mov ds,si ; Reset data segment + pop dword [fdctab] ; Restore FDC table +.patch: ; When we have full code, intercept here + mov si,bailmsg + + ; Write error message, this assumes screen page 0 +.loop: lodsb + and al,al + jz .done + mov ah,0Eh ; Write to screen as TTY + mov bx,0007h ; Attribute + int 10h + jmp short .loop +.done: + cbw ; AH <- 0 + int 16h ; Wait for keypress + int 19h ; And try once more to boot... +.norge: jmp short .norge ; If int 19h returned; this is the end + +; ; Truncate BP to MaxTransfer ; maxtrans: @@ -559,10 +555,11 @@ maxtrans: mov bp,[MaxTransfer] .ok: ret + ; ; Error message on failure ; -bailmsg: db 'ERR', 0Dh, 0Ah, 0 +bailmsg: db 'Boot failed', 0Dh, 0Ah, 0 %if 1 bs_checkpt_off equ ($-$$) @@ -598,7 +595,7 @@ syslinux_banner db 0Dh, 0Ah align 8, db 0 ldlinux_magic dd LDLINUX_MAGIC - dd HEXDATE + dd LDLINUX_MAGIC^HEXDATE ; ; This area is patched by the installer. It is found by looking for @@ -694,6 +691,22 @@ verify_checksum: ; ----------------------------------------------------------------------------- ; +; +; writestr: write a null-terminated string to the console +; This assumes we're on page 0. This is only used for early +; messages, so it should be OK. +; +writestr: +.loop: lodsb + and al,al + jz .return + mov ah,0Eh ; Write to screen as TTY + mov bx,0007h ; Attribute + int 10h + jmp short .loop +.return: ret + +; ; getlinsecsr: save registers, call getlinsec, restore registers ; getlinsecsr: pushad |