; -----------------------------------------------------------------------
;
; Copyright 1994-2009 H. Peter Anvin - All Rights Reserved
; Copyright 2009-2011 Intel Corporation; author: H. Peter Anvin
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
; Boston MA 02110-1301, USA; either version 2 of the License, or
; (at your option) any later version; incorporated herein by reference.
;
; -----------------------------------------------------------------------
;
; diskstart.inc
;
; Common early-bootstrap code for harddisk-based Syslinux derivatives.
;
Sect1Ptr0_VAL equ 0xdeadbeef
Sect1Ptr1_VAL equ 0xfeedface
%include "diskboot.inc"
; ===========================================================================
; Padding after the (minimum) 512-byte boot sector so that the rest of
; the file has aligned sectors, even if they are larger than 512 bytes.
; ===========================================================================
section .init
align_pad zb 512
; ===========================================================================
; Start of LDLINUX.SYS
; ===========================================================================
LDLINUX_SYS equ ($-$$)+TEXT_START
ldlinux_sys:
early_banner db CR, LF, MY_NAME, ' ', VERSION_STR, ' ', 0
db CR, LF, 1Ah ; EOF if we "type" this in DOS
alignz 8
ldlinux_magic dd LDLINUX_MAGIC
dd LDLINUX_MAGIC^HEXDATE
;
; This area is patched by the installer. It is found by looking for
; LDLINUX_MAGIC, plus 8 bytes.
;
SUBVOL_MAX equ 256
CURRENTDIR_MAX equ FILENAME_MAX
patch_area:
DataSectors dw 0 ; Number of sectors (not including bootsec)
ADVSectors dw 0 ; Additional sectors for ADVs
LDLDwords dd 0 ; Total dwords starting at ldlinux_sys,
CheckSum dd 0 ; Checksum starting at ldlinux_sys
; value = LDLINUX_MAGIC - [sum of dwords]
MaxTransfer dw 127 ; Max sectors to transfer
EPAPtr dw EPA - LDLINUX_SYS ; Pointer to the extended patch area
;
; Extended patch area -- this is in .data16 so it doesn't occupy space in
; the first sector. Use this structure for anything that isn't used by
; the first sector itself.
;
section .data16
alignz 2
EPA:
ADVSecPtr dw ADVSec0 - LDLINUX_SYS
CurrentDirPtr dw CurrentDirName-LDLINUX_SYS ; Current directory name string
CurrentDirLen dw CURRENTDIR_MAX
SubvolPtr dw SubvolName-LDLINUX_SYS
SubvolLen dw SUBVOL_MAX
SecPtrOffset dw SectorPtrs-LDLINUX_SYS
SecPtrCnt dw (SectorPtrsEnd - SectorPtrs)/10
;
; Boot sector patch pointers
;
Sect1Ptr0Ptr dw Sect1Ptr0 - bootsec ; Pointers to Sector 1 location
Sect1Ptr1Ptr dw Sect1Ptr1 - bootsec
RAIDPatchPtr dw kaboom.again - bootsec ; Patch to INT 18h in RAID mode
;
; Pointer to the Syslinux banner
;
BannerPtr dw syslinux_banner - LDLINUX_SYS
;
; Base directory name and subvolume, if applicable.
;
%define HAVE_CURRENTDIRNAME
global CurrentDirName:data hidden, SubvolName:data hidden
CurrentDirName times CURRENTDIR_MAX db 0
SubvolName times SUBVOL_MAX db 0
section .init
ldlinux_ent:
;
; Note that some BIOSes are buggy and run the boot sector at 07C0:0000
; instead of 0000:7C00 and the like. We don't want to add anything
; more to the boot sector, so it is written to not assume a fixed
; value in CS, but we don't want to deal with that anymore from now
; on.
;
jmp 0:.next ; Normalize CS:IP
.next: sti ; In case of broken INT 13h BIOSes
;
; Tell the user we got this far
;
mov si,early_banner
call writestr_early
;
; Checksum data thus far
;
mov si,ldlinux_sys
mov cx,[bsBytesPerSec]
shr cx,2
mov edx,-LDLINUX_MAGIC
.checksum:
lodsd
add edx,eax
loop .checksum
mov [CheckSum],edx ; Save intermediate result
movzx ebx,si ; Start of the next sector
;
; Tell the user if we're using EBIOS or CBIOS
;
print_bios:
mov si,cbios_name
cmp byte [getonesec.jmp+1],(getonesec_ebios-(getonesec.jmp+2))
jne .cbios
mov si,ebios_name
mov byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
.cbios:
mov [BIOSName],si
call writestr_early
section .earlybss
global BIOSName
alignb 2
%define HAVE_BIOSNAME 1
BIOSName resw 1
section .init
;
; Now we read the rest of LDLINUX.SYS.
;
load_rest:
push bx ; LSW of load address
lea esi,[SectorPtrs]
mov cx,[DataSectors]
dec cx ; Minus this sector
.get_chunk:
jcxz .done
mov eax,[si]
mov edx,[si+4]
movzx ebp,word [si+8]
sub cx,bp
push ebx
shr ebx,4 ; Convert to a segment
mov es,bx
xor bx,bx
call getlinsec
pop ebx
imul bp,[bsBytesPerSec] ; Will be < 64K
add ebx,ebp
add si,10
jmp .get_chunk
.done:
;
; All loaded up, verify that we got what we needed.
; Note: the checksum field is embedded in the checksum region, so
; by the time we get to the end it should all cancel out.
;
verify_checksum:
pop si ; LSW of load address
movzx eax,word [bsBytesPerSec]
shr ax,2
mov ecx,[LDLDwords] ; Total dwords
sub ecx,eax ; ... minus one sector
mov eax,[CheckSum]
.checksum:
add eax,[si]
add si,4
jnz .nowrap
; Handle segment wrap
mov dx,ds
add dx,1000h
mov ds,dx
.nowrap:
dec ecx
jnz .checksum
mov ds,cx
and eax,eax ; Should be zero
jz all_read ; We're cool, go for it!
;
; Uh-oh, something went bad...
;
mov si,checksumerr_msg
call writestr_early
jmp kaboom
;
; -----------------------------------------------------------------------------
; Subroutines that have to be in the first sector
; -----------------------------------------------------------------------------
;
; getlinsec: load a sequence of BP floppy sector given by the linear sector
; number in EAX into the buffer at ES:BX. We try to optimize
; by loading up to a whole track at a time, but the user
; is responsible for not crossing a 64K boundary.
; (Yes, BP is weird for a count, but it was available...)
;
; On return, BX points to the first byte after the transferred
; block.
;
; This routine assumes CS == DS.
;
global getlinsec:function hidden
getlinsec:
pushad
add eax,[Hidden] ; Add partition offset
adc edx,[Hidden+4]
.jmp: jmp strict short getlinsec_cbios
;
; 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
pushad
mov ah,42h ; Extended Read
push ds
push ss
pop ds
call xint13
pop ds
popad
lea sp,[si+16] ; Remove DAPA
jc .error
pop bp
add eax,edi ; Advance sector pointer
adc edx,0
sub bp,di ; Sectors left
imul di,[bsBytesPerSec]
add bx,di ; Advance buffer pointer
and bp,bp
jnz .loop
popad
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
call xint13
popad
loop .retry ; CX-- and jump if not zero
;shr word [MaxTransfer],1 ; Reduce the transfer size
;jnz .retry2
; Total failure. Try falling back to CBIOS.
mov byte [getlinsec.jmp+1],(getlinsec_cbios-(getlinsec.jmp+2))
;mov byte [MaxTransfer],63 ; Max possibe CBIOS transfer
pop bp
; ... fall through ...
;
; getlinsec_cbios:
;
; getlinsec implementation for legacy CBIOS
;
getlinsec_cbios:
.loop:
push edx
push eax
push bp
push bx
movzx esi,word [bsSecPerTrack]
movzx edi,word [bsHeads]
;
; Dividing by sectors to get (track,sector): we may have
; up to 2^18 tracks, so we need to use 32-bit arithmetric.
;
div esi
xor cx,cx
xchg cx,dx ; CX <- sector index (0-based)
; EDX <- 0
; eax = track #
div edi ; Convert track to head/cyl
cmp eax,1023 ; Outside the CHS range?
ja kaboom
;
; Now we have AX = cyl, DX = head, CX = sector (0-based),
; BP = sectors to transfer, SI = bsSecPerTrack,
; ES:BX = data target
;
call maxtrans ; Enforce maximum transfer size
; Must not cross track boundaries, so BP <= SI-CX
sub si,cx
cmp bp,si
jna .bp_ok
mov bp,si
.bp_ok:
shl ah,6 ; Because IBM was STOOPID
; and thought 8 bits were enough
; then thought 10 bits were enough...
inc cx ; Sector numbers are 1-based, sigh
or cl,ah
mov ch,al
mov dh,dl
xchg ax,bp ; Sector to transfer count
mov ah,02h ; Read sectors
mov bp,retry_count
.retry:
pushad
call xint13
popad
jc .error
.resume:
movzx ecx,al ; ECX <- sectors transferred
imul ax,[bsBytesPerSec] ; 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
popad
ret
.error:
dec bp
jnz .retry
xchg ax,bp ; Sectors transferred <- 0
shr word [MaxTransfer],1
jnz .resume
jmp kaboom
maxtrans:
cmp bp,[MaxTransfer]
jna .ok
mov bp,[MaxTransfer]
.ok: ret
;
;
; writestr_early: 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_early:
pushad
.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: popad
ret
;
; Checksum error message
;
checksumerr_msg db ' Load error - ', 0 ; Boot failed appended
;
; BIOS type string
;
cbios_name db 'CHS', 0 ; CHS/CBIOS
ebios_name db 'EDD', 0 ; EDD/EBIOS
;
; Debug routine
;
%ifdef debug
safedumpregs:
cmp word [Debug_Magic],0D00Dh
jnz nc_return
jmp dumpregs
%endif
rl_checkpt equ $ ; Must be <= 8000h
rl_checkpt_off equ $-ldlinux_sys
%ifndef DEPEND
%if rl_checkpt_off > 512-10 ; Need minimum one extent
%assign rl_checkpt_overflow rl_checkpt_off - (512-10)
%error Sector 1 overflow by rl_checkpt_overflow bytes
%endif
%endif
;
; Extent pointers... each extent contains an 8-byte LBA and an 2-byte
; sector count. In most cases, we will only ever need a handful of
; extents, but we have to assume a maximally fragmented system where each
; extent contains only one sector.
;
alignz 2
MaxInitDataSize equ 96 << 10
MaxLMA equ LDLINUX_SYS+MaxInitDataSize
SectorPtrs zb 10*(MaxInitDataSize >> MIN_SECTOR_SHIFT)
SectorPtrsEnd equ $
; ----------------------------------------------------------------------------
; End of code and data that have to be in the first sector
; ----------------------------------------------------------------------------
section .text16
all_read:
; We enter here with ES scrambled...
xor ax,ax
mov es,ax
;
; Let the user (and programmer!) know we got this far. This used to be
; in Sector 1, but makes a lot more sense here.
;
mov si,late_banner
call writestr_early
mov si,copyright_str
call writestr_early
;
; Insane hack to expand the DOS superblock to dwords
;
expand_super:
xor eax,eax
mov si,superblock
mov di,SuperInfo
mov cx,superinfo_size
.loop:
lodsw
dec si
stosd ; Store expanded word
xor ah,ah
stosd ; Store expanded byte
loop .loop
;
; Common initialization code
;
%include "init.inc"
pushad
mov eax,ROOT_FS_OPS
movzx dx,byte [DriveNumber]
; DH = 0: we are boot from disk not CDROM
mov ecx,[Hidden]
mov ebx,[Hidden+4]
mov si,[bsHeads]
mov di,[bsSecPerTrack]
movzx ebp,word [MaxTransfer]
pm_call pm_fs_init
pm_call load_env32
popad
section .bss16
SuperInfo resq 16 ; The first 16 bytes expanded 8 times
;
; Banner information not needed in sector 1
;
section .data16
global syslinux_banner
syslinux_banner db CR, LF, MY_NAME, ' ', VERSION_STR
late_banner db ' ', DATE_STR, 0
section .text16