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|
; -*- fundamental -*- (asm-mode sucks)
; ****************************************************************************
;
; extlinux.asm
;
; A program to boot Linux kernels off an ext2/ext3 filesystem.
;
; Copyright (C) 1994-2007 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., 53 Temple Place Ste 330,
; Boston MA 02111-1307, USA; either version 2 of the License, or
; (at your option) any later version; incorporated herein by reference.
;
; ****************************************************************************
%define IS_EXTLINUX 1
%include "head.inc"
%include "ext2_fs.inc"
;
; Some semi-configurable constants... change on your own risk.
;
my_id equ extlinux_id
; NASM 0.98.38 croaks if these are equ's rather than macros...
FILENAME_MAX_LG2 equ 8 ; log2(Max filename size Including final null)
FILENAME_MAX equ (1 << FILENAME_MAX_LG2) ; Max mangled filename size
NULLFILE equ 0 ; Null character == empty filename
NULLOFFSET equ 0 ; Position in which to look
retry_count equ 16 ; How patient are we with the disk?
%assign HIGHMEM_SLOP 0 ; Avoid this much memory near the top
LDLINUX_MAGIC equ 0x3eb202fe ; A random number to identify ourselves with
MAX_OPEN_LG2 equ 6 ; log2(Max number of open files)
MAX_OPEN equ (1 << MAX_OPEN_LG2)
SECTOR_SHIFT equ 9
SECTOR_SIZE equ (1 << SECTOR_SHIFT)
MAX_SYMLINKS equ 64 ; Maximum number of symlinks per lookup
SYMLINK_SECTORS equ 2 ; Max number of sectors in a symlink
; (should be >= FILENAME_MAX)
;
; This is what we need to do when idle
;
%macro RESET_IDLE 0
; Nothing
%endmacro
%macro DO_IDLE 0
; Nothing
%endmacro
;
; The following structure is used for "virtual kernels"; i.e. LILO-style
; option labels. The options we permit here are `kernel' and `append
; Since there is no room in the bottom 64K for all of these, we
; stick them at vk_seg:0000 and copy them down before we need them.
;
struc vkernel
vk_vname: resb FILENAME_MAX ; Virtual name **MUST BE FIRST!**
vk_rname: resb FILENAME_MAX ; Real name
vk_appendlen: resw 1
vk_type: resb 1 ; Type of file
alignb 4
vk_append: resb max_cmd_len+1 ; Command line
alignb 4
vk_end: equ $ ; Should be <= vk_size
endstruc
;
; Segment assignments in the bottom 640K
; Stick to the low 512K in case we're using something like M-systems flash
; which load a driver into low RAM (evil!!)
;
; 0000h - main code/data segment (and BIOS segment)
;
real_mode_seg equ 4000h
cache_seg equ 3000h ; 64K area for metadata cache
vk_seg equ 2000h ; Virtual kernels
xfer_buf_seg equ 1000h ; Bounce buffer for I/O to high mem
comboot_seg equ real_mode_seg ; COMBOOT image loading zone
;
; File structure. This holds the information for each currently open file.
;
struc open_file_t
file_left resd 1 ; Number of sectors left (0 = free)
file_sector resd 1 ; Next linear sector to read
file_in_sec resd 1 ; Sector where inode lives
file_in_off resw 1
file_mode resw 1
endstruc
%ifndef DEPEND
%if (open_file_t_size & (open_file_t_size-1))
%error "open_file_t is not a power of 2"
%endif
%endif
; ---------------------------------------------------------------------------
; BEGIN CODE
; ---------------------------------------------------------------------------
;
; Memory below this point is reserved for the BIOS and the MBR
;
section .earlybss
trackbufsize equ 8192
trackbuf resb trackbufsize ; Track buffer goes here
getcbuf resb trackbufsize
; ends at 4800h
section .bss1
SuperBlock resb 1024 ; ext2 superblock
SuperInfo resq 16 ; DOS superblock expanded
ClustSize resd 1 ; Bytes/cluster ("block")
SecPerClust resd 1 ; Sectors/cluster
ClustMask resd 1 ; Sectors/cluster - 1
PtrsPerBlock1 resd 1 ; Pointers/cluster
PtrsPerBlock2 resd 1 ; (Pointers/cluster)^2
DriveNumber resb 1 ; BIOS drive number
ClustShift resb 1 ; Shift count for sectors/cluster
ClustByteShift resb 1 ; Shift count for bytes/cluster
alignb open_file_t_size
Files resb MAX_OPEN*open_file_t_size
;
; Constants for the xfer_buf_seg
;
; The xfer_buf_seg is also used to store message file buffers. We
; need two trackbuffers (text and graphics), plus a work buffer
; for the graphics decompressor.
;
xbs_textbuf equ 0 ; Also hard-coded, do not change
xbs_vgabuf equ trackbufsize
xbs_vgatmpbuf equ 2*trackbufsize
section .text
;
; Some of the things that have to be saved very early are saved
; "close" to the initial stack pointer offset, in order to
; reduce the code size...
;
StackBuf equ $-44-32 ; Start the stack here (grow down - 4K)
PartInfo equ StackBuf ; Saved partition table entry
FloppyTable equ PartInfo+16 ; Floppy info table (must follow PartInfo)
OrigFDCTabPtr equ StackBuf-8 ; The 2nd high dword on the stack
OrigESDI equ StackBuf-4 ; The high dword on the stack
;
; Primary entry point. Tempting as though it may be, we can't put the
; initial "cli" here; the jmp opcode in the first byte is part of the
; "magic number" (using the term very loosely) for the DOS superblock.
;
bootsec equ $
jmp short start ; 2 bytes
nop ; 1 byte
;
; "Superblock" follows -- it's in the boot sector, so it's already
; loaded and ready for us
;
bsOemName db 'EXTLINUX' ; The SYS command sets this, so...
;
; These are the fields we actually care about. We end up expanding them
; all to dword size early in the code, so generate labels for both
; the expanded and unexpanded versions.
;
%macro superb 1
bx %+ %1 equ SuperInfo+($-superblock)*8+4
bs %+ %1 equ $
zb 1
%endmacro
%macro superw 1
bx %+ %1 equ SuperInfo+($-superblock)*8
bs %+ %1 equ $
zw 1
%endmacro
%macro superd 1
bx %+ %1 equ $ ; no expansion for dwords
bs %+ %1 equ $
zd 1
%endmacro
superblock equ $
superw BytesPerSec
superb SecPerClust
superw ResSectors
superb FATs
superw RootDirEnts
superw Sectors
superb Media
superw FATsecs
superw SecPerTrack
superw Heads
superinfo_size equ ($-superblock)-1 ; How much to expand
superd Hidden
superd HugeSectors
;
; This is as far as FAT12/16 and FAT32 are consistent
;
zb 54 ; FAT12/16 need 26 more bytes,
; FAT32 need 54 more bytes
superblock_len equ $-superblock
;
; Note we don't check the constraints above now; we did that at install
; time (we hope!)
;
start:
cli ; No interrupts yet, please
cld ; Copy upwards
;
; Set up the stack
;
xor ax,ax
mov ss,ax
mov sp,StackBuf ; Just below BSS
push es ; Save initial ES:DI -> $PnP pointer
push di
mov es,ax
;
; DS:SI may contain a partition table entry. Preserve it for us.
;
mov cx,8 ; Save partition info
mov di,PartInfo
rep movsw
mov ds,ax ; Now we can initialize DS...
;
; Now sautee the BIOS floppy info block to that it will support decent-
; size transfers; the floppy block is 11 bytes and is stored in the
; INT 1Eh vector (brilliant waste of resources, eh?)
;
; Of course, if BIOSes had been properly programmed, we wouldn't have
; had to waste precious space with this code.
;
mov bx,fdctab
lfs si,[bx] ; FS:SI -> original fdctab
push fs ; Save on stack in case we need to bail
push si
; Save the old fdctab even if hard disk so the stack layout
; is the same. The instructions above do not change the flags
mov [DriveNumber],dl ; Save drive number in DL
and dl,dl ; If floppy disk (00-7F), assume no
; partition table
js harddisk
floppy:
mov cl,6 ; 12 bytes (CX == 0)
; es:di -> FloppyTable already
; This should be safe to do now, interrupts are off...
mov [bx],di ; FloppyTable
mov [bx+2],ax ; Segment 0
fs rep movsw ; Faster to move words
mov cl,[bsSecPerTrack] ; Patch the sector count
mov [di-8],cl
; AX == 0 here
int 13h ; Some BIOSes need this
jmp short not_harddisk
;
; The drive number and possibly partition information was passed to us
; by the BIOS or previous boot loader (MBR). Current "best practice" is to
; trust that rather than what the superblock contains.
;
; Would it be better to zero out bsHidden if we don't have a partition table?
;
; Note: di points to beyond the end of PartInfo
;
harddisk:
test byte [di-16],7Fh ; Sanity check: "active flag" should
jnz no_partition ; be 00 or 80
mov eax,[di-8] ; Partition offset (dword)
mov [bsHidden],eax
no_partition:
;
; Get disk drive parameters (don't trust the superblock.) Don't do this for
; floppy drives -- INT 13:08 on floppy drives will (may?) return info about
; what the *drive* supports, not about the *media*. Fortunately floppy disks
; tend to have a fixed, well-defined geometry which is stored in the superblock.
;
; DL == drive # still
mov ah,08h
int 13h
jc no_driveparm
and ah,ah
jnz no_driveparm
shr dx,8
inc dx ; Contains # of heads - 1
mov [bsHeads],dx
and cx,3fh
mov [bsSecPerTrack],cx
no_driveparm:
not_harddisk:
;
; Ready to enable interrupts, captain
;
sti
;
; Do we have EBIOS (EDD)?
;
eddcheck:
mov bx,55AAh
mov ah,41h ; EDD existence query
mov dl,[DriveNumber]
int 13h
jc .noedd
cmp bx,0AA55h
jne .noedd
test cl,1 ; Extended disk access functionality set
jz .noedd
;
; We have EDD support...
;
mov byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
.noedd:
;
; Load the first sector of LDLINUX.SYS; this used to be all proper
; with parsing the superblock and root directory; it doesn't fit
; together with EBIOS support, unfortunately.
;
mov eax,[FirstSector] ; Sector start
mov bx,ldlinux_sys ; Where to load it
call getonesec
; Some modicum of integrity checking
cmp dword [ldlinux_magic+4],LDLINUX_MAGIC^HEXDATE
jne kaboom
; Go for it...
jmp ldlinux_ent
;
; getonesec: get one disk sector
;
getonesec:
mov bp,1 ; One sector
; Fall through
;
; 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, and trashes most registers.
;
; Stylistic note: use "xchg" instead of "mov" when the source is a register
; that is dead from that point; this saves space. However, please keep
; the order to dst,src to keep things sane.
;
getlinsec:
add eax,[bsHidden] ; Add partition offset
xor edx,edx ; Zero-extend LBA (eventually allow 64 bits)
.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 dl,[DriveNumber]
push ds
push ss
pop ds ; DS <- SS
mov ah,42h ; Extended Read
int 13h
pop ds
popad
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
mov dl,[DriveNumber]
int 13h
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
; We should test this, but it doesn't fit...
; cmp eax,1023
; ja .error
;
; 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
mov dl,[DriveNumber]
xchg ax,bp ; Sector to transfer count
mov ah,02h ; Read sectors
mov bp,retry_count
.retry:
pushad
int 13h
popad
jc .error
.resume:
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
ret
.error:
dec bp
jnz .retry
xchg ax,bp ; Sectors transferred <- 0
shr word [MaxTransfer],1
jnz .resume
; 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
.again: int 16h ; Wait for keypress
; NB: replaced by int 18h if
; chosen at install time..
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:
cmp bp,[MaxTransfer]
jna .ok
mov bp,[MaxTransfer]
.ok: ret
;
; Error message on failure
;
bailmsg: db 'Boot error', 0Dh, 0Ah, 0
; This fails if the boot sector overflows
zb 1F8h-($-$$)
FirstSector dd 0xDEADBEEF ; Location of sector 1
MaxTransfer dw 0x007F ; Max transfer size
; This field will be filled in 0xAA55 by the installer, but we abuse it
; to house a pointer to the INT 16h instruction at
; kaboom.again, which gets patched to INT 18h in RAID mode.
bootsignature dw kaboom.again-bootsec
;
; ===========================================================================
; End of boot sector
; ===========================================================================
; Start of LDLINUX.SYS
; ===========================================================================
ldlinux_sys:
syslinux_banner db 0Dh, 0Ah
db 'EXTLINUX '
db version_str, ' ', date, ' ', 0
db 0Dh, 0Ah, 1Ah ; EOF if we "type" this in DOS
align 8, db 0
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.
;
patch_area:
LDLDwords dw 0 ; Total dwords starting at ldlinux_sys,
; not including ADVs
LDLSectors dw 0 ; Number of sectors, not including
; bootsec & this sec, but including the two ADVs
CheckSum dd 0 ; Checksum starting at ldlinux_sys
; value = LDLINUX_MAGIC - [sum of dwords]
CurrentDir dd 2 ; "Current" directory inode number
; Space for up to 64 sectors, the theoretical maximum
SectorPtrs times 64 dd 0
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
.next:
;
; Tell the user we got this far
;
mov si,syslinux_banner
call writestr
;
; Tell the user if we're using EBIOS or CBIOS
;
print_bios:
mov si,cbios_name
cmp byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
jne .cbios
mov si,ebios_name
.cbios:
mov [BIOSName],si
call writestr
section .bss
%define HAVE_BIOSNAME 1
BIOSName resw 1
section .text
;
; Now we read the rest of LDLINUX.SYS. Don't bother loading the first
; sector again, though.
;
load_rest:
mov si,SectorPtrs
mov bx,7C00h+2*SECTOR_SIZE ; Where we start loading
mov cx,[LDLSectors]
.get_chunk:
jcxz .done
xor bp,bp
lodsd ; First sector of this chunk
mov edx,eax
.make_chunk:
inc bp
dec cx
jz .chunk_ready
inc edx ; Next linear sector
cmp [si],edx ; Does it match
jnz .chunk_ready ; If not, this is it
add si,4 ; If so, add sector to chunk
jmp short .make_chunk
.chunk_ready:
call getlinsecsr
shl bp,SECTOR_SHIFT
add bx,bp
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:
mov si,ldlinux_sys
mov cx,[LDLDwords]
mov edx,-LDLINUX_MAGIC
.checksum:
lodsd
add edx,eax
loop .checksum
and edx,edx ; Should be zero
jz all_read ; We're cool, go for it!
;
; Uh-oh, something went bad...
;
mov si,checksumerr_msg
call writestr
jmp kaboom
;
; -----------------------------------------------------------------------------
; Subroutines that have to be in the first sector
; -----------------------------------------------------------------------------
;
;
; 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
call getlinsec
popad
ret
;
; Checksum error message
;
checksumerr_msg db ' Load error - ', 0 ; Boot failed appended
;
; BIOS type string
;
cbios_name db 'CBIOS', 0
ebios_name db 'EBIOS', 0
;
; 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 ($-$$)
%ifndef DEPEND
%if rl_checkpt_off > 400h
%error "Sector 1 overflow"
%endif
%endif
; ----------------------------------------------------------------------------
; End of code and data that have to be in the first sector
; ----------------------------------------------------------------------------
all_read:
;
; 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,copyright_str
call writestr
;
; 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
;
; Load the real (ext2) superblock; 1024 bytes long at offset 1024
;
mov bx,SuperBlock
mov eax,1024 >> SECTOR_SHIFT
mov bp,ax
call getlinsec
;
; Compute some values...
;
xor edx,edx
inc edx
; s_log_block_size = log2(blocksize) - 10
mov cl,[SuperBlock+s_log_block_size]
add cl,10
mov [ClustByteShift],cl
mov eax,edx
shl eax,cl
mov [ClustSize],eax
sub cl,SECTOR_SHIFT
mov [ClustShift],cl
shr eax,SECTOR_SHIFT
mov [SecPerClust],eax
dec eax
mov [ClustMask],eax
add cl,SECTOR_SHIFT-2 ; 4 bytes/pointer
shl edx,cl
mov [PtrsPerBlock1],edx
shl edx,cl
mov [PtrsPerBlock2],edx
;
; Common initialization code
;
%include "init.inc"
%include "cpuinit.inc"
;
; Initialize the metadata cache
;
call initcache
;
; Now, everything is "up and running"... patch kaboom for more
; verbosity and using the full screen system
;
; E9 = JMP NEAR
mov dword [kaboom.patch],0e9h+((kaboom2-(kaboom.patch+3)) << 8)
;
; Now we're all set to start with our *real* business. First load the
; configuration file (if any) and parse it.
;
; In previous versions I avoided using 32-bit registers because of a
; rumour some BIOSes clobbered the upper half of 32-bit registers at
; random. I figure, though, that if there are any of those still left
; they probably won't be trying to install Linux on them...
;
; The code is still ripe with 16-bitisms, though. Not worth the hassle
; to take'm out. In fact, we may want to put them back if we're going
; to boot ELKS at some point.
;
;
; Load configuration file
;
load_config:
mov si,config_name ; Save config file name
mov di,ConfigName
call strcpy
mov di,ConfigName
call open
jz no_config_file
;
; Now we have the config file open. Parse the config file and
; run the user interface.
;
%include "ui.inc"
;
; getlinsec_ext: same as getlinsec, except load any sector from the zero
; block as all zeros; use to load any data derived
; from an ext2 block pointer, i.e. anything *except the
; superblock.*
;
getonesec_ext:
mov bp,1
getlinsec_ext:
cmp eax,[SecPerClust]
jae getlinsec ; Nothing fancy
; If we get here, at least part of what we want is in the
; zero block. Zero one sector at a time and loop.
push eax
push cx
xchg di,bx
xor eax,eax
mov cx,SECTOR_SIZE >> 2
rep stosd
xchg di,bx
pop cx
pop eax
inc eax
dec bp
jnz getlinsec_ext
ret
;
; allocate_file: Allocate a file structure
;
; If successful:
; ZF set
; BX = file pointer
; In unsuccessful:
; ZF clear
;
allocate_file:
TRACER 'a'
push cx
mov bx,Files
mov cx,MAX_OPEN
.check: cmp dword [bx], byte 0
je .found
add bx,open_file_t_size ; ZF = 0
loop .check
; ZF = 0 if we fell out of the loop
.found: pop cx
ret
;
; open_inode:
; Open a file indicated by an inode number in EAX
;
; NOTE: This file considers finding a zero-length file an
; error. This is so we don't have to deal with that special
; case elsewhere in the program (most loops have the test
; at the end).
;
; If successful:
; ZF clear
; SI = file pointer
; DX:AX = EAX = file length in bytes
; ThisInode = the first 128 bytes of the inode
; If unsuccessful
; ZF set
;
; Assumes CS == DS == ES.
;
open_inode.allocate_failure:
xor eax,eax
pop bx
pop di
ret
open_inode:
push di
push bx
call allocate_file
jnz .allocate_failure
push cx
push gs
; First, get the appropriate inode group and index
dec eax ; There is no inode 0
xor edx,edx
mov [bx+file_sector],edx
div dword [SuperBlock+s_inodes_per_group]
; EAX = inode group; EDX = inode within group
push edx
; Now, we need the block group descriptor.
; To get that, we first need the relevant descriptor block.
shl eax, ext2_group_desc_lg2size ; Get byte offset in desc table
xor edx,edx
div dword [ClustSize]
; eax = block #, edx = offset in block
add eax,dword [SuperBlock+s_first_data_block]
inc eax ; s_first_data_block+1
mov cl,[ClustShift]
shl eax,cl
push edx
shr edx,SECTOR_SHIFT
add eax,edx
pop edx
and dx,SECTOR_SIZE-1
call getcachesector ; Get the group descriptor
add si,dx
mov esi,[gs:si+bg_inode_table] ; Get inode table block #
pop eax ; Get inode within group
movzx edx, word [SuperBlock+s_inode_size]
mul edx
; edx:eax = byte offset in inode table
div dword [ClustSize]
; eax = block # versus inode table, edx = offset in block
add eax,esi
shl eax,cl ; Turn into sector
push dx
shr edx,SECTOR_SHIFT
add eax,edx
mov [bx+file_in_sec],eax
pop dx
and dx,SECTOR_SIZE-1
mov [bx+file_in_off],dx
call getcachesector
add si,dx
mov cx,EXT2_GOOD_OLD_INODE_SIZE >> 2
mov di,ThisInode
gs rep movsd
mov ax,[ThisInode+i_mode]
mov [bx+file_mode],ax
mov eax,[ThisInode+i_size]
push eax
add eax,SECTOR_SIZE-1
shr eax,SECTOR_SHIFT
mov [bx+file_left],eax
pop eax
mov si,bx
mov edx,eax
shr edx,16 ; 16-bitism, sigh
and eax,eax ; ZF clear unless zero-length file
pop gs
pop cx
pop bx
pop di
ret
section .bss
alignb 4
ThisInode resb EXT2_GOOD_OLD_INODE_SIZE ; The most recently opened inode
section .text
;
; close_file:
; Deallocates a file structure (pointer in SI)
; Assumes CS == DS.
;
close_file:
and si,si
jz .closed
mov dword [si],0 ; First dword == file_left
.closed: ret
;
; searchdir:
; Search the root directory for a pre-mangled filename in DS:DI.
;
; NOTE: This file considers finding a zero-length file an
; error. This is so we don't have to deal with that special
; case elsewhere in the program (most loops have the test
; at the end).
;
; If successful:
; ZF clear
; SI = file pointer
; DX:AX = EAX = file length in bytes
; If unsuccessful
; ZF set
;
; Assumes CS == DS == ES; *** IS THIS CORRECT ***?
;
searchdir:
push bx
push cx
push bp
mov byte [SymlinkCtr],MAX_SYMLINKS
mov eax,[CurrentDir]
.begin_path:
.leadingslash:
cmp byte [di],'/' ; Absolute filename?
jne .gotdir
mov eax,EXT2_ROOT_INO
inc di ; Skip slash
jmp .leadingslash
.gotdir:
; At this point, EAX contains the directory inode,
; and DS:DI contains a pathname tail.
.open:
push eax ; Save directory inode
call open_inode
jz .done ; If error, done
mov cx,[si+file_mode]
shr cx,S_IFSHIFT ; Get file type
cmp cx,T_IFDIR
je .directory
add sp,4 ; Drop directory inode
cmp cx,T_IFREG
je .file
cmp cx,T_IFLNK
je .symlink
; Otherwise, something bad...
.err:
call close_file
.err_noclose:
xor eax,eax
xor si,si
cwd ; DX <- 0
.done:
and eax,eax ; Set/clear ZF
pop bp
pop cx
pop bx
ret
;
; It's a file.
;
.file:
cmp byte [di],0 ; End of path?
je .done ; If so, done
jmp .err ; Otherwise, error
;
; It's a directory.
;
.directory:
pop dword [ThisDir] ; Remember what directory we're searching
cmp byte [di],0 ; More path?
je .err ; If not, bad
.skipslash: ; Skip redundant slashes
cmp byte [di],'/'
jne .readdir
inc di
jmp .skipslash
.readdir:
mov bx,trackbuf
push bx
mov cx,[SecPerClust]
call getfssec
pop bx
pushf ; Save EOF flag
push si ; Save filesystem pointer
.getent:
cmp dword [bx+d_inode],0
je .endblock
push di
movzx cx,byte [bx+d_name_len]
lea si,[bx+d_name]
repe cmpsb
je .maybe
.nope:
pop di
add bx,[bx+d_rec_len]
jmp .getent
.endblock:
pop si
popf
jnc .readdir ; There is more
jmp .err ; Otherwise badness...
.maybe:
mov eax,[bx+d_inode]
; Does this match the end of the requested filename?
cmp byte [di],0
je .finish
cmp byte [di],'/'
jne .nope
; We found something; now we need to open the file
.finish:
pop bx ; Adjust stack (di)
pop si
call close_file ; Close directory
pop bx ; Adjust stack (flags)
jmp .open
;
; It's a symlink. We have to determine if it's a fast symlink
; (data stored in the inode) or not (data stored as a regular
; file.) Either which way, we start from the directory
; which we just visited if relative, or from the root directory
; if absolute, and append any remaining part of the path.
;
.symlink:
dec byte [SymlinkCtr]
jz .err ; Too many symlink references
cmp eax,SYMLINK_SECTORS*SECTOR_SIZE
jae .err ; Symlink too long
; Computation for fast symlink, as defined by ext2/3 spec
xor ecx,ecx
cmp [ThisInode+i_file_acl],ecx
setne cl ; ECX <- i_file_acl ? 1 : 0
cmp [ThisInode+i_blocks],ecx
jne .slow_symlink
; It's a fast symlink
.fast_symlink:
call close_file ; We've got all we need
mov si,ThisInode+i_block
push di
mov di,SymlinkTmpBuf
mov ecx,eax
rep movsb
pop si
.symlink_finish:
cmp byte [si],0
je .no_slash
mov al,'/'
stosb
.no_slash:
mov bp,SymlinkTmpBufEnd
call strecpy
jc .err_noclose ; Buffer overflow
; Now copy it to the "real" buffer; we need to have
; two buffers so we avoid overwriting the tail on the
; next copy
mov si,SymlinkTmpBuf
mov di,SymlinkBuf
push di
call strcpy
pop di
mov eax,[ThisDir] ; Resume searching previous directory
jmp .begin_path
.slow_symlink:
mov bx,SymlinkTmpBuf
mov cx,SYMLINK_SECTORS
call getfssec
; The EOF closed the file
mov si,di ; SI = filename tail
mov di,SymlinkTmpBuf
add di,ax ; AX = file length
jmp .symlink_finish
section .bss
alignb 4
SymlinkBuf resb SYMLINK_SECTORS*SECTOR_SIZE+64
SymlinkTmpBuf equ trackbuf
SymlinkTmpBufEnd equ trackbuf+SYMLINK_SECTORS*SECTOR_SIZE+64
ThisDir resd 1
SymlinkCtr resb 1
section .text
;
; mangle_name: Mangle a filename pointed to by DS:SI into a buffer pointed
; to by ES:DI; ends on encountering any whitespace.
; DI is preserved.
;
; This verifies that a filename is < FILENAME_MAX characters,
; doesn't contain whitespace, zero-pads the output buffer,
; and removes redundant slashes,
; so "repe cmpsb" can do a compare, and the
; path-searching routine gets a bit of an easier job.
;
; FIX: we may want to support \-escapes here (and this would
; be the place.)
;
mangle_name:
push di
push bx
xor ax,ax
mov cx,FILENAME_MAX-1
mov bx,di
.mn_loop:
lodsb
cmp al,' ' ; If control or space, end
jna .mn_end
cmp al,ah ; Repeated slash?
je .mn_skip
xor ah,ah
cmp al,'/'
jne .mn_ok
mov ah,al
.mn_ok stosb
.mn_skip: loop .mn_loop
.mn_end:
cmp bx,di ; At the beginning of the buffer?
jbe .mn_zero
cmp byte [di-1],'/' ; Terminal slash?
jne .mn_zero
.mn_kill: dec di ; If so, remove it
inc cx
jmp short .mn_end
.mn_zero:
inc cx ; At least one null byte
xor ax,ax ; Zero-fill name
rep stosb
pop bx
pop di
ret ; Done
;
; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled
; filename to the conventional representation. This is needed
; for the BOOT_IMAGE= parameter for the kernel.
; NOTE: A 13-byte buffer is mandatory, even if the string is
; known to be shorter.
;
; DS:SI -> input mangled file name
; ES:DI -> output buffer
;
; On return, DI points to the first byte after the output name,
; which is set to a null byte.
;
unmangle_name: call strcpy
dec di ; Point to final null byte
ret
;
;
; kaboom2: once everything is loaded, replace the part of kaboom
; starting with "kaboom.patch" with this part
kaboom2:
mov si,err_bootfailed
call cwritestr
cmp byte [kaboom.again+1],18h ; INT 18h version?
je .int18
call getchar
call vgaclearmode
int 19h ; And try once more to boot...
.norge: jmp short .norge ; If int 19h returned; this is the end
.int18:
call vgaclearmode
int 18h
.noreg: jmp short .noreg ; Nynorsk
;
; linsector: Convert a linear sector index in a file to a linear sector number
; EAX -> linear sector number
; DS:SI -> open_file_t
;
; Returns next sector number in EAX; CF on EOF (not an error!)
;
linsector:
push gs
push ebx
push esi
push edi
push ecx
push edx
push ebp
push eax ; Save sector index
mov cl,[ClustShift]
shr eax,cl ; Convert to block number
push eax
mov eax,[si+file_in_sec]
mov bx,si
call getcachesector ; Get inode
add si,[bx+file_in_off] ; Get *our* inode
pop eax
lea ebx,[i_block+4*eax]
cmp eax,EXT2_NDIR_BLOCKS
jb .direct
mov ebx,i_block+4*EXT2_IND_BLOCK
sub eax,EXT2_NDIR_BLOCKS
mov ebp,[PtrsPerBlock1]
cmp eax,ebp
jb .ind1
mov ebx,i_block+4*EXT2_DIND_BLOCK
sub eax,ebp
mov ebp,[PtrsPerBlock2]
cmp eax,ebp
jb .ind2
mov ebx,i_block+4*EXT2_TIND_BLOCK
sub eax,ebp
.ind3:
; Triple indirect; eax contains the block no
; with respect to the start of the tind area;
; ebx contains the pointer to the tind block.
xor edx,edx
div dword [PtrsPerBlock2]
; EAX = which dind block, EDX = pointer within dind block
push ax
shr eax,SECTOR_SHIFT-2
mov ebp,[gs:si+bx]
shl ebp,cl
add eax,ebp
call getcachesector
pop bx
and bx,(SECTOR_SIZE >> 2)-1
shl bx,2
mov eax,edx ; The ind2 code wants the remainder...
.ind2:
; Double indirect; eax contains the block no
; with respect to the start of the dind area;
; ebx contains the pointer to the dind block.
xor edx,edx
div dword [PtrsPerBlock1]
; EAX = which ind block, EDX = pointer within ind block
push ax
shr eax,SECTOR_SHIFT-2
mov ebp,[gs:si+bx]
shl ebp,cl
add eax,ebp
call getcachesector
pop bx
and bx,(SECTOR_SIZE >> 2)-1
shl bx,2
mov eax,edx ; The int1 code wants the remainder...
.ind1:
; Single indirect; eax contains the block no
; with respect to the start of the ind area;
; ebx contains the pointer to the ind block.
push ax
shr eax,SECTOR_SHIFT-2
mov ebp,[gs:si+bx]
shl ebp,cl
add eax,ebp
call getcachesector
pop bx
and bx,(SECTOR_SIZE >> 2)-1
shl bx,2
.direct:
mov ebx,[gs:bx+si] ; Get the pointer
pop eax ; Get the sector index again
shl ebx,cl ; Convert block number to sector
and eax,[ClustMask] ; Add offset within block
add eax,ebx
pop ebp
pop edx
pop ecx
pop edi
pop esi
pop ebx
pop gs
ret
;
; getfssec: Get multiple sectors from a file
;
; Same as above, except SI is a pointer to a open_file_t
;
; ES:BX -> Buffer
; DS:SI -> Pointer to open_file_t
; CX -> Sector count (0FFFFh = until end of file)
; Must not exceed the ES segment
; Returns CF=1 on EOF (not necessarily error)
; All arguments are advanced to reflect data read.
;
getfssec:
push ebp
push eax
push edx
push edi
movzx ecx,cx
cmp ecx,[si] ; Number of sectors left
jbe .lenok
mov cx,[si]
.lenok:
.getfragment:
mov eax,[si+file_sector] ; Current start index
mov edi,eax
call linsector
push eax ; Fragment start sector
mov edx,eax
xor ebp,ebp ; Fragment sector count
.getseccnt:
inc bp
dec cx
jz .do_read
xor eax,eax
mov ax,es
shl ax,4
add ax,bx ; Now DI = how far into 64K block we are
not ax ; Bytes left in 64K block
inc eax
shr eax,SECTOR_SHIFT ; Sectors left in 64K block
cmp bp,ax
jnb .do_read ; Unless there is at least 1 more sector room...
inc edi ; Sector index
inc edx ; Linearly next sector
mov eax,edi
call linsector
; jc .do_read
cmp edx,eax
je .getseccnt
.do_read:
pop eax ; Linear start sector
pushad
call getlinsec_ext
popad
push bp
shl bp,9
add bx,bp ; Adjust buffer pointer
pop bp
add [si+file_sector],ebp ; Next sector index
sub [si],ebp ; Sectors consumed
jcxz .done
jnz .getfragment
; Fall through
.done:
cmp dword [si],1 ; Did we run out of file?
; CF set if [SI] < 1, i.e. == 0
pop edi
pop edx
pop eax
pop ebp
ret
; -----------------------------------------------------------------------------
; Common modules
; -----------------------------------------------------------------------------
%include "getc.inc" ; getc et al
%include "conio.inc" ; Console I/O
%include "plaincon.inc" ; writechr
%include "writestr.inc" ; String output
%include "configinit.inc" ; Initialize configuration
%include "parseconfig.inc" ; High-level config file handling
%include "parsecmd.inc" ; Low-level config file handling
%include "bcopy32.inc" ; 32-bit bcopy
%include "loadhigh.inc" ; Load a file into high memory
%include "font.inc" ; VGA font stuff
%include "graphics.inc" ; VGA graphics
%include "highmem.inc" ; High memory sizing
%include "strcpy.inc" ; strcpy()
%include "strecpy.inc" ; strcpy with end pointer check
%include "cache.inc" ; Metadata disk cache
%include "adv.inc" ; Auxillary Data Vector
; -----------------------------------------------------------------------------
; Begin data section
; -----------------------------------------------------------------------------
section .data
copyright_str db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
db CR, LF, 0
err_bootfailed db CR, LF, 'Boot failed: please change disks and press '
db 'a key to continue.', CR, LF, 0
config_name db 'extlinux.conf',0 ; Unmangled form
;
; Command line options we'd like to take a look at
;
; mem= and vga= are handled as normal 32-bit integer values
initrd_cmd db 'initrd='
initrd_cmd_len equ 7
;
; Config file keyword table
;
%include "keywords.inc"
;
; Extensions to search for (in *forward* order).
;
align 4, db 0
exten_table: db '.cbt' ; COMBOOT (specific)
db '.img' ; Disk image
db '.bs', 0 ; Boot sector
db '.com' ; COMBOOT (same as DOS)
db '.c32' ; COM32
exten_table_end:
dd 0, 0 ; Need 8 null bytes here
;
; Misc initialized (data) variables
;
%ifdef debug ; This code for debugging only
debug_magic dw 0D00Dh ; Debug code sentinel
%endif
alignb 4, db 0
BufSafe dw trackbufsize/SECTOR_SIZE ; Clusters we can load into trackbuf
BufSafeBytes dw trackbufsize ; = how many bytes?
%ifndef DEPEND
%if ( trackbufsize % SECTOR_SIZE ) != 0
%error trackbufsize must be a multiple of SECTOR_SIZE
%endif
%endif
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