kolibrios/kernel/trunk/bootloader/extended_primary_loader/fat32/kordldr.f32.asm

674 lines
22 KiB
NASM
Raw Normal View History

; Copyright (c) 2008-2009, diamond
; All rights reserved.
;
; Redistribution and use in source and binary forms, with or without
; modification, are permitted provided that the following conditions are met:
; * Redistributions of source code must retain the above copyright
; notice, this list of conditions and the following disclaimer.
; * Redistributions in binary form must reproduce the above copyright
; notice, this list of conditions and the following disclaimer in the
; documentation and/or other materials provided with the distribution.
; * Neither the name of the <organization> nor the
; names of its contributors may be used to endorse or promote products
; derived from this software without specific prior written permission.
;
; THIS SOFTWARE IS PROVIDED BY Alexey Teplov aka <Lrz> ''AS IS'' AND ANY
; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
; DISCLAIMED. IN NO EVENT SHALL <copyright holder> BE LIABLE FOR ANY
; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
; (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;*****************************************************************************
org 0x7E00
; the KordOS FAT32 bootsector loads first cluster of this file to 0:7E00 and transfers control to here
; ss:bp = 0:7C00
; ds = 0
virtual at bp
rb 3 ; BS_jmpBoot
rb 8 ; BS_OEMName, ignored
dw ? ; BPB_BytsPerSec
BPB_SecsPerClus db ?
BPB_RsvdSecCnt dw ?
BPB_NumFATs db ?
BPB_RootEntCnt dw ?
dw ? ; BPB_TotSec16
db ? ; BPB_Media
dw ? ; BPB_FATSz16 = 0 for FAT32
BPB_SecPerTrk dw ?
BPB_NumHeads dw ?
BPB_HiddSec dd ?
dd ? ; BPB_TotSec32
BPB_FATSz32 dd ?
BPB_ExtFlags dw ?
dw ? ; BPB_FSVer
BPB_RootClus dd ?
filesize:
dw ? ; BPB_FSInfo
dw ? ; BPB_BkBootSec
rb 12 ; BPB_Reserved
BS_DrvNum db ?
db ? ; BS_Reserved1
db ? ; BS_BootSig
dd ? ; BS_VolID
; rb 11 ; BS_VolLab
; rb 5 ; BS_FilSysType, first 5 bytes
read_sectors32 dw ?
read_sectors2 dw ?
err_ dw ?
noloader dw ?
cachelimit dw ?
fatcachehead rw 2
fatcacheend dw ?
rb 3 ; BS_FilSysType, last 3 bytes
curseg dw ?
num_sectors dd ?
cur_cluster dd ?
next_cluster dd ?
flags dw ?
cur_delta dd ?
end virtual
; procedures from boot sector
; LBA version
lba_read_sectors2 = 7CD6h
lba_err = 7CAAh
lba_noloader = 7CA7h ; = lba_err - 3
; CHS version
chs_read_sectors2 = 7CD2h
chs_err = 7CA6h
chs_noloader = 7CA3h ; = chs_err - 3
push eax cx ; save our position on disk
; determine version of bootsector (LBA vs CHS)
mov [read_sectors2], chs_read_sectors2
mov bx, chs_err
mov [err_], bx
; mov [noloader], chs_noloader
cmp byte [bx], 0xE8 ; [chs_err] = 0xE8 for CHS version, 0x14 for LBA version
jz @f
add [read_sectors2], lba_read_sectors2 - chs_read_sectors2
add [err_], lba_err - chs_err
; mov [noloader], lba_noloader
@@:
xor bx, bx
; determine size of cache for folders
int 12h ; ax = size of available base memory in Kb
sub ax, 92000h / 1024
jae @f
nomem:
mov si, nomem_str
jmp [err_]
@@:
shr ax, 3
mov [cachelimit], ax ; size of cache - 1
mov es, bx
; no folders in cache yet
mov di, foldcache_clus
mov cx, 8*4/2 + 1
xor ax, ax
rep stosw
; bootsector code caches one FAT sector, [bp-14], in 6000:0000
; initialize our (more advanced) FAT caching from this
mov di, 8400h
mov cx, di
lea si, [fatcachehead]
mov [si], si ; no sectors in cache:
mov [si+2], si ; 'prev' & 'next' links point to self
mov [fatcacheend], di ; first free item = 8400h
stosw ; 'next cached sector' link
stosw ; 'prev cached sector' link
mov eax, [bp-14]
stosd ; first sector number in cache
test eax, eax
js @f
mov [si], cx ; 'first cached sector' link = 8400h
mov [si+2], cx ; 'next cached sector' link = 8400h
mov [fatcacheend], di ; first free item = 8406h
@@:
; if cluster = sector, we need to read second part of our file
; (bootsector loads only first cluster of kordldr.f32)
pop cx eax ; restore our position on disk
cmp cx, 1
ja kordldr_full
sub eax, [bp-10]
inc eax
inc eax ; eax = first cluster of kordldr.f32
call get_next_cluster
jc @f
; jmp [noloader]
mov ax, [err_]
sub ax, 3
jmp ax
@@:
dec eax
dec eax
push 0x800
pop es
call [read_sectors2]
kordldr_full:
; bootsector code has read some data of root directory to 8000:0000
; initialize our folder caching from this
mov eax, [BPB_RootClus]
mov [foldcache_clus], eax
mov cx, [curseg]
mov ax, 8000h
sub cx, ax ; cx = size of data read in paragraphs (0x10 bytes)
shr cx, 1 ; cx = size of folder data read in entries (0x20 bytes)
mov [foldcache_size], cx
shl cx, 4
push ds
mov ds, ax
push 0x9000
pop es
xor si, si
xor di, di
rep movsw
pop ds
; ...continue loading...
mov di, secondary_loader_info
call load_file
test bx, bx
mov bx, [err_]
jz @f
mov si, aKernelNotFound
jmp bx
@@:
; for subsequent calls to callback function, hook error handler
; push hooked_err / ret
mov dword [bx], 0x68 + (hooked_err shl 8) + (0xC3 shl 24)
; set registers for secondary loader
mov ah, [bp-2] ; drive id
mov al, 'f'
btr ax, 15
jnc @f
mov al, 'h'
@@:
mov bx, '32'
mov si, callback
jmp far [si+secondary_loader_info-callback]
nomem_str db 'No memory',0
cluster2sector:
sub eax, 2
clustersz2sectorsz:
movzx ecx, [BPB_SecsPerClus]
mul ecx
ret
get_next_cluster:
; in: eax = cluster
; out: if there is next cluster: CF=1, eax = next cluster
; out: if there is no next cluster: CF=0
push di bx
push ds es
push ss
pop ds
push ss
pop es
push ax
shr eax, 7
; eax = FAT sector number; look in cache
mov di, 8400h
.cache_lookup:
cmp di, [fatcacheend]
jae .not_in_cache
scasd
scasd
jnz .cache_lookup
.in_cache:
sub di, 8
; delete this sector from the list
push si
mov si, [di]
mov bx, [di+2]
mov [si+2], bx
mov [bx], si
pop si
jmp @f
.not_in_cache:
; cache miss
; cache is full?
mov di, [fatcacheend]
cmp di, 8C00h
jnz .cache_not_full
; yes, delete the oldest entry
mov di, [fatcachehead]
mov bx, [di]
mov [fatcachehead], bx
push word [di+2]
pop word [bx+2]
jmp .cache_append
.cache_not_full:
; no, allocate new sector
add [fatcacheend], 8
.cache_append:
; read FAT
mov [di+4], eax
pushad
lea cx, [di + 0x10000 - 0x8400 + (0x6000 shr (9-4-3))] ; +0x10000 - for FASM
shl cx, 9-4-3
mov es, cx
xor bx, bx
mov cx, 1
add eax, [bp-6] ; FAT start
sub eax, [bp-10]
call [read_sectors2]
popad
@@:
; add new sector to the end of list
mov bx, di
xchg bx, [fatcachehead+2]
push word [bx]
pop word [di]
mov [bx], di
mov [di+2], bx
; get requested item
lea ax, [di + 0x10000 - 0x8400 + (0x6000 shr (9-4-3))]
pop di
and di, 0x7F
shl di, 2
shl ax, 9-4-3
mov ds, ax
and byte [di+3], 0x0F
mov eax, [di]
pop es ds
pop bx di
;and eax, 0x0FFFFFFF
cmp eax, 0x0FFFFFF7
ret
if $ > 0x8000
error 'get_next_cluster must fit in first sector of kordldr.f32!'
end if
load_file:
; in: ss:bp = 0:7C00
; in: ds:di -> information structure
; dw:dw address
; dw limit in 4Kb blocks (0x1000 bytes) (must be non-zero and not greater than 0x100)
; ASCIIZ name
; out: bx = status: bx=0 - ok, bx=1 - file is too big, only part of file was loaded, bx=2 - file not found
; out: dx:ax = file size (0xFFFFFFFF if file not found)
mov eax, [BPB_RootClus] ; start from root directory
or dword [filesize], -1 ; initialize file size with invalid value
lea si, [di+6]
parse_dir_loop:
; convert name to FAT name
push di
push ax
push ss
pop es
; convert ASCIIZ filename to FAT name
filename equ bp
mov di, filename
push di
mov cx, 8+3
mov al, ' '
rep stosb
pop di
mov cl, 8 ; 8 symbols per name
mov bl, 1
nameloop:
lodsb
test al, al
jz namedone
cmp al, '/'
jz namedone
cmp al, '.'
jz namedot
dec cx
js badname
cmp al, 'a'
jb @f
cmp al, 'z'
ja @f
sub al, 'a'-'A'
@@:
stosb
jmp nameloop
namedot:
inc bx
jp badname
add di, cx
mov cl, 3
jmp nameloop
badname: ; do not make direct js/jp to notfound_pop:
; this generates long forms of conditional jumps and results in longer code
jmp notfound_pop
namedone:
; scan directory
pop ax ; eax = cluster of directory
; high word of eax is preserved by operations above
push ds
push si
; read a folder sector-by-sector and scan
; first, try to use the cache
push ss
pop ds
mov di, foldcache_mark
xor bx, bx
mov cx, [cachelimit]
@@:
lea si, [di+bx]
mov edx, dword [foldcache_clus+si-foldcache_mark+bx]
cmp edx, eax
jz cacheok
test edx, edx
jz cacheadd ; the cache has place for new entry
inc bx
inc bx
dec cx
jns @b
; the folder is not present in the cache, so add it
; the cache is full; find the oldest entry and replace it with the new one
mov bx, -2
mov dx, [cachelimit]
@@:
inc bx
inc bx
cmp word [di+bx], dx ; marks have values 0 through [cachelimit]
jnz @b
lea si, [di+bx]
cacheadd:
or word [di+bx], 0xFFFF ; very big value, it will be changed soon
and [foldcache_size+di-foldcache_mark+bx], 0 ; no folder items yet
mov dword [foldcache_clus+si-foldcache_mark+bx], eax
cacheok:
; update cache marks
mov dx, [di+bx]
mov cx, [foldcache_size+di-foldcache_mark+bx]
mov di, [cachelimit]
add di, di
cacheupdate:
cmp [foldcache_mark+di], dx
adc [foldcache_mark+di], 0
dec di
dec di
jns cacheupdate
and [foldcache_mark+bx], 0
; done, bx contains (position in cache)*2
;mov dx, bx
;shl dx, 8 ; dx = (position in cache)*0x2000/0x10
;add dx, 0x9000
lea dx, [bx + 0x90]
xchg dl, dh
mov ds, dx
mov si, filename ; ss:si -> filename in FAT style
call scan_for_filename
jz lookup_done
; cache miss, read folder data from disk
mov bx, cx
shr bx, 4
shl cx, 5
mov di, cx ; es:di -> free space in cache entry
; external loop: scan clusters
folder_next_cluster:
; internal loop: scan sectors in cluster
push eax
call cluster2sector
folder_next_sector:
; skip first bx sectors
dec bx
jns folder_skip_sector
push cx
push es di
push 0x8000
pop es
xor bx, bx
mov cx, 1
push es
push eax
call [read_sectors2]
pop eax
; copy data to the cache...
pop ds
pop di es
cmp di, 0x2000 ; ...if there is free space, of course
jae @f
pusha
mov cx, 0x100
xor si, si
rep movsw
mov di, es
shr di, 8
add [ss:foldcache_size+di-0x90], 0x10 ; 0x10 new entries in the cache
popa
@@:
push es
mov cl, 0x10 ; ch=0 at this point
call scan_for_filename
pop es
pop cx
jz lookup_done_pop
folder_skip_sector:
inc eax
loop folder_next_sector
pop eax ; eax = current cluster
call get_next_cluster
jc folder_next_cluster
stc
push eax
lookup_done_pop:
pop eax
lookup_done:
pop si
; CF=1 <=> failed
jnc found
pop ds
notfound:
pop di
notfound2:
mov bx, 2 ; file not found
mov ax, 0xFFFF
mov dx, ax ; invalid file size
ret
notfound_pop:
pop ax
jmp notfound
found:
mov eax, [di+20-2]
mov edx, [di+28]
mov ax, [di+26] ; get cluster
test byte [di+11], 10h ; directory?
pop ds
pop di
jz regular_file
cmp byte [si-1], 0
jz notfound2 ; don't read directories as regular files
; ok, we have found a directory and the caller requested a file into it
jmp parse_dir_loop ; restart with new cluster in ax
regular_file:
cmp byte [si-1], 0
jnz notfound2 ; file does not contain another files
; ok, we have found a regular file and the caller requested it
; save file size
mov [filesize], edx
mov si, [di+4] ; [ds:di+4] = limit in 4K blocks
shl si, 3
push si
les bx, [di] ; es:bx -> buffer
clusloop:
; eax = first cluster, top of stack contains limit in sectors
mov esi, eax ; remember current cluster
xor ecx, ecx ; ecx will contain number of consecutive clusters
mov [cur_delta], ecx
mov edi, eax
clusfind:
inc edi
inc ecx
call get_next_cluster
jnc clusread
cmp eax, edi
jz clusfind
stc
clusread:
pop di ; limit in sectors
movzx edi, di
push eax ; save next cluster
pushf ; save flags
; read cx clusters, starting from si
; calculate number of sectors
xchg eax, ecx
call clustersz2sectorsz
mov [num_sectors], eax
jmp @f
continue_load_file:
les bx, [di] ; es:bx -> buffer
movzx edi, word [di+4] ; di = limit in 4K blocks
shl di, 3 ; now di = limit in sectors
mov eax, [num_sectors]
mov esi, [cur_cluster]
push [next_cluster]
push [flags]
test eax, eax
jz nextclus
@@:
; eax = number of sectors; compare with limit
cmp eax, edi
seta dl
push dx ; limit was exceeded?
jbe @f
mov eax, edi
@@:
sub di, ax ; calculate new limit
sub [num_sectors], eax
mov [cur_cluster], esi
; calculate starting sector
push ax
xchg eax, esi
call cluster2sector
pop cx
add eax, [cur_delta]
add [cur_delta], ecx
; read
call [read_sectors2]
pop dx
; next cluster?
nextclus:
popf
pop eax
mov [next_cluster], eax
pushf
pop [flags]
jnc @f ; no next cluster => return
mov dl, 1
test di, di
jz @f ; if there is next cluster but current limit is 0 => return: limit exceeded
push di
jmp clusloop ; all is ok, continue
hooked_err:
mov sp, 7C00h-14-2 ; restore stack
mov dl, 3 ; return: read error
@@:
mov bl, dl
mov bh, 0
mov ax, [filesize]
mov dx, [filesize+2]
ret
scan_for_filename:
; in: ss:si -> 11-bytes FAT name
; in: ds:0 -> part of directory data
; in: cx = number of entries
; in: bh = 0
; out: if found: CF=0, ZF=1, es:di -> directory entry
; out: if not found, but continue required: CF=1 and ZF=0
; out: if not found and zero item reached: CF=1 and ZF=1
push ds
pop es
xor di, di
push cx
jcxz snoent
sloop:
cmp byte [di], bh
jz snotfound
test byte [di+11], 8 ; volume label?
jnz scont ; ignore volume labels
pusha
mov cx, 11
repz cmps byte [ss:si], byte [es:di]
popa
jz sdone
scont:
add di, 0x20
loop sloop
snoent:
inc cx ; clear ZF flag
snotfound:
stc
sdone:
pop cx
lrdret:
ret
; Callback function for secondary loader
callback:
; in: ax = function number; only functions 1 and 2 are defined for now
; save caller's stack
mov dx, ss
mov cx, sp
; set our stack (required because we need ss=0)
xor si, si
mov ss, si
mov sp, 7C00h-10
mov bp, 7C00h
push dx
push cx
; call our function
stc ; unsupported function
dec ax
jz callback_readfile
dec ax
jnz callback_ret
; function 2: continue loading file
; can be called only after function 1 returned value bx=1 (only part of file was loaded)
; in: ds:di -> information structure
; dw:dw address
; dw limit in 4Kb blocks (0x1000 bytes) (must be non-zero and not greater than 0x100)
; out: bx=0 - ok, bx=1 - still only part of file was loaded, bx=3 - read error
; out: dx:ax = file size
call continue_load_file
jmp callback_ret_succ
callback_readfile:
; function 1: read file
; in: ds:di -> information structure
; dw:dw address
; dw limit in 4Kb blocks (0x1000 bytes) (must be non-zero and not greater than 0x100)
; ASCIIZ name
; out: bx=0 - ok, bx=1 - file is too big, only part of file was loaded, bx=2 - file not found, bx=3 - read error
; out: dx:ax = file size (0xFFFFFFFF if file was not found)
call load_file
callback_ret_succ:
clc ; function is supported
callback_ret:
; restore caller's stack
pop cx
pop ss
mov sp, cx
; return to caller
retf
secondary_loader_info:
dw 0, 0x1000
dw 0x30000 / 0x1000
db 'kernel.mnt',0
aKernelNotFound db 'Fatal error: cannot load the kernel',0
;if $ > 0x8200
;error 'total size of kordldr.f32 must not exceed 1024 bytes!'
;end if
;foldcache_clus dd 0,0,0,0,0,0,0,0 ; start with no folders in cache
;foldcache_mark dw 0
; rw 7
;foldcache_size rw 8
foldcache_clus rd 8
foldcache_mark rw 8
foldcache_size rw 8