; $Id$
%include "gdtnasm.inc"
[ORG 0x7c00]
jmp start
nop
id db 'UbixFS' ;file system id
version dd 1h ; Filing System Version
fs_start dd 257 ; LBA address for start of root dir
krnl_size dd 59 ; Kernel size in sectors, starts at sector 1
BytesPerSector dw 512
SectorsPerTrack dw 18
TotalHeads dw 2
TotalSectors dd 2880 ; 1474560/512 for a 1.44meg disk
file_entry_nextdata equ 273 ; Offset in file_entry structure to the nextdata LBA pointer
data_entry_data equ 9 ; Offset in data_entry structure to the data
bootdrv db 0
start:
xor ax, ax
mov ds, ax
mov [bootdrv], dl
; First get into protected mode
cli
n5:
in al, 0x64 ;Enable A20 {4A} {5}
test al, 2
jnz n5
mov al, 0xD1
out 0x64, al
n6:
in al, 0x64
test al, 2
jnz n6
mov al, 0xDF
out 0x60, al
lgdt [gdtinfo] ;Load GDT
mov ecx, CR0 ;Switch to protected mode
inc cx
mov CR0, ecx
mov ax, flat_data-gdt_table ; Selector for 4Gb data seg
mov ds, ax ; {2} Extend limit for ds
mov es, ax ; Extend limit for es
mov fs, ax ; fs and...
mov gs, ax ; gs
dec cx ; switch back to real mode
mov CR0, ecx
sti
xor ax, ax
mov ds, ax
mov dl, [bootdrv]
mov bx, 0x60
mov es, bx
mov eax, 1
mov ecx, [krnl_size]
mov di, 1
load_loop:
call read_sectors
inc eax
mov bx, es
add bx, 32
mov es, bx
loop load_loop
; Turn off the floppy motor, its annoying leaving it on !
mov edx,0x3f2
mov al,0x0c
out dx,al
;lets convert the ELF file to a linear binary so we can execute it
cmp dword [0x600],464c457fh ; The ELF signature is \07fELF
jne ldr_ELF_err ; Ugh... not an ELF file !!!
cmp word [0x600+4],101h ; It should be statically linked etc.
jne ldr_ELF_err
cmp byte [0x600+6],1
jne ldr_ELF_err
jmp short skip_err_handler
ldr_ELF_err:
mov ax, 'E'+0x0E00
mov bx, 7
int 10h
mov al, 'L'
int 10h
mov al, 'F'
int 10h
cli
hlt
skip_err_handler:
mov eax, [0x600+18h]
mov [krnl_entry], eax
xor ecx,ecx ; Get the number of sections in cx
mov cx,[0x600+2ch]
sectionloop:
dec cx ; Next section
push cx ; Save cx on the stack while we load
; the section into memory
mov bx, 0x600 ; access image location
mov ax,[bx+2ah] ; Get the program header entry size
mul cx ; Calculate the offset from the start
; of the program header table
add ax,[bx+1ch] ; ax <= PHT offset + PHT entry offset
add bx,ax ; bx <= ax(PHT offset + PHT entry offset)
; + image location of ELF file (0x600)
cmp dword [bx],1 ; Does this section have to be
; loaded into memory ?
jne nextsect ; No, next section
mov dword ecx,[bx+10h] ; Get the size of the segment in the
; ELF file
mov dword edi,[bx+8h] ; Get the memory address of the sect.
mov dword eax,[bx+14h] ; eax <= the size of the section
mov dword ebx,[bx+4h] ; Get the offset of the segment in
; the ELF file
add ebx, 0x600 ;
; set up for memcopy
mov edx, edi ; edx <- set dest addr
add edi, ecx ; move past part which will be copied
sub eax, ecx ; eax <- store zero fill size
; ebx is already source addr
; ecx is already count
; set up for memcopy
;mov esi, 0x600
;add esi, ecx
;mov ecx, edx
;call memcopy
call nonmajicmemcpy
; warnng, ,assume zero-fill < 64K
;test ax,ax ; This amount needs to be zeroed
;jz nextsect ; It's ok, next section
; store zero fill size
;mov ecx, eax
;add edi,edx ; Zero the memory from this address
;xor ax,ax ; edi is an absolute address
;mov ecx,ebx
;call zero_memblock ; Zero the rest of the section
nextsect:
pop cx ; Restore our section count
or cx,cx ; Was this the last one ?
jnz sectionloop
; Re-enter protected mode ! A20 is already enabled
;mov ax,0x4F01
;mov cx,0x4115
;mov bx,0x100
;mov es,bx
;xor di,di
;xor bx,bx
;int 0x10
;mov ax,0x4F02
;mov bx,0x4115
;int 0x10
;mov ax, 0x4f0a
;xor bx,bx
;int 0x10
;xor eax,eax
;mov ax,es
;mov bx,di
;xor dx,dx
;mov es,dx
;mov si, 0x3000
;mov [es:si],ax
;mov [es:si+4],bx
;mov [es:si+8],cx
cli ; No interrupts please at all
lgdt [gdtinfo]
mov ecx, cr0
inc cx
mov cr0, ecx
mov ax, flat_data-gdt_table
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
jmp dword (flat_code-gdt_table):pmode1
pmode1:
[BITS 32]
push dword 2
popfd
mov eax, [krnl_entry]
call eax
cli
hlt
;Hang the system..
hang: jmp hang
[BITS 16]
read_sectors:
; Input:
; EAX = LBN
; DI = sector count
; ES = segment
; Output:
; BL = low byte of ES
; EBX high half cleared
; DL = 0x80
; EDX high half cleared
; ESI = 0
pusha
cdq ;edx = 0
movzx ebx, byte [SectorsPerTrack]
div ebx ;EAX=track ;EDX=sector-1
mov cx, dx ;CL=sector-1 ;CH=0
inc cx ;CL=Sector number
xor dx, dx
mov bl, [TotalHeads]
div ebx
mov dh, dl ;Head
mov dl, [bootdrv] ;Drive 0
xchg ch, al ;CH=Low 8 bits of cylinder number; AL=0
shr ax, 2 ;AL[6:7]=High two bits of cylinder; AH=0
or cl, al ;CX = Cylinder and sector
mov ax, di ;AX = Maximum sectors to xfer
retry: mov ah, 2 ;Read
xor bx, bx
int 13h
jc retry
popa
ret
; zero_memblock: Fills the specified memory block with zeros (0x0)
;
; Takes parameters:
; ax = segment/selector of memory to be cleared
; edi = offset of memory to be cleared
; ecx = number of bytes to clear
;
; Returns:
; nothing
;zero_memblock:
; push eax ; Save the registers
; push edi
; push ecx
; push es
; mov es,ax
; xor eax,eax ; Fill the memory with zeros (0x0)
; cld ; Clear the direction flag; rep increments di
; a32 rep stosb ; Fill the memory (one byte at a time)
; pop es ; Restore the registers
; pop ecx
; pop edi
; pop eax
; ret ; Return to the main program
; Parameters
; DS:ESI = Source
; DS:EDI = Destination
; CX = length
;memcopy:
; pusha
;memcopy_loop:
; mov al, [esi]
; mov [edi], al
; inc edi
; inc esi
; loop memcopy_loop
; popa
; ret
; edx = dest
; ebx = source
; ecx = count
;
; all other registers maintained
nonmajicmemcpy:
pusha
; preserve segments
push ds
push es
push cx ; [stack] <- 'left-over' after full 256 byte copies
xor ax, ax
; break size into 256 byte chuunks
shr ecx, 8 ; cx <- number of 256 byte copies to perform
mov bp, cx ; bp <- number of 256 byte copies to perform
mov cl, 4
; break destination into 256 byte chuunks
xchg al, dl ; al <- initial 'offset' of destination
; edx <- 16 X initial 'segment' of destination
shr edx, cl ; dx <- initial 'segment' of destination
; break source into 256 byte chuunks
xchg ah, bl ; ah <- initial 'offset' of source
; ebx <- 16 X initial 'segment' of source
shr ebx, cl ; bx <- initial 'segment' of source
cld ; clear direction flag
inc bp ; pre-increment 256 section count
nonmajicmemcpy_loop256:
movzx si, ah ; restore initial source addr
movzx di, al ; restore initial dest addr
; restore/set segment addrs
mov ds, bx
mov es, dx
; done?
dec bp
jz nonmajicmemcpy_rest
; copy one 256 byte run
mov cx, 0100h
a16 rep movsb
; move 'segments' 256 bytes forwards
; (eax = [es:ds])
add bx, 0010h
add dx, 0010h
; continue
jmp nonmajicmemcpy_loop256
nonmajicmemcpy_rest:
pop cx ; restore 'left-over' after full 256 byte copies
inc cl ; pre increment count
nonmajicmemcpy_restloop:
dec cl
jz nonmajicmemcpy_done
movsb
jmp nonmajicmemcpy_restloop
nonmajicmemcpy_done:
; restore segments
pop es
pop ds
popa
ret
gdtinfo:
dw gdtlength
dd gdt_table
;********* GDT TABLE
gdt_table:
null_desc desc 0,0,0
flat_code desc 0, 0xFFFFF, D_CODE + D_READ + D_BIG + D_BIG_LIM
flat_data desc 0, 0xFFFFF, D_DATA + D_WRITE + D_BIG + D_BIG_LIM
gdtlength equ $ - gdt_table - 1
;********* END GDT TABLE
krnl_entry dd 0
times 510-($-$$) db 0
dw 0xAA55
