; Memory below this point is reserved for the BIOS and the MBR
;
absolute 1000h
-trackbuf equ $ ; Track buffer goes here
-trackbufsize equ 16384 ; Safe size of track buffer
-; trackbuf ends at 5000h
+trackbufsize equ 8192
+trackbuf resb trackbufsize ; Track buffer goes here
+getcbuf resb trackbufsize
+; ends at 5000h
;
; Expanded superblock
SuperInfo equ $
resq 16 ; The first 16 bytes expanded 8 times
- ;
- ; These need to follow SuperInfo
- ;
+
+FAT resd 1 ; Location of (first) FAT
RootDir resd 1 ; Location of root directory
DataArea resd 1 ; Location of data area
-RootDirSize resw 1 ; Root dir size in sectors
-DirScanCtr resw 1 ; Used while searching directory
-EndofDirSec resw 1 ; = trackbuf+bsBytesPerSec-31
+RootDirSize resd 1 ; Root dir size in sectors
+TotalSectors resd 1 ; Total number of sectors
+EndSector resd 1 ; Location of filesystem end
alignb 4
E820Buf resd 5 ; INT 15:E820 data buffer
PMESP resd 1 ; Protected-mode ESP
ClustPerMoby resd 1 ; Clusters per 64K
ClustSize resd 1 ; Bytes/cluster
+ClustMask resd 1 ; Sectors/cluster - 1
KernelName resb 12 ; Mangled name for kernel
; (note the spare byte after!)
OrigKernelExt resd 1 ; Original kernel extension
VGACluster resw 1 ; Cluster pointer for VGA image file
VGAFilePtr resw 1 ; Pointer into VGAFileBuf
Com32SysSP resw 1 ; SP saved during COM32 syscall
+DirScanCtr resw 1 ; OBSOLETE FIX THIS
+EndofDirSec resw 1 ; OBSOLETE FIX THIS
CachePtrs times (65536/SECTOR_SIZE) resw 1
NextCacheSlot resw 1
CursorDX equ $
DisplayMask resb 1 ; Display modes mask
CopySuper resb 1 ; Distinguish .bs versus .bss
DriveNumber resb 1 ; BIOS drive number
+ClustShift resb 1 ; Shift count for sectors/cluster
+ClustByteShift resb 1 ; Shift count for bytes/cluster
MNameBuf resb 11 ; Generic mangled file name buffer
InitRD resb 11 ; initrd= mangled name
KernelCName resb 13 ; Unmangled kernel name
; 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 $
; LDLINUX_MAGIC, plus 4 bytes.
;
patch_area:
-TotalDwords dw 0 ; Total dwords starting at ldlinux_sys
-TotalSectors dw 0 ; Number of sectors minus bootsec, this sec
-CheckSum dd 0 ; Checksum starting at ldlinux_sys
- ; value = LDLINUX_MAGIC - [sum of dwords]
+LDLDwords dw 0 ; Total dwords starting at ldlinux_sys
+LDLSectors dw 0 ; Number of sectors - (bootsec+this sec)
+CheckSum dd 0 ; Checksum starting at ldlinux_sys
+ ; value = LDLINUX_MAGIC - [sum of dwords]
; Space for up to 64 sectors, the theoretical maximum
SectorPtrs times 64 dd 0
load_rest:
mov si,SectorPtrs
mov bx,7C00h+2*SECTOR_SIZE ; Where we start loading
- mov cx,[TotalSectors]
+ mov cx,[LDLSectors]
.get_chunk:
jcxz .done
;
verify_checksum:
mov si,ldlinux_sys
- mov cx,[TotalDwords]
+ mov cx,[LDLDwords]
mov edx,-LDLINUX_MAGIC
.checksum:
lodsd
;
; How big is a cluster, really? Also figure out how many clusters
-; will fit in an 8K buffer, and how many sectors and bytes that is
+; will fit in the trackbuf, and how many sectors and bytes that is
+;
+; FIX THIS: We shouldn't rely on integral sectors in the trackbuf
+; anymore...
;
mov edi,[bxBytesPerSec] ; Used a lot below
mov eax,[SecPerClust]
mov [BufSafeBytes],ax
add ax,getcbuf ; Size of getcbuf is the same
mov [EndOfGetCBuf],ax ; as for trackbuf
+
;
-; FAT12, FAT16 or FAT28^H^H32? This computation is fscking ridiculous...
+; Compute some information about this filesystem.
+;
+
+; First, generate the map of regions
+genfatinfo:
+ mov edx,[bxSectors]
+ and dx,dx
+ jz .have_secs
+ mov edx,[bsHugeSectors]
+.have_secs:
+ mov [TotalSectors],edx
+
+ mov eax,[bsHidden] ; Hidden sectors aren't included
+ add edx,eax
+ mov [EndSector],edx
+
+ add eax,[bxResSectors]
+ mov [FAT],eax ; Beginning of FAT
+ mov edx,[bxFATsecs]
+ and dx,dx
+ jz .have_fatsecs
+ mov edx,[bootsec+36] ; FAT32 BPB_FATsz32
+.have_fatsecs:
+ imul edx,[bxFATs]
+ add eax,edx
+ mov [RootDir],eax ; Beginning of root directory
+
+ mov edx,[bxRootDirEnts]
+ add dx,512-32
+ shr dx,9-5
+ mov [RootDirSize],edx
+ add eax,edx
+ mov [DataArea],eax ; Beginning of data area
+
+; Next, generate a cluster size shift count and mask
+ mov eax,[bxSecPerClust]
+ bsr cx,ax
+ mov [ClustShift],cl
+ push cx
+ add cl,9
+ mov [ClustByteShift],cl
+ pop cx
+ dec ax
+ mov [ClustMask],eax
+ inc ax
+ shl eax,9
+ mov [ClustSize],eax
+
+;
+; FAT12, FAT16 or FAT28^H^H32? This computation is fscking ridiculous.
;
getfattype:
- mov eax,[bxSectors]
- and ax,ax
- jnz .have_secs
- mov eax,[bsHugeSectors]
-.have_secs: add eax,[bsHidden] ; These are not included
- sub eax,[RootDir] ; Start of root directory
- movzx ebx,word [RootDirSize]
- sub eax,ebx ; Subtract root directory size
- xor edx,edx
- div esi ; Convert to clusters
+ mov eax,[EndSector]
+ sub eax,[DataArea]
+ shr eax,cl ; cl == ClustShift
mov cl,nextcluster_fat12-(nextcluster+2)
- cmp eax,4086 ; FAT12 limit
- jna .setsize
+ cmp eax,4085 ; FAT12 limit
+ jb .setsize
mov cl,nextcluster_fat16-(nextcluster+2)
- cmp eax,65526 ; FAT16 limit
- jna .setsize
+ cmp eax,65525 ; FAT16 limit
+ jb .setsize
mov cl,nextcluster_fat28-(nextcluster+2)
.setsize:
mov byte [nextcluster+1],cl
-
-
-
;
; Common initialization code
;
ac_ret1: ret
;
-; searchdir: Search the root directory for a pre-mangled filename in
-; DS:DI. This routine is similar to the one in the boot
-; sector, but is a little less Draconian when it comes to
-; error handling, plus it reads the root directory in
-; larger chunks than a sector at a time (which is probably
-; a waste of coding effort, but I like to do things right).
-;
-; FIXME: usually we can load the entire root dir in memory,
-; and files are usually at the beginning anyway. It probably
-; would be worthwhile to remember if we have the first chunk
-; in memory and skip the load if that (it would speed up online
-; help, mainly.)
+; 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
linuxauto_len equ $-linuxauto_cmd
boot_image db 'BOOT_IMAGE='
boot_image_len equ $-boot_image
+
+ align 4, db 0 ; Pad out any unfinished dword
ldlinux_end equ $
ldlinux_len equ $-ldlinux_magic
-;
-; Put the getcbuf right after the code, aligned on a sector boundary
-;
-end_of_code equ (ldlinux_end-bootsec)+7C00h
-getcbuf equ (end_of_code + 511) & 0FE00h
; VGA font buffer at the end of memory (so loading a font works even
; in graphics mode.)
; This is a compile-time assert that we didn't run out of space
%ifndef DEPEND
-%if (getcbuf+trackbufsize) > vgafontbuf
+%if (ldlinux_end-bootsec+7C00h) > vgafontbuf
%error "Out of memory, better reorganize something..."
%endif
%endif
projects / platform / upstream / syslinux.git / commitdiff