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authorH. Peter Anvin <hpa@zytor.com>2010-01-25 09:41:53 -0800
committerH. Peter Anvin <hpa@zytor.com>2010-01-25 09:41:53 -0800
commit9ce3e9ca7775032be2bad8ce80fd72eb60af7d69 (patch)
treefa9d109149de405dfc2051635a8710b05e0c8e13 /core
parentdbbff6e3ff4ce7e2c1fd84b42559c312656c2d69 (diff)
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FAT: generate EOF depending on exceeding the number of clusters
Generate EOF by comparing to the actual number of clusters. We have to compute the number of clusters in the filesystem anyway during setup, so save the number and use it for the EOF computation. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'core')
-rw-r--r--core/ldlinux.asm32
1 files changed, 20 insertions, 12 deletions
diff --git a/core/ldlinux.asm b/core/ldlinux.asm
index 70f9c715..0808e6e8 100644
--- a/core/ldlinux.asm
+++ b/core/ldlinux.asm
@@ -116,6 +116,7 @@ RootDirSize resd 1 ; Root dir size in sectors
TotalSectors resd 1 ; Total number of sectors
ClustSize resd 1 ; Bytes/cluster
ClustMask resd 1 ; Sectors/cluster - 1
+Clusters resd 1 ; Total number of clusters
CopySuper resb 1 ; Distinguish .bs versus .bss
DriveNumber resb 1 ; BIOS drive number
ClustShift resb 1 ; Shift count for sectors/cluster
@@ -183,24 +184,31 @@ getfattype:
sub eax,[DataArea]
shr eax,cl ; cl == ClustShift
mov cl,nextcluster_fat12-(nextcluster+2)
- cmp eax,4085 ; FAT12 limit
- jb .setsize
+ cmp eax,0xFF4 ; FAT12 limit
+ jbe .setsize
mov cl,nextcluster_fat16-(nextcluster+2)
- cmp eax,65525 ; FAT16 limit
- jb .setsize
+ cmp eax,0xFFF4 ; FAT16 limit
+ jbe .setsize
;
; FAT32, root directory is a cluster chain
;
+ mov ecx,0x0FFFFFF4 ; Max possible cluster count
+ cmp eax,ecx
+ jb .oksize
+ mov eax,ecx
+.oksize:
+
mov cl,[ClustShift]
- mov eax,[bootsec+44] ; Root directory cluster
- sub eax,2
- shl eax,cl
- add eax,[DataArea]
- mov [RootDir],eax
+ mov edx,[bootsec+44] ; Root directory cluster
+ sub edx,2
+ shl edx,cl
+ add edx,[DataArea]
+ mov [RootDir],edx
mov cl,nextcluster_fat28-(nextcluster+2)
mov byte [SuperSize],superblock_len_fat32
.setsize:
mov byte [nextcluster+1],cl
+ mov [Clusters],eax ; Total clusters
;
; Common initialization code
@@ -1243,7 +1251,7 @@ nextcluster_fat12:
.even: and cx,0FFFh
movzx edi,cx
lea ax,[di-2]
- cmp ax,0FF5h
+ cmp ax,[Clusters]
pop si
pop cx
pop bx
@@ -1266,7 +1274,7 @@ nextcluster_fat16:
and bx,1FEh
movzx edi,word [gs:si+bx]
lea ax,[di-2]
- cmp ax,0FFF5h
+ cmp ax,[Clusters]
pop bx
pop si
pop eax
@@ -1288,7 +1296,7 @@ nextcluster_fat28:
mov edi,dword [gs:si+bx]
and edi,0FFFFFFFh ; 28 bits only
lea eax,[edi-2]
- cmp eax,0FFFFFF5h
+ cmp eax,[Clusters]
pop bx
pop si
pop eax