[syslinux:master] FAT: generate EOF depending on exceeding the number of clusters

[syslinux-bot for H. Peter Anvin]

Commit-ID:  9ce3e9ca7775032be2bad8ce80fd72eb60af7d69
Gitweb:     http://syslinux.zytor.com/commit/9ce3e9ca7775032be2bad8ce80fd72eb60af7d69
Author:     H. Peter Anvin <hpa at zytor.com>
AuthorDate: Mon, 25 Jan 2010 09:41:53 -0800
Committer:  H. Peter Anvin <hpa at zytor.com>
CommitDate: Mon, 25 Jan 2010 09:41:53 -0800

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 at zytor.com>


---
 core/ldlinux.asm |   32 ++++++++++++++++++++------------
 1 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/core/ldlinux.asm b/core/ldlinux.asm
index 70f9c71..0808e6e 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