Possible bug in FAT dir listing

Chris Johns chrisj at rtems.org
Wed Jan 14 00:15:26 CST 2009


Gene Smith wrote:
> I formatted an MMC card on linux with gparted as FAT16. I copy one file 
> to it called freddy.txt I unmount and dump the partition with dd. The 
> root directory entry appears like this:
> :
> 003d5f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
> 003d600: 4166 0072 0065 0064 0064 000f 0055 7900  Af.r.e.d.d...Uy.
> 003d610: 2e00 7400 7800 7400 0000 0000 ffff ffff  ..t.x.t.........
> 003d620: 4652 4544 4459 2020 5458 5420 0000 9100  FREDDY  TXT ....
> 003d630: 2e3a 2d3a 0000 6eb5 2c3a 0300 1300 0000  .:-:..n.,:......
> 003d640: 0000 0000 0000 0000 0000 0000 0000 0000  ................
> :
> 
> There are two entries. One starts with A and seems to be unicode of some 
> sort (32 bytes at 3d600) while the 2nd is conventional ASCII and is 32 
> bytes at 3d620.
> 
> When I mount on rtems and do ls in the shell I see this:
> 
> [/mnt] # ls
> Af              FREDDY.TXT
> 
> The entry that starts with A shows up as "Af". From what I have read it 
> should actually be ignored and not printed because the byte at 3d60b is 
> 0x0f. The 0x0f is the file attributes indicating this is a volume label, 
> system file, hidden file and read-only. This is a key that it should not 
> be displayed. (Why this filename gets put in I don't know. I think 
> windows does the same.)
> 
> Both of these sites mention that the attribute flag 0xf means don't show 
> the file:
> http://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html
> http://home.teleport.com/~brainy/lfn.htm
> 
> This also explains why a volume label shows up as a file in rtems when 
> doing ls. It should be ignored too.
> 
> AFAICT, there is no code in the rtems FAT library to ignore files when 
> these attribute flags are set. I only see the "directory" attribute 
> checked in some places.
> 

I think the FAT code is ok rather I suspect this is a result of the ls 
command's handling of the attributes for the directory. Could you please file 
a PR with RTEMS bugzilla ? I ported this command from Unix and it must have 
some issues.

Regards
Chris

> -gene
> 
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