Re: [Linux-NTFS-Dev] 64 bit bug in super.c

[Anton A. <ai...@ca...>]

Hi,

Sorry for the delay in replying.

On Tue, 25 Mar 2003, Philipp Thomas wrote:
> The latest NTFS code in 2.5.65 still has this code in
> super.c(parse_ntfs_boot_sector):
> 
>     /*
>      * Get the size of the volume in clusters and check for 64-bit-ness.
>      * Windows currently only uses 32 bits to save the clusters so we do
>      * the same as it is much faster on 32-bit CPUs.
>      */
>     if ((u64)ll >= 1ULL << (sizeof(unsigned long) * 8)) {
>         ntfs_error(vol->sb, "Cannot handle %i-bit clusters. Sorry.",
>                 sizeof(unsigned long) * 4);
>         return FALSE;
>     }
> 
> Now on AMD64 (aka x86-64, Hammer), long is 64 bit wide, so the test resolves to:
> 
>       (u64 >= 1ULL << 64)
> 
> which effectively is
> 
>        (u64 >= 0)
> 
> So, as expected, mounting a NTFS partiton fails.

Grrr. Silly 64 bit architectures. The above test was designed with ULL =
128 bit in mind and not ULL = UL which the x86-64 seems to have. The test
really should only be:

    if ((u64)ll >= (1ULL << 32)) {
        ntfs_error(vol->sb, "Cannot handle 64-bit clusters. Sorry.");
        return FALSE;
    }

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cantab.net> (replace at with @)
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/