Re: [Info-mtools] What does it take to support FAT12 dialects?

[Alexander Huemer]

On Wed, May 19, 2021 at 05:10:13PM +0200, Pali Rohár wrote:
> Hello! Is linux kernel able to mount image and access content of this
> filesystem? Can you provide example of such image? I can look at it...

I have to admit that I didn't try before. Indeed, the kernel seems to be 
able to mount a 1.2M image just fine! At least an `ls` shows content and 
the md5sum of a known file is correct.
A 2.4M image is being mounted, but `ls` shows garbage, and this is 
ending up in the kernel ring buffer:

May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 0000abda)
May 19 15:17:28 void kernel: FAT-fs (loop0): Filesystem has been set read-only
May 19 15:17:28 void kernel: FAT-fs (loop0): error, invalid access to FAT 
(entry 0x00000a53)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 00007007)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 0000a389)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 000070d1)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 000070d1)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 0000129f)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 0000fdff)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 000071d1)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 000070d1)
May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: invalid 
start cluster (i_pos 0, start 0000129f)

I'll provide images off-list.

Thank you!

-Alex