[U-Boot-Users] RFC: extended image formats

[Txema Lopez <tlopez@aotek.es>]

Jerry Van Baren wrote:

>Wolfgang Denk wrote:
>  
>
>>Hello,
>>
>>I'm trying to figure out what could be done to add (at least in some
>>cases) more information to U-Boot images. 
>>
>>In this case, the existing CRC32 checksum is not sufficient;
>>therequirement is to use some stronger hashes (md5 or sha1) to verify
>>the correctness of the kernel and file system images.
>>
>>A similar thing happened not so long ago when we discussed how to add
>>the OFT blob.
>>
>>Here some thoughts:
>>
>>* The original 64 byte header is tabu and cannot be changed to provide
>>  compatibility to existing versions.
>>
>>* A quick & dirty hack could use a multi-file image to add - for
>>  example - the SHA1 checksum as separate image in addition to the
>>  kernel (and eventually file system) image(s).
>>
>>  Add an OFT blob, and the confusion is perfect.
>>
>>Seems we need a more structured approach.
>>
>>I would like to use this opportunity to collect ideas and suggestions
>>for a more generalized  solution  that  is  flexible  and  extensible
>>enough to handle not only the current , but also future requirements.
>>At least some of them ;-)
>>
>>All input welcome...
>>
>>Best regards,
>>
>>Wolfgang Denk
>>    
>>
>
>Two possibilities come to mind for using (abusing) the original 64 byte 
>header:
>
>1) If we put an ASCII-hex hash _as_ the name, we could support a 16 byte 
>(128 bit) hash.  The name would no longer be pronounceable :-P, but it 
>_would_ be unique.  An MD5 hash is typically a 32-character hexadecimal 
>number. [Ref: <http://en.wikipedia.org/wiki/MD5>]
>
>2) The name is 32 bytes.  If we trimmed the maximum name length to 28 
>bytes, we could use the last 4 bytes as a pointer to a hash.  Bleah, not 
>much/any better than the multi-file approach.
>
>gvb
>  
>
What about an image tail?. The last 2 longs of the name could be changed by:
u32 tail_magic_number; /* A magic number to detect an image with a tail */
u32 tail_offset; /* Offset to the tail from the image header */

The tail structure will add the new information for the next versions of 
U-Boot.



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