Syslinux - Mar 2014 - Checking CRC (of bzImage) before loading

On 03/19/2014 01:30 PM, Gene Cumm wrote:
> On Wed, Mar 19, 2014 at 4:16 PM, Mau Z <zmau1962 at gmail.com> wrote:
>> Hi,
>>
>> I am wondering how to implement the following customer's
requirement :
>> The system is a stand alone embedded system with no operator (with
Linux).
>> There is one SSD for the system's usage (and that is where the
system loads
>> from).
>>
>> The requirement is to have a duplication of the Linux Image, and that
>> syslinux should calculate CRC of "the first image" (say
bzImage_1).
>> If the CRC is correct then load the image, if the CRC is not correct,
than
>> syslinux should try "the other image" (say bzImage_2).
>> If even that is no good do nothing.
>>
>> Any suggestions as to how to implement the requirement ?
> 
> A custom COM32 module.  Look at ifcpu.c32 for an example of an if-else
> module and the crypto functions in com32/util/
> 
Or we could make the Linux loader (load_linux.c) throw an error on a bad
CRC, which is probably a good idea anyway.  Then the ONERROR option can
be used for the fallback.

	-hpa

On Mar 19, 2014 5:22 PM, "H. Peter Anvin" <hpa at zytor.com>
wrote:
> Or we could make the Linux loader (load_linux.c) throw an error on a bad
> CRC, which is probably a good idea anyway.  Then the ONERROR option can
> be used for the fallback.
>
>         -hpa
Sounds like an excellent idea.  Should linux.c32 get an override option (in
case of a non-compliant kernel-like binary)?

--Gene

On 03/19/2014 04:10 PM, Gene Cumm wrote:
> On Mar 19, 2014 5:22 PM, "H. Peter Anvin" <hpa at zytor.com
> <mailto:hpa at zytor.com>> wrote:
> 
>> Or we could make the Linux loader (load_linux.c) throw an error on a
bad
>> CRC, which is probably a good idea anyway.  Then the ONERROR option can
>> be used for the fallback.
>>
>>         -hpa
> 
> Sounds like an excellent idea.  Should linux.c32 get an override option
> (in case of a non-compliant kernel-like binary)?
> 
It would probably be a good idea.  Most such binaries will probably have
an older protocol number (no CRC), but an override seems sane at least.

	-hpa