[vbox-dev] Updating _DMI_ needs updating _SM_

[Jan Schunk]

Yes, the DMI Entry is part of the SM entry, as I also wrote (31 = 0x1f).
But the second checksum at 15h is only for the 15 Bytes (0x0f) stating 
at 10h.
The entries we are talking about are part of SMBIOS specification, so 
the values inside are described in the document.
There may be a BIOS checksum but not here.

Frank Mehnert wrote:
> Of course there is a BIOS checksum but this is not mentioned in the
> SMBIOS specification because the SMBIOS is only a part of the normal
> system BIOS.
>
> Furthermore, as you can see in the source code, 'Entry Point Length'
> is 0x1f so it includes the following DMI table. Therefore the checksum
> at offset 04 includes also the DMI table.
>
> Which Windows tool did you use to check the SMBIOS checksum?
>
> Thanks,
>
> Frank
>
> On Monday 02 April 2012 17:10:52 Jan Schunk wrote:
>> Additionally I looked at the definition in the standards document.
>> There is no BIOS checksum in the structure. Both checksums are only
>> checksum of the EP itself.
>>
>> This means, other calculation has also to be changed:
>> -        for (unsigned i = 0; i<  pThis->cbPcBios; i++)
>>
>> +        for (unsigned i = VBOX_DMI_TABLE_OFFSET; i<
>> VBOX_DMI_TABLE_OFFSET + 0x10; i++)
>>
>>
>> http://www.dmtf.org/sites/default/files/standards/documents/DSP0134v2.5Fina
>> l.pdf
>>
>> 04h Entry Point Structure  BYTE
>> Checksum of the Entry Point Structure (EPS).
>> This value, when Checksum  added to all other bytes in the EPS,
>> will result in the value 00h (using 8-bit addition calculations).
>> Values in the EPS are summed starting at offset 00h, for Entry Point
>> Length bytes
>>
>> 15h Intermediate Checksum BYTE
>> Checksum of Intermediate Entry Point Structure (IEPS).
>> This value, when added to all other bytes in the IEPS,
>> will result in the value 00h (using 8-bit addition calculations).
>> Values in the IEPS are summed starting at offset 10h, for 0Fh bytes.