Re: Obtaining the UUID of the system for a PXE boot

[Holger Goetz <holgerg@hgsys.de>]

Hi,

looks i could need some help here.

I've moved the smbios module from commands/i386 to commands and added 
some casts to make the compiler happy. As I need a x86_64-efi grub.
What i see now is that the "_SM_" signature is not found: "Failed to 
locate entry point structure"  some added grub_dprintf's show all zeros 
in the memory area.
Actually when i use the "dump" command to display the memory in the area 
that gets swiped (0xf0000..0x10000) it (also) only displays "00"s.
Is there some memory mapping required in x86_64 mode to access the 
memory area properly? I did cross check w/ the Linux kernel efi code and 
syslinux all basically do the same searching.

Thanks,
Holger



On 19.07.2013 18:31, David Michael wrote:
> Hi,
>
> On Fri, Jul 19, 2013 at 10:24 AM, Holger Goetz <holgerg@hgsys.de> wrote:
>> Yes it's towards the right direction. But it is 32bit only if i understand
>> correctly, and it basically is a memory access to fixed/hardcoded  MEMORY
>> address (0x80000001). to pick the veondor id and machine info.
> It's true that I've mostly been using the module on 32-bit virtual
> machines, so it hasn't really been tested elsewhere.  However, I'm not
> sure I understand what you mean by the hard-coded memory address.  The
> first function grub_smbios_locate_eps searches for the SMBIOS entry
> point structure as described in the spec.  The table entries are then
> read at the table address found in the EPS, not a hard-coded location.
>
>> I have only 64bit - UEFI here - therefore the approach w/ first searching
>> the SMBIOS infoblock in memory is probably required. And then properly walk
>> through the info-tables/blocks to get to the UUID entry. It doesn'T need to
>> be a fixed info to be retrieved from the SMBIOS memory - maybe a generic
>> function to query/search a specific entry and return that to be assigned to
>> a variable would be more flexible.
> The module's command-line interface does use a (dumb) query/search
> method.  You can specify the desired entry's type and/or handle and
> the data to retrieve from it.  For example the following command
> prints the machine name (i.e. the string at offset 5 in an entry with
> type 1).
>
>          smbios -t 1 -s 5
>
> I think you may have found the first patch I sent in that old thread,
> which was for different functionality.  The SMBIOS module can be
> downloaded from the list archive[1].
>
> Unfortunately it doesn't have any convenient functions to output a
> usable UUID.  It shouldn't take much to add one: the variable "entry"
> in the "main" function is a pointer to the matched entry, so entry[8]
> through entry[23] is the UUID in a call "smbios -t 1 ...".  I've
> verified these bytes correspond to dmidecode output on my physical
> hardware with the following.
>
>          for i in 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
>          do smbios -t 1 -b $i
>          done
>
> If the module isn't salvageable on UEFI, maybe I can send out an
> updated version whenever I upgrade to such a system.
>
> Thanks.
>
> David
>
> [1] https://lists.gnu.org/archive/html/grub-devel/2013-04/binx8am8MvVSh.bin
>
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