Re: 64 Bit Support?

Re: 64 Bit Support?

[Jeroen Dekkers]

At Sun, 17 Jun 2007 17:11:44 -0600,
David Broadfoot wrote:
> I am wondering if there is plans for Grub 2 to be able to be compiled 
> and run in a 64 bit enviroment. I am a part of the Cross-LFS Dev. team, 
> and Under the pure 64 bit system, we have to use a 32 static version of 
> grub compiled on a 32 computer in order to get it to boot, or use 
> *Cough* lilo.
> 
> Thanks for your time

It already works. You need to have a compiler that can generate 32-bit
code however, because the boot part of GRUB needs to be in 32-bit. We
currently also have a build dependency on 32-bit libc and liblzo.

I'm using a pure 64-bit Debian system with 32-bit libc and liblzo
packages installed and that works fine.

Jeroen Dekkers

Re: 64 Bit Support?

[Robert Millan]

On Sun, Jun 17, 2007 at 02:16:41AM +0200, Jeroen Dekkers wrote:
> At Sun, 17 Jun 2007 17:11:44 -0600,
> David Broadfoot wrote:
> > I am wondering if there is plans for Grub 2 to be able to be compiled 
> > and run in a 64 bit enviroment. I am a part of the Cross-LFS Dev. team, 
> > and Under the pure 64 bit system, we have to use a 32 static version of 
> > grub compiled on a 32 computer in order to get it to boot, or use 
> > *Cough* lilo.
> > 
> > Thanks for your time
> 
> It already works. You need to have a compiler that can generate 32-bit
> code however, because the boot part of GRUB needs to be in 32-bit. We
> currently also have a build dependency on 32-bit libc and liblzo.
> 
> I'm using a pure 64-bit Debian system with 32-bit libc and liblzo
> packages installed and that works fine.

Debian sid needs more packages for biarch support.  To be safe, I suggest:

  apt-get build-dep grub2

-- 
Robert Millan

My spam trap is honeypot@aybabtu.com.  Note: this address is only intended
for spam harvesters.  Writing to it will get you added to my black list.

Re: 64 Bit Support?

[Stefan Reinauer]

* Robert Millan <rmh@aybabtu.com> [070617 11:26]:
> On Sun, Jun 17, 2007 at 02:16:41AM +0200, Jeroen Dekkers wrote:
> > At Sun, 17 Jun 2007 17:11:44 -0600,
> > David Broadfoot wrote:
> > > I am wondering if there is plans for Grub 2 to be able to be compiled 
> > > and run in a 64 bit enviroment. I am a part of the Cross-LFS Dev. team, 
> > > and Under the pure 64 bit system, we have to use a 32 static version of 
> > > grub compiled on a 32 computer in order to get it to boot, or use 
> > > *Cough* lilo.
> > > 
> > > Thanks for your time

Interesting would also be to boot pure 64bit kernels. I think some of
the BSDs have their bootloader switch to 64bit long mode, so the kernel
does not have to dot this anymore. Maybe grub could do the same thing.

-- 
coresystems GmbH • Brahmsstr. 16 • D-79104 Freiburg i. Br.
      Tel.: +49 761 7668825 • Fax: +49 761 7664613
Email: info@coresystems.de  • http://www.coresystems.de/

Re: 64 Bit Support?

[Jeroen Dekkers]

At Sun, 17 Jun 2007 11:37:15 +0200,
Stefan Reinauer wrote:
> 
> * Robert Millan <rmh@aybabtu.com> [070617 11:26]:
> > On Sun, Jun 17, 2007 at 02:16:41AM +0200, Jeroen Dekkers wrote:
> > > At Sun, 17 Jun 2007 17:11:44 -0600,
> > > David Broadfoot wrote:
> > > > I am wondering if there is plans for Grub 2 to be able to be compiled 
> > > > and run in a 64 bit enviroment. I am a part of the Cross-LFS Dev. team, 
> > > > and Under the pure 64 bit system, we have to use a 32 static version of 
> > > > grub compiled on a 32 computer in order to get it to boot, or use 
> > > > *Cough* lilo.
> > > > 
> > > > Thanks for your time
> 
> Interesting would also be to boot pure 64bit kernels. I think some of
> the BSDs have their bootloader switch to 64bit long mode, so the kernel
> does not have to dot this anymore. Maybe grub could do the same thing.

To enable long mode you have to enable paging and I don't think the
bootloader should be doing things like that. I also don't see any
problems with the OS enabling long mode.

Jeroen Dekkers

Re: 64 Bit Support?

[Stefan Reinauer]

* Jeroen Dekkers <jeroen@vrijschrift.org> [070617 13:03]:
> > Interesting would also be to boot pure 64bit kernels. I think some of
> > the BSDs have their bootloader switch to 64bit long mode, so the kernel
> > does not have to dot this anymore. Maybe grub could do the same thing.
> 
> To enable long mode you have to enable paging and I don't think the
> bootloader should be doing things like that. I also don't see any
> problems with the OS enabling long mode.

Yes, enabling long mode is overly complex and was not well designed,
imho. So I partly agree. We considered enabling long mode in LinuxBIOS a
while ago, to avoid the same "old cruft" situation like with 16bit BIOS
and 32bit OS. But you can not enable long mode without a huge amount of
overhead (ie. paging), so it can only be done when the RAM controller is
enabled and RAM is working. By that time accessing 64bit address space
has already become a lot less interesting for the boot firmware. So the
next place where it would make sense at all is in the bootloader.

The problem might be that Grub2 locks out existing operating systems, 
if it does not support switching to long mode itself. I read rumours
only, so I might be completely wrong.

Is anyone booting non-Linux OSes like FreeBSD, NetBSD, OpenBSD,
OpenSolaris, etc with GRUB2 yet? 

Stefan

-- 
coresystems GmbH • Brahmsstr. 16 • D-79104 Freiburg i. Br.
      Tel.: +49 761 7668825 • Fax: +49 761 7664613
Email: info@coresystems.de  • http://www.coresystems.de/

Re: 64 Bit Support?

[Constantine Kousoulos]

Stefan Reinauer wrote:
> The problem might be that Grub2 locks out existing operating systems, 
> if it does not support switching to long mode itself. I read rumours
> only, so I might be completely wrong.
> 
> Is anyone booting non-Linux OSes like FreeBSD, NetBSD, OpenBSD,
> OpenSolaris, etc with GRUB2 yet? 
> 

Excuse me for stepping into this discussion. I've trying for a 
while to load an elf64 kernel using GRUB2 and i have failed so 
far. The reasons for this are many and they can answer why not 
many people use GRUB2 to load their oses. Firstly, the next 
version of the multiboot specification does not correspond to the 
current implementation of GRUB2. It describes many things that 
GRUB2 does not do. This creates confusion and disappointment. 
Besides that document, there is virtually no other doc for  GRUB2. 
Secondly, the wiki's entries on testing GRUB2 on x86 need serious 
update. Thirdly, if anyone cares to use a boot loader nowdays, 
he/she expects to support loading elf64 images. Although GRUB2 is 
supposed to do that, in practice that is not completely true. One 
reason is because none of the GRUB2 developers cared to state 
explicitly that GRUB2 does not set up long mode. Personally, i 
found out about it the hard way by looking into source code. In 
addition to that, i think that there are a few other bugs that 
prevent GRUB2 from loading elf64 images. Lastly, i found very 
little support from the grub-devel mailing list. Since GRUB2 is 
still in development and there is little documentation, i expected 
to find a little more feedback than the one i got lately. I think 
that giving no feedback to normal users puts people off from using 
GRUB2.

I think that the above problems need to be addressed in order for 
GRUB2 to be an even greater piece of software than Grub Legacy 
currently is.

Regards,
Constantine

Re: 64 Bit Support?

[Andrei E. Warkentin]

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Heh, UEFI x64 runs in long mode, and it has no problems doing things  
like that. To linearly map the first 4GB you need a whole of 24KB  
worth of page tables (using 2m pages). And the code to enter long  
mode directly from RM is pretty trivial. RM->16PM->LM.


Andrei Evgenievich Warkentin
andrey.warkentin@gmail.com
Cell: (+1) (847) 321-15-55


17.06.2007, в 4:03, Jeroen Dekkers писал(а):

> At Sun, 17 Jun 2007 11:37:15 +0200,
> Stefan Reinauer wrote:
>>
>> * Robert Millan <rmh@aybabtu.com> [070617 11:26]:
>>> On Sun, Jun 17, 2007 at 02:16:41AM +0200, Jeroen Dekkers wrote:
>>>> At Sun, 17 Jun 2007 17:11:44 -0600,
>>>> David Broadfoot wrote:
>>>>> I am wondering if there is plans for Grub 2 to be able to be  
>>>>> compiled
>>>>> and run in a 64 bit enviroment. I am a part of the Cross-LFS  
>>>>> Dev. team,
>>>>> and Under the pure 64 bit system, we have to use a 32 static  
>>>>> version of
>>>>> grub compiled on a 32 computer in order to get it to boot, or use
>>>>> *Cough* lilo.
>>>>>
>>>>> Thanks for your time
>>
>> Interesting would also be to boot pure 64bit kernels. I think some of
>> the BSDs have their bootloader switch to 64bit long mode, so the  
>> kernel
>> does not have to dot this anymore. Maybe grub could do the same  
>> thing.
>
> To enable long mode you have to enable paging and I don't think the
> bootloader should be doing things like that. I also don't see any
> problems with the OS enabling long mode.
>
> Jeroen Dekkers
>
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel


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Re: 64 Bit Support?

[Andrei E. Warkentin]

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I wouldn't go as far as saying it is overly complex. If all you want  
to do is linearly map the first 4GB (which is likely enough), you can  
just pre-build the like... 6 or 7 tables you need (with 2m pages) in  
an assembly source along with a 64-bit GDT and dummy IDT. Obviously  
at start-up you're going to relocate that chunk out of ROM (for  
firmware), but that's like what... another 5-6 instructions?

Andrei Evgenievich Warkentin
andrey.warkentin@gmail.com
Cell: (+1) (847) 321-15-55


17.06.2007, в 4:24, Stefan Reinauer писал(а):

> * Jeroen Dekkers <jeroen@vrijschrift.org> [070617 13:03]:
>>> Interesting would also be to boot pure 64bit kernels. I think  
>>> some of
>>> the BSDs have their bootloader switch to 64bit long mode, so the  
>>> kernel
>>> does not have to dot this anymore. Maybe grub could do the same  
>>> thing.
>>
>> To enable long mode you have to enable paging and I don't think the
>> bootloader should be doing things like that. I also don't see any
>> problems with the OS enabling long mode.
>
> Yes, enabling long mode is overly complex and was not well designed,
> imho. So I partly agree. We considered enabling long mode in  
> LinuxBIOS a
> while ago, to avoid the same "old cruft" situation like with 16bit  
> BIOS
> and 32bit OS. But you can not enable long mode without a huge  
> amount of
> overhead (ie. paging), so it can only be done when the RAM  
> controller is
> enabled and RAM is working. By that time accessing 64bit address space
> has already become a lot less interesting for the boot firmware. So  
> the
> next place where it would make sense at all is in the bootloader.
>
> The problem might be that Grub2 locks out existing operating systems,
> if it does not support switching to long mode itself. I read rumours
> only, so I might be completely wrong.
>
> Is anyone booting non-Linux OSes like FreeBSD, NetBSD, OpenBSD,
> OpenSolaris, etc with GRUB2 yet?
>
> Stefan
>
> -- 
> coresystems GmbH ∙ Brahmsstr. 16 ∙ D-79104 Freiburg i. Br.
>       Tel.: +49 761 7668825 ∙ Fax: +49 761 7664613
> Email: info@coresystems.de  ∙ http://www.coresystems.de/
>
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel


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Re: 64 Bit Support?

[Jeroen Dekkers]

At Sun, 17 Jun 2007 12:29:43 -0700,
Andrei E. Warkentin wrote:
> Heh, UEFI x64 runs in long mode, and it has no problems doing things  
> like that. To linearly map the first 4GB you need a whole of 24KB  
> worth of page tables (using 2m pages). And the code to enter long  
> mode directly from RM is pretty trivial. RM->16PM->LM.

But UEFI doesn't need to be booted by a BIOS. We actually want to
install the GRUB2 core into the gap that exists between the partition
table and the first partition that usually starts on the second
head. This gap is 62 sectors, or 31KB. Just a bit more than your
page tables.

Jeroen Dekkers

64 Bit Support?

[David Broadfoot]

I am wondering if there is plans for Grub 2 to be able to be compiled 
and run in a 64 bit enviroment. I am a part of the Cross-LFS Dev. team, 
and Under the pure 64 bit system, we have to use a 32 static version of 
grub compiled on a 32 computer in order to get it to boot, or use 
*Cough* lilo.

Thanks for your time

Dave B
Cross-lfs.org