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Howto create a crosscompiler/64bits kernel on 32bit install.
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okapi
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Joined: 11 Feb 2003
Posts: 42
Location: Bromont, Canada

PostPosted: Sun Dec 04, 2005 10:50 pm    Post subject: Howto create a crosscompiler/64bits kernel on 32bit install. Reply with quote

Here's a little howto on how to create a crosscompiler and a 64bits kernel on a 32bit install running on amd64.
Code:
emerge sys-devel/crossdev

Build your crosscompiler.
Code:
crossdev -t x86_64-pc-linux-gnu

Clean up your kernel source tree. (This step is very important because 32bits configs are different than 64bits)
Code:
make ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu- mrproper

Configure your kernel.
Code:
make ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu- menuconfig

Note:

It is a good idea to use the option General Setup ---> Local version - append to kernel release with somthing like -x86_64 if you dont want to overwrite you running kernel and modules.

Don't forget to set Executable file formats / Emulations --->IA32 Emulation or be a fool!


Compile your kernel.
Code:
make ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu-

Code:
make ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu- modules_install

Code:
make ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu- install


Create a new Grub or Lilo entry.

And Voila! You now have a 64bits Kernel and a 64bits crosscompiler.
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satanskin
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Joined: 25 Apr 2005
Posts: 353

PostPosted: Wed Dec 07, 2005 7:49 am    Post subject: Reply with quote

Just to make things extremely clear, is this for running on a 64-bit processor or a 32-bit processor to compile 64-bit binaries?
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okapi
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Joined: 11 Feb 2003
Posts: 42
Location: Bromont, Canada

PostPosted: Wed Dec 07, 2005 12:22 pm    Post subject: Reply with quote

satanskin wrote:
Just to make things extremely clear, is this for running on a 64-bit processor or a 32-bit processor to compile 64-bit binaries?


I recently changed my MoBo and Cpu. I have a Athlon64 running in 32bit on my old athlon-xp install.
_________________
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCS d++(-) s: a40 C+++>++++$ ULS++++$ P- L+++ E--- W+++ N+ o++ K? w---
!O M- V-- PS+ PE- Y+(++) PGP++>+++ t+ 5 X+++ R tv b+ DI++ D G e++ h--
r++ y+++
------END GEEK CODE BLOCK------
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Skotlex
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Joined: 13 Mar 2004
Posts: 273

PostPosted: Mon Apr 04, 2011 8:16 pm    Post subject: Reply with quote

*brushes dust off topic* Ahem, it's been five years, but this guide is exactly what I was looking for. I've been searching for a while on a way to test out a 64-bit kernel on an otherwise pure 32-bit system.

I hope the guide still works (I will try it in a while), but I have two questions that should be addressed for those who want to follow this:

  • Will using modules work as normally, or must this kernel be static and have all modules compiled in?
  • What about nvidia graphic cards users? Is there some guide/right method of compilation, or you shouldn't even try? Or is nouveau the only way?


EDIT: So here are my findings:

1. If you want a crosscompiler ONLY for building your 64bit kernel, you can change the command:
Code:
crossdev -t x86_64-pc-linux-gnu

for
Code:
crossdev -t x86_64-pc-linux-gnu -s1

As that will only give you a GCC capable of producing 64bit executables.

2. Current kernels have a 'Cross-compiler tool prefix' (CONFIG_CROSS_COMPILE) which is a good way to store the CROSS_COMPILE variable. By setting CONFIG_CROSS_COMPILE=x86_64-pc-linux-gnu-, you can change the compilation commands from:
Code:
make ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu-

to
Code:
make ARCH=x86_64


3. nvidia-drivers seems to be a hassle to compile, because the X11 driver should be compiled in 32bit while the kernel module in 64bit :/ I just dumped that and changed to Nouveau, that was way easier.

All in all, this guide still works.
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alex6
Tux's lil' helper
Tux's lil' helper


Joined: 18 Jul 2011
Posts: 139

PostPosted: Tue Jul 09, 2013 10:10 am    Post subject: Reply with quote

This guide still work 10 years after but I'm surprised in all this time there is still no workaround for nvidia !!!!
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