Build 64-bit kernel on 32-bit system

[Gordon Messmer]

john wendel wrote:
>> john wendel wrote:
>>>
>>> Much to my surprise, there isn't a 32 vs 64 bit toggle in the kernel 
>>> config. Google confused me, but did tell me I require a 64bit 
>>> toolchain. This seems bogus, since the kernel is self contained. I 
>>> think it should be enough just to set the proper gcc options.
...
> Yes, I'll do a 64bit F10. Just wanted to experiment, and maybe learn a 
> little something while I'm waiting for F10.

If that's your goal, you can do that.  You do need a 64 bit toolchain. 
If you run "gcc --help -v" you'll notice that ld doesn't support 64 bit 
targets.

The first thing you'll need to do is build the toolchain for 64 bit 
cross-compiling.  Once that's available, you should be able to use it to 
create a 64 bit kernel.  That's pretty much the way that you'd always 
build an OS for a foreign CPU.  Build the toolchain first, then compile 
the OS using that toolchain, then create a boot disk using the 
cross-compiled binaries.  Don't get confused by the fact that 64 bit 
CPUs are backward compatible.  You need to treat them like a completely 
foreign CPU.