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Compiling for a different-ish platform: crossdev didn't help
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PeGa!
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PostPosted: Fri Sep 01, 2017 5:28 am    Post subject: Compiling for a different-ish platform: crossdev didn't help Reply with quote

Hi,

In an Atom n2600 I've got Funtoo (x86_64) installed with a very tight set of CFLAGS (safe ones, but very specific for the architecture) and while the system runs very smooth, it's a royal PITA when it comes the time for compiling.

That being said, I need to install new software into the atom (e.g. Chromium, and while this is a valid example, it's not the only packages I need to install), and as compiling is taking ages, I wanted to compile it in a more powerful system, for later packaging with -B and subsequent installation with -K.

I've attempted a crossdev setup with my desktop (AMD Vishera 8350, Gentoo x86_64), but either I didn't understand the crossdev concept, or it refused to compile to the same architecture.

The thing is, both processors and systems are x86_64, only that the Atom has a very reduced instruction set; that being said, there are some incompatibilities between platforms.

I attempted a kvm setup with n270 CPU settings, which somehow the guest OS (systemrescuecd) understood as i686 platform; aside from that specific setup, any other setup I do on kvm ends with SIGILL interruptions, which prevents me for doing any useful operation when chrooting for the first time into the new environment.

For kvm use, this is what I did:

- Created the kvm VM (choosing n270 as CPU)
- Booted it with systemrescuecd
- rsync'ed the netbook's filesystem (funtoo) into the kvm VM
- Chrooted into the kvm VM
- any useful operation (emege, grub-install, even the file operation ends with SIGILL) doesn't appear to work, resulting in SIGILLs.

I'd appreciate any hints on what are my options from here.

Thanks in advance.
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xaviermiller
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PostPosted: Fri Sep 01, 2017 7:49 am    Post subject: Reply with quote

Hi,

In your case, crossdev will not help. Did you try a simple 64 bits chroot ?
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NeddySeagoon
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PostPosted: Fri Sep 01, 2017 8:32 am    Post subject: Reply with quote

Moved from Kernel & Hardware to Unsupported Software.

It a Funtoo install, not Gentoo.

Crossdev is for building for say a Raspberry Pi, which is arm7a or AArch64 on an Intel/AMD CPU.

distcc can help you.
Install it everywhere and set up and start the daemon on the helpers.
Add distcc and distcc-pump to FEATURES an your atom.
That will try to expert the preprocessing and compiling to the helpers. The atom still does everything else.

If that's not enough, the following demands that your atom CPU instruction set is a subset of the helper.
Any instructions the helper cannot execute must not be used.

Make a chroot on the hepler and set up a BINHOST there. The chroot is identical to the atom install
except some things, like repositories can be shared.

Export the atom root fs over NFS to a helper, then chroot into it from the helper.
This is slower that the BINHOST approach as everything happen over the network.
You can speed it up my sharing repositories and local build space.
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