netdev - Re: [PATCH 00/14] ARM BPF jit compiler improvements

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Date:   Thu, 12 Jul 2018 22:35:47 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 00/14] ARM BPF jit compiler improvements

On Thu, Jul 12, 2018 at 11:12:45PM +0200, Daniel Borkmann wrote:
> On 07/12/2018 11:02 PM, Russell King - ARM Linux wrote:
> > On Thu, Jul 12, 2018 at 09:02:41PM +0200, Daniel Borkmann wrote:
> >> Applied to bpf-next, thanks a lot Russell!
> > 
> > Thanks, I've just sent four more patches, which is the sum total of
> > what I'm intending to send for BPF improvements for the next merge
> > window.
> 
> Great, thanks a lot for the batch of improvements, Russell!
> 
> Did you manage to get the BPF kselftest suite working on arm32 under
> tools/testing/selftests/bpf/? In particular the test_verfier with
> bpf_jit_enabled set to 1 and test_kmod.sh has a bigger number of
> runtime tests that would stress it.

I have a big issue with almost all of the tools/ subdirectory, and
that is that it isn't "portable".

It seems that cross-build environments just weren't considered when
the tools subdirectory was created - it appears to require the entire
kernel tree and build tree to be accessible on the target in order
to build almost everything there.  (I also exclusively do split-object
builds, I never do an in-source-tree build.)

At least perf has the ability to ask Kbuild to package it up as a
tar.* file.  That can be easily transported to the target as a
self-contained buildable tree, and then be able to built from that.

My cross-build environment for the kernel is just for building
kernels, it does not have the facilities to build for userspace - I
have a wide range of userspaces across targets, with a multitude of
different glibc versions, and even when they're compatible versions,
they're built differently.

As far as I can see, basically, most tools/ stuff requires too much
effort to work around this to be of any use to me.  Even if I did
unpick it from the kernel source tree by hand, that would be wasted
effort, because I'd need to repeat that same process whenever
anything there gets updated.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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