Re: samples don't build on v4.18

On Wed, Aug 15, 2018 at 12:34 PM, Jakub Kicinski
[off-list ref] wrote:

On Tue, 14 Aug 2018 20:01:32 -0700, Joel Fernandes wrote:

quoted

On Tue, Aug 14, 2018 at 06:22:21PM -0700, Joel Fernandes wrote:

quoted

Forgot to add the patch author, doing so now. thanks

On Tue, Aug 14, 2018 at 6:20 PM, Joel Fernandes [off-list ref] wrote:

quoted

Hi,
When building BPF samples on v4.18, I get the following errors:

$ cd samples/bpf/
$ make

Auto-detecting system features:
...                        libelf: [ OFF ]
...                           bpf: [ OFF ]

No libelf found
Makefile:213: recipe for target 'elfdep' failed
-----------

I bissected it down to commit 5f9380572b4bb24f60cd492b1

Author: Jakub Kicinski [off-list ref]
Date:   Thu May 10 10:24:39 2018 -0700

    samples: bpf: compile and link against full libbpf
---------

Checking out a kernel before this commit makes the samples build. Also I do
have libelf on my system.

Any thoughts on this issue?

There is some weirdness going on with my kernel tree. If I do a fresh clone
of v4.18 and build samples, everything works.

However if I take my existing checkout, do a:
git clean -f -d
make mrproper

Then I try to build the samples, I get the "No libelf found".

Obviously the existing checked out kernel tree is in some weird state that I
am not yet able to fix. But atleast if I blow the whole tree and clone again,
I'm able to build...

Is this related to the intermittent "No libelf found" issues that were
recently discussed?

Can't reproduce, could you provide all exact commands you run to see
this, including the initial clone?

Not sure if you saw that I replied to my own email. As I was saying,
doing a fresh clone and build of the kernel tree makes things work for
me. The problematic kernel tree which I cloned many months ago was the
one I was using when I reported the issue.

On the problematic tree, the steps I did to reproduce issue were:
git clean -f -d
make mrproper
make x86_64_defconfig
cd samples/bpf/
make

I have since moved onto using the fresh cloned tree since that's working for me.

I will let you know if I run into this again. Thanks for your time!

 - Joel