On Mon, 19 Oct 2020 16:12:12 -0400, Don Zickus wrote:
> Sorry about that.  I thought things were failing because of ARK infra but
> now they are failing due to libbpf on s390x.  Does bpf compile there?
> 
[...]
> 00:01:25   LINK     resolve_btfids
> 00:04:11 libbpf: non-native ELF endianness is not supported

Thanks for the log. The problem seems to be the cross-compiling.

While eBPF was supposed to be architecture independent byte code, the
authors failed in reaching the goal - eBPF is not endianess neutral.
eBPF byte code compiled on a little endian machine cannot be used on a
big endian machine and vice versa.

Now, libbpf does non-trivial rewriting of eBPF code (you can think of
it as a compiler of sort). And apparently, libbpf compiled and running
on a little endian machine cannot handle big endian eBPF byte code.

I'm not sure what exactly is causing this failure. My guess would be
CONFIG_DEBUG_INFO_BTF. If I'm right, we'll probably have to disable it
on s390x while cross compiling for the time being. Could you try a
cross-compile with CONFIG_DEBUG_INFO_BTF disabled? It's something that
will have to be done only for cross-compiling, we want that config
option enabled on native builds.


On a related note, if this is the cause of the CKI failures, I wonder
why the log snippet you quoted was not the very first thing in the
emails? We talked about the CKI email format before and I think there's
still a lot of room for improvements there. It should be immediately
obvious what went wrong from the email, while currently, it requires a
CKI expert to actually interpret it.

Thanks,

 Jiri
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