Re: [selftests/bpf] 69d96519db: kernel_selftests.bpf.test_socket_cookie.fail

[Rong Chen]

On 6/22/19 6:27 AM, Stanislav Fomichev wrote:
> On 06/21, Andrii Nakryiko wrote:
> > )
> >
> > On Fri, Jun 21, 2019 at 9:11 AM Stanislav Fomichev <sdf@xxxxxxxxxxx> wrote:
> > > On 06/21, kernel test robot wrote:
> > > > FYI, we noticed the following commit (built with gcc-7):
> > > >
> > > > commit: 69d96519dbf0bfa1868dc8597d4b9b2cdeb009d7 ("selftests/bpf: convert socket_cookie test to sk storage")
> > > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> > > >
> > > > in testcase: kernel_selftests
> > > > with following parameters:
> > > >
> > > >        group: kselftests-00
> > > >
> > > > test-description: The kernel contains a set of "self tests" under the tools/testing/selftests/ directory. These are intended to be small unit tests to exercise individual code paths in the kernel.
> > > > test-url: https://www.kernel.org/doc/Documentation/kselftest.txt
> > > >
> > > >
> > > > on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 4G
> > > >
> > > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> > > >
> > > >
> > > > If you fix the issue, kindly add following tag
> > > > Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx>
> > > >
> > > > # selftests: bpf: test_socket_cookie
> > > > # libbpf: failed to create map (name: 'socket_cookies'): Invalid
> > > > # argument
> > > Another case of old clang trying to create a map that depends on BTF?
> > > Should we maybe switch those BTF checks in the kernel to return
> > > EOPNOTSUPP to make it easy to diagnose?
> > For older compilers that don't generate DATASEC/VAR, you'll see a clear message:
> >
> > libbpf: DATASEC '.maps' not found.
> >
> > So this must be something else. I just confirmed with clang version
> > 7.0.20180201 that for ./test_socket_cookie that's the first line
> > that's emitted on failure.
> Thanks for checking, I also took a look at the attached kernel_selftests.xz,
> here is what it has:
> 2019-06-21 11:58:35 ln -sf /usr/bin/clang-6.0 /usr/bin/clang
> 2019-06-21 11:58:35 ln -sf /usr/bin/llc-6.0 /usr/bin/llc
> ...
> # BTF libbpf test[1] (test_btf_haskv.o): SKIP. No ELF .BTF found
> # BTF libbpf test[2] (test_btf_nokv.o): SKIP. No ELF .BTF found
> ...
> # Test case #0 (btf_dump_test_case_syntax): test_btf_dump_case:71:FAIL
> # failed to load test BTF: -2
> # Test case #1 (btf_dump_test_case_ordering): test_btf_dump_case:71:FAIL
> # failed to load test BTF: -2
> ...
>
> And so on. So there is clearly an old clang that doesn't emit any
> BTF. And I also don't see your recent abd29c931459 before 69d96519dbf0 in
> linux-next, that's why it doesn't complain about missing/corrupt BTF.
>
> We need to convince lkp people to upgrade clang, otherwise, I suppose,
> we'll get more of these reportings after your recent df0b77925982 :-(

Thanks for the clarification, we'll upgrade clang asap.

Best Regards,
Rong Chen


> > > > # libbpf: failed to load object './socket_cookie_prog.o'
> > > > # (test_socket_cookie.c:149: errno: Invalid argument) Failed to load
> > > > # ./socket_cookie_prog.o
> > > > # FAILED
> > > > not ok 15 selftests: bpf: test_socket_cookie
> > > >
> > > >
> > > >
> > > >
> > > > To reproduce:
> > > >
> > > >          # build kernel
> > > >        cd linux
> > > >        cp config-5.2.0-rc2-00598-g69d9651 .config
> > > >        make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 olddefconfig
> > > >        make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 prepare
> > > >        make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 modules_prepare
> > > >        make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 SHELL=/bin/bash
> > > >        make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 bzImage
> > > >
> > > >
> > > >          git clone https://github.com/intel/lkp-tests.git
> > > >          cd lkp-tests
> > > >          bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email
> > > >
> > > >
> > > >
> > > > Thanks,
> > > > Rong Chen
> > <mega snip>