Re: bpf selftest compiling error

[Shung-Hsi Yu <shung-hsi.yu@suse.com>]

On Thu, May 19, 2022 at 01:10:42PM +0100, Quentin Monnet wrote:
> 2022-05-19 09:21 UTC+0100 ~ Jean-Philippe Brucker <jean-philippe@linaro.org>
> > Hi,
> > 
> > On Wed, May 18, 2022 at 10:51:44PM +0800, Shung-Hsi Yu wrote:
> >> On Thu, May 12, 2022 at 06:12:36PM -0700, Vincent Li wrote:
> >>> On Thu, May 12, 2022 at 5:49 PM Vincent Li <vincent.mc.li@gmail.com> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> I cloned the bpf-next and tried to compile the bpf selftest.
> >>>>
> >>>> first I got error
> >>>>
> >>>> "
> >>>> CC      /usr/src/bpf
> >>>> next/tools/testing/selftests/bpf/tools/build/bpftool/xlated_dumper.o
> >>>>
> >>>> make[1]: *** No rule to make target
> >>>> '/usr/src/bpf-next/tools/include/asm-generic/bitops/find.h', needed by
> >>>> '/usr/src/bpf-next/tools/testing/selftests/bpf/tools/build/bpftool/btf_dumper.o'.
> >>>> Stop.
> >>
> >> I also ran into the same issue on bpf-next, and the error seems rather
> >> absurd as
> >>
> >>   1. asm-generic/bitops/find.h was removed back in 47d8c15615c0a "include:
> >>      move find.h from asm_generic to linux", so perhaps this error has
> >>      something to do with Makefile.asm-generic
> >>   2. normal way of building bpftool with `make tools/bpf/bpftool` still
> >>      works fine
> >>
> >> Anyway removing ARCH= CROSS_COMPILE= in the bpf selftests Makefile
> >> (reverting change added in ea79020a2d9e "selftests/bpf: Enable
> >> cross-building with clang") can be used as a workaround to get the build
> >> working again. Adding the commit author to the thread to see if there is
> >> better approach available.
> > 
> > Could you share the commands that lead to this error?  And did you make
> > sure to clean the build tree?  I often get errors when building tools
> > because my toolchains changed and some dependencies in generated .*.d
> > files do not exist anymore.

In hindsight I likely did a clean after removing the cross-compile
environment variables, and that's probably what made the build work, not the
removal of ARCH= CROSS_COMPILE=. Sorry for jumping to conclusion.

> > I can't reproduce this specific error on today's linux-next (but found
> > another issue with out-of-tree build that I'll investigate). This is what
> > I run, on an x86 host for an x86 target:
> > 
> >  $ make defconfig
> >  $ cat tools/testing/selftests/bpf/config >> .config
> >    # and enable CONFIG_DEBUG_INFO_BTF
> >  $ make
> >  $ make -C tools/testing/selftests TARGETS=bpf SKIP_TARGETS=
> > 
> > Thanks,
> > Jean
> 
> Hi, for what it's worth I also observed the same today in samples/bpf;
> but after "make clean" the issue disappeared, and I can't reproduce it
> anymore.
> 
> Quentin

I also can't get the error to reproduce.

Thanks,
Shung-Hsi