Re: perf build broken seemingly due to libbpf changes, checking...

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Thu, Jan 6, 2022 at 1:42 PM Ian Rogers <irogers@google.com> wrote:
>
> On Thu, Jan 6, 2022 at 11:48 AM Arnaldo Carvalho de Melo
> <acme@kernel.org> wrote:
> >
> > Em Thu, Jan 06, 2022 at 04:44:14PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > Em Thu, Jan 06, 2022 at 04:34:46PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > > After merging torvalds/master to perf/urgent I'm getting this:
> > > >
> > > > util/bpf-event.c:25:21: error: no previous prototype for ‘btf__load_from_kernel_by_id’ [-Werror=missing-prototypes]
> > > >    25 | struct btf * __weak btf__load_from_kernel_by_id(__u32 id)
> > > >       |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > util/bpf-event.c:37:1: error: no previous prototype for ‘bpf_object__next_program’ [-Werror=missing-prototypes]
> > > >    37 | bpf_object__next_program(const struct bpf_object *obj, struct bpf_program *prev)
> > > >       | ^~~~~~~~~~~~~~~~~~~~~~~~
> > > > util/bpf-event.c:46:1: error: no previous prototype for ‘bpf_object__next_map’ [-Werror=missing-prototypes]
> > > >    46 | bpf_object__next_map(const struct bpf_object *obj, const struct bpf_map *prev)
> > > >       | ^~~~~~~~~~~~~~~~~~~~
> > > > util/bpf-event.c:55:1: error: no previous prototype for ‘btf__raw_data’ [-Werror=missing-prototypes]
> > > >    55 | btf__raw_data(const struct btf *btf_ro, __u32 *size)
> > > >       | ^~~~~~~~~~~~~
> > > > cc1: all warnings being treated as errors
> > > > make[4]: *** [/var/home/acme/git/perf/tools/build/Makefile.build:96: /tmp/build/perf/util/bpf-event.o] Error 1
> > > > make[4]: *** Waiting for unfinished jobs....
> > > > util/bpf_counter.c: In function ‘bpf_target_prog_name’:
> > > > util/bpf_counter.c:82:15: error: implicit declaration of function ‘btf__load_from_kernel_by_id’ [-Werror=implicit-function-declaration]
> > > >    82 |         btf = btf__load_from_kernel_by_id(info_linear->info.btf_id);
> > > >       |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > util/bpf_counter.c:82:13: error: assignment to ‘struct btf *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
> > > >    82 |         btf = btf__load_from_kernel_by_id(info_linear->info.btf_id);
> > > >       |             ^
> > > > cc1: all warnings being treated as errors
> > > > make[4]: *** [/var/home/acme/git/perf/tools/build/Makefile.build:96: /tmp/build/perf/util/bpf_counter.o] Error 1
> > > >
> > > > I'm checking now...
> > > >
> > > > BTW I test perf builds with:
> > > >
> > > > make -k BUILD_BPF_SKEL=1 CORESIGHT=1 PYTHON=python3 O=/tmp/build/perf -C tools/perf install-bin && git status && perf test python
> > >
> > > Nevermind, this was due to a patch by Ian Rogers I was testing,
> > > bisecting get up to the last patch, since I had merged torvalds/master
> > > today it got me to a wrong correlation, sorry for the disturbance.
> > >
> > > For reference, this is the patch:
> > >
> > > http://lore.kernel.org/lkml/20220106072627.476524-1-irogers@google.com
> >
> > Ian, I have libbpf-devel installed:
> >
> > ⬢[acme@toolbox perf]$ rpm -qa | grep libbpf
> > libbpf-0.4.0-1.fc34.x86_64
> > libbpf-devel-0.4.0-1.fc34.x86_64
> > ⬢[acme@toolbox perf]$
> >
> > But I'm not using LIBBPF_DYNAMIC=1, so you can't just give precedence to
> > system headers for all of the homies in tools/lib/.
> >
> > I bet that if I remove the libbpf-devel package it works, yeah, just
> > tested. So we need to make those overrides dependent on using
> > LIBBPF_DYNAMIC=1, LIBTRACEEVENT_DYNAMIC=1, etc and avoid the big hammer
> > that is -Itools/lib/, using a more finegrained approach, right?
>
> Ugh, this is messy. The -I for tools/lib is overloaded and being used
> in tools/perf/util/bpf-event.c so that bpf/bpf.h, bpf/btf.h and

can you do `make install` for libbpf instead and have it install
headers into a dedicated target directory which can be added into -I
search path. Quentin did this for all the other libbpf users in kernel
tree (bpftool, resolve_btfids, etc) and it works great.


> bpf/libbpf.h can be found. Likewise, for tools/perf/util/debug.c it is
> used to pick up traceevent/event-parse.h.
>
> Assuming  LIBBPF_DYNAMIC=1 and LIBTRACEEVENT_DYNAMIC=1 then we get
> different combinations of:
> libtraceevent >= 1.3 && libbpf >= 0.6 - -I is broken for debug.c,
> -idirafter okay
> libtraceevent >= 1.3 && libbpf < 0.6 - -I is broken for debug.c,
> -idirafter broken for bpf-event.c
> libtraceevent < 1.3 && libbpf >= 0.6 - -I should build okay but
> headers mismatched, -idirafter okay
> libtraceevent < 1.3 && libbpf < 0.6 - -I will fail to link
> bpf-event.c, -idirafter broken for bpf-event.c
>
> As the choice of -I and -idirafter are binary then there will always
> be a way to break the build. We could modify the build so that the
> -I/-idirafter only applies to the affected C files. This postpones the
> problem to when libbpf and libtracevent are in the same file, which
> doesn't happen currently. I think if you want the dynamic behavior
> then you need to use idirafter.
>
> Thanks,
> Ian