Re: [PATCH bpf-next] bpf: add --skip_encoding_btf_inconsistent_proto, --btf_gen_optimized to pahole flags for v1.25

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Feb 14, 2023 at 01:17:56PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Feb 14, 2023 at 01:27:43PM +0100, Jiri Olsa escreveu:
> > On Mon, Feb 13, 2023 at 07:12:33PM -0800, Alexei Starovoitov wrote:
> > > On Thu, Feb 9, 2023 at 5:29 AM Alan Maguire <alan.maguire@oracle.com> wrote:
> > > >
> > > > v1.25 of pahole supports filtering out functions with multiple
> > > > inconsistent function prototypes or optimized-out parameters
> > > > from the BTF representation.  These present problems because
> > > > there is no additional info in BTF saying which inconsistent
> > > > prototype matches which function instance to help guide
> > > > attachment, and functions with optimized-out parameters can
> > > > lead to incorrect assumptions about register contents.
> > > >
> > > > So for now, filter out such functions while adding BTF
> > > > representations for functions that have "."-suffixes
> > > > (foo.isra.0) but not optimized-out parameters.
> > > >
> > > > This patch assumes changes in [1] land and pahole is bumped
> > > > to v1.25.
> > > >
> > > > [1] https://lore.kernel.org/bpf/1675790102-23037-1-git-send-email-alan.maguire@oracle.com/
> > > >
> > > > Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
> > > > Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> > > >
> > > > ---
> > > >  scripts/pahole-flags.sh | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
> > > > index 1f1f1d3..728d551 100755
> > > > --- a/scripts/pahole-flags.sh
> > > > +++ b/scripts/pahole-flags.sh
> > > > @@ -23,5 +23,8 @@ if [ "${pahole_ver}" -ge "124" ]; then
> > > >         # see PAHOLE_HAS_LANG_EXCLUDE
> > > >         extra_paholeopt="${extra_paholeopt} --lang_exclude=rust"
> > > >  fi
> > > > +if [ "${pahole_ver}" -ge "125" ]; then
> > > > +       extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_inconsistent_proto --btf_gen_optimized"
> > > > +fi
> > > 
> > > We landed this too soon.
> > > #229     tracing_struct:FAIL
> > > is failing now.
> > > since bpf_testmod.ko is missing a bunch of functions though they're global.
> > > 
> > 
> > hum, didn't see this one failing.. I'll try that again
> 
> /me too, redoing tests her, with gcc and clang, running selftests on a
> system booted with a kernel built with pahole 1.25, etc.

ok, can't see that with gcc, but reproduced with clang 16

resolve_btfids complains because those functions are not in btf

  BTFIDS  vmlinux
WARN: resolve_btfids: unresolved symbol tcp_reno_cong_avoid
WARN: resolve_btfids: unresolved symbol should_failslab
WARN: resolve_btfids: unresolved symbol should_fail_alloc_page
WARN: resolve_btfids: unresolved symbol cubictcp_cong_avoid
WARN: resolve_btfids: unresolved symbol bpf_xdp_metadata_rx_timestamp
WARN: resolve_btfids: unresolved symbol bpf_xdp_metadata_rx_hash
WARN: resolve_btfids: unresolved symbol bpf_task_kptr_get
WARN: resolve_btfids: unresolved symbol bpf_task_acquire_not_zero
WARN: resolve_btfids: unresolved symbol bpf_rdonly_cast
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_static_unused_arg
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_ref
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_pass_ctx
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_pass2
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_pass1
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_mem_len_pass1
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_mem_len_fail2
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_mem_len_fail1
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_kptr_get
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_fail3
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_fail2
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_fail1
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test_acquire
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test2
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_test1
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_memb_release
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_memb1_release
WARN: resolve_btfids: unresolved symbol bpf_kfunc_call_int_mem_release
  NM      System.map

jirka