netdev - Re: [PATCH bpf-next] libbpf: emit diff of mismatched public API, if any

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Date:   Wed, 22 May 2019 10:45:37 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Stanislav Fomichev <sdf@...ichev.me>
Cc:     Alexei Starovoitov <ast@...com>, Andrii Nakryiko <andriin@...com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next] libbpf: emit diff of mismatched public API, if any

On Wed, May 22, 2019 at 9:46 AM Stanislav Fomichev <sdf@...ichev.me> wrote:
>
> On 05/22, Alexei Starovoitov wrote:
> > On 5/22/19 9:15 AM, Andrii Nakryiko wrote:
> > > It's easy to have a mismatch of "intended to be public" vs really
> > > exposed API functions. While Makefile does check for this mismatch, if
> > > it actually occurs it's not trivial to determine which functions are
> > > accidentally exposed. This patch dumps out a diff showing what's not
> > > supposed to be exposed facilitating easier fixing.
> > >
> > > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > > ---
> > >   tools/lib/bpf/.gitignore | 2 ++
> > >   tools/lib/bpf/Makefile   | 8 ++++++++
> > >   2 files changed, 10 insertions(+)
> > >
> > > diff --git a/tools/lib/bpf/.gitignore b/tools/lib/bpf/.gitignore
> > > index d9e9dec04605..c7306e858e2e 100644
> > > --- a/tools/lib/bpf/.gitignore
> > > +++ b/tools/lib/bpf/.gitignore
> > > @@ -3,3 +3,5 @@ libbpf.pc
> > >   FEATURE-DUMP.libbpf
> > >   test_libbpf
> > >   libbpf.so.*
> > > +libbpf_global_syms.tmp
> > > +libbpf_versioned_syms.tmp
> > > diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> > > index f91639bf5650..7e7d6d851713 100644
> > > --- a/tools/lib/bpf/Makefile
> > > +++ b/tools/lib/bpf/Makefile
> > > @@ -204,6 +204,14 @@ check_abi: $(OUTPUT)libbpf.so
> > >                  "versioned symbols in $^ ($(VERSIONED_SYM_COUNT))." \
> > >                  "Please make sure all LIBBPF_API symbols are"       \
> > >                  "versioned in $(VERSION_SCRIPT)." >&2;              \
> > > +           readelf -s --wide $(OUTPUT)libbpf-in.o |                 \
> > > +               awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$8}'|   \
> > > +               sort -u > $(OUTPUT)libbpf_global_syms.tmp;           \
> > > +           readelf -s --wide $(OUTPUT)libbpf.so |                   \
> > > +               grep -Eo '[^ ]+@...BPF_' | cut -d@ -f1 |             \
> > > +               sort -u > $(OUTPUT)libbpf_versioned_syms.tmp;        \
> > > +           diff -u $(OUTPUT)libbpf_global_syms.tmp                  \
> > > +                $(OUTPUT)libbpf_versioned_syms.tmp;                 \
> > >             exit 1;                                                  \
> >
> > good idea.
> > how about removing tmp files instead of adding them to .gitignore?
> We should be able to do it without any temp files. At least in bash
> one can do:
>
> diff -u <(readelf -s --wide ${OUTPUT}libbpf-in.o | \
>           awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $8}' | \
>           sort -u) \
>         <(readelf -s --wide ${OUTPUT}libbpf.so | \
>           grep -Eo '[^ ]+@...BPF_' | cut -d@ -f1 | \
>           sort -u)
>
> But might be complicated in the makefile :-/

that was my initial implementation, but it doesn't work in Makefile,
as it's bash-specific