Re: [PATCH] btf_encoder: Add extra checks for symbol names

[Sedat Dilek <sedat.dilek@gmail.com>]

On Thu, Jan 21, 2021 at 2:38 PM Arnaldo Carvalho de Melo
<arnaldo.melo@gmail.com> wrote:
>
> Em Tue, Jan 12, 2021 at 04:27:59PM -0800, Tom Stellard escreveu:
> > On 1/12/21 10:40 AM, Jiri Olsa wrote:
> > > When processing kernel image build by clang we can
> > > find some functions without the name, which causes
> > > pahole to segfault.
> > >
> > > Adding extra checks to make sure we always have
> > > function's name defined before using it.
> > >
> >
> > I backported this patch to pahole 1.19, and I can confirm it fixes the
> > segfault for me.
>
> I'm applying v2 for this patch and based on your above statement I'm
> adding a:
>
> Tested-by: Tom Stellard <tstellar@redhat.com>
>
> Ok?
>
> Who originally reported this?
>

The origin was AFAICS the thread where I asked initially [1].

Tom reported in the same thread in [2] that pahole segfaults.

Later in the thread Jiri offered a draft of this patch after doing some tests.

I have tested all diffs and v1 and v2 of Jiri's patch.
( Anyway, latest pahole ToT plus Jiri's patch did not solve my origin problem. )

So up to you Arnaldo for the credits.

- Sedat -

[1] https://marc.info/?t=161036949500004&r=1&w=2
[2] https://marc.info/?t=161036949500004&r=1&w=2

> - Arnaldo
>
> > -Tom
> >
> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > > ---
> > >   btf_encoder.c | 8 ++++++--
> > >   1 file changed, 6 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/btf_encoder.c b/btf_encoder.c
> > > index 333973054b61..17f7a14f2ef0 100644
> > > --- a/btf_encoder.c
> > > +++ b/btf_encoder.c
> > > @@ -72,6 +72,8 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym)
> > >     if (elf_sym__type(sym) != STT_FUNC)
> > >             return 0;
> > > +   if (!elf_sym__name(sym, btfe->symtab))
> > > +           return 0;
> > >     if (functions_cnt == functions_alloc) {
> > >             functions_alloc = max(1000, functions_alloc * 3 / 2);
> > > @@ -730,9 +732,11 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
> > >             if (!has_arg_names(cu, &fn->proto))
> > >                     continue;
> > >             if (functions_cnt) {
> > > -                   struct elf_function *func;
> > > +                   const char *name = function__name(fn, cu);
> > > +                   struct elf_function *func = NULL;
> > > -                   func = find_function(btfe, function__name(fn, cu));
> > > +                   if (name)
> > > +                           func = find_function(btfe, name);
> > >                     if (!func || func->generated)
> > >                             continue;
> > >                     func->generated = true;
> > >
> >
>
> --
>
> - Arnaldo