Re: [PATCH 1/2] btf_encoder: Make encoding vars into BTF optional.

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Fri, Sep 18, 2020 at 02:26:14PM -0700, Hao Luo escreveu:
> How about '--btf_encode_vars'? It is actually encoding BTF_KIND_VAR.

Sounds good as it references both its for BTF and that is for KIND_VAR.

- Arnaldo
 
> Hao
> 
> On Fri, Sep 18, 2020 at 2:24 PM Arnaldo Carvalho de Melo
> <acme@kernel.org> wrote:
> >
> > Em Fri, Sep 18, 2020 at 01:40:57PM -0700, Hao Luo escreveu:
> > > Introduce an option --btf_encode_symbols to pahole so that pahole
> > > will only encode global symbols upon request. On the kernel side,
> > > we can add a Kconfig to turn on this feature. This would make the
> > > rollout of pahole v1.18 safe against potential bugs in the feature
> > > introduced in commit f3d9054ba8ff ("btf_encoder: Teach pahole to
> > > store percpu variables in vmlinux BTF.").
> >
> > 'encode_symbols' is too generic, please rename it to
> > encode_global_symbols or something like that.
> >
> > - Arnaldo
> >
> > > Signed-off-by: Hao Luo <haoluo@google.com>
> > > ---
> > >  btf_encoder.c |  5 ++++-
> > >  btf_encoder.h |  2 +-
> > >  pahole.c      | 11 ++++++++++-
> > >  3 files changed, 15 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/btf_encoder.c b/btf_encoder.c
> > > index 982f59d..54ffdd1 100644
> > > --- a/btf_encoder.c
> > > +++ b/btf_encoder.c
> > > @@ -237,7 +237,7 @@ static struct variable *hashaddr__find_variable(const struct hlist_head hashtabl
> > >       return NULL;
> > >  }
> > >
> > > -int cu__encode_btf(struct cu *cu, int verbose, bool force)
> > > +int cu__encode_btf(struct cu *cu, int verbose, bool force, bool encode_symbols)
> > >  {
> > >       bool add_index_type = false;
> > >       uint32_t type_id_off;
> > > @@ -314,6 +314,9 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force)
> > >               }
> > >       }
> > >
> > > +     /* if there is no request to encode symbols, just finish. */
> > > +     if (!encode_symbols)
> > > +             goto out;
> > >
> > >       if (btfe->percpu_shndx == 0 || !btfe->symtab)
> > >               goto out;
> > > diff --git a/btf_encoder.h b/btf_encoder.h
> > > index bca2348..f2e95fe 100644
> > > --- a/btf_encoder.h
> > > +++ b/btf_encoder.h
> > > @@ -13,6 +13,6 @@ struct cu;
> > >
> > >  int btf_encoder__encode();
> > >
> > > -int cu__encode_btf(struct cu *cu, int verbose, bool force);
> > > +int cu__encode_btf(struct cu *cu, int verbose, bool force, bool encode_symbols);
> > >
> > >  #endif /* _BTF_ENCODER_H_ */
> > > diff --git a/pahole.c b/pahole.c
> > > index e1cde61..079d951 100644
> > > --- a/pahole.c
> > > +++ b/pahole.c
> > > @@ -26,6 +26,7 @@
> > >  static bool btf_encode;
> > >  static bool ctf_encode;
> > >  static bool first_obj_only;
> > > +static bool btf_encode_symbols;
> > >
> > >  static uint8_t class__include_anonymous;
> > >  static uint8_t class__include_nested_anonymous;
> > > @@ -809,6 +810,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
> > >  #define ARGP_header_type        314
> > >  #define ARGP_size_bytes                 315
> > >  #define ARGP_range              316
> > > +#define ARGP_btf_encode_symbols         317
> > >
> > >  static const struct argp_option pahole__options[] = {
> > >       {
> > > @@ -1087,6 +1089,11 @@ static const struct argp_option pahole__options[] = {
> > >               .key  = 'J',
> > >               .doc  = "Encode as BTF",
> > >       },
> > > +     {
> > > +             .name = "btf_encode_symbols",
> > > +             .key  = ARGP_btf_encode_symbols,
> > > +             .doc  = "Encode global symbols in BTF. Off by default."
> > > +     },
> > >       {
> > >               .name = "force",
> > >               .key  = 'j',
> > > @@ -1207,6 +1214,8 @@ static error_t pahole__options_parser(int key, char *arg,
> > >               conf.range = arg;                       break;
> > >       case ARGP_header_type:
> > >               conf.header_type = arg;                 break;
> > > +     case ARGP_btf_encode_symbols:
> > > +             btf_encode_symbols = true;              break;
> > >       default:
> > >               return ARGP_ERR_UNKNOWN;
> > >       }
> > > @@ -2352,7 +2361,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
> > >               goto filter_it;
> > >
> > >       if (btf_encode) {
> > > -             cu__encode_btf(cu, global_verbose, force);
> > > +             cu__encode_btf(cu, global_verbose, force, btf_encode_symbols);
> > >               return LSK__KEEPIT;
> > >       }
> > >
> > > --
> > > 2.28.0.681.g6f77f65b4e-goog
> > >
> >
> > --
> >
> > - Arnaldo

-- 

- Arnaldo