| Message ID | 20211023120452.212885-3-jolsa@kernel.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: Fix BTF data for modules | expand |
On Sat, Oct 23, 2021 at 5:05 AM Jiri Olsa <jolsa@redhat.com> wrote: > > The s390x compiler generates multiple definitions of the same struct > and dedup algorithm does not seem to handle this at the moment. > > I found code in dedup that seems to handle such situation for arrays, > and added btf_dedup_is_equiv call for structs. > > With this change I can no longer see vmlinux's structs in kernel > module BTF data, but I have no idea if that breaks anything else. > I'm pretty sure this is not the right way to handle this. Let's figure out what is causing a difference in types (i.e., why they are not equivalent), before attempting to patch up BTF dedup algorithm. > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > --- > tools/lib/bpf/btf.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c > index 3a01c4b7f36a..ec164d0cee30 100644 > --- a/tools/lib/bpf/btf.c > +++ b/tools/lib/bpf/btf.c > @@ -3920,8 +3920,16 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id, > * types within a single CU. So work around that by explicitly > * allowing identical array types here. > */ > - return hypot_type_id == cand_id || > - btf_dedup_identical_arrays(d, hypot_type_id, cand_id); > + struct btf_type *t; > + > + if (hypot_type_id == cand_id) > + return 1; > + t = btf_type_by_id(d->btf, hypot_type_id); > + if (btf_is_array(t)) > + return btf_dedup_identical_arrays(d, hypot_type_id, cand_id); > + if (btf_is_struct(t)) > + return btf_dedup_is_equiv(d, hypot_type_id, cand_id); > + return 0; > } > > if (btf_dedup_hypot_map_add(d, canon_id, cand_id)) > -- > 2.31.1 >
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 3a01c4b7f36a..ec164d0cee30 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -3920,8 +3920,16 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id, * types within a single CU. So work around that by explicitly * allowing identical array types here. */ - return hypot_type_id == cand_id || - btf_dedup_identical_arrays(d, hypot_type_id, cand_id); + struct btf_type *t; + + if (hypot_type_id == cand_id) + return 1; + t = btf_type_by_id(d->btf, hypot_type_id); + if (btf_is_array(t)) + return btf_dedup_identical_arrays(d, hypot_type_id, cand_id); + if (btf_is_struct(t)) + return btf_dedup_is_equiv(d, hypot_type_id, cand_id); + return 0; } if (btf_dedup_hypot_map_add(d, canon_id, cand_id))
The s390x compiler generates multiple definitions of the same struct and dedup algorithm does not seem to handle this at the moment. I found code in dedup that seems to handle such situation for arrays, and added btf_dedup_is_equiv call for structs. With this change I can no longer see vmlinux's structs in kernel module BTF data, but I have no idea if that breaks anything else. Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- tools/lib/bpf/btf.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)