On Mon, Aug 01, 2022 at 03:21:58PM -0700, David Faust wrote: > > > On 8/1/22 13:24, Jiri Olsa wrote: > > On Sun, Jul 31, 2022 at 05:26:49PM -0600, James Hilliard wrote: > >> The GNU assembler generates an empty .bss section. This is a well > >> established behavior in GAS that happens in all supported targets. > >> > >> The LLVM assembler doesn't generate an empty .bss section. > >> > >> bpftool chokes on the empty .bss section. > >> > >> Additionally in bpf_object__elf_collect the sec_desc->data is not > >> initialized when a section is not recognized. In this case, this > >> happens with .comment. > >> > >> So we must check that sec_desc->data is initialized before checking > >> if the size is 0. > > > > oops David send same change but I asked him to move the check > > to bpf_object__elf_collect [1] .. but with your explanation this > > fix actualy looks fine to me > > FWIW, I only just got back to actually making that change. This > patch has a much better explanation than the one I sent so +1 from > me also thanks, I'm acking this one then Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> jirka > > David > > > > > jirka > > > > > > [1] https://lore.kernel.org/bpf/YuKaFiZ+ksB5f0Ye@krava/ > > > >> > >> Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx> > >> Cc: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx> > >> --- > >> tools/lib/bpf/libbpf.c | 4 ++++ > >> 1 file changed, 4 insertions(+) > >> > >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > >> index 50d41815f431..77e3797cf75a 100644 > >> --- a/tools/lib/bpf/libbpf.c > >> +++ b/tools/lib/bpf/libbpf.c > >> @@ -1642,6 +1642,10 @@ static int bpf_object__init_global_data_maps(struct bpf_object *obj) > >> for (sec_idx = 1; sec_idx < obj->efile.sec_cnt; sec_idx++) { > >> sec_desc = &obj->efile.secs[sec_idx]; > >> > >> + /* Skip recognized sections with size 0. */ > >> + if (sec_desc->data && sec_desc->data->d_size == 0) > >> + continue; > >> + > >> switch (sec_desc->sec_type) { > >> case SEC_DATA: > >> sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx)); > >> -- > >> 2.34.1 > >>
