On Wed, Sep 30, 2020 at 12:02 AM Tony Ambardar <tony.ambardar@xxxxxxxxx> wrote:
>
> [adding Michael Ellerman, linux-ppc maintainer]
>
> Hello Justin,
>
> On Tue, 29 Sep 2020 at 14:54, Justin Forbes <jmforbes@xxxxxxxxxxx> wrote:
> >
> > On Tue, Sep 29, 2020 at 6:53 AM Greg Kroah-Hartman
> > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > From: Tony Ambardar <tony.ambardar@xxxxxxxxx>
> > >
> > > [ Upstream commit 746f534a4809e07f427f7d13d10f3a6a9641e5c3 ]
> > >
> > > Encountered the following failure building libbpf from kernel 5.8.5 sources
> > > with GCC 8.4.0 and binutils 2.34: (long paths shortened)
> > >
> > > Warning: Num of global symbols in sharedobjs/libbpf-in.o (234) does NOT
> > > match with num of versioned symbols in libbpf.so (236). Please make sure
> > > all LIBBPF_API symbols are versioned in libbpf.map.
> > > # --- libbpf_global_syms.tmp 2020-09-02 07:30:58.920084380 +0000
> > > # +++ libbpf_versioned_syms.tmp 2020-09-02 07:30:58.924084388 +0000
> > > @@ -1,3 +1,5 @@
> > > +_fini
> > > +_init
> > > bpf_btf_get_fd_by_id
> > > bpf_btf_get_next_id
> > > bpf_create_map
> > > make[4]: *** [Makefile:210: check_abi] Error 1
> > >
> > > Investigation shows _fini and _init are actually local symbols counted
> > > amongst global ones:
> > >
> > > $ readelf --dyn-syms --wide libbpf.so|head -10
> > >
> > > Symbol table '.dynsym' contains 343 entries:
> > > Num: Value Size Type Bind Vis Ndx Name
> > > 0: 00000000 0 NOTYPE LOCAL DEFAULT UND
> > > 1: 00004098 0 SECTION LOCAL DEFAULT 11
> > > 2: 00004098 8 FUNC LOCAL DEFAULT 11 _init@@LIBBPF_0.0.1
> > > 3: 00023040 8 FUNC LOCAL DEFAULT 14 _fini@@LIBBPF_0.0.1
> > > 4: 00000000 0 OBJECT GLOBAL DEFAULT ABS LIBBPF_0.0.4
> > > 5: 00000000 0 OBJECT GLOBAL DEFAULT ABS LIBBPF_0.0.1
> > > 6: 0000ffa4 8 FUNC GLOBAL DEFAULT 12 bpf_object__find_map_by_offset@@LIBBPF_0.0.1
> > >
> > > A previous commit filtered global symbols in sharedobjs/libbpf-in.o. Do the
> > > same with the libbpf.so DSO for consistent comparison.
> > >
> > > Fixes: 306b267cb3c4 ("libbpf: Verify versioned symbols")
> > > Signed-off-by: Tony Ambardar <Tony.Ambardar@xxxxxxxxx>
> > > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> > > Acked-by: Andrii Nakryiko <andriin@xxxxxx>
> > > Link: https://lore.kernel.org/bpf/20200905214831.1565465-1-Tony.Ambardar@xxxxxxxxx
> > > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> >
> > This seems to work everywhere else, but breaks PPC64LE.
> >
>
> I also ran into a PPC build error while working on some bpf problems,
> but it seemed
> like a pre-existing PPC issue. I did submit an upstream fix, which is
> marked for stable
> and being reviewed by Michael. See here for discussion and the patch:
> https://lkml.org/lkml/2020/9/17/668.
>
> Is that the same problem you encountered? Does that patch address your issue?
It is not, the issue I see is:
Warning: Num of global symbols in sharedobjs/libbpf-in.o (259) does
NOT match with num of versioned symbols in libbpf.so (50). Please make
sure all LIBBPF_API symbols are versioned in libbpf.map.
I only see it on ppc64le with this patch, all other arch that Fedora
builds are fine (x86_64, i686, aarch64, armv7, s390). If I revert
this patch, all builds succeed. We are using gcc 10.2.1 though.
Justin
>
> Thanks,
> Tony
>
> > Justin
> >
> > > ---
> > > tools/lib/bpf/Makefile | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > --- a/tools/lib/bpf/Makefile
> > > +++ b/tools/lib/bpf/Makefile
> > > @@ -152,6 +152,7 @@ GLOBAL_SYM_COUNT = $(shell readelf -s --
> > > awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
> > > sort -u | wc -l)
> > > VERSIONED_SYM_COUNT = $(shell readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
> > > + awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}' | \
> > > grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | sort -u | wc -l)
> > >
> > > CMD_TARGETS = $(LIB_TARGET) $(PC_FILE)
> > > @@ -219,6 +220,7 @@ check_abi: $(OUTPUT)libbpf.so
> > > awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'| \
> > > sort -u > $(OUTPUT)libbpf_global_syms.tmp; \
> > > readelf --dyn-syms --wide $(OUTPUT)libbpf.so | \
> > > + awk '/GLOBAL/ && /DEFAULT/ && !/UND/ {print $$NF}'| \
> > > grep -Eo '[^ ]+@LIBBPF_' | cut -d@ -f1 | \
> > > sort -u > $(OUTPUT)libbpf_versioned_syms.tmp; \
> > > diff -u $(OUTPUT)libbpf_global_syms.tmp \
> > >
> > >
