On 26/01/2018 03:16, Alexei Starovoitov wrote: > On Fri, Jan 26, 2018 at 01:39:30AM +0100, Mickaël Salaün wrote: >> Do not build lib/bpf/bpf.o with this Makefile but use the one from the >> library directory. This avoid making a buggy bpf.o file (e.g. missing >> symbols). > > could you provide an example? > What symbols will be missing? > I don't think there is an issue with existing Makefile.
You can run this commands: make -C samples/bpf; nm tools/lib/bpf/bpf.o > a; make -C tools/lib/bpf; nm tools/lib/bpf/bpf.o > b; diff -u a b Symbols like bzero and sys_bpf are missing with the samples/bpf Makefile, which makes the bpf.o shrink from 25K to 7K. > >> This patch is useful if some code (e.g. Landlock tests) needs both the >> bpf.o (from tools/lib/bpf) and the bpf_load.o (from samples/bpf). > > is that some future patches? Yes, I'll send them next week. > > we're trying to move everything form samples/bpf/ into selftests/bpf/ > and convert to use libbpf.a instead of obsolete bpf_load.c > Please use this approach for landlock as well. Ok, it should be better with this lib. > >> Signed-off-by: Mickaël Salaün <m...@digikod.net> >> Cc: Alexei Starovoitov <a...@kernel.org> >> Cc: Daniel Borkmann <dan...@iogearbox.net> >> --- >> >> This is not a complet fix because the call to multi_depend with >> $(host-cmulti) from scripts/Makefile.host force the build of bpf.o >> anyway. I'm not sure how to completely avoid this automatic build >> though. >> --- >> samples/bpf/Makefile | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile >> index 7f61a3d57fa7..64335bb94f9f 100644 >> --- a/samples/bpf/Makefile >> +++ b/samples/bpf/Makefile >> @@ -201,13 +201,16 @@ CLANG_ARCH_ARGS = -target $(ARCH) >> endif >> >> # Trick to allow make to be run from this directory >> -all: >> +all: $(LIBBPF) >> $(MAKE) -C ../../ $(CURDIR)/ >> >> clean: >> $(MAKE) -C ../../ M=$(CURDIR) clean >> @rm -f *~ >> >> +$(LIBBPF): FORCE >> + $(MAKE) -C $(dir $@) $(notdir $@) >> + >> $(obj)/syscall_nrs.s: $(src)/syscall_nrs.c >> $(call if_changed_dep,cc_s_c) >> >> -- >> 2.15.1 >> >
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