Re: [PATCH v1] samples/bpf: Fix build out of source tree - Stanislav Fomichev via Linux-kernel-mentees

From: Stanislav Fomichev via Linux-kernel-mentees <linux-kernel-mentees@lists.linuxfoundation.org>
To: Anh Tuan Phan <tuananhlfc@gmail.com>
Cc: daniel@iogearbox.net, martin.lau@linux.dev, ast@kernel.org,
	andrii@kernel.org, bpf@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH v1] samples/bpf: Fix build out of source tree
Date: Fri, 7 Jul 2023 09:53:08 -0700	[thread overview]
Message-ID: <ZKhC9G5ouGOviSOG@google.com> (raw)
In-Reply-To: <51aa1dd7-86d0-ed08-1142-f229513ad316@gmail.com>

On 07/07, Anh Tuan Phan wrote:
> 
> 
> On 7/7/23 01:09, Stanislav Fomichev wrote:
> > On 07/06, Anh Tuan Phan wrote:
> >> This commit fixes a few compilation issues when building out of source
> >> tree. The command that I used to build samples/bpf:
> >>
> >> export KBUILD_OUTPUT=/tmp
> >> make V=1 M=samples/bpf
> >>
> >> The compilation failed since it tried to find the header files in the
> >> wrong places between output directory and source tree directory
> >>
> >> Signed-off-by: Anh Tuan Phan <tuananhlfc@gmail.com>
> >> ---
> >>  samples/bpf/Makefile        | 8 ++++----
> >>  samples/bpf/Makefile.target | 2 +-
> >>  2 files changed, 5 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> >> index 615f24ebc49c..32469aaa82d5 100644
> >> --- a/samples/bpf/Makefile
> >> +++ b/samples/bpf/Makefile
> >> @@ -341,10 +341,10 @@ $(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
> >>  # Override includes for xdp_sample_user.o because $(srctree)/usr/include in
> >>  # TPROGS_CFLAGS causes conflicts
> >>  XDP_SAMPLE_CFLAGS += -Wall -O2 \
> >> -		     -I$(src)/../../tools/include \
> >> +		     -I$(srctree)/tools/include \
> > 
> > [..]
> > 
> >>  		     -I$(src)/../../tools/include/uapi \
> > 
> > Does this $(src) need to be changed as well?
> 
> I think this line doesn't affect the build. I removed it and it still
> compiles (after "make -C samples/bpf clean"). I guess xdp_sample_user.c
> doesn't include any file in tools/include/uapi. Am I missing something
> or should I remove this line?

You might have these headers installed on your system already if
it compiles without this part. So I'd keep this part but do
s/src/srctree/ (and remove ../..).

> > 
> > 
> >>  		     -I$(LIBBPF_INCLUDE) \
> >> -		     -I$(src)/../../tools/testing/selftests/bpf
> >> +		     -I$(srctree)/tools/testing/selftests/bpf
> >>
> >>  $(obj)/$(XDP_SAMPLE): TPROGS_CFLAGS = $(XDP_SAMPLE_CFLAGS)
> >>  $(obj)/$(XDP_SAMPLE): $(src)/xdp_sample_user.h $(src)/xdp_sample_shared.h
> >> @@ -393,7 +393,7 @@ $(obj)/xdp_router_ipv4.bpf.o: $(obj)/xdp_sample.bpf.o
> >>  $(obj)/%.bpf.o: $(src)/%.bpf.c $(obj)/vmlinux.h $(src)/xdp_sample.bpf.h
> >> $(src)/xdp_sample_shared.h
> >>  	@echo "  CLANG-BPF " $@
> >>  	$(Q)$(CLANG) -g -O2 -target bpf -D__TARGET_ARCH_$(SRCARCH) \
> >> -		-Wno-compare-distinct-pointer-types -I$(srctree)/include \
> >> +		-Wno-compare-distinct-pointer-types -I$(obj) -I$(srctree)/include \
> >>  		-I$(srctree)/samples/bpf -I$(srctree)/tools/include \
> >>  		-I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \
> >>  		-c $(filter %.bpf.c,$^) -o $@
> >> @@ -412,7 +412,7 @@ xdp_router_ipv4.skel.h-deps := xdp_router_ipv4.bpf.o
> >> xdp_sample.bpf.o
> >>
> >>  LINKED_BPF_SRCS := $(patsubst %.bpf.o,%.bpf.c,$(foreach
> >> skel,$(LINKED_SKELS),$($(skel)-deps)))
> >>
> >> -BPF_SRCS_LINKED := $(notdir $(wildcard $(src)/*.bpf.c))
> >> +BPF_SRCS_LINKED := $(notdir $(wildcard $(srctree)/$(src)/*.bpf.c))
> >>  BPF_OBJS_LINKED := $(patsubst %.bpf.c,$(obj)/%.bpf.o, $(BPF_SRCS_LINKED))
> >>  BPF_SKELS_LINKED := $(addprefix $(obj)/,$(LINKED_SKELS))
> >>
> >> diff --git a/samples/bpf/Makefile.target b/samples/bpf/Makefile.target
> >> index 7621f55e2947..86a454cfb080 100644
> >> --- a/samples/bpf/Makefile.target
> >> +++ b/samples/bpf/Makefile.target
> >> @@ -41,7 +41,7 @@ _tprogc_flags   = $(TPROGS_CFLAGS) \
> >>                   $(TPROGCFLAGS_$(basetarget).o)
> >>
> >>  # $(objtree)/$(obj) for including generated headers from checkin source
> >> files
> > 
> > [..]
> > 
> >> -ifeq ($(KBUILD_EXTMOD),)
> >> +ifneq ($(KBUILD_EXTMOD),)
> > 
> > This parts seems to be copy-pasted all over the place in its 'ifeq'
> > form. What is it doing and why is it needed?
> > 
> >>  ifdef building_out_of_srctree
> >>  _tprogc_flags   += -I $(objtree)/$(obj)
> >>  endif
> >> -- 
> >> 2.34.1
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