netdev - [PATCH bpf-next 3/4] samples: bpf: fix build after move to compiling full libbpf.a

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Date:   Fri, 11 May 2018 17:17:28 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     alexei.starovoitov@...il.com, daniel@...earbox.net
Cc:     oss-drivers@...ronome.com, netdev@...r.kernel.org,
        Björn Töpel <bjorn.topel@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH bpf-next 3/4] samples: bpf: fix build after move to compiling full libbpf.a

There are many ways users may compile samples, some of them got
broken by commit 5f9380572b4b ("samples: bpf: compile and link
against full libbpf").  Improve path resolution and make libbpf
building a dependency of source files to force its build.

Samples should now again build with any of:
 cd samples/bpf; make
 make samples/bpf
 make -C samples/bpf
 cd samples/bpf; make O=builddir
 make samples/bpf O=builddir
 make -C samples/bpf O=builddir

Fixes: 5f9380572b4b ("samples: bpf: compile and link against full libbpf")
Reported-by: Björn Töpel <bjorn.topel@...il.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
---
 samples/bpf/Makefile | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 9e255ca4059a..bed205ab1f81 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -1,4 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
+
+BPF_SAMPLES_PATH ?= $(abspath $(srctree)/$(src))
+TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools
+
 # List of programs to build
 hostprogs-y := test_lru_dist
 hostprogs-y += sock_example
@@ -49,7 +53,8 @@ hostprogs-y += xdpsock
 hostprogs-y += xdp_fwd
 
 # Libbpf dependencies
-LIBBPF := ../../tools/lib/bpf/libbpf.a
+LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a
+
 CGROUP_HELPERS := ../../tools/testing/selftests/bpf/cgroup_helpers.o
 TRACE_HELPERS := ../../tools/testing/selftests/bpf/trace_helpers.o
 
@@ -233,15 +238,15 @@ CLANG_ARCH_ARGS = -target $(ARCH)
 endif
 
 # Trick to allow make to be run from this directory
-all: $(LIBBPF)
-	$(MAKE) -C ../../ $(CURDIR)/
+all:
+	$(MAKE) -C ../../ $(CURDIR)/ BPF_SAMPLES_PATH=$(CURDIR)
 
 clean:
 	$(MAKE) -C ../../ M=$(CURDIR) clean
 	@rm -f *~
 
 $(LIBBPF): FORCE
-	$(MAKE) -C $(dir $@)
+	$(MAKE) -C $(dir $@) O= srctree=$(BPF_SAMPLES_PATH)/../../
 
 $(obj)/syscall_nrs.s:	$(src)/syscall_nrs.c
 	$(call if_changed_dep,cc_s_c)
@@ -272,7 +277,8 @@ verify_target_bpf: verify_cmds
 		exit 2; \
 	else true; fi
 
-$(src)/*.c: verify_target_bpf
+$(BPF_SAMPLES_PATH)/*.c: verify_target_bpf $(LIBBPF)
+$(src)/*.c: verify_target_bpf $(LIBBPF)
 
 $(obj)/tracex5_kern.o: $(obj)/syscall_nrs.h
 
-- 
2.17.0