[v3,bpf-next,11/14] libbpf: makefile: add C/CXX/LDFLAGS to libbpf.so and test_libpf targets

Message ID 20190916105433.11404-12-ivan.khoronzhuk@linaro.org
State New
Headers show
Series
  • samples: bpf: improve/fix cross-compilation
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Commit Message

Ivan Khoronzhuk Sept. 16, 2019, 10:54 a.m.
In case of LDFLAGS and EXTRA_CC/CXX flags there is no way to pass them
correctly to build command, for instance when --sysroot is used or
external libraries are used, like -lelf, wich can be absent in
toolchain. This can be used for samples/bpf cross-compiling allowing
to get elf lib from sysroot.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>

---
 tools/lib/bpf/Makefile | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

-- 
2.17.1

Comments

Ivan Khoronzhuk Sept. 18, 2019, 11:05 a.m. | #1
On Tue, Sep 17, 2019 at 10:19:22PM -0700, Andrii Nakryiko wrote:
>On Mon, Sep 16, 2019 at 4:00 AM Ivan Khoronzhuk

><ivan.khoronzhuk@linaro.org> wrote:

>>

>> In case of LDFLAGS and EXTRA_CC/CXX flags there is no way to pass them

>> correctly to build command, for instance when --sysroot is used or

>> external libraries are used, like -lelf, wich can be absent in

>> toolchain. This can be used for samples/bpf cross-compiling allowing

>> to get elf lib from sysroot.

>>

>> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>

>> ---

>>  tools/lib/bpf/Makefile | 11 ++++++++---

>>  1 file changed, 8 insertions(+), 3 deletions(-)

>>

>> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile

>> index c6f94cffe06e..bccfa556ef4e 100644

>> --- a/tools/lib/bpf/Makefile

>> +++ b/tools/lib/bpf/Makefile

>> @@ -94,6 +94,10 @@ else

>>    CFLAGS := -g -Wall

>>  endif

>>

>> +ifdef EXTRA_CXXFLAGS

>> +  CXXFLAGS := $(EXTRA_CXXFLAGS)

>> +endif

>> +

>>  ifeq ($(feature-libelf-mmap), 1)

>>    override CFLAGS += -DHAVE_LIBELF_MMAP_SUPPORT

>>  endif

>> @@ -176,8 +180,9 @@ $(BPF_IN): force elfdep bpfdep

>>  $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)

>>

>>  $(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN)

>> -       $(QUIET_LINK)$(CC) --shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \

>> -                                   -Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@

>> +       $(QUIET_LINK)$(CC) $(LDFLAGS) \

>> +               --shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \

>> +               -Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@

>>         @ln -sf $(@F) $(OUTPUT)libbpf.so

>>         @ln -sf $(@F) $(OUTPUT)libbpf.so.$(LIBBPF_MAJOR_VERSION)

>>

>> @@ -185,7 +190,7 @@ $(OUTPUT)libbpf.a: $(BPF_IN)

>>         $(QUIET_LINK)$(RM) $@; $(AR) rcs $@ $^

>>

>>  $(OUTPUT)test_libbpf: test_libbpf.cpp $(OUTPUT)libbpf.a

>> -       $(QUIET_LINK)$(CXX) $(INCLUDES) $^ -lelf -o $@

>> +       $(QUIET_LINK)$(CXX) $(CXXFLAGS) $(LDFLAGS) $(INCLUDES) $^ -lelf -o $@

>

>Instead of doing ifdef EXTRA_CXXFLAGS bit above, you can just include

>both $(CXXFLAGS) and $(EXTRA_CXXFLAGS), which will do the right thing

>(and is actually recommended my make documentation way to do this).

It's good practice to follow existent style, I've done similar way as for
CFLAGS + EXTRACFLAGS here, didn't want to verify it can impact on
smth else. And my goal is not to correct everything but embed my
functionality, series tool large w/o it.

>

>But actually, there is no need to use C++ compiler here,

>test_libbpf.cpp can just be plain C. Do you mind renaming it to .c and

>using C compiler instead?

Seems like, will try in next v.

>

>>

>>  $(OUTPUT)libbpf.pc:

>>         $(QUIET_GEN)sed -e "s|@PREFIX@|$(prefix)|" \

>> --

>> 2.17.1

>>


-- 
Regards,
Ivan Khoronzhuk

Patch

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index c6f94cffe06e..bccfa556ef4e 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -94,6 +94,10 @@  else
   CFLAGS := -g -Wall
 endif
 
+ifdef EXTRA_CXXFLAGS
+  CXXFLAGS := $(EXTRA_CXXFLAGS)
+endif
+
 ifeq ($(feature-libelf-mmap), 1)
   override CFLAGS += -DHAVE_LIBELF_MMAP_SUPPORT
 endif
@@ -176,8 +180,9 @@  $(BPF_IN): force elfdep bpfdep
 $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)
 
 $(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN)
-	$(QUIET_LINK)$(CC) --shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \
-				    -Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@
+	$(QUIET_LINK)$(CC) $(LDFLAGS) \
+		--shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \
+		-Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@
 	@ln -sf $(@F) $(OUTPUT)libbpf.so
 	@ln -sf $(@F) $(OUTPUT)libbpf.so.$(LIBBPF_MAJOR_VERSION)
 
@@ -185,7 +190,7 @@  $(OUTPUT)libbpf.a: $(BPF_IN)
 	$(QUIET_LINK)$(RM) $@; $(AR) rcs $@ $^
 
 $(OUTPUT)test_libbpf: test_libbpf.cpp $(OUTPUT)libbpf.a
-	$(QUIET_LINK)$(CXX) $(INCLUDES) $^ -lelf -o $@
+	$(QUIET_LINK)$(CXX) $(CXXFLAGS) $(LDFLAGS) $(INCLUDES) $^ -lelf -o $@
 
 $(OUTPUT)libbpf.pc:
 	$(QUIET_GEN)sed -e "s|@PREFIX@|$(prefix)|" \