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From: Sedat Dilek <sedat.dilek@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org, Andrii Nakryiko <andrii@kernel.org>,
	Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
	kernel-team@fb.com, Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH bpf-next 3/5] selftests/bpf: fix test_cpp compilation failure with clang
Date: Sun, 11 Apr 2021 19:31:08 +0200	[thread overview]
Message-ID: <CA+icZUWwSg4Nd+AzAMx8Os4iAfs=40zeoYn0eVKg3Cy7fB5Cow@mail.gmail.com> (raw)
In-Reply-To: <7c82c0f5-2a96-7a5c-b090-f26c9351786c@fb.com>

On Sun, Apr 11, 2021 at 7:20 PM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 4/11/21 3:47 AM, Sedat Dilek wrote:
> > On Sat, Apr 10, 2021 at 6:49 PM Yonghong Song <yhs@fb.com> wrote:
> >>
> >> With clang compiler:
> >>    make -j60 LLVM=1 LLVM_IAS=1  <=== compile kernel
> >>    make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1
> >> the test_cpp build failed due to the failure:
> >>    warning: treating 'c-header' input as 'c++-header' when in C++ mode, this behavior is deprecated [-Wdeprecated]
> >>    clang-13: warning: cannot specify -o when generating multiple output files
> >>
> >> test_cpp compilation flag looks like:
> >>    clang++ -g -Og -rdynamic -Wall -I<...> ... \
> >>    -Dbpf_prog_load=bpf_prog_test_load -Dbpf_load_program=bpf_test_load_program \
> >>    test_cpp.cpp <...>/test_core_extern.skel.h <...>/libbpf.a <...>/test_stub.o \
> >>    -lcap -lelf -lz -lrt -lpthread -o <...>/test_cpp
> >>
> >> The clang++ compiler complains the header file in the command line.
> >> Let us remove the header file from the command line which is not intended
> >> any way, and this fixed the problem.
> >>
> >> Signed-off-by: Yonghong Song <yhs@fb.com>
> >> ---
> >>   tools/testing/selftests/bpf/Makefile | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> >> index 6448c626498f..bbd61cc3889b 100644
> >> --- a/tools/testing/selftests/bpf/Makefile
> >> +++ b/tools/testing/selftests/bpf/Makefile
> >> @@ -481,7 +481,7 @@ $(OUTPUT)/test_verifier: test_verifier.c verifier/tests.h $(BPFOBJ) | $(OUTPUT)
> >>   # Make sure we are able to include and link libbpf against c++.
> >>   $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
> >>          $(call msg,CXX,,$@)
> >> -       $(Q)$(CXX) $(CFLAGS) $^ $(LDLIBS) -o $@
> >> +       $(Q)$(CXX) $(CFLAGS) test_cpp.cpp $(BPFOBJ) $(LDLIBS) -o $@
> >>
> >>   # Benchmark runner
> >>   $(OUTPUT)/bench_%.o: benchs/bench_%.c bench.h
> >> --
> >> 2.30.2
> >>
> >
> > NOTE: bpf-next might be different from my build-environment.
> >
> > Yonghong, can you please re-test by adding explicitly CXX=g++ to your make line?
> >
> > Here I have:
> >
> > $ grep test_cpp make-log_tools-testing-selftests-bpf_clang_clang++.txt
> > 1907:clang++ -g -rdynamic -Wall -O2 -DHAVE_GENHDR
> > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf
> > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/include
> > -I/home/dileks/src/linux-kernel/git/include/generated
> > -I/home/dileks/src/linux-kernel/git/tools/lib
> > -I/home/dileks/src/linux-kernel/git/tools/include
> > -I/home/dileks/src/linux-kernel/git/tools/include/uapi
> > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf
> > -Wno-unused-command-line-argument -Wno-format-security
> > -Dbpf_prog_load=bpf_prog_test_load
> > -Dbpf_load_program=bpf_test_load_program test_cpp.cpp
> > /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a
> > -lcap -lelf -lz -lrt -lpthread -o
> > /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_cpp
> >
> > This clang++ line does not include <...>/test_core_extern.skel.h ^^^
> >
> > $ grep test_core_extern.skel.h
> > make-log_tools-testing-selftests-bpf_clang_clang++.txt
> > 704:/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/sbin/bpftool
> > gen skeleton /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_co
> > re_extern.o > /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_core_extern.skel.h
> > 1592:/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/sbin/bpftool
> > gen skeleton /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/no_alu
> > 32/test_core_extern.o >
> > /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/no_alu32/test_core_extern.skel.h
> >
> > Checking test_cpp:
> >
> > $ /opt/llvm-toolchain/bin/llvm-objdump-12 -Dr test_cpp | grep extern
> > 0000000000417e50 <cmp_externs>:
> >   417e54: 75 22                         jne     0x417e78 <cmp_externs+0x28>
> >   417e59: 75 10                         jne     0x417e6b <cmp_externs+0x1b>
> >   417e61: 75 21                         jne     0x417e84 <cmp_externs+0x34>
> >   417e69: 75 1e                         jne     0x417e89 <cmp_externs+0x39>
> >   417e87: eb f2                         jmp     0x417e7b <cmp_externs+0x2b>
> >   417e8c: eb ed                         jmp     0x417e7b <cmp_externs+0x2b>
> >
> > $ /opt/llvm-toolchain/bin/llvm-objdump-12 -Dr test_cpp | grep core_extern
> > [ EMPTY ]
> >
> > When compiled with g++ in an earlier setup this contained "core_extern".
> >
> > With this version of your patchser it breaks *here* when using CXX=g++
> > (and uses /usr/bin/ld as linker):
> >
> > g++ -g -rdynamic -Wall -O2 -DHAVE_GENHDR
> > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf
> > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/b
> > pf/tools/include -I/home/dileks/src/linux-kernel/git/include/generated
> > -I/home/dileks/src/linux-kernel/git/tools/lib
> > -I/home/dileks/src/linux-kernel/git/tools/include
> > -I/home/dileks/src/linux-kernel/git/tools/include/uapi
> > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf
> > -Wno-unused-command-line-argument -Wno-format-security
> > -Dbpf_prog_load=bpf_prog_test_load
> > -Dbpf_load_program=bpf_test_load_program test_cpp.cpp
> > /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a
> > -lcap -lelf -lz -lrt -lpthread -o
> > /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_cpp
> >
> > /usr/bin/ld: /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a(libbpf-in.o):
> > relocation R_X86_64_32 against `.rodata.str1.1' ca
> > n not be used when making a PIE object; recompile with -fPIE
> > collect2: error: ld returned 1 exit status
> > make: *** [Makefile:457:
> > /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_cpp]
> > Error 1
>
> I cannot reproduce the issue with g++ with bpf-next, my command line is
>
> g++ -g -Og -rdynamic -Wall
> -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf
> -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include
> -I/home/yhs/work/bpf-next/include/generated
> -I/home/yhs/work/bpf-next/tools/lib
> -I/home/yhs/work/bpf-next/tools/include
> -I/home/yhs/work/bpf-next/tools/include/uapi
> -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf
> -Wno-unused-command-line-argument -Wno-format-security
> -Dbpf_prog_load=bpf_prog_test_load
> -Dbpf_load_program=bpf_test_load_program test_cpp.cpp
> /home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a
> -lcap -lelf -lz -lrt -lpthread -o
> /home/yhs/work/bpf-next/tools/testing/selftests/bpf/test_cpp
>
> I modified to
> g++ -g -rdynamic -Wall -O2 -DHAVE_GENHDR
> -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf ...
> and cannot reproduce the issue.
> The macro HAVE_GENHDR is only effect for test_verifier.
>
>
> Could you try to run the above g++ command by adding
> test_core_extern.skel.h back, something like
>
>  > g++ -g -rdynamic -Wall -O2 -DHAVE_GENHDR
>  > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf
>  > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/b
>  > pf/tools/include -I/home/dileks/src/linux-kernel/git/include/generated
>  > -I/home/dileks/src/linux-kernel/git/tools/lib
>  > -I/home/dileks/src/linux-kernel/git/tools/include
>  > -I/home/dileks/src/linux-kernel/git/tools/include/uapi
>  > -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf
>  > -Wno-unused-command-line-argument -Wno-format-security
>  > -Dbpf_prog_load=bpf_prog_test_load
>  > -Dbpf_load_program=bpf_test_load_program test_cpp.cpp
>  > test_core_extern.skel.h
>  >
> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a
>  > -lcap -lelf -lz -lrt -lpthread -o
>  > /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_cpp
>
> The issue could be somewhere else?
>

I have seen all that *skel* was reworked in bpf-next, so this is an issue here.

Adding test_core_extern.skel.h:

$ cd /tools/testing/selftests/bpf/

$ file test_core_extern.skel.h
test_core_extern.skel.h: C source, ASCII text

$ g++ -g -rdynamic -Wall -O2 -DHAVE_GENHDR
-I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf
-I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/include
-I/home/dileks/src/linux-kernel/git/include/generated
-I/home/dileks/src/linux-kernel/git/tools/lib
-I/home/dileks/src/linux-kernel/git/tools/include
-I/home/dileks/src/linux-kernel/git/tools/include/uapi
-I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf
-Wno-unused-command-line-argument -Wno-format-security
-Dbpf_prog_load=bpf_prog_test_load
-Dbpf_load_program=bpf_test_load_program test_cpp.cpp
test_core_extern.skel.h
/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a
-lcap -lelf -lz -lrt -lpthread -o
/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_cpp
/usr/bin/ld: /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a(libbpf-in.o):
relocation R_X86_64_32 against `.rodata.str1.1' ca
n not be used when making a PIE object; recompile with -fPIE
collect2: error: ld returned 1 exit status

Write that test_cpp.cpp in C :-)?

BTW, did you check (llvm-)objdump output?

$ /opt/llvm-toolchain/bin/llvm-objdump-12 -Dr test_cpp | grep core_extern

- Sedat -

> >
> > $ grep test_cpp ../make-log_tools-testing-selftests-bpf_clang_g++.txt
> > | grep test_core_extern.skel.h
> > [ EMPTY ]
> >
> > As said I do NOT use bpf-next.
> >
> > - Sedat -
> >
> >
> >
> > - Sedat -
> >

  reply	other threads:[~2021-04-11 17:31 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-10 16:49 [PATCH bpf-next 0/5] support build selftests/bpf with clang Yonghong Song
2021-04-10 16:49 ` [PATCH bpf-next 1/5] selftests: set CC to clang in lib.mk if LLVM is set Yonghong Song
2021-04-11 10:22   ` Sedat Dilek
2021-04-11 16:51     ` Yonghong Song
2021-04-11 17:10       ` Sedat Dilek
2021-04-10 16:49 ` [PATCH bpf-next 2/5] tools: allow proper CC/CXX/... override with LLVM=1 in Makefile.include Yonghong Song
2021-04-11 10:24   ` Sedat Dilek
2021-04-11 16:52     ` Yonghong Song
2021-04-10 16:49 ` [PATCH bpf-next 3/5] selftests/bpf: fix test_cpp compilation failure with clang Yonghong Song
2021-04-11 10:47   ` Sedat Dilek
2021-04-11 17:20     ` Yonghong Song
2021-04-11 17:31       ` Sedat Dilek [this message]
2021-04-11 19:08         ` Yonghong Song
2021-04-12  4:47           ` Sedat Dilek
2021-04-12  5:42             ` Yonghong Song
2021-04-12  6:06               ` Sedat Dilek
2021-04-12 14:15                 ` Yonghong Song
2021-04-13  4:32   ` Andrii Nakryiko
2021-04-13  6:12     ` Yonghong Song
2021-04-13 17:50       ` Andrii Nakryiko
2021-04-10 16:49 ` [PATCH bpf-next 4/5] selftests/bpf: silence clang compilation warnings Yonghong Song
2021-04-11 11:12   ` Sedat Dilek
2021-04-11 17:40     ` Yonghong Song
2021-04-10 16:49 ` [PATCH bpf-next 5/5] bpftool: fix a clang compilation warning Yonghong Song
2021-04-11 11:05   ` Sedat Dilek
2021-04-11 17:24     ` Yonghong Song
2021-04-10 17:23 ` [PATCH bpf-next 0/5] support build selftests/bpf with clang Alexei Starovoitov
2021-04-10 17:38   ` Yonghong Song
2021-04-10 19:19 ` Sedat Dilek
2021-04-11 16:46   ` Yonghong Song

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