Re: [PATCH dwarves] dwarf_loader: handle DWARF5 DW_OP_addrx properly

[Yonghong Song <yhs@fb.com>]

On 4/4/21 11:55 PM, Sedat Dilek wrote:
> On Mon, Apr 5, 2021 at 4:24 AM Yonghong Song <yhs@fb.com> wrote:
>>
>>
>>
>> On 4/4/21 10:25 AM, Sedat Dilek wrote:
>>> On Sun, Apr 4, 2021 at 6:40 PM Yonghong Song <yhs@fb.com> wrote:
>>>>
>>>>
>>>>
>>>> On 4/4/21 5:46 AM, Sedat Dilek wrote:
>> [...]
>>>>> Next build-error:
>>>>>
>>>>> 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
>>>>> -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/test_core_extern.skel.h
>>>>> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a
>>>>> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_stub.o
>>>>> -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:455:
>>>>> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_cpp]
>>>>> Error 1
>>>>> make: Leaving directory
>>>>> '/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf'
>>>>>
>>>>> LOL, I was not aware that there is usage of *** CXX*** in tools
>>>>> directory (see g++ line and /usr/bin/ld ?).
>>>>>
>>>>> So, I changed my $MAKE_OPTS to use "CXX=clang++".
>>>>
>>>> In kernel, if LLVM=1 is set, we have:
>>>>
>>>> ifneq ($(LLVM),)
>>>> HOSTCC  = clang
>>>> HOSTCXX = clang++
>>>> else
>>>> HOSTCC  = gcc
>>>> HOSTCXX = g++
>>>> endif
>>>>
>>>> ifneq ($(LLVM),)
>>>> CC              = clang
>>>> LD              = ld.lld
>>>> AR              = llvm-ar
>>>> NM              = llvm-nm
>>>> OBJCOPY         = llvm-objcopy
>>>> OBJDUMP         = llvm-objdump
>>>> READELF         = llvm-readelf
>>>> STRIP           = llvm-strip
>>>> else
>>>> CC              = $(CROSS_COMPILE)gcc
>>>> LD              = $(CROSS_COMPILE)ld
>>>> AR              = $(CROSS_COMPILE)ar
>>>> NM              = $(CROSS_COMPILE)nm
>>>> OBJCOPY         = $(CROSS_COMPILE)objcopy
>>>> OBJDUMP         = $(CROSS_COMPILE)objdump
>>>> READELF         = $(CROSS_COMPILE)readelf
>>>> STRIP           = $(CROSS_COMPILE)strip
>>>> endif
>>>>
>>>> So if you have right path, you don't need to set HOSTCC and HOSTCXX
>>>> explicitly.
>>>>
>>>
>>> That is all correct with HOSTCXX but there is no CXX=... assignment
>>> otherwise test_cpp will use g++ as demonstrated.
>>
>> This is not a kernel Makefile issue.
>>
>> We have:
>> testing/selftests/bpf/Makefile:CXX ?= $(CROSS_COMPILE)g++
>>
>> So you need to explicit add CXX=clang++ when compiling
>> bpf selftests with LLVM=1 LLVM_IAS=1.
>>
> 
> NOPE.
> 
> $ echo $MAKE $MAKE_OPTS
> make V=1 LLVM=1 LLVM_IAS=1 CXX=clang++ PAHOLE=/opt/pahole/bin/pahole
> 
> $ LC_ALL=C $MAKE $MAKE_OPTS -C tools/testing/selftests/bpf/ 2>&1 | tee
> ../make-log_tools-testing-selftests-bpf_llvm-1-llvm_ias-1_cxx-clang.txt
> 
> This breaks again like reported before:
> 
> 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
> -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/test_core_extern.skel.h
> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a
> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_stub.o
> -lcap -lelf -lz -lrt -lpthread -o
> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_cpp
> 
> clang-12: warning: treating 'c-header' input as 'c++-header' when in
> C++ mode, this behavior is deprecated [-Wdeprecated]
> clang-12: error: cannot specify -o when generating multiple output files
> make: *** [Makefile:455:
> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_cpp]
> Error 1
> make: Leaving directory
> '/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf'
> 
> Do you know some magic CXX flags to be passed?

I tested in my environment. The reason is LC_ALL=C.
Without LC_ALL=C, make succeeded and with it, test_cpp
compilation failed. Is it possible for you to drop
LC_ALL=C for bpf selftests?

The following command succeeded for me:
    make -C tools/testing/selftests/bpf -j60 LLVM=1 V=1 CXX=clang++ CC=clang


> 
> The only solution is to suppress the build of test_cpp (see
> TEST_GEN_PROGS_EXTENDED):
> 
> $ git diff tools/testing/selftests/bpf/Makefile
> diff --git a/tools/testing/selftests/bpf/Makefile
> b/tools/testing/selftests/bpf/Makefile
> index 044bfdcf5b74..cf7c7c8f72cf 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -77,8 +77,8 @@ TEST_PROGS_EXTENDED := with_addr.sh \
> # Compile but not part of 'make run_tests'
> TEST_GEN_PROGS_EXTENDED = test_sock_addr test_skb_cgroup_id_user \
>         flow_dissector_load test_flow_dissector test_tcp_check_syncookie_user \
> -       test_lirc_mode2_user xdping test_cpp runqslower bench bpf_testmod.ko \
> -       xdpxceiver
> +       test_lirc_mode2_user xdping runqslower bench bpf_testmod.ko xdpxceiver
> +       # test_cpp # Suppress the build when CXX=clang++ is used
> 
> TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read
> 
> I have attached both make-logs with and without suppressing the build
> of test_cpp and the diff.
> 
> - Sedat -
> 
>>
>>>
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