> This shows a new build-error:
>
> clang  -g -D__TARGET_ARCH_x86 -mlittle-endian
> -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/tools/include
> -I/home/dileks/src/linux-kernel/git/tools/t
> esting/selftests/bpf
> -I/home/dileks/src/linux-kernel/git/tools/include/uapi
> -I/home/dileks/src/linux-kernel/git/tools/testing/selftests/usr/include
> -idirafter /usr/loc
> al/include -idirafter /opt/llvm-toolchain/lib/clang/12.0.0/include
> -idirafter /usr/include/x86_64-linux-gnu -idirafter /usr/include
> -Wno-compare-distinct-pointer-type
> s -DENABLE_ATOMICS_TESTS -O2 -target bpf -c
> progs/test_sk_storage_tracing.c -o
> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_sk_storage_tracing.o-mcpu=v3
> progs/test_sk_storage_tracing.c:38:18: error: use of undeclared
> identifier 'BPF_TCP_CLOSE'
>        if (newstate == BPF_TCP_CLOSE)
>                        ^
> 1 error generated.
> make: *** [Makefile:414:
> /home/dileks/src/linux-kernel/git/tools/testing/selftests/bpf/test_sk_storage_tracing.o]
> Error 1
>

I was able to fix this by adding appropriate enums from <linux/bpf.h>.

$ git diff
diff --git a/tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c
b/tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c
index 8e94e5c080aa..3c7508f48ce0 100644
--- a/tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c
+++ b/tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c
@@ -6,6 +6,28 @@
#include <bpf/bpf_core_read.h>
#include <bpf/bpf_helpers.h>

+/* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
+ * changes between the TCP and BPF versions. Ideally this should never happen.
+ * If it does, we need to add code to convert them before calling
+ * the BPF sock_ops function.
+ */
+enum {
+       BPF_TCP_ESTABLISHED = 1,
+       BPF_TCP_SYN_SENT,
+       BPF_TCP_SYN_RECV,
+       BPF_TCP_FIN_WAIT1,
+       BPF_TCP_FIN_WAIT2,
+       BPF_TCP_TIME_WAIT,
+       BPF_TCP_CLOSE,
+       BPF_TCP_CLOSE_WAIT,
+       BPF_TCP_LAST_ACK,
+       BPF_TCP_LISTEN,
+       BPF_TCP_CLOSING,        /* Now a valid state */
+       BPF_TCP_NEW_SYN_RECV,
+
+       BPF_TCP_MAX_STATES      /* Leave at the end! */
+};
+
struct sk_stg {
       __u32 pid;
       __u32 last_notclose_state;

NOTE: Attached as a diff as Gmail might truncate it.

[ Q ] Should these enums be in vmlinux.h - if so why are they missing?

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++".

$ echo $PATH
/opt/llvm-toolchain/bin:/opt/proxychains-ng/bin:/home/dileks/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games

$ echo $MAKE $MAKE_OPTS
make V=1 HOSTCC=clang HOSTCXX=clang++ HOSTLD=ld.lld CC=clang
CXX=clang++ LD=ld.lld LLVM=1 LLVM_IAS=1 PAHOLE=/opt/pahole/bin/pahole

$ clang --version
dileks clang version 12.0.0 (https://github.com/llvm/llvm-project.git
04ba60cfe598e41084fb848daae47e0ed910fa7d)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/llvm-toolchain/bin
$ ld.lld --version
LLD 12.0.0 (https://github.com/llvm/llvm-project.git
04ba60cfe598e41084fb848daae47e0ed910fa7d) (compatible with GNU
linkers)

$ LC_ALL=C $MAKE $MAKE_OPTS -C tools/testing/selftests/bpf/

This breaks like this:

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/selftes
ts/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/incl
ude -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_loa
d_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/to
ols/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

OK, I see in bpf-next includes several fixes like:

commit a0964f526df6facd4e12a4c416185013026eecf9
"selftests/bpf: Add multi-file statically linked BPF object file test"

...and to "selftests: xsk".

Finally, I was able to build by suppressing the build of "test_cpp"
and "xdpxceiver":

$ git diff tools/testing/selftests/bpf/Makefile
diff --git a/tools/testing/selftests/bpf/Makefile
b/tools/testing/selftests/bpf/Makefile
index 044bfdcf5b74..d9b19524b2d4 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
+       # test_cpp xdpxceiver

TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read

This diff is also attached before Gmail eats it.

Yonghong Song as you described your build-environment and checking
requirements for clang-13 in bpf-next (see [1]), I am unsure if I want
to upgrade LLVM toolchain to v13-git and use bpf-next as the new
kernel base.
Lemme see if I get LLVM/Clang v13-git from Debian/experimental and/or
<apt.llvm.org>.

- Sedat -

[1] https://git.kernel.org/bpf/bpf-next/c/2ba4badca9977b64c966b0177920daadbd5501fe
[2] https://git.kernel.org/bpf/bpf-next/c/a0964f526df6facd4e12a4c416185013026eecf9