On 2023-01-30 16:03, Alexei Starovoitov wrote:

On Mon, Jan 30, 2023 at 10:36 AM Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

...

Use $(KHDR_INCLUDES) as lookup path for kernel headers. This prevents building against kernel headers from the build environment in scenarios where kernel headers are installed into a specific output directory (O=...).

Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Acked-by: Shuah Khan skhan@linuxfoundation.org Cc: bpf@vger.kernel.org Cc: Shuah Khan shuah@kernel.org Cc: linux-kselftest@vger.kernel.org Cc: Ingo Molnar mingo@redhat.com Cc: Alexei Starovoitov ast@kernel.org Cc: Daniel Borkmann daniel@iogearbox.net Cc: Andrii Nakryiko andrii@kernel.org Cc: Martin KaFai Lau martin.lau@linux.dev Cc: Song Liu song@kernel.org Cc: Yonghong Song yhs@fb.com Cc: John Fastabend john.fastabend@gmail.com Cc: KP Singh kpsingh@kernel.org Cc: Stanislav Fomichev sdf@google.com Cc: Hao Luo haoluo@google.com Cc: Jiri Olsa jolsa@kernel.org Cc: Mykola Lysenko mykolal@fb.com Cc: stable@vger.kernel.org [5.18+]

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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 c22c43bbee19..6998c816afef 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -327,7 +327,7 @@ endif CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH)) BPF_CFLAGS = -g -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN) \ -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR) \

•        -I$(abspath $(OUTPUT)/../usr/include)
  

•        $(KHDR_INCLUDES)
  

It breaks the build: https://github.com/kernel-patches/bpf/actions/runs/4047075637/jobs/696065524...

make[1]: *** No rule to make target '/linux/bpf.h', needed by '/tmp/work/bpf/bpf/tools/testing/selftests/bpf/bpf-helpers.rst'. Stop.

I finally figured out why I did not catch it in my own testing: it appears that the bpf selftest is special: it's not built when issuing "make" from tools/testing/selftests/. Perhaps that's also why Shuah did not see any issues with my bpf patches:

tools/testing/selftests/Makefile:

# User can optionally provide a TARGETS skiplist. By default we skip # BPF since it has cutting edge build time dependencies which require # more effort to install. SKIP_TARGETS ?= bpf

It appears that the baseline bpf selftest on v6.2-rc6 does not build on my system:

CLNG-BPF [test_maps] test_bpf_nf.bpf.o progs/test_bpf_nf.c:156:7: error: no member named 'mark' in 'struct nf_conn' ct->mark = 77; ~~ ^ progs/test_bpf_nf.c:160:42: error: use of undeclared identifier 'NF_NAT_MANIP_SRC' bpf_ct_set_nat_info(ct, &saddr, sport, NF_NAT_MANIP_SRC); ^ progs/test_bpf_nf.c:163:42: error: use of undeclared identifier 'NF_NAT_MANIP_DST' bpf_ct_set_nat_info(ct, &daddr, dport, NF_NAT_MANIP_DST); ^ progs/test_bpf_nf.c:187:38: error: no member named 'mark' in 'struct nf_conn' test_insert_lookup_mark = ct_lk->mark; ~~~~~ ^ progs/test_bpf_nf.c:189:12: error: use of undeclared identifier 'IPS_CONFIRMED' IPS_CONFIRMED | IPS_SEEN_REPLY); ^ progs/test_bpf_nf.c:189:28: error: use of undeclared identifier 'IPS_SEEN_REPLY' IPS_CONFIRMED | IPS_SEEN_REPLY); ^ progs/test_bpf_nf.c:209:11: error: no member named 'mark' in 'struct nf_conn' if (ct->mark == 42) { ~~ ^ progs/test_bpf_nf.c:210:8: error: no member named 'mark' in 'struct nf_conn' ct->mark++; ~~ ^ progs/test_bpf_nf.c:211:33: error: no member named 'mark' in 'struct nf_conn' test_exist_lookup_mark = ct->mark; ~~ ^ 9 errors generated.

Based on this: https://lore.kernel.org/bpf/37649bee-5eb3-93a2-ac57-56eb375ef8cd@iogearbox.n...

It appears that NF_CONNTRACK_MARK should be set to =y. Perhaps it should be detected at selftest build time and skipped rather than failing to build ? It appears to be a case where a user-space selftest depends on internal kernel data structures:

Ref. include/net/netfilter/nf_conntrack.h:struct nf_conn

After setting this config option, it fails at:

GEN-SKEL [test_progs] test_kfunc_dynptr_param.skel.h libbpf: sec '?lsm.s/bpf': corrupted program 'not_ptr_to_stack', offset 48, size 0 Error: failed to open BPF object file: Invalid argument make: *** [Makefile:546: /home/efficios/git/linux/tools/testing/selftests/bpf/test_kfunc_dynptr_param.skel.h] Error 234 make: *** Deleting file '/home/efficios/git/linux/tools/testing/selftests/bpf/test_kfunc_dynptr_param.skel.h'

Based on this issue: https://github.com/libbpf/libbpf-bootstrap/issues/12 it appears that bpf selftests are only meant to be used against a set of pre-specified kernel configurations. README.rst confirms that. So let's use tools/testing/selftests/bpf/config.x86_64 with make olddefconfig for my kernel build then. It would have been less unexpected for the bpf selftests to report incorrect or missing kernel config options rather than limiting the supported set to specific configuration files provided by the bpf selftests. This limits the testing coverage to very few kernel configurations.

It still does not work. I need to explicitly enable BPF_SYSCALL=y which is not present in the bpf selftests config.x86_64. Then I can explicitly reenable DEBUG_INFO_BTF=y. It appears that config.x86_64 is outdated in the bpf selftests. It also misses NF_CONNTRACK_MARK=y. So let's assume that config.x86_64 is outdated and broken and go with tools/testing/selftests/bpf/config followed by make olddefconfig.

No more luck, this time the bpf kernel config misses the DEBUG_KERNEL=y, which is needed for DEBUG_INFO and DEBUG_INFO_BTF.

Now it's:

CLANG /home/efficios/git/linux/tools/testing/selftests/bpf/tools/build/bpftool/profiler.bpf.o skeleton/profiler.bpf.c:18:21: error: invalid application of 'sizeof' to an incomplete type 'struct bpf_perf_event_value' __uint(value_size, sizeof(struct bpf_perf_event_value)); [...]

And that's where I give up. Has anyone else succeeded in building bpf selftests locally ?

Thanks,

Mathieu