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Date:   Thu, 14 Apr 2022 22:45:03 +0000
To:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>
From:   Alexander Lobakin <alobakin@pm.me>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
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        KP Singh <kpsingh@kernel.org>,
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        Jakub Kicinski <kuba@kernel.org>,
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        Magnus Karlsson <magnus.karlsson@intel.com>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
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        netdev@vger.kernel.org, bpf@vger.kernel.org, llvm@lists.linux.dev
Reply-To: Alexander Lobakin <alobakin@pm.me>
Subject: [PATCH bpf-next 02/11] bpf: always emit struct bpf_perf_link BTF
Message-ID: <20220414223704.341028-3-alobakin@pm.me>
In-Reply-To: <20220414223704.341028-1-alobakin@pm.me>
References: <20220414223704.341028-1-alobakin@pm.me>
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When building bpftool with !CONFIG_PERF_EVENTS:

skeleton/pid_iter.bpf.c:47:14: error: incomplete definition of type 'struct=
 bpf_perf_link'
        perf_link =3D container_of(link, struct bpf_perf_link, link);
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:74:22: note: e=
xpanded from macro 'container_of'
                ((type *)(__mptr - offsetof(type, member)));    \
                                   ^~~~~~~~~~~~~~~~~~~~~~
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:68:60: note: e=
xpanded from macro 'offsetof'
 #define offsetof(TYPE, MEMBER)  ((unsigned long)&((TYPE *)0)->MEMBER)
                                                  ~~~~~~~~~~~^
skeleton/pid_iter.bpf.c:44:9: note: forward declaration of 'struct bpf_perf=
_link'
        struct bpf_perf_link *perf_link;
               ^

&bpf_perf_link is being defined and used only under the ifdef.
Move it out of the block and explicitly emit a BTF to fix
compilation.

Fixes: cbdaf71f7e65 ("bpftool: Add bpf_cookie to link output")
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
---
 kernel/bpf/syscall.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e9621cfa09f2..34fdf27d14cf 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2952,12 +2952,12 @@ static const struct bpf_link_ops bpf_raw_tp_link_lo=
ps =3D {
 =09.fill_link_info =3D bpf_raw_tp_link_fill_link_info,
 };

-#ifdef CONFIG_PERF_EVENTS
 struct bpf_perf_link {
 =09struct bpf_link link;
 =09struct file *perf_file;
 };

+#ifdef CONFIG_PERF_EVENTS
 static void bpf_perf_link_release(struct bpf_link *link)
 {
 =09struct bpf_perf_link *perf_link =3D container_of(link, struct bpf_perf_=
link, link);
@@ -4333,6 +4333,7 @@ static int link_create(union bpf_attr *attr, bpfptr_t=
 uattr)
 #endif
 =09case BPF_PROG_TYPE_PERF_EVENT:
 =09case BPF_PROG_TYPE_TRACEPOINT:
+=09=09BTF_TYPE_EMIT(struct bpf_perf_link);
 =09=09ret =3D bpf_perf_link_attach(attr, prog);
 =09=09break;
 =09case BPF_PROG_TYPE_KPROBE:
--
2.35.2