linux-kernel - [PATCH 1/2] [net-next] bpf: fix link error without CONFIG

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Date:   Thu,  2 Nov 2017 12:05:51 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "David S. Miller" <davem@...emloft.net>,
        Edward Cree <ecree@...arflare.com>,
        John Fastabend <john.fastabend@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] [net-next] bpf: fix link error without CONFIG_NET

I ran into this link error with the latest net-next plus linux-next
trees when networking is disabled:

kernel/bpf/verifier.o:(.rodata+0x2958): undefined reference to `tc_cls_act_analyzer_ops'
kernel/bpf/verifier.o:(.rodata+0x2970): undefined reference to `xdp_analyzer_ops'

It seems that the code was written to deal with varying contents of
the arrray, but the actual #ifdef was missing. Both tc_cls_act_analyzer_ops
and xdp_analyzer_ops are defined in the core networking code, so adding
a check for CONFIG_NET seems appropriate here, and I've verified this with
many randconfig builds

Fixes: 4f9218aaf8a4 ("bpf: move knowledge about post-translation offsets out of verifier")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Since there hasn't been a linux-next release in two weeks, I'm not
entirely sure this is still needed, but from looking of the net-next
contents it seems it is. I did not check any other trees that might
have a fix already.
---
 kernel/bpf/verifier.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2bb6d6aa7085..750aff880ecb 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4561,8 +4561,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
 }
 
 static const struct bpf_verifier_ops * const bpf_analyzer_ops[] = {
+#ifdef CONFIG_NET
 	[BPF_PROG_TYPE_XDP]		= &xdp_analyzer_ops,
 	[BPF_PROG_TYPE_SCHED_CLS]	= &tc_cls_act_analyzer_ops,
+#endif
 };
 
 int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops,
-- 
2.9.0