netdev - [PATCH 1/2] bpf: Fix build for disabled CONFIG_DEBUG_INFO

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Message-Id: <20200714102534.299280-1-jolsa@kernel.org>
Date:   Tue, 14 Jul 2020 12:25:33 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH 1/2] bpf: Fix build for disabled CONFIG_DEBUG_INFO_BTF option

Stephen reported following linker warnings on powerpc build:

  ld: warning: orphan section `.BTF_ids' from `kernel/trace/bpf_trace.o' being placed in section `.BTF_ids'
  ld: warning: orphan section `.BTF_ids' from `kernel/bpf/btf.o' being placed in section `.BTF_ids'
  ld: warning: orphan section `.BTF_ids' from `kernel/bpf/stackmap.o' being placed in section `.BTF_ids'
  ld: warning: orphan section `.BTF_ids' from `net/core/filter.o' being placed in section `.BTF_ids'
  ld: warning: orphan section `.BTF_ids' from `kernel/trace/bpf_trace.o' being placed in section `.BTF_ids'

It's because we generated .BTF_ids section even when
CONFIG_DEBUG_INFO_BTF is not enabled. Fixing this by
generating empty btf_id arrays for this case.

Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 include/linux/btf_ids.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
index fe019774f8a7..b3c73db9587c 100644
--- a/include/linux/btf_ids.h
+++ b/include/linux/btf_ids.h
@@ -3,6 +3,8 @@
 #ifndef _LINUX_BTF_IDS_H
 #define _LINUX_BTF_IDS_H
 
+#ifdef CONFIG_DEBUG_INFO_BTF
+
 #include <linux/compiler.h> /* for __PASTE */
 
 /*
@@ -83,5 +85,12 @@ asm(							\
 ".zero 4                                       \n"	\
 ".popsection;                                  \n");
 
+#else
+
+#define BTF_ID_LIST(name) static u32 name[5];
+#define BTF_ID(prefix, name)
+#define BTF_ID_UNUSED
+
+#endif /* CONFIG_DEBUG_INFO_BTF */
 
 #endif
-- 
2.25.4