linux-kernel - [PATCH 27/29] samples/bpf: Be consistent with bpf_load_program bpf

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Date:   Tue, 20 Dec 2016 14:03:56 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Joe Stringer <joe@....org>, Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Wang Nan <wangnan0@...wei.com>
Subject: [PATCH 27/29] samples/bpf: Be consistent with bpf_load_program bpf_insn parameter

From: Arnaldo Carvalho de Melo <acme@...hat.com>

Only one of the examples declare the bpf_insn bpf proggie as a const:

  $ grep 'struct bpf_insn [a-z]' samples/bpf/*.c
  samples/bpf/fds_example.c:	static const struct bpf_insn insns[] = {
  samples/bpf/sock_example.c:	struct bpf_insn prog[] = {
  samples/bpf/test_cgrp2_attach2.c:	struct bpf_insn prog[] = {
  samples/bpf/test_cgrp2_attach.c:	struct bpf_insn prog[] = {
  samples/bpf/test_cgrp2_sock.c:	struct bpf_insn prog[] = {
  $

Which causes this warning:

  [root@...65a7d6272 linux]# make -j4 O=/tmp/build/linux samples/bpf/
  <SNIP>
     HOSTCC  samples/bpf/fds_example.o
  /git/linux/samples/bpf/fds_example.c: In function 'bpf_prog_create':
  /git/linux/samples/bpf/fds_example.c:63:6: warning: passing argument 2 of 'bpf_load_program' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
        insns, insns_cnt, "GPL", 0,
        ^~~~~
  In file included from /git/linux/samples/bpf/libbpf.h:5:0,
                   from /git/linux/samples/bpf/bpf_load.h:4,
                   from /git/linux/samples/bpf/fds_example.c:15:
  /git/linux/tools/lib/bpf/bpf.h:31:5: note: expected 'struct bpf_insn *' but argument is of type 'const struct bpf_insn *'
   int bpf_load_program(enum bpf_prog_type type, struct bpf_insn *insns,
       ^~~~~~~~~~~~~~~~
    HOSTCC  samples/bpf/sockex1_user.o

So just ditch that 'const' to reduce build noise, leaving changing the
bpf_load_program() bpf_insn parameter to const to a later patch, if deemed
adequate.

Cc: Joe Stringer <joe@....org>
Cc: Alexei Starovoitov <ast@...com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/n/tip-1z5xee8n3oa66jf62bpv16ed@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 samples/bpf/fds_example.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/fds_example.c b/samples/bpf/fds_example.c
index 6245062844d1..a5cddc99cccd 100644
--- a/samples/bpf/fds_example.c
+++ b/samples/bpf/fds_example.c
@@ -49,7 +49,7 @@ static int bpf_map_create(void)
 
 static int bpf_prog_create(const char *object)
 {
-	static const struct bpf_insn insns[] = {
+	static struct bpf_insn insns[] = {
 		BPF_MOV64_IMM(BPF_REG_0, 1),
 		BPF_EXIT_INSN(),
 	};
-- 
2.9.3