netdev - [PATCH 7/7] libbpf: Return const struct btf_var_secinfo from btf_var

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Date:   Fri,  6 Sep 2019 09:31:44 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Andrii Nakryiko <andriin@...com>, Yonghong Song <yhs@...com>,
        Martin KaFai Lau <kafai@...com>
Subject: [PATCH 7/7] libbpf: Return const struct btf_var_secinfo from btf_var_secinfos inline function

I'm getting following errors when compiling with -Wcast-qual:

  bpf/btf.h: In function ‘btf_var_secinfo* btf_var_secinfos(const btf_type*)’:
  bpf/btf.h:302:41: warning: cast from type ‘const btf_type*’ to type
  ‘btf_var_secinfo*’ casts away qualifiers [-Wcast-qual]
    302 |  return (struct btf_var_secinfo *)(t + 1);
        |                                         ^

The argument is const so the cast to following struct btf_var_secinfo
pointer should be const as well. Casting the const away in btf.c call
where it's correctly used without const in deduplication code.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/lib/bpf/btf.c | 5 +++--
 tools/lib/bpf/btf.h | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index b5121c79fd9f..32527622792d 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -526,7 +526,8 @@ static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
 
 	t->size = size;
 
-	for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
+	for (i = 0, vsi = (struct btf_var_secinfo *) btf_var_secinfos(t);
+	     i < vars; i++, vsi++) {
 		t_var = btf__type_by_id(btf, vsi->type);
 		var = btf_var(t_var);
 
@@ -2830,7 +2831,7 @@ static int btf_dedup_remap_type(struct btf_dedup *d, __u32 type_id)
 	}
 
 	case BTF_KIND_DATASEC: {
-		struct btf_var_secinfo *var = btf_var_secinfos(t);
+		struct btf_var_secinfo *var = (struct btf_var_secinfo *) btf_var_secinfos(t);
 		__u16 vlen = btf_vlen(t);
 
 		for (i = 0; i < vlen; i++) {
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 480dbe780fa7..ecccde0988b1 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -296,10 +296,10 @@ static inline const struct btf_var *btf_var(const struct btf_type *t)
 	return (const struct btf_var *)(t + 1);
 }
 
-static inline struct btf_var_secinfo *
+static inline const struct btf_var_secinfo *
 btf_var_secinfos(const struct btf_type *t)
 {
-	return (struct btf_var_secinfo *)(t + 1);
+	return (const struct btf_var_secinfo *)(t + 1);
 }
 
 #ifdef __cplusplus
-- 
2.21.0