netdev - [PATCH bpf-next] bpftool: Fix pretty print dump for maps without BTF loaded

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Date:   Wed, 16 Feb 2022 10:21:02 +0100
From:   Jiri Olsa <jolsa@...nel.org>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     Yinjun Zhang <yinjun.zhang@...igine.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: [PATCH bpf-next] bpftool: Fix pretty print dump for maps without BTF loaded

The commit e5043894b21f ("bpftool: Use libbpf_get_error() to check error")
fails to dump map without BTF loaded in pretty mode (-p option).

Fixing this by making sure get_map_kv_btf won't fail in case there's
no BTF available for the map.

Cc: Yinjun Zhang <yinjun.zhang@...igine.com>
Fixes: e5043894b21f ("bpftool: Use libbpf_get_error() to check error")
Suggested-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/bpf/bpftool/map.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 7a341a472ea4..8562add7417d 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -805,29 +805,28 @@ static int maps_have_btf(int *fds, int nb_fds)
 
 static struct btf *btf_vmlinux;
 
-static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
+static int get_map_kv_btf(const struct bpf_map_info *info, struct btf **btf)
 {
-	struct btf *btf = NULL;
+	int err = 0;
 
 	if (info->btf_vmlinux_value_type_id) {
 		if (!btf_vmlinux) {
 			btf_vmlinux = libbpf_find_kernel_btf();
-			if (libbpf_get_error(btf_vmlinux))
+			err = libbpf_get_error(btf_vmlinux);
+			if (err) {
 				p_err("failed to get kernel btf");
+				return err;
+			}
 		}
-		return btf_vmlinux;
+		*btf = btf_vmlinux;
 	} else if (info->btf_value_type_id) {
-		int err;
-
-		btf = btf__load_from_kernel_by_id(info->btf_id);
-		err = libbpf_get_error(btf);
-		if (err) {
+		*btf = btf__load_from_kernel_by_id(info->btf_id);
+		err = libbpf_get_error(*btf);
+		if (err)
 			p_err("failed to get btf");
-			btf = ERR_PTR(err);
-		}
 	}
 
-	return btf;
+	return err;
 }
 
 static void free_map_kv_btf(struct btf *btf)
@@ -862,8 +861,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 	prev_key = NULL;
 
 	if (wtr) {
-		btf = get_map_kv_btf(info);
-		err = libbpf_get_error(btf);
+		err = get_map_kv_btf(info, &btf);
 		if (err) {
 			goto exit_free;
 		}
@@ -1054,8 +1052,7 @@ static void print_key_value(struct bpf_map_info *info, void *key,
 	json_writer_t *btf_wtr;
 	struct btf *btf;
 
-	btf = get_map_kv_btf(info);
-	if (libbpf_get_error(btf))
+	if (get_map_kv_btf(info, &btf))
 		return;
 
 	if (json_output) {
-- 
2.35.1