linux-kernel - [PATCH v3] libbpf: Improve debug message when the base BTF cannot be found

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Message-ID: <Z0YqzQ5lNz7obQG7@bolson-desk>
Date: Tue, 26 Nov 2024 14:08:45 -0600
From: Ben Olson <matthew.olson@...el.com>
To: Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>,
	<bpf@...r.kernel.org>
CC: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
	<daniel@...earbox.net>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu
	<song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, John Fastabend
	<john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Stanislav Fomichev
	<sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	<bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v3] libbpf: Improve debug message when the base BTF cannot be
 found

When running `bpftool` on a kernel module installed in `/lib/modules...`,
this error is encountered if the user does not specify `--base-btf` to
point to a valid base BTF (e.g. usually in `/sys/kernel/btf/vmlinux`).
However, looking at the debug output to determine the cause of the error
simply says `Invalid BTF string section`, which does not point to the
actual source of the error. This just improves that debug message to tell
users what happened.

Signed-off-by: Ben Olson <matthew.olson@...el.com>
---
 tools/lib/bpf/btf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 12468ae0d573..a4ae2df68b91 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -283,7 +283,7 @@ static int btf_parse_str_sec(struct btf *btf)
 		return -EINVAL;
 	}
 	if (!btf->base_btf && start[0]) {
-		pr_debug("Invalid BTF string section\n");
+		pr_debug("Malformed BTF string section, did you forget to provide base BTF?\n");
 		return -EINVAL;
 	}
 	return 0;
-- 
2.47.0