netdev - [PATCH bpf-next v4 1/2] bpf: clean-up bpf_verifier_vlog() for BPF_LOG

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Message-ID: <20211201073458.2731595-2-houtao1@huawei.com>
Date:   Wed, 1 Dec 2021 15:34:57 +0800
From:   Hou Tao <houtao1@...wei.com>
To:     Alexei Starovoitov <ast@...nel.org>
CC:     Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>, <houtao1@...wei.com>
Subject: [PATCH bpf-next v4 1/2] bpf: clean-up bpf_verifier_vlog() for BPF_LOG_KERNEL log level

An extra newline will output for bpf_log() with BPF_LOG_KERNEL level
as shown below:

[   52.095704] BPF:The function test_3 has 12 arguments. Too many.
[   52.095704]
[   52.096896] Error in parsing func ptr test_3 in struct bpf_dummy_ops

Now all bpf_log() are ended by newline, but not all btf_verifier_log()
are ended by newline, so checking whether or not the log message
has the trailing newline and adding a newline if not.

Also there is no need to calculate the left userspace buffer size
for kernel log output and to truncate the output by '\0' which
has already been done by vscnprintf(), so only do these for
userspace log output.

Signed-off-by: Hou Tao <houtao1@...wei.com>
Acked-by: Yonghong Song <yhs@...com>
Acked-by: Martin KaFai Lau <kafai@...com>
---
 kernel/bpf/verifier.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6cfd628ae3e4..722aea00d44e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -293,13 +293,15 @@ void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,
 	WARN_ONCE(n >= BPF_VERIFIER_TMP_LOG_SIZE - 1,
 		  "verifier log line truncated - local buffer too short\n");
 
-	n = min(log->len_total - log->len_used - 1, n);
-	log->kbuf[n] = '\0';
-
 	if (log->level == BPF_LOG_KERNEL) {
-		pr_err("BPF:%s\n", log->kbuf);
+		bool newline = n > 0 && log->kbuf[n - 1] == '\n';
+
+		pr_err("BPF: %s%s", log->kbuf, newline ? "" : "\n");
 		return;
 	}
+
+	n = min(log->len_total - log->len_used - 1, n);
+	log->kbuf[n] = '\0';
 	if (!copy_to_user(log->ubuf + log->len_used, log->kbuf, n + 1))
 		log->len_used += n;
 	else
-- 
2.29.2