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From: Feng zhou <zhoufeng.zf@bytedance.com>
To: netdev@vger.kernel.org
Cc: stephen@networkplumber.org, kuznet@ms2.inr.ac.ru,
	duanxiongchun@bytedance.com, wangdongdong.6@bytedance.com,
	chenzhuowen.simon@bytedance.com, zhoufeng.zf@bytedance.com
Subject: [PATCH] lib/bpf: Fix btf_load error lead to enable debug log
Date: Thu, 29 Jul 2021 12:55:16 +0800	[thread overview]
Message-ID: <20210729045516.7373-1-zhoufeng.zf@bytedance.com> (raw)

From: Feng Zhou <zhoufeng.zf@bytedance.com>

Use tc with no verbose, when bpf_btf_attach fail,
the conditions:
"if (fd < 0 && (errno == ENOSPC || !ctx->log_size))"
will make ctx->log_size != 0. And then, bpf_prog_attach,
ctx->log_size != 0. so enable debug log.
The verifier log sometimes is so chatty on larger programs.
bpf_prog_attach is failed.
"Log buffer too small to dump verifier log 16777215 bytes (9 tries)!"

BTF load failure does not affect prog load. prog still work.
So when BTF/PROG load fail, enlarge log_size and re-fail with
having verbose.

Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
---
 lib/bpf_legacy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/bpf_legacy.c b/lib/bpf_legacy.c
index 8a03b9c2..d824388c 100644
--- a/lib/bpf_legacy.c
+++ b/lib/bpf_legacy.c
@@ -1531,7 +1531,7 @@ retry:
 		 * into our buffer. Still, try to give a debuggable error
 		 * log for the user, so enlarge it and re-fail.
 		 */
-		if (fd < 0 && (errno == ENOSPC || !ctx->log_size)) {
+		if (fd < 0 && errno == ENOSPC) {
 			if (tries++ < 10 && !bpf_log_realloc(ctx))
 				goto retry;
 
@@ -2069,7 +2069,7 @@ retry:
 	fd = bpf_btf_load(ctx->btf_data->d_buf, ctx->btf_data->d_size,
 			  ctx->log, ctx->log_size);
 	if (fd < 0 || ctx->verbose) {
-		if (fd < 0 && (errno == ENOSPC || !ctx->log_size)) {
+		if (fd < 0 && errno == ENOSPC) {
 			if (tries++ < 10 && !bpf_log_realloc(ctx))
 				goto retry;
 
-- 
2.11.0

next             reply	other threads:[~2021-07-29  4:55 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29  4:55 Feng zhou [this message]
2021-07-30 18:40 ` [PATCH] lib/bpf: Fix btf_load error lead to enable debug log Andrii Nakryiko
2021-08-01  5:59   ` [External] " zhoufeng
  -- strict thread matches above, loose matches on Subject: below --
2021-07-28  9:33 Feng zhou
2021-07-29  4:02 ` zhoufeng

find likely ancestor, descendant, or conflicting patches for this message:
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