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From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <ast@kernel.org>, <daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>
Subject: [PATCH v2 bpf-next 01/12] libbpf: fix bpf_prog_load() log_buf logic for log_level 0
Date: Wed, 8 Dec 2021 16:49:09 -0800	[thread overview]
Message-ID: <20211209004920.4085377-2-andrii@kernel.org> (raw)
In-Reply-To: <20211209004920.4085377-1-andrii@kernel.org>

To unify libbpf APIs behavior w.r.t. log_buf and log_level, fix
bpf_prog_load() to follow the same logic as bpf_btf_load() and
high-level bpf_object__load() API will follow in the subsequent patches:
  - if log_level is 0 and non-NULL log_buf is provided by a user, attempt
    load operation initially with no log_buf and log_level set;
  - if successful, we are done, return new FD;
  - on error, retry the load operation with log_level bumped to 1 and
    log_buf set; this way verbose logging will be requested only when we
    are sure that there is a failure, but will be fast in the
    common/expected success case.

Of course, user can still specify log_level > 0 from the very beginning
to force log collection.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/bpf.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 4e7836e1a7b5..c7627fc18952 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -303,10 +303,6 @@ int bpf_prog_load_v0_6_0(enum bpf_prog_type prog_type,
 	if (log_level && !log_buf)
 		return libbpf_err(-EINVAL);
 
-	attr.log_level = log_level;
-	attr.log_buf = ptr_to_u64(log_buf);
-	attr.log_size = log_size;
-
 	func_info_rec_size = OPTS_GET(opts, func_info_rec_size, 0);
 	func_info = OPTS_GET(opts, func_info, NULL);
 	attr.func_info_rec_size = func_info_rec_size;
@@ -321,6 +317,12 @@ int bpf_prog_load_v0_6_0(enum bpf_prog_type prog_type,
 
 	attr.fd_array = ptr_to_u64(OPTS_GET(opts, fd_array, NULL));
 
+	if (log_level) {
+		attr.log_buf = ptr_to_u64(log_buf);
+		attr.log_size = log_size;
+		attr.log_level = log_level;
+	}
+
 	fd = sys_bpf_prog_load(&attr, sizeof(attr), attempts);
 	if (fd >= 0)
 		return fd;
@@ -366,16 +368,17 @@ int bpf_prog_load_v0_6_0(enum bpf_prog_type prog_type,
 			goto done;
 	}
 
-	if (log_level || !log_buf)
-		goto done;
+	if (log_level == 0 && !log_buf) {
+		/* log_level == 0 with non-NULL log_buf requires retrying on error
+		 * with log_level == 1 and log_buf/log_buf_size set, to get details of
+		 * failure
+		 */
+		attr.log_buf = ptr_to_u64(log_buf);
+		attr.log_size = log_size;
+		attr.log_level = 1;
 
-	/* Try again with log */
-	log_buf[0] = 0;
-	attr.log_buf = ptr_to_u64(log_buf);
-	attr.log_size = log_size;
-	attr.log_level = 1;
-
-	fd = sys_bpf_prog_load(&attr, sizeof(attr), attempts);
+		fd = sys_bpf_prog_load(&attr, sizeof(attr), attempts);
+	}
 done:
 	/* free() doesn't affect errno, so we don't need to restore it */
 	free(finfo);
-- 
2.30.2


  reply	other threads:[~2021-12-09  0:51 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-09  0:49 [PATCH v2 bpf-next 00/12] Enhance and rework logging controls in libbpf Andrii Nakryiko
2021-12-09  0:49 ` Andrii Nakryiko [this message]
2021-12-09  6:26   ` [PATCH v2 bpf-next 01/12] libbpf: fix bpf_prog_load() log_buf logic for log_level 0 John Fastabend
2021-12-09  7:01     ` Andrii Nakryiko
2021-12-09 19:44       ` Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 02/12] libbpf: add OPTS-based bpf_btf_load() API Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 03/12] libbpf: allow passing preallocated log_buf when loading BTF into kernel Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 04/12] libbpf: allow passing user log setting through bpf_object_open_opts Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 05/12] libbpf: improve logging around BPF program loading Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 06/12] libbpf: preserve kernel error code and remove kprobe prog type guessing Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 07/12] libbpf: add per-program log buffer setter and getter Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 08/12] libbpf: deprecate bpf_object__load_xattr() Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 09/12] selftests/bpf: replace all uses of bpf_load_btf() with bpf_btf_load() Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 10/12] selftests/bpf: add test for libbpf's custom log_buf behavior Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 11/12] selftests/bpf: remove the only use of deprecated bpf_object__load_xattr() Andrii Nakryiko
2021-12-09  0:49 ` [PATCH v2 bpf-next 12/12] bpftool: switch bpf_object__load_xattr() to bpf_object__load() Andrii Nakryiko

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