[bpf-next v4] bpf: adjust btf load error logging

[Jordan Rome <linux@jordanrome.com>]

For kernels where btf is not mandatory
we should log loading errors with `pr_info`
and not retry where we increase the log level
as this is just added noise.

Signed-off-by: Jordan Rome <linux@jordanrome.com>
---
 tools/lib/bpf/btf.c             | 36 ++++++++++++++++++---------------
 tools/lib/bpf/libbpf.c          |  3 ++-
 tools/lib/bpf/libbpf_internal.h |  2 +-
 3 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index eea99c766a20..7da4807451bb 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1379,9 +1379,10 @@ static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endi

 int btf_load_into_kernel(struct btf *btf,
 			 char *log_buf, size_t log_sz, __u32 log_level,
-			 int token_fd)
+			 int token_fd, bool btf_mandatory)
 {
 	LIBBPF_OPTS(bpf_btf_load_opts, opts);
+	enum libbpf_print_level print_level;
 	__u32 buf_sz = 0, raw_size;
 	char *buf = NULL, *tmp;
 	void *raw_data;
@@ -1435,22 +1436,25 @@ int btf_load_into_kernel(struct btf *btf,

 	btf->fd = bpf_btf_load(raw_data, raw_size, &opts);
 	if (btf->fd < 0) {
-		/* time to turn on verbose mode and try again */
-		if (log_level == 0) {
-			log_level = 1;
-			goto retry_load;
+		if (btf_mandatory) {
+			/* time to turn on verbose mode and try again */
+			if (log_level == 0) {
+				log_level = 1;
+				goto retry_load;
+			}
+			/* only retry if caller didn't provide custom log_buf, but
+			 * make sure we can never overflow buf_sz
+			 */
+			if (!log_buf && errno == ENOSPC && buf_sz <= UINT_MAX / 2)
+				goto retry_load;
 		}
-		/* only retry if caller didn't provide custom log_buf, but
-		 * make sure we can never overflow buf_sz
-		 */
-		if (!log_buf && errno == ENOSPC && buf_sz <= UINT_MAX / 2)
-			goto retry_load;
-
 		err = -errno;
-		pr_warn("BTF loading error: %s\n", errstr(err));
-		/* don't print out contents of custom log_buf */
-		if (!log_buf && buf[0])
-			pr_warn("-- BEGIN BTF LOAD LOG ---\n%s\n-- END BTF LOAD LOG --\n", buf);
+		print_level = btf_mandatory ? LIBBPF_WARN : LIBBPF_INFO;
+		__pr(print_level, "BTF loading error: %s\n", errstr(err));
+		if (!log_buf && log_level)
+			__pr(print_level,
+			     "-- BEGIN BTF LOAD LOG ---\n%s\n-- END BTF LOAD LOG --\n",
+			     buf);
 	}

 done:
@@ -1460,7 +1464,7 @@ int btf_load_into_kernel(struct btf *btf,

 int btf__load_into_kernel(struct btf *btf)
 {
-	return btf_load_into_kernel(btf, NULL, 0, 0, 0);
+	return btf_load_into_kernel(btf, NULL, 0, 0, 0, true);
 }

 int btf__fd(const struct btf *btf)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8e32286854ef..2cb3f067a12e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3604,9 +3604,10 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 		 */
 		btf__set_fd(kern_btf, 0);
 	} else {
+		btf_mandatory = kernel_needs_btf(obj);
 		/* currently BPF_BTF_LOAD only supports log_level 1 */
 		err = btf_load_into_kernel(kern_btf, obj->log_buf, obj->log_size,
-					   obj->log_level ? 1 : 0, obj->token_fd);
+					   obj->log_level ? 1 : 0, obj->token_fd, btf_mandatory);
 	}
 	if (sanitize) {
 		if (!err) {
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index de498e2dd6b0..f1de2ba462c3 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -408,7 +408,7 @@ int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
 			 int token_fd);
 int btf_load_into_kernel(struct btf *btf,
 			 char *log_buf, size_t log_sz, __u32 log_level,
-			 int token_fd);
+			 int token_fd, bool btf_mandatory);

 struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf);
 void btf_get_kernel_prefix_kind(enum bpf_attach_type attach_type,
--
2.47.1