linux-kernel - [PATCH bpf-next 2/2] bpftool: output message if no helpers found in feature probing

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Message-Id: <20220504161356.3497972-3-milan@mdaverde.com>
Date:   Wed,  4 May 2022 12:13:32 -0400
From:   Milan Landaverde <milan@...verde.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     milan@...verde.com, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Paul Chaignon <paul@...valent.com>,
        Niklas Söderlund <niklas.soderlund@...igine.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next 2/2] bpftool: output message if no helpers found in feature probing

Currently in libbpf, we have hardcoded program types that are not
supported for helper function probing (e.g. tracing, ext, lsm).
Due to this (and other legitimate failures), bpftool feature probe returns
empty for those program type helper functions.

Instead of implying to the user that there are no helper functions
available for a program type, we output a message to the user explaining
that helper function probing failed for that program type.

Signed-off-by: Milan Landaverde <milan@...verde.com>
---
 tools/bpf/bpftool/feature.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
index c532c8855c24..d12f46051aac 100644
--- a/tools/bpf/bpftool/feature.c
+++ b/tools/bpf/bpftool/feature.c
@@ -690,7 +690,7 @@ probe_helper_ifindex(enum bpf_func_id id, enum bpf_prog_type prog_type,
 	return res;
 }
 
-static void
+static bool
 probe_helper_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
 			  const char *define_prefix, unsigned int id,
 			  const char *ptype_name, __u32 ifindex)
@@ -723,6 +723,8 @@ probe_helper_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
 		if (res)
 			printf("\n\t- %s", helper_name[id]);
 	}
+
+	return res;
 }
 
 static void
@@ -732,6 +734,7 @@ probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
 	const char *ptype_name = prog_type_name[prog_type];
 	char feat_name[128];
 	unsigned int id;
+	bool probe_res = false;
 
 	if (ifindex)
 		/* Only test helpers for offload-able program types */
@@ -764,7 +767,7 @@ probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
 				continue;
 			/* fallthrough */
 		default:
-			probe_helper_for_progtype(prog_type, supported_type,
+			probe_res |= probe_helper_for_progtype(prog_type, supported_type,
 						  define_prefix, id, ptype_name,
 						  ifindex);
 		}
@@ -772,8 +775,17 @@ probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
 
 	if (json_output)
 		jsonw_end_array(json_wtr);
-	else if (!define_prefix)
+	else if (!define_prefix) {
 		printf("\n");
+		if (!probe_res) {
+			if (!supported_type)
+				printf("\tProgram type not supported\n");
+			else
+				printf("\tCould not determine which helpers are available\n");
+		}
+	}
+
+
 }
 
 static void
-- 
2.32.0