linux-kernel - [PATCH bpf-next 1/2] bpftool: adjust for error codes from libbpf probes

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Message-Id: <20220504161356.3497972-2-milan@mdaverde.com>
Date:   Wed,  4 May 2022 12:13:31 -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 1/2] bpftool: adjust for error codes from libbpf probes

Originally [1], libbpf's (now deprecated) probe functions returned a bool
to acknowledge support but the new APIs return an int with a possible
negative error code to reflect probe failure. This change decides for
bpftool to declare maps and helpers are not available on probe failures.

[1]: https://lore.kernel.org/bpf/20220202225916.3313522-3-andrii@kernel.org/

Signed-off-by: Milan Landaverde <milan@...verde.com>
---
 tools/bpf/bpftool/feature.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
index be130e35462f..c532c8855c24 100644
--- a/tools/bpf/bpftool/feature.c
+++ b/tools/bpf/bpftool/feature.c
@@ -638,7 +638,7 @@ probe_map_type(enum bpf_map_type map_type, const char *define_prefix,
 
 		res = probe_map_type_ifindex(map_type, ifindex);
 	} else {
-		res = libbpf_probe_bpf_map_type(map_type, NULL);
+		res = libbpf_probe_bpf_map_type(map_type, NULL) > 0;
 	}
 
 	/* Probe result depends on the success of map creation, no additional
@@ -701,7 +701,7 @@ probe_helper_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
 		if (ifindex)
 			res = probe_helper_ifindex(id, prog_type, ifindex);
 		else
-			res = libbpf_probe_bpf_helper(prog_type, id, NULL);
+			res = libbpf_probe_bpf_helper(prog_type, id, NULL) > 0;
 #ifdef USE_LIBCAP
 		/* Probe may succeed even if program load fails, for
 		 * unprivileged users check that we did not fail because of
-- 
2.32.0