linux-kernel - [PATCH bpf-next v2] bpf: Fix 'dubious one-bit signed bitfield' warnings

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Date:   Mon, 11 Jul 2022 10:12:00 +0200
From:   Matthieu Baerts <matthieu.baerts@...sares.net>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Eduard Zingerman <eddyz87@...il.com>
Cc:     mptcp@...ts.linux.dev,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2] bpf: Fix 'dubious one-bit signed bitfield' warnings

Our CI[1] reported these warnings when using Sparse:

  $ touch net/mptcp/bpf.c
  $ make C=1 net/mptcp/bpf.o
  net/mptcp/bpf.c: note: in included file:
  include/linux/bpf_verifier.h:348:26: error: dubious one-bit signed bitfield
  include/linux/bpf_verifier.h:349:29: error: dubious one-bit signed bitfield

Set them as 'unsigned' to avoid warnings.

[1] https://github.com/multipath-tcp/mptcp_net-next/actions/runs/2643588487

Fixes: 1ade23711971 ("bpf: Inline calls to bpf_loop when callback is known")
Signed-off-by: Matthieu Baerts <matthieu.baerts@...sares.net>
---

Notes:
    v2: switch from 'bool' to 'unsigned int' (Yonghong Song)

 include/linux/bpf_verifier.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 81b19669efba..2e3bad8640dc 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -345,10 +345,10 @@ struct bpf_verifier_state_list {
 };
 
 struct bpf_loop_inline_state {
-	int initialized:1; /* set to true upon first entry */
-	int fit_for_inline:1; /* true if callback function is the same
-			       * at each call and flags are always zero
-			       */
+	unsigned int initialized:1; /* set to true upon first entry */
+	unsigned int fit_for_inline:1; /* true if callback function is the same
+					* at each call and flags are always zero
+					*/
 	u32 callback_subprogno; /* valid when fit_for_inline is true */
 };
 
-- 
2.36.1