Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 21 Apr 2022 00:39:57 +0000
To:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>
From:   Alexander Lobakin <alobakin@pm.me>
Cc:     Alexander Lobakin <alobakin@pm.me>,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Song Liu <songliubraving@fb.com>,
        Kumar Kartikeya Dwivedi <memxor@gmail.com>,
        bpf@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Reply-To: Alexander Lobakin <alobakin@pm.me>
Subject: [PATCH v2 bpf 11/11] samples/bpf: xdpsock: fix -Wmaybe-uninitialized
Message-ID: <20220421003152.339542-12-alobakin@pm.me>
In-Reply-To: <20220421003152.339542-1-alobakin@pm.me>
References: <20220421003152.339542-1-alobakin@pm.me>
Feedback-ID: 22809121:user:proton
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Fix two sort-of-false-positives in the xdpsock userspace part:

samples/bpf/xdpsock_user.c: In function 'main':
samples/bpf/xdpsock_user.c:1531:47: warning: 'tv_usec' may be used uninitia=
lized in this function [-Wmaybe-uninitialized]
 1531 |                         pktgen_hdr->tv_usec =3D htonl(tv_usec);
      |                                               ^~~~~~~~~~~~~~
samples/bpf/xdpsock_user.c:1500:26: note: 'tv_usec' was declared here
 1500 |         u32 idx, tv_sec, tv_usec;
      |                          ^~~~~~~
samples/bpf/xdpsock_user.c:1530:46: warning: 'tv_sec' may be used uninitial=
ized in this function [-Wmaybe-uninitialized]
 1530 |                         pktgen_hdr->tv_sec =3D htonl(tv_sec);
      |                                              ^~~~~~~~~~~~~
samples/bpf/xdpsock_user.c:1500:18: note: 'tv_sec' was declared here
 1500 |         u32 idx, tv_sec, tv_usec;
      |                  ^~~~~~

Both variables are always initialized when @opt_tstamp =3D=3D true and
they're being used also only when @opt_tstamp =3D=3D true. However, that
variable comes from the BSS and is being toggled from another
function. They can't be executed simultaneously to actually trigger
undefined behaviour, but purely technically it is a correct warning.
Just initialize them with zeroes.

Fixes: eb68db45b747 ("samples/bpf: xdpsock: Add timestamp for Tx-only opera=
tion")
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
---
 samples/bpf/xdpsock_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index 9747d47a0a8f..a6d8291c8b38 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -1497,7 +1497,7 @@ static void rx_drop_all(void)
 static int tx_only(struct xsk_socket_info *xsk, u32 *frame_nb,
 =09=09   int batch_size, unsigned long tx_ns)
 {
-=09u32 idx, tv_sec, tv_usec;
+=09u32 idx, tv_sec =3D 0, tv_usec =3D 0;
 =09unsigned int i;

 =09while (xsk_ring_prod__reserve(&xsk->tx, batch_size, &idx) <
--
2.36.0