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Thu, 13 Aug 2020 13:52:23 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id r3sm11137607wro.1.2020.08.13.13.52.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Aug 2020 13:52:22 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 500A5180493; Thu, 13 Aug 2020 22:52:22 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Daniel Borkmann , Andrii Nakryiko Cc: Alexei Starovoitov , Networking , bpf Subject: Re: [PATCH bpf] libbpf: Prevent overriding errno when logging errors In-Reply-To: <868b8e78-f0ae-8e59-1816-92051acba1f5@iogearbox.net> References: <20200813142905.160381-1-toke@redhat.com> <87d03u1fyj.fsf@toke.dk> <868b8e78-f0ae-8e59-1816-92051acba1f5@iogearbox.net> X-Clacks-Overhead: GNU Terry Pratchett Date: Thu, 13 Aug 2020 22:52:22 +0200 Message-ID: <87a6yy1d6h.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Daniel Borkmann writes: > On 8/13/20 9:52 PM, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> Andrii Nakryiko writes: >>> On Thu, Aug 13, 2020 at 7:29 AM Toke H=C3=B8iland-J=C3=B8rgensen wrote: >>>> >>>> Turns out there were a few more instances where libbpf didn't save the >>>> errno before writing an error message, causing errno to be overridden = by >>>> the printf() return and the error disappearing if logging is enabled. >>>> >>>> Signed-off-by: Toke H=C3=B8iland-J=C3=B8rgensen >>>> --- >>> >>> Acked-by: Andrii Nakryiko >>> >>>> tools/lib/bpf/libbpf.c | 12 +++++++----- >>>> 1 file changed, 7 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c >>>> index 0a06124f7999..fd256440e233 100644 >>>> --- a/tools/lib/bpf/libbpf.c >>>> +++ b/tools/lib/bpf/libbpf.c >>>> @@ -3478,10 +3478,11 @@ bpf_object__probe_global_data(struct bpf_objec= t *obj) >>>> >>>> map =3D bpf_create_map_xattr(&map_attr); >>>> if (map < 0) { >>>> - cp =3D libbpf_strerror_r(errno, errmsg, sizeof(errmsg)= ); >>>> + ret =3D -errno; >>>> + cp =3D libbpf_strerror_r(-ret, errmsg, sizeof(errmsg)); >>> >>> fyi, libbpf_strerror_r() is smart enough to work with both negative >>> and positive error numbers (it basically takes abs(err)), so no need >>> to ensure it's positive here and below. >>=20 >> Noted. Although that also means it doesn't hurt either, I suppose; so >> not going to bother respinning this unless someone insists :) > > Fixed up while applying, thanks! Great, thanks! -Toke