From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Alexei Starovoitov" <ast@kernel.org>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"David Miller" <davem@davemloft.net>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next v2 3/6] libbpf: Propagate EPERM to caller on program load
Date: Fri, 8 Nov 2019 15:17:58 -0800 [thread overview]
Message-ID: <20191108231757.7egzqebli6gcplfq@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <CAEf4BzZxcvhZG-FHF+0iqia72q3YA0dCgsgFchibiW7dkFQm2A@mail.gmail.com>
On Fri, Nov 08, 2019 at 02:50:43PM -0800, Andrii Nakryiko wrote:
> On Fri, Nov 8, 2019 at 1:33 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> >
> > From: Toke Høiland-Jørgensen <toke@redhat.com>
> >
> > When loading an eBPF program, libbpf overrides the return code for EPERM
> > errors instead of returning it to the caller. This makes it hard to figure
> > out what went wrong on load.
> >
> > In particular, EPERM is returned when the system rlimit is too low to lock
> > the memory required for the BPF program. Previously, this was somewhat
> > obscured because the rlimit error would be hit on map creation (which does
> > return it correctly). However, since maps can now be reused, object load
> > can proceed all the way to loading programs without hitting the error;
> > propagating it even in this case makes it possible for the caller to react
> > appropriately (and, e.g., attempt to raise the rlimit before retrying).
> >
> > Acked-by: Song Liu <songliubraving@fb.com>
> > Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> > ---
> > tools/lib/bpf/libbpf.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index cea61b2ec9d3..582c0fd16697 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -3721,7 +3721,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
> > free(log_buf);
> > goto retry_load;
> > }
> > - ret = -LIBBPF_ERRNO__LOAD;
> > + ret = (errno == EPERM) ? -errno : -LIBBPF_ERRNO__LOAD;
ouch. so libbpf was supressing all errnos for loading and that was a commit
from 2015. No wonder it's hard to debug. I grepped every where I could and it
doesn't look like anyone is using this code. There are other codes that can
come from sys_bpf(prog_load). Not sure why such decision was made back then. I
guess noone was really paying attention. I think we better propagate all codes.
I don't see why EPERM should be special.
next prev parent reply other threads:[~2019-11-08 23:18 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-08 21:33 [PATCH bpf-next v2 0/6] libbpf: Fix pinning and error message bugs and add new getters Toke Høiland-Jørgensen
2019-11-08 21:33 ` [PATCH bpf-next v2 1/6] libbpf: Unpin auto-pinned maps if loading fails Toke Høiland-Jørgensen
2019-11-08 21:41 ` David Miller
2019-11-08 22:40 ` Andrii Nakryiko
2019-11-08 23:33 ` Toke Høiland-Jørgensen
2019-11-08 23:35 ` Andrii Nakryiko
2019-11-08 21:33 ` [PATCH bpf-next v2 2/6] selftests/bpf: Add tests for automatic map unpinning on load failure Toke Høiland-Jørgensen
2019-11-08 21:41 ` David Miller
2019-11-08 22:00 ` Song Liu
2019-11-08 22:43 ` Andrii Nakryiko
2019-11-08 21:33 ` [PATCH bpf-next v2 3/6] libbpf: Propagate EPERM to caller on program load Toke Høiland-Jørgensen
2019-11-08 21:43 ` David Miller
2019-11-08 22:50 ` Andrii Nakryiko
2019-11-08 23:17 ` Alexei Starovoitov [this message]
2019-11-08 23:32 ` Toke Høiland-Jørgensen
2019-11-08 21:33 ` [PATCH bpf-next v2 4/6] libbpf: Use pr_warn() when printing netlink errors Toke Høiland-Jørgensen
2019-11-08 21:43 ` David Miller
2019-11-08 22:52 ` Andrii Nakryiko
2019-11-08 21:33 ` [PATCH bpf-next v2 5/6] libbpf: Add bpf_get_link_xdp_info() function to get more XDP information Toke Høiland-Jørgensen
2019-11-08 21:43 ` David Miller
2019-11-08 23:10 ` Andrii Nakryiko
2019-11-08 21:33 ` [PATCH bpf-next v2 6/6] libbpf: Add getter for program size Toke Høiland-Jørgensen
2019-11-08 21:43 ` David Miller
2019-11-08 23:16 ` Andrii Nakryiko
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