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From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: 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 14:50:43 -0800	[thread overview]
Message-ID: <CAEf4BzZxcvhZG-FHF+0iqia72q3YA0dCgsgFchibiW7dkFQm2A@mail.gmail.com> (raw)
In-Reply-To: <157324878850.910124.10106029353677591175.stgit@toke.dk>

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;
>         cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
>         pr_warn("load bpf program failed: %s\n", cp);
>
> @@ -3749,7 +3749,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
>                         }
>                 }
>
> -               if (log_buf)
> +               if (log_buf && ret != -EPERM)
>                         ret = -LIBBPF_ERRNO__KVER;

This whole special casing of EPERM looks weird. Should we just pass
through all the errors instead?

But also, I don't think you can assume that if you get EPERM, then it
must be setrlimit problem...


>         }
>
>

  parent reply	other threads:[~2019-11-08 22:50 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 [this message]
2019-11-08 23:17     ` Alexei Starovoitov
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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