On Fri, Nov 8, 2019 at 1:33 PM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
>
> From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
>
> 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@xxxxxx>
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> ---
> 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...
> }
>
>
