On Thu, Aug 13, 2020 at 7:29 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> 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 Høiland-Jørgensen <toke@xxxxxxxxxx>
> ---
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
> 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_object *obj)
>
> map = bpf_create_map_xattr(&map_attr);
> if (map < 0) {
> - cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
> + ret = -errno;
> + cp = 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.
> pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
> - __func__, cp, errno);
> - return -errno;
> + __func__, cp, -ret);
> + return ret;
> }
>
> insns[0].imm = map;
> @@ -6012,9 +6013,10 @@ int bpf_program__pin_instance(struct bpf_program *prog, const char *path,
> }
>
> if (bpf_obj_pin(prog->instances.fds[instance], path)) {
> - cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
> + err = -errno;
> + cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
> pr_warn("failed to pin program: %s\n", cp);
> - return -errno;
> + return err;
> }
> pr_debug("pinned program '%s'\n", path);
>
> --
> 2.28.0
>
