libbpf: Prevent overriding errno when logging errors

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@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200813142905.160381-1-toke@redhat.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0a06124f7999ad4484c9b4dc3c7c8ab6467e462f..0d48c18d5030a79777b449741750655dec16cd24 100644 (file)
--- 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));
                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);