Re: [PATCH v2 bpf-next 3/3] libbpf: add BTF-defined map-in-map support

On Tue, Apr 28, 2020 at 11:03 AM Alexei Starovoitov
[off-list ref] wrote:

On Mon, Apr 27, 2020 at 11:41:39PM -0700, Andrii Nakryiko wrote:

quoted

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index 60aad054eea1..e3a6e9a1f5b4 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h

@@ -12,6 +12,7 @@

 #define __uint(name, val) int (*name)[val]
 #define __type(name, val) typeof(val) *name
+#define __inner(name, val) typeof(val) *name[]

...

quoted

+++ b/tools/testing/selftests/bpf/progs/test_btf_map_in_map.c

@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2020 Facebook */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+struct inner_map {
+     __uint(type, BPF_MAP_TYPE_ARRAY);
+     __uint(max_entries, 1);
+     __type(key, int);
+     __type(value, int);
+} inner_map1 SEC(".maps"),
+  inner_map2 SEC(".maps");
+
+struct outer_arr {
+     __uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+     __uint(max_entries, 3);
+     __uint(key_size, sizeof(int));
+     __uint(value_size, sizeof(int));
+     /* it's possible to use anonymous struct as inner map definition here */
+     __inner(values, struct {
+             __uint(type, BPF_MAP_TYPE_ARRAY);
+             /* changing max_entries to 2 will fail during load
+              * due to incompatibility with inner_map definition */
+             __uint(max_entries, 1);
+             __type(key, int);
+             __type(value, int);
+     });

How about renaming it s/__inner/__array/ ?
Because that's what it defines from BTF pov.

Sounds good, will update.