Merge branch 'BTF-map-in-map'

Andrii Nakryiko says:

====================
This patch set teaches libbpf how to declare and initialize ARRAY_OF_MAPS and
HASH_OF_MAPS maps. See patch #3 for all the details.

Patch #1 refactors parsing BTF definition of map to re-use it cleanly for
inner map definition parsing.

Patch #2 refactors map creation and destruction logic for reuse. It also fixes
existing bug with not closing successfully created maps when bpf_object map
creation overall fails.

Patch #3 adds support for an extension of BTF-defined map syntax, as well as
parsing, recording, and use of relocations to allow declaratively initialize
outer maps with references to inner maps.

v1->v2:
  - rename __inner to __array (Alexei).
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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 __array(name, val) typeof(val) *name[]
 
 /* Helper macro to print out debug messages */
 #define bpf_printk(fmt, ...)				\

tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <test_progs.h>
+
+#include "test_btf_map_in_map.skel.h"
+
+void test_btf_map_in_map(void)
+{
+	int duration = 0, err, key = 0, val;
+	struct test_btf_map_in_map* skel;
+
+	skel = test_btf_map_in_map__open_and_load();
+	if (CHECK(!skel, "skel_open", "failed to open&load skeleton\n"))
+		return;
+
+	err = test_btf_map_in_map__attach(skel);
+	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
+		goto cleanup;
+
+	/* inner1 = input, inner2 = input + 1 */
+	val = bpf_map__fd(skel->maps.inner_map1);
+	bpf_map_update_elem(bpf_map__fd(skel->maps.outer_arr), &key, &val, 0);
+	val = bpf_map__fd(skel->maps.inner_map2);
+	bpf_map_update_elem(bpf_map__fd(skel->maps.outer_hash), &key, &val, 0);
+	skel->bss->input = 1;
+	usleep(1);
+
+	bpf_map_lookup_elem(bpf_map__fd(skel->maps.inner_map1), &key, &val);
+	CHECK(val != 1, "inner1", "got %d != exp %d\n", val, 1);
+	bpf_map_lookup_elem(bpf_map__fd(skel->maps.inner_map2), &key, &val);
+	CHECK(val != 2, "inner2", "got %d != exp %d\n", val, 2);
+
+	/* inner1 = input + 1, inner2 = input */
+	val = bpf_map__fd(skel->maps.inner_map2);
+	bpf_map_update_elem(bpf_map__fd(skel->maps.outer_arr), &key, &val, 0);
+	val = bpf_map__fd(skel->maps.inner_map1);
+	bpf_map_update_elem(bpf_map__fd(skel->maps.outer_hash), &key, &val, 0);
+	skel->bss->input = 3;
+	usleep(1);
+
+	bpf_map_lookup_elem(bpf_map__fd(skel->maps.inner_map1), &key, &val);
+	CHECK(val != 4, "inner1", "got %d != exp %d\n", val, 4);
+	bpf_map_lookup_elem(bpf_map__fd(skel->maps.inner_map2), &key, &val);
+	CHECK(val != 3, "inner2", "got %d != exp %d\n", val, 3);
+
+cleanup:
+	test_btf_map_in_map__destroy(skel);
+}

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

+/* 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 */
+	__array(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);
+	});
+} outer_arr SEC(".maps") = {
+	/* (void *) cast is necessary because we didn't use `struct inner_map`
+	 * in __inner(values, ...)
+	 * Actually, a conscious effort is required to screw up initialization
+	 * of inner map slots, which is a great thing!
+	 */
+	.values = { (void *)&inner_map1, 0, (void *)&inner_map2 },
+};
+
+struct outer_hash {
+	__uint(type, BPF_MAP_TYPE_HASH_OF_MAPS);
+	__uint(max_entries, 5);
+	__uint(key_size, sizeof(int));
+	/* Here everything works flawlessly due to reuse of struct inner_map
+	 * and compiler will complain at the attempt to use non-inner_map
+	 * references below. This is great experience.
+	 */
+	__array(values, struct inner_map);
+} outer_hash SEC(".maps") = {
+	.values = {
+		[0] = &inner_map2,
+		[4] = &inner_map1,
+	},
+};
+
+int input = 0;
+
+SEC("raw_tp/sys_enter")
+int handle__sys_enter(void *ctx)
+{
+	struct inner_map *inner_map;
+	int key = 0, val;
+
+	inner_map = bpf_map_lookup_elem(&outer_arr, &key);
+	if (!inner_map)
+		return 1;
+	val = input;
+	bpf_map_update_elem(inner_map, &key, &val, 0);
+
+	inner_map = bpf_map_lookup_elem(&outer_hash, &key);
+	if (!inner_map)
+		return 1;
+	val = input + 1;
+	bpf_map_update_elem(inner_map, &key, &val, 0);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";