selftests/bpf: Add a test with bpf_timer in inner map.

Check that map-in-map supports bpf timers.

Check that indirect "recursion" of timer callbacks works:
timer_cb1() { bpf_timer_set_callback(timer_cb2); }
timer_cb2() { bpf_timer_set_callback(timer_cb1); }

Check that
  bpf_map_release
    htab_free_prealloced_timers
      bpf_timer_cancel_and_free
        hrtimer_cancel
works while timer cb is running.
"while true; do ./test_progs -t timer_mim; done"
is a great stress test. It caught missing timer cancel in htab->extra_elems.

timer_mim_reject.c is a negative test that checks
that timer<->map mismatch is prevented.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-12-alexei.starovoitov@gmail.com

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

@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <test_progs.h>
+#include "timer_mim.skel.h"
+#include "timer_mim_reject.skel.h"
+
+static int timer_mim(struct timer_mim *timer_skel)
+{
+	__u32 duration = 0, retval;
+	__u64 cnt1, cnt2;
+	int err, prog_fd, key1 = 1;
+
+	err = timer_mim__attach(timer_skel);
+	if (!ASSERT_OK(err, "timer_attach"))
+		return err;
+
+	prog_fd = bpf_program__fd(timer_skel->progs.test1);
+	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
+				NULL, NULL, &retval, &duration);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(retval, 0, "test_run");
+	timer_mim__detach(timer_skel);
+
+	/* check that timer_cb[12] are incrementing 'cnt' */
+	cnt1 = READ_ONCE(timer_skel->bss->cnt);
+	usleep(200); /* 100 times more than interval */
+	cnt2 = READ_ONCE(timer_skel->bss->cnt);
+	ASSERT_GT(cnt2, cnt1, "cnt");
+
+	ASSERT_EQ(timer_skel->bss->err, 0, "err");
+	/* check that code paths completed */
+	ASSERT_EQ(timer_skel->bss->ok, 1 | 2, "ok");
+
+	close(bpf_map__fd(timer_skel->maps.inner_htab));
+	err = bpf_map_delete_elem(bpf_map__fd(timer_skel->maps.outer_arr), &key1);
+	ASSERT_EQ(err, 0, "delete inner map");
+
+	/* check that timer_cb[12] are no longer running */
+	cnt1 = READ_ONCE(timer_skel->bss->cnt);
+	usleep(200);
+	cnt2 = READ_ONCE(timer_skel->bss->cnt);
+	ASSERT_EQ(cnt2, cnt1, "cnt");
+
+	return 0;
+}
+
+void test_timer_mim(void)
+{
+	struct timer_mim_reject *timer_reject_skel = NULL;
+	libbpf_print_fn_t old_print_fn = NULL;
+	struct timer_mim *timer_skel = NULL;
+	int err;
+
+	old_print_fn = libbpf_set_print(NULL);
+	timer_reject_skel = timer_mim_reject__open_and_load();
+	libbpf_set_print(old_print_fn);
+	if (!ASSERT_ERR_PTR(timer_reject_skel, "timer_reject_skel_load"))
+		goto cleanup;
+
+	timer_skel = timer_mim__open_and_load();
+	if (!ASSERT_OK_PTR(timer_skel, "timer_skel_load"))
+		goto cleanup;
+
+	err = timer_mim(timer_skel);
+	ASSERT_OK(err, "timer_mim");
+cleanup:
+	timer_mim__destroy(timer_skel);
+	timer_mim_reject__destroy(timer_reject_skel);
+}

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

@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <linux/bpf.h>
+#include <time.h>
+#include <errno.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_tcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+struct hmap_elem {
+	int pad; /* unused */
+	struct bpf_timer timer;
+};
+
+struct inner_map {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, 1024);
+	__type(key, int);
+	__type(value, struct hmap_elem);
+} inner_htab SEC(".maps");
+
+#define ARRAY_KEY 1
+#define HASH_KEY 1234
+
+struct outer_arr {
+	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+	__uint(max_entries, 2);
+	__uint(key_size, sizeof(int));
+	__uint(value_size, sizeof(int));
+	__array(values, struct inner_map);
+} outer_arr SEC(".maps") = {
+	.values = { [ARRAY_KEY] = &inner_htab },
+};
+
+__u64 err;
+__u64 ok;
+__u64 cnt;
+
+static int timer_cb1(void *map, int *key, struct hmap_elem *val);
+
+static int timer_cb2(void *map, int *key, struct hmap_elem *val)
+{
+	cnt++;
+	bpf_timer_set_callback(&val->timer, timer_cb1);
+	if (bpf_timer_start(&val->timer, 1000, 0))
+		err |= 1;
+	ok |= 1;
+	return 0;
+}
+
+/* callback for inner hash map */
+static int timer_cb1(void *map, int *key, struct hmap_elem *val)
+{
+	cnt++;
+	bpf_timer_set_callback(&val->timer, timer_cb2);
+	if (bpf_timer_start(&val->timer, 1000, 0))
+		err |= 2;
+	/* Do a lookup to make sure 'map' and 'key' pointers are correct */
+	bpf_map_lookup_elem(map, key);
+	ok |= 2;
+	return 0;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(test1, int a)
+{
+	struct hmap_elem init = {};
+	struct bpf_map *inner_map;
+	struct hmap_elem *val;
+	int array_key = ARRAY_KEY;
+	int hash_key = HASH_KEY;
+
+	inner_map = bpf_map_lookup_elem(&outer_arr, &array_key);
+	if (!inner_map)
+		return 0;
+
+	bpf_map_update_elem(inner_map, &hash_key, &init, 0);
+	val = bpf_map_lookup_elem(inner_map, &hash_key);
+	if (!val)
+		return 0;
+
+	bpf_timer_init(&val->timer, inner_map, CLOCK_MONOTONIC);
+	if (bpf_timer_set_callback(&val->timer, timer_cb1))
+		err |= 4;
+	if (bpf_timer_start(&val->timer, 0, 0))
+		err |= 8;
+	return 0;
+}

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

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <linux/bpf.h>
+#include <time.h>
+#include <errno.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_tcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+struct hmap_elem {
+	int pad; /* unused */
+	struct bpf_timer timer;
+};
+
+struct inner_map {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, 1024);
+	__type(key, int);
+	__type(value, struct hmap_elem);
+} inner_htab SEC(".maps");
+
+#define ARRAY_KEY 1
+#define ARRAY_KEY2 2
+#define HASH_KEY 1234
+
+struct outer_arr {
+	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+	__uint(max_entries, 2);
+	__uint(key_size, sizeof(int));
+	__uint(value_size, sizeof(int));
+	__array(values, struct inner_map);
+} outer_arr SEC(".maps") = {
+	.values = { [ARRAY_KEY] = &inner_htab },
+};
+
+__u64 err;
+__u64 ok;
+__u64 cnt;
+
+/* callback for inner hash map */
+static int timer_cb(void *map, int *key, struct hmap_elem *val)
+{
+	return 0;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(test1, int a)
+{
+	struct hmap_elem init = {};
+	struct bpf_map *inner_map, *inner_map2;
+	struct hmap_elem *val;
+	int array_key = ARRAY_KEY;
+	int array_key2 = ARRAY_KEY2;
+	int hash_key = HASH_KEY;
+
+	inner_map = bpf_map_lookup_elem(&outer_arr, &array_key);
+	if (!inner_map)
+		return 0;
+
+	inner_map2 = bpf_map_lookup_elem(&outer_arr, &array_key2);
+	if (!inner_map2)
+		return 0;
+	bpf_map_update_elem(inner_map, &hash_key, &init, 0);
+	val = bpf_map_lookup_elem(inner_map, &hash_key);
+	if (!val)
+		return 0;
+
+	bpf_timer_init(&val->timer, inner_map2, CLOCK_MONOTONIC);
+	if (bpf_timer_set_callback(&val->timer, timer_cb))
+		err |= 4;
+	if (bpf_timer_start(&val->timer, 0, 0))
+		err |= 8;
+	return 0;
+}