selftests/bpf: Add refcounted_kptr tests

Test refcounted local kptr functionality added in previous patches in
the series.

Usecases which pass verification:

* Add refcounted local kptr to both tree and list. Then, read and -
  possibly, depending on test variant - delete from tree, then list.
  * Also test doing read-and-maybe-delete in opposite order
* Stash a refcounted local kptr in a map_value, then add it to a
  rbtree. Read from both, possibly deleting after tree read.
* Add refcounted local kptr to both tree and list. Then, try reading and
  deleting twice from one of the collections.
* bpf_refcount_acquire of just-added non-owning ref should work, as
  should bpf_refcount_acquire of owning ref just out of bpf_obj_new

Usecases which fail verification:

* The simple successful bpf_refcount_acquire cases from above should
  both fail to verify if the newly-acquired owning ref is not dropped

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230415201811.343116-10-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 72 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
new file mode 100644
index 000000000000..efcb308f80ad
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_experimental.h"
+#include "bpf_misc.h"
+
+struct node_acquire {
+	long key;
+	long data;
+	struct bpf_rb_node node;
+	struct bpf_refcount refcount;
+};
+
+#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
+private(A) struct bpf_spin_lock glock;
+private(A) struct bpf_rb_root groot __contains(node_acquire, node);
+
+static bool less(struct bpf_rb_node *a, const struct bpf_rb_node *b)
+{
+	struct node_acquire *node_a;
+	struct node_acquire *node_b;
+
+	node_a = container_of(a, struct node_acquire, node);
+	node_b = container_of(b, struct node_acquire, node);
+
+	return node_a->key < node_b->key;
+}
+
+SEC("?tc")
+__failure __msg("Unreleased reference id=3 alloc_insn=21")
+long rbtree_refcounted_node_ref_escapes(void *ctx)
+{
+	struct node_acquire *n, *m;
+
+	n = bpf_obj_new(typeof(*n));
+	if (!n)
+		return 1;
+
+	bpf_spin_lock(&glock);
+	bpf_rbtree_add(&groot, &n->node, less);
+	/* m becomes an owning ref but is never drop'd or added to a tree */
+	m = bpf_refcount_acquire(n);
+	bpf_spin_unlock(&glock);
+
+	m->key = 2;
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("Unreleased reference id=3 alloc_insn=9")
+long rbtree_refcounted_node_ref_escapes_owning_input(void *ctx)
+{
+	struct node_acquire *n, *m;
+
+	n = bpf_obj_new(typeof(*n));
+	if (!n)
+		return 1;
+
+	/* m becomes an owning ref but is never drop'd or added to a tree */
+	m = bpf_refcount_acquire(n);
+	m->key = 2;
+
+	bpf_spin_lock(&glock);
+	bpf_rbtree_add(&groot, &n->node, less);
+	bpf_spin_unlock(&glock);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";