selftests/bpf: Test attach rejection for struct_ops arena programs

Exercise fentry, fexit, and freplace programs that target a struct_ops
callback with an arena context argument. Verify each load is rejected with
-EOPNOTSUPP and the arena-specific verifier diagnostic.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260808003938.3486067-15-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>

2 files changed, 79 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_arena.c b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_arena.c
index 323d707c543f..940ec2cda0d5 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_arena.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_arena.c
@@ -3,6 +3,7 @@
 #include <test_progs.h>
 
 #include "struct_ops_arena.skel.h"
+#include "struct_ops_arena_attach.skel.h"
 #include "struct_ops_arena_fail.skel.h"
 
 #if defined(__x86_64__)
@@ -49,6 +50,57 @@ static void arena_arg_fail(void)
 
 	struct_ops_arena_fail__destroy(skel);
 }
+
+static void arena_arg_attach_one(int target_fd, const char *prog_name)
+{
+	struct struct_ops_arena_attach *skel;
+	struct bpf_program *prog, *pos;
+	char log_buf[64 * 1024];
+	int err;
+
+	skel = struct_ops_arena_attach__open();
+	if (!ASSERT_OK_PTR(skel, "struct_ops_arena_attach__open"))
+		return;
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, prog_name))
+		goto out;
+
+	bpf_object__for_each_program(pos, skel->obj)
+		bpf_program__set_autoload(pos, pos == prog);
+
+	err = bpf_program__set_attach_target(prog, target_fd, "test_arena_cb");
+	if (!ASSERT_OK(err, "set_attach_target"))
+		goto out;
+
+	log_buf[0] = '\0';
+	bpf_program__set_log_buf(prog, log_buf, sizeof(log_buf));
+	err = struct_ops_arena_attach__load(skel);
+
+	ASSERT_EQ(err, -EOPNOTSUPP, prog_name);
+	ASSERT_HAS_SUBSTR(log_buf, "Cannot attach to a target with arena context arguments",
+			  "verifier_log");
+
+out:
+	struct_ops_arena_attach__destroy(skel);
+}
+
+static void arena_arg_attach(void)
+{
+	struct struct_ops_arena *skel;
+	int target_fd;
+
+	skel = struct_ops_arena__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "struct_ops_arena__open_and_load"))
+		return;
+
+	target_fd = bpf_program__fd(skel->progs.test_arena_cb);
+	arena_arg_attach_one(target_fd, "fentry_test_arena");
+	arena_arg_attach_one(target_fd, "fexit_test_arena");
+	arena_arg_attach_one(target_fd, "freplace_test_arena");
+
+	struct_ops_arena__destroy(skel);
+}
 #endif
 
 /*
@@ -68,6 +120,8 @@ void serial_test_struct_ops_arena(void)
 		arena_arg();
 	if (test__start_subtest("arena_arg_fail"))
 		arena_arg_fail();
+	if (test__start_subtest("arena_arg_attach"))
+		arena_arg_attach();
 #else
 	test__skip();
 #endif
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_arena_attach.c b/tools/testing/selftests/bpf/progs/struct_ops_arena_attach.c
new file mode 100644
index 000000000000..081a770307e5
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/struct_ops_arena_attach.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+SEC("fentry")
+int BPF_PROG(fentry_test_arena, unsigned long long *st_ops_ctx)
+{
+	return 0;
+}
+
+SEC("fexit")
+int BPF_PROG(fexit_test_arena, unsigned long long *st_ops_ctx, int ret)
+{
+	return 0;
+}
+
+SEC("freplace")
+int freplace_test_arena(unsigned long long *st_ops_ctx)
+{
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";