selftests/bpf: Test bpf_program__clone() attach_btf_id override

Add a test that verifies bpf_program__clone() respects caller-provided
attach_btf_id in bpf_prog_load_opts.

The BPF program has SEC("fentry/bpf_fentry_test1"). It is cloned twice
from the same prepared object: first with no opts, verifying the
callback resolves attach_btf_id from sec_name to bpf_fentry_test1;
then with attach_btf_id overridden to bpf_fentry_test2, verifying the
loaded program is actually attached to bpf_fentry_test2. Both results
are checked via bpf_prog_get_info_by_fd().

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260317-veristat_prepare-v4-3-74193d4cc9d9@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/clone_attach_btf_id.c b/tools/testing/selftests/bpf/prog_tests/clone_attach_btf_id.c
new file mode 100644 (file)
index 0000000..1c3e28e
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/clone_attach_btf_id.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta */
+#include <test_progs.h>
+#include "clone_attach_btf_id.skel.h"
+
+/*
+ * Test that bpf_program__clone() respects caller-provided attach_btf_id
+ * override via bpf_prog_load_opts.
+ *
+ * The BPF program has SEC("fentry/bpf_fentry_test1"). Clone it twice
+ * from the same prepared object: first with no opts (callback resolves
+ * attach_btf_id from sec_name), then with attach_btf_id overridden to
+ * bpf_fentry_test2. Verify each loaded program's attach_btf_id via
+ * bpf_prog_get_info_by_fd().
+ */
+
+static int get_prog_attach_btf_id(int prog_fd)
+{
+       struct bpf_prog_info info = {};
+       __u32 info_len = sizeof(info);
+       int err;
+
+       err = bpf_prog_get_info_by_fd(prog_fd, &info, &info_len);
+       if (err)
+               return err;
+       return info.attach_btf_id;
+}
+
+void test_clone_attach_btf_id(void)
+{
+       struct clone_attach_btf_id *skel;
+       int fd1 = -1, fd2 = -1, err;
+       int btf_id_test1, btf_id_test2;
+
+       btf_id_test1 = libbpf_find_vmlinux_btf_id("bpf_fentry_test1", BPF_TRACE_FENTRY);
+       if (!ASSERT_GT(btf_id_test1, 0, "find_btf_id_test1"))
+               return;
+
+       btf_id_test2 = libbpf_find_vmlinux_btf_id("bpf_fentry_test2", BPF_TRACE_FENTRY);
+       if (!ASSERT_GT(btf_id_test2, 0, "find_btf_id_test2"))
+               return;
+
+       skel = clone_attach_btf_id__open();
+       if (!ASSERT_OK_PTR(skel, "skel_open"))
+               return;
+
+       err = bpf_object__prepare(skel->obj);
+       if (!ASSERT_OK(err, "obj_prepare"))
+               goto out;
+
+       /* Clone with no opts — callback resolves BTF from sec_name */
+       fd1 = bpf_program__clone(skel->progs.fentry_handler, NULL);
+       if (!ASSERT_GE(fd1, 0, "clone_default"))
+               goto out;
+       ASSERT_EQ(get_prog_attach_btf_id(fd1), btf_id_test1,
+                 "attach_btf_id_default");
+
+       /*
+        * Clone with attach_btf_id override pointing to a different
+        * function. The BPF program never accesses arguments, so the
+        * load succeeds regardless of signature mismatch.
+        */
+       LIBBPF_OPTS(bpf_prog_load_opts, opts,
+                   .attach_btf_id = btf_id_test2,
+       );
+       fd2 = bpf_program__clone(skel->progs.fentry_handler, &opts);
+       if (!ASSERT_GE(fd2, 0, "clone_override"))
+               goto out;
+       ASSERT_EQ(get_prog_attach_btf_id(fd2), btf_id_test2,
+                 "attach_btf_id_override");
+
+out:
+       if (fd1 >= 0)
+               close(fd1);
+       if (fd2 >= 0)
+               close(fd2);
+       clone_attach_btf_id__destroy(skel);
+}

diff --git a/tools/testing/selftests/bpf/progs/clone_attach_btf_id.c b/tools/testing/selftests/bpf/progs/clone_attach_btf_id.c
new file mode 100644 (file)
index 0000000..0ffa3ec
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/clone_attach_btf_id.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(fentry_handler, int a)
+{
+       return 0;
+}