Apparently, no existing selftest covers it. Add a new one where
we load cgroup/bind4 program and attach fentry to it.
Calling bpf_obj_get_info_by_fd on the fentry program
should return non-zero btf_id/btf_obj_id instead of crashing the kernel.
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/attach_to_bpf.c | 109 ++++++++++++++++++
.../selftests/bpf/progs/attach_to_bpf.c | 12 ++
2 files changed, 121 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
create mode 100644 tools/testing/selftests/bpf/progs/attach_to_bpf.c
diff --git a/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
new file mode 100644
index 000000000000..fcf726c5ff0f
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <bpf/btf.h>
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "attach_to_bpf.skel.h"
+
+char bpf_log_buf[BPF_LOG_BUF_SIZE];
+
+static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)
+{
+ struct bpf_prog_info info = {};
+ __u32 info_len = sizeof(info);
+ struct btf *btf;
+ int err;
+
+ err = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);
+ if (err)
+ return err;
+
+ if (!info.btf_id)
+ return -EINVAL;
+
+ btf = btf__load_from_kernel_by_id(info.btf_id);
+ err = libbpf_get_error(btf);
+ if (err)
+ return err;
+
+ err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
+ btf__free(btf);
+ if (err <= 0)
+ return err;
+
+ return err;
+}
+
+int load_fentry(int attach_prog_fd, int attach_btf_id)
+{
+ LIBBPF_OPTS(bpf_prog_load_opts, opts,
+ .expected_attach_type = BPF_TRACE_FENTRY,
+ .attach_prog_fd = attach_prog_fd,
+ .attach_btf_id = attach_btf_id,
+ .log_buf = bpf_log_buf,
+ .log_size = sizeof(bpf_log_buf),
+ );
+ struct bpf_insn insns[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ int ret;
+
+ ret = bpf_prog_load(BPF_PROG_TYPE_TRACING,
+ "bind4_fentry",
+ "GPL",
+ insns,
+ ARRAY_SIZE(insns),
+ &opts);
+ if (ret)
+ printf("verifier log: %s\n", bpf_log_buf);
+ return ret;
+}
+
+void test_attach_to_bpf(void)
+{
+ struct attach_to_bpf *skel = NULL;
+ struct bpf_prog_info info = {};
+ __u32 info_len = sizeof(info);
+ int cgroup_fd = -1;
+ int fentry_fd = -1;
+ int btf_id;
+
+ cgroup_fd = test__join_cgroup("/attach_to_bpf");
+ if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
+ return;
+
+ skel = attach_to_bpf__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel"))
+ goto cleanup;
+
+ skel->links.bind4 = bpf_program__attach_cgroup(skel->progs.bind4, cgroup_fd);
+ if (!ASSERT_OK_PTR(skel, "bpf_program__attach_cgroup"))
+ goto cleanup;
+
+ btf_id = find_prog_btf_id("bind4", bpf_program__fd(skel->progs.bind4));
+ if (!ASSERT_GE(btf_id, 0, "find_prog_btf_id"))
+ goto cleanup;
+
+ fentry_fd = load_fentry(bpf_program__fd(skel->progs.bind4), btf_id);
+ if (!ASSERT_GE(fentry_fd, 0, "load_fentry"))
+ goto cleanup;
+
+ /* Make sure bpf_obj_get_info_by_fd works correctly when attaching
+ * to another BPF program.
+ */
+
+ if (!ASSERT_OK(bpf_obj_get_info_by_fd(fentry_fd, &info, &info_len),
+ "bpf_obj_get_info_by_fd"))
+ goto cleanup;
+
+ ASSERT_EQ(info.btf_id, 0, "info.btf_id");
+ ASSERT_GT(info.attach_btf_id, 0, "info.attach_btf_id");
+ ASSERT_GT(info.attach_btf_obj_id, 0, "info.attach_btf_obj_id");
+
+cleanup:
+ close(cgroup_fd);
+ close(fentry_fd);
+ attach_to_bpf__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/attach_to_bpf.c b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
new file mode 100644
index 000000000000..3f111fe96f8f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("cgroup/bind4")
+int bind4(struct bpf_sock_addr *ctx)
+{
+ return 1;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.37.1.455.g008518b4e5-goog
