[PATCH RESEND v3 bpf-next 09/14] selftests/bpf: add BPF token-enabled BPF_BTF_LOAD selftest

[Andrii Nakryiko <andrii@xxxxxxxxxx>]

Add a simple test validating that BTF loading can be done from
unprivileged process through delegated BPF token.

Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
 .../testing/selftests/bpf/prog_tests/token.c  | 60 +++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
index 0f832f9178a2..113cd4786a70 100644
--- a/tools/testing/selftests/bpf/prog_tests/token.c
+++ b/tools/testing/selftests/bpf/prog_tests/token.c
@@ -142,10 +142,70 @@ static void subtest_map_token(void)
 		ASSERT_OK(restore_priv_caps(old_caps), "restore_caps");
 }
 
+static void subtest_btf_token(void)
+{
+	LIBBPF_OPTS(bpf_token_create_opts, token_opts);
+	LIBBPF_OPTS(bpf_btf_load_opts, btf_opts);
+	int token_fd = 0, btf_fd = 0, err;
+	const void *raw_btf_data;
+	struct btf *btf = NULL;
+	__u32 raw_btf_size;
+	__u64 old_caps = 0;
+
+	/* create BPF token allowing BPF_BTF_LOAD command */
+	token_opts.allowed_cmds = 1ULL << BPF_BTF_LOAD;
+	err = bpf_token_create(-EBADF, TOKEN_PATH, &token_opts);
+	if (!ASSERT_OK(err, "token_create"))
+		return;
+
+	/* drop privileges to test token_fd passing */
+	if (!ASSERT_OK(drop_priv_caps(&old_caps), "drop_caps"))
+		goto cleanup;
+
+	token_fd = bpf_obj_get(TOKEN_PATH);
+	if (!ASSERT_GT(token_fd, 0, "token_get"))
+		goto cleanup;
+
+	btf = btf__new_empty();
+	if (!ASSERT_OK_PTR(btf, "empty_btf"))
+		goto cleanup;
+
+	ASSERT_GT(btf__add_int(btf, "int", 4, 0), 0, "int_type");
+
+	raw_btf_data = btf__raw_data(btf, &raw_btf_size);
+	if (!ASSERT_OK_PTR(raw_btf_data, "raw_btf_data"))
+		goto cleanup;
+
+	/* validate we can successfully load new BTF with token */
+	btf_opts.token_fd = token_fd;
+	btf_fd = bpf_btf_load(raw_btf_data, raw_btf_size, &btf_opts);
+	if (!ASSERT_GT(btf_fd, 0, "btf_fd"))
+		goto cleanup;
+	close(btf_fd);
+
+	/* now validate that we *cannot* load BTF without token */
+	btf_opts.token_fd = 0;
+	btf_fd = bpf_btf_load(raw_btf_data, raw_btf_size, &btf_opts);
+	if (!ASSERT_EQ(btf_fd, -EPERM, "btf_fd_eperm"))
+		goto cleanup;
+
+cleanup:
+	btf__free(btf);
+	if (btf_fd > 0)
+		close(btf_fd);
+	if (token_fd)
+		close(token_fd);
+	unlink(TOKEN_PATH);
+	if (old_caps)
+		ASSERT_OK(restore_priv_caps(old_caps), "restore_caps");
+}
+
 void test_token(void)
 {
 	if (test__start_subtest("token_create"))
 		subtest_token_create();
 	if (test__start_subtest("map_token"))
 		subtest_map_token();
+	if (test__start_subtest("btf_token"))
+		subtest_btf_token();
 }
-- 
2.34.1