Recently issues were observed with module BTF deduplication failures
[1]. Add a dedup selftest that ensures that core kernel types are
referenced from split BTF as base BTF types. To do this use bpf_testmod
functions which utilize core kernel types, specifically
ssize_t
bpf_testmod_test_write(struct file *file, struct kobject *kobj,
struct bin_attribute *bin_attr,
char *buf, loff_t off, size_t len);
__bpf_kfunc struct sock *bpf_kfunc_call_test3(struct sock *sk);
__bpf_kfunc void bpf_kfunc_call_test_pass_ctx(struct __sk_buff *skb);
For each of these ensure that the types they reference -
struct file, struct kobject, struct bin_attr etc - are in base BTF.
Note that because bpf_testmod.ko is built with distilled base BTF
the associated reference types - i.e. the PTR that points at a
"struct file" - will be in split BTF. As a result the test resolves
typedef and pointer references and verifies the pointed-at or
typedef'ed type is in base BTF. Because we use BTF from
/sys/kernel/btf/bpf_testmod relocation has occurred for the
referenced types and they will be base - not distilled base - types.
For large-scale dedup issues, we see such types appear in split BTF and
as a result this test fails. Hence it is proposed as a test which will
fail when large-scale dedup issues have occurred.
[1] https://lore.kernel.org/dwarves/CAADnVQL+-LiJGXwxD3jEUrOonO-fX0SZC8496dVzUXvfkB7gYQ@xxxxxxxxxxxxxx/
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
.../bpf/prog_tests/btf_dedup_split.c | 101 ++++++++++++++++++
1 file changed, 101 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c b/tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c
index d9024c7a892a..5bc15bb6b7ce 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c
@@ -440,6 +440,105 @@ static void test_split_dup_struct_in_cu()
btf__free(btf1);
}
+/* Ensure module split BTF dedup worked correctly; when dedup fails badly
+ * core kernel types are in split BTF also, so ensure that references to
+ * such types point at base - not split - BTF.
+ *
+ * bpf_testmod_test_write() has multiple core kernel type parameters;
+ *
+ * ssize_t
+ * bpf_testmod_test_write(struct file *file, struct kobject *kobj,
+ * struct bin_attribute *bin_attr,
+ * char *buf, loff_t off, size_t len);
+ *
+ * Ensure each of the FUNC_PROTO params is a core kernel type.
+ *
+ * Do the same for
+ *
+ * __bpf_kfunc struct sock *bpf_kfunc_call_test3(struct sock *sk);
+ *
+ * ...and
+ *
+ * __bpf_kfunc void bpf_kfunc_call_test_pass_ctx(struct __sk_buff *skb);
+ *
+ */
+const char *mod_funcs[] = {
+ "bpf_testmod_test_write",
+ "bpf_kfunc_call_test3",
+ "bpf_kfunc_call_test_pass_ctx"
+};
+
+static void test_split_module(void)
+{
+ struct btf *vmlinux_btf, *btf1 = NULL;
+ int i, nr_base_types;
+
+ vmlinux_btf = btf__load_vmlinux_btf();
+ if (!ASSERT_OK_PTR(vmlinux_btf, "vmlinux_btf"))
+ return;
+ nr_base_types = btf__type_cnt(vmlinux_btf);
+ if (!ASSERT_GT(nr_base_types, 0, "nr_base_types"))
+ goto cleanup;
+
+ btf1 = btf__parse_split("/sys/kernel/btf/bpf_testmod", vmlinux_btf);
+ if (!ASSERT_OK_PTR(btf1, "split_btf"))
+ return;
+
+ for (i = 0; i < ARRAY_SIZE(mod_funcs); i++) {
+ const struct btf_param *p;
+ const struct btf_type *t;
+ __u16 vlen;
+ __u32 id;
+ int j;
+
+ id = btf__find_by_name_kind(btf1, mod_funcs[i], BTF_KIND_FUNC);
+ if (!ASSERT_GE(id, nr_base_types, "func_id"))
+ goto cleanup;
+ t = btf__type_by_id(btf1, id);
+ if (!ASSERT_OK_PTR(t, "func_id_type"))
+ goto cleanup;
+ t = btf__type_by_id(btf1, t->type);
+ if (!ASSERT_OK_PTR(t, "func_proto_id_type"))
+ goto cleanup;
+ if (!ASSERT_EQ(btf_is_func_proto(t), true, "is_func_proto"))
+ goto cleanup;
+ vlen = btf_vlen(t);
+
+ for (j = 0, p = btf_params(t); j < vlen; j++, p++) {
+ /* bpf_testmod uses resilient split BTF, so any
+ * reference types will be added to split BTF and their
+ * associated targets will be base BTF types; for example
+ * for a "struct sock *" the PTR will be in split BTF
+ * while the "struct sock" will be in base.
+ *
+ * In some cases like loff_t we have to resolve
+ * multiple typedefs hence the while() loop below.
+ *
+ * Note that resilient split BTF generation depends
+ * on pahole version, so we do not assert that
+ * reference types are in split BTF, as if pahole
+ * does not support resilient split BTF they will
+ * also be base BTF types.
+ */
+ id = p->type;
+ do {
+ t = btf__type_by_id(btf1, id);
+ if (!ASSERT_OK_PTR(t, "param_ref_type"))
+ goto cleanup;
+ if (!btf_is_mod(t) && !btf_is_ptr(t) && !btf_is_typedef(t))
+ break;
+ id = t->type;
+ } while (true);
+
+ if (!ASSERT_LT(id, nr_base_types, "verify_base_type"))
+ goto cleanup;
+ }
+ }
+cleanup:
+ btf__free(btf1);
+ btf__free(vmlinux_btf);
+}
+
void test_btf_dedup_split()
{
if (test__start_subtest("split_simple"))
@@ -450,4 +549,6 @@ void test_btf_dedup_split()
test_split_fwd_resolve();
if (test__start_subtest("split_dup_struct_in_cu"))
test_split_dup_struct_in_cu();
+ if (test__start_subtest("split_module"))
+ test_split_module();
}
--
2.39.3
