selftests/bpf: Add struct_ops prog private stack tests

Add three tests for struct_ops using private stack.
  ./test_progs -t struct_ops_private_stack
  #336/1   struct_ops_private_stack/private_stack:OK
  #336/2   struct_ops_private_stack/private_stack_fail:OK
  #336/3   struct_ops_private_stack/private_stack_recur:OK
  #336     struct_ops_private_stack:OK

The following is a snippet of a struct_ops check_member() implementation:

	u32 moff = __btf_member_bit_offset(t, member) / 8;
	switch (moff) {
	case offsetof(struct bpf_testmod_ops3, test_1):
        	prog->aux->priv_stack_requested = true;
                prog->aux->recursion_detected = test_1_recursion_detected;
        	fallthrough;
	default:
        	break;
	}
	return 0;

The first test is with nested two different callback functions where the
first prog has more than 512 byte stack size (including subprogs) with
private stack enabled.

The second test is a negative test where the second prog has more than 512
byte stack size without private stack enabled.

The third test is the same callback function recursing itself. At run time,
the jit trampoline recursion check kicks in to prevent the recursion. The
recursion_detected() callback function is implemented by the bpf_testmod,
the following message in dmesg
  bpf_testmod: oh no, recursing into test_1, recursion_misses 1
demonstrates the callback function is indeed triggered when recursion miss
happens.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20241112163938.2225528-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 104 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 987d41af71d2..cc9dde507aba 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -245,6 +245,39 @@ __bpf_kfunc void bpf_testmod_ctx_release(struct bpf_testmod_ctx *ctx)
 		call_rcu(&ctx->rcu, testmod_free_cb);
 }
 
+static struct bpf_testmod_ops3 *st_ops3;
+
+static int bpf_testmod_test_3(void)
+{
+	return 0;
+}
+
+static int bpf_testmod_test_4(void)
+{
+	return 0;
+}
+
+static struct bpf_testmod_ops3 __bpf_testmod_ops3 = {
+	.test_1 = bpf_testmod_test_3,
+	.test_2 = bpf_testmod_test_4,
+};
+
+static void bpf_testmod_test_struct_ops3(void)
+{
+	if (st_ops3)
+		st_ops3->test_1();
+}
+
+__bpf_kfunc void bpf_testmod_ops3_call_test_1(void)
+{
+	st_ops3->test_1();
+}
+
+__bpf_kfunc void bpf_testmod_ops3_call_test_2(void)
+{
+	st_ops3->test_2();
+}
+
 struct bpf_testmod_btf_type_tag_1 {
 	int a;
 };
@@ -382,6 +415,8 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj,
 
 	(void)trace_bpf_testmod_test_raw_tp_null(NULL);
 
+	bpf_testmod_test_struct_ops3();
+
 	struct_arg3 = kmalloc((sizeof(struct bpf_testmod_struct_arg_3) +
 				sizeof(int)), GFP_KERNEL);
 	if (struct_arg3 != NULL) {
@@ -586,6 +621,8 @@ BTF_ID_FLAGS(func, bpf_kfunc_trusted_num_test, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_kfunc_rcu_task_test, KF_RCU)
 BTF_ID_FLAGS(func, bpf_testmod_ctx_create, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_testmod_ctx_release, KF_RELEASE)
+BTF_ID_FLAGS(func, bpf_testmod_ops3_call_test_1)
+BTF_ID_FLAGS(func, bpf_testmod_ops3_call_test_2)
 BTF_KFUNCS_END(bpf_testmod_common_kfunc_ids)
 
 BTF_ID_LIST(bpf_testmod_dtor_ids)
@@ -1096,6 +1133,10 @@ static const struct bpf_verifier_ops bpf_testmod_verifier_ops = {
 	.is_valid_access = bpf_testmod_ops_is_valid_access,
 };
 
+static const struct bpf_verifier_ops bpf_testmod_verifier_ops3 = {
+	.is_valid_access = bpf_testmod_ops_is_valid_access,
+};
+
 static int bpf_dummy_reg(void *kdata, struct bpf_link *link)
 {
 	struct bpf_testmod_ops *ops = kdata;
@@ -1175,6 +1216,68 @@ struct bpf_struct_ops bpf_testmod_ops2 = {
 	.owner = THIS_MODULE,
 };
 
+static int st_ops3_reg(void *kdata, struct bpf_link *link)
+{
+	int err = 0;
+
+	mutex_lock(&st_ops_mutex);
+	if (st_ops3) {
+		pr_err("st_ops has already been registered\n");
+		err = -EEXIST;
+		goto unlock;
+	}
+	st_ops3 = kdata;
+
+unlock:
+	mutex_unlock(&st_ops_mutex);
+	return err;
+}
+
+static void st_ops3_unreg(void *kdata, struct bpf_link *link)
+{
+	mutex_lock(&st_ops_mutex);
+	st_ops3 = NULL;
+	mutex_unlock(&st_ops_mutex);
+}
+
+static void test_1_recursion_detected(struct bpf_prog *prog)
+{
+	struct bpf_prog_stats *stats;
+
+	stats = this_cpu_ptr(prog->stats);
+	printk("bpf_testmod: oh no, recursing into test_1, recursion_misses %llu",
+	       u64_stats_read(&stats->misses));
+}
+
+static int st_ops3_check_member(const struct btf_type *t,
+				const struct btf_member *member,
+				const struct bpf_prog *prog)
+{
+	u32 moff = __btf_member_bit_offset(t, member) / 8;
+
+	switch (moff) {
+	case offsetof(struct bpf_testmod_ops3, test_1):
+		prog->aux->priv_stack_requested = true;
+		prog->aux->recursion_detected = test_1_recursion_detected;
+		fallthrough;
+	default:
+		break;
+	}
+	return 0;
+}
+
+struct bpf_struct_ops bpf_testmod_ops3 = {
+	.verifier_ops = &bpf_testmod_verifier_ops3,
+	.init = bpf_testmod_ops_init,
+	.init_member = bpf_testmod_ops_init_member,
+	.reg = st_ops3_reg,
+	.unreg = st_ops3_unreg,
+	.check_member = st_ops3_check_member,
+	.cfi_stubs = &__bpf_testmod_ops3,
+	.name = "bpf_testmod_ops3",
+	.owner = THIS_MODULE,
+};
+
 static int bpf_test_mod_st_ops__test_prologue(struct st_ops_args *args)
 {
 	return 0;
@@ -1333,6 +1436,7 @@ static int bpf_testmod_init(void)
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_bpf_struct_ops(&bpf_bpf_testmod_ops, bpf_testmod_ops);
 	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops2, bpf_testmod_ops2);
+	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops3, bpf_testmod_ops3);
 	ret = ret ?: register_bpf_struct_ops(&testmod_st_ops, bpf_testmod_st_ops);
 	ret = ret ?: register_btf_id_dtor_kfuncs(bpf_testmod_dtors,
 						 ARRAY_SIZE(bpf_testmod_dtors),