On Sat, Oct 16, 2021 at 08:48:04PM +0800, Hou Tao wrote:

+static struct bpf_dummy_ops_test_args *
+dummy_ops_init_args(const union bpf_attr *kattr, unsigned int nr)
+{
+	__u32 size_in;
+	struct bpf_dummy_ops_test_args *args;
+	void __user *ctx_in;
+	void __user *u_state;
+
+	if (!nr || nr > MAX_BPF_FUNC_ARGS)
+		return ERR_PTR(-EINVAL);
+
+	size_in = kattr->test.ctx_size_in;
+	if (size_in != sizeof(u64) * nr)
+		return ERR_PTR(-EINVAL);
+
+	args = kzalloc(sizeof(*args), GFP_KERNEL);
+	if (!args)
+		return ERR_PTR(-ENOMEM);
+
+	ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
+	if (copy_from_user(args->args, ctx_in, size_in))

args is leaked.

+		return ERR_PTR(-EFAULT);
+
+	u_state = u64_to_user_ptr(args->args[0]);
+	if (!u_state)
+		return args;
+
+	if (copy_from_user(&args->state, u_state, sizeof(args->state))) {
+		kfree(args);
+		return ERR_PTR(-EFAULT);
+	}
+
+	return args;
+}

[ ... ]

+int bpf_dummy_struct_ops_test_run(struct bpf_prog *prog,
+				  const union bpf_attr *kattr,
+				  union bpf_attr __user *uattr)
+{
+	const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
+	const struct btf_type *func_proto = prog->aux->attach_func_proto;
+	struct bpf_dummy_ops_test_args *args = NULL;
+	struct bpf_tramp_progs *tprogs = NULL;

args = NULL and tprogs = NULL are not needed.

+	void *image = NULL;
+	unsigned int op_idx;
+	int err;
+	int prog_ret;
+
+	args = dummy_ops_init_args(kattr, btf_type_vlen(func_proto));
+	if (IS_ERR(args))
+		return PTR_ERR(args);
+
+	tprogs = kcalloc(BPF_TRAMP_MAX, sizeof(*tprogs), GFP_KERNEL);
+	if (!tprogs) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	image = bpf_jit_alloc_exec(PAGE_SIZE);
+	if (!image) {
+		err = -ENOMEM;
+		goto out;
+	}
+	set_vm_flush_reset_perms(image);
+
+	op_idx = prog->expected_attach_type;
+	err = bpf_struct_ops_prepare_trampoline(tprogs, prog,
+						&st_ops->func_models[op_idx],
+						image, image + PAGE_SIZE);
+	if (err < 0)
+		goto out;
+
+	set_memory_ro((long)image, 1);
+	set_memory_x((long)image, 1);
+	prog_ret = dummy_ops_call_op(image, args);
+
+	err = dummy_ops_copy_args(args);
+	if (err)
+		goto out;
+	if (put_user(prog_ret, &uattr->test.retval))
+		err = -EFAULT;
+out:
+	kfree(args);
+	bpf_jit_free_exec(image);
+	kfree(tprogs);
+	return err;
+}
+
+static int bpf_dummy_init(struct btf *btf)
+{
+	s32 type_id;
+
+	type_id = btf_find_by_name_kind(btf, "bpf_dummy_ops_state",
+					BTF_KIND_STRUCT);
+	if (type_id < 0)
+		return -EINVAL;
+
+	dummy_ops_state = btf_type_by_id(btf, type_id);

Probably just do btf_find_by_name_kind("bpf_dummy_ops_state")
in bpf_dummy_ops_btf_struct_access() during each test.   There is
no need to optimize and cache it only for the testing purpose.

+
+	return 0;
+}
+
+static bool bpf_dummy_ops_is_valid_access(int off, int size,
+					  enum bpf_access_type type,
+					  const struct bpf_prog *prog,
+					  struct bpf_insn_access_aux *info)
+{
+	return bpf_check_btf_func_ctx_access(off, size, type, prog, info);
+}
+
+static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
+					   const struct btf *btf,
+					   const struct btf_type *t, int off,
+					   int size, enum bpf_access_type atype,
+					   u32 *next_btf_id)
+{
+	int err;
+
+	if (atype != BPF_READ && t != dummy_ops_state) {

I think this can be further simplified.  The only struct that
the bpf_prog can access is bpf_dummy_ops_state, so the
"atype != BPF_READ" test can be removed.  The log message
then needs to be adjusted.

Others lgtm.

+		bpf_log(log, "only write to bpf_dummy_ops_state is supported\n");
+		return -EACCES;
+	}
+
+	err = btf_struct_access(log, btf, t, off, size, atype, next_btf_id);
+	if (err < 0)
+		return err;
+
+	return atype == BPF_READ ? err : NOT_INIT;
+}