1 //
2 // Copyright (C) 2020 The Android Open Source Project
3 //
4 // Licensed under the Apache License, Version 2.0 (the "License");
5 // you may not use this file except in compliance with the License.
6 // You may obtain a copy of the License at
7 //
8 //      http://www.apache.org/licenses/LICENSE-2.0
9 //
10 // Unless required by applicable law or agreed to in writing, software
11 // distributed under the License is distributed on an "AS IS" BASIS,
12 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 // See the License for the specific language governing permissions and
14 // limitations under the License.
15 
16 #pragma once
17 
18 #include <cstdint>
19 #include <memory>
20 #include <set>
21 
22 #include <tss2/tss2_esys.h>
23 
24 /**
25  * Object slot manager for TPM memory. The TPM can only hold a fixed number of
26  * objects at once. Some TPM operations are defined to consume slots either
27  * temporarily or until the resource is explicitly unloaded.
28  *
29  * This implementation is intended for future extension, to track what objects
30  * are resident if we run out of space, or implement optimizations like LRU
31  * caching to avoid re-loading often-used resources.
32  */
33 class TpmResourceManager {
34 public:
35   class ObjectSlot {
36   public:
37     friend class TpmResourceManager;
38 
39     ~ObjectSlot();
40 
41     ESYS_TR get();
42     void set(ESYS_TR resource);
43   private:
44     ObjectSlot(TpmResourceManager* resource_manager);
45     ObjectSlot(TpmResourceManager* resource_manager, ESYS_TR resource);
46 
47     TpmResourceManager* resource_manager_;
48     ESYS_TR resource_;
49   };
50 
51   TpmResourceManager(ESYS_CONTEXT* esys);
52   ~TpmResourceManager();
53 
54   ESYS_CONTEXT* Esys();
55   std::shared_ptr<ObjectSlot> ReserveSlot();
56 private:
57   ESYS_CONTEXT* esys_;
58   const std::uint32_t maximum_object_slots_;
59   std::atomic<std::uint32_t> used_slots_;
60 };
61 
62 using TpmObjectSlot = std::shared_ptr<TpmResourceManager::ObjectSlot>;
63