David Brazdil | f6a8a55 | 2018-01-15 18:10:50 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2018 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 | |
| 17 | #ifndef ART_RUNTIME_HIDDEN_API_ACCESS_FLAGS_H_ |
| 18 | #define ART_RUNTIME_HIDDEN_API_ACCESS_FLAGS_H_ |
| 19 | |
| 20 | #include "base/bit_utils.h" |
David Sehr | 8c0961f | 2018-01-23 16:11:38 -0800 | [diff] [blame] | 21 | #include "dex/modifiers.h" |
David Brazdil | f6a8a55 | 2018-01-15 18:10:50 +0000 | [diff] [blame] | 22 | |
| 23 | namespace art { |
| 24 | |
| 25 | /* This class is used for encoding and decoding access flags of class members |
| 26 | * from the boot class path. These access flags might contain additional two bits |
| 27 | * of information on whether the given class member should be hidden from apps |
| 28 | * and under what circumstances. |
| 29 | * |
| 30 | * The encoding is different inside DexFile, where we are concerned with size, |
| 31 | * and at runtime where we want to optimize for speed of access. The class |
| 32 | * provides helper functions to decode/encode both of them. |
| 33 | * |
| 34 | * Encoding in DexFile |
| 35 | * =================== |
| 36 | * |
| 37 | * First bit is encoded as inversion of visibility flags (public/private/protected). |
| 38 | * At most one can be set for any given class member. If two or three are set, |
| 39 | * this is interpreted as the first bit being set and actual visibility flags |
| 40 | * being the complement of the encoded flags. |
| 41 | * |
| 42 | * Second bit is either encoded as bit 5 for fields and non-native methods, where |
| 43 | * it carries no other meaning. If a method is native (bit 8 set), bit 9 is used. |
| 44 | * |
| 45 | * Bits were selected so that they never increase the length of unsigned LEB-128 |
| 46 | * encoding of the access flags. |
| 47 | * |
| 48 | * Encoding at runtime |
| 49 | * =================== |
| 50 | * |
| 51 | * Two bits are set aside in the uint32_t access flags in the intrinsics ordinal |
| 52 | * space (thus intrinsics need to be special-cased). These are two consecutive |
| 53 | * bits and they are directly used to store the integer value of the ApiList |
| 54 | * enum values. |
| 55 | * |
| 56 | */ |
| 57 | class HiddenApiAccessFlags { |
| 58 | public: |
| 59 | enum ApiList { |
| 60 | kWhitelist = 0, |
| 61 | kLightGreylist, |
| 62 | kDarkGreylist, |
| 63 | kBlacklist, |
| 64 | }; |
| 65 | |
| 66 | static ALWAYS_INLINE ApiList DecodeFromDex(uint32_t dex_access_flags) { |
| 67 | DexHiddenAccessFlags flags(dex_access_flags); |
| 68 | uint32_t int_value = (flags.IsFirstBitSet() ? 1 : 0) + (flags.IsSecondBitSet() ? 2 : 0); |
| 69 | return static_cast<ApiList>(int_value); |
| 70 | } |
| 71 | |
| 72 | static ALWAYS_INLINE uint32_t RemoveFromDex(uint32_t dex_access_flags) { |
| 73 | DexHiddenAccessFlags flags(dex_access_flags); |
| 74 | flags.SetFirstBit(false); |
| 75 | flags.SetSecondBit(false); |
| 76 | return flags.GetEncoding(); |
| 77 | } |
| 78 | |
| 79 | static ALWAYS_INLINE uint32_t EncodeForDex(uint32_t dex_access_flags, ApiList value) { |
| 80 | DexHiddenAccessFlags flags(RemoveFromDex(dex_access_flags)); |
| 81 | uint32_t int_value = static_cast<uint32_t>(value); |
| 82 | flags.SetFirstBit((int_value & 1) != 0); |
| 83 | flags.SetSecondBit((int_value & 2) != 0); |
| 84 | return flags.GetEncoding(); |
| 85 | } |
| 86 | |
| 87 | static ALWAYS_INLINE ApiList DecodeFromRuntime(uint32_t runtime_access_flags) { |
| 88 | if ((runtime_access_flags & kAccIntrinsic) != 0) { |
| 89 | return kWhitelist; |
| 90 | } else { |
| 91 | uint32_t int_value = (runtime_access_flags & kAccHiddenApiBits) >> kAccFlagsShift; |
| 92 | return static_cast<ApiList>(int_value); |
| 93 | } |
| 94 | } |
| 95 | |
| 96 | static ALWAYS_INLINE uint32_t EncodeForRuntime(uint32_t runtime_access_flags, ApiList value) { |
| 97 | CHECK_EQ(runtime_access_flags & kAccIntrinsic, 0u); |
| 98 | |
| 99 | uint32_t hidden_api_flags = static_cast<uint32_t>(value) << kAccFlagsShift; |
| 100 | CHECK_EQ(hidden_api_flags & ~kAccHiddenApiBits, 0u); |
| 101 | |
| 102 | runtime_access_flags &= ~kAccHiddenApiBits; |
| 103 | return runtime_access_flags | hidden_api_flags; |
| 104 | } |
| 105 | |
| 106 | private: |
| 107 | static const int kAccFlagsShift = CTZ(kAccHiddenApiBits); |
| 108 | static_assert(IsPowerOfTwo((kAccHiddenApiBits >> kAccFlagsShift) + 1), |
| 109 | "kAccHiddenApiBits are not continuous"); |
| 110 | |
| 111 | struct DexHiddenAccessFlags { |
| 112 | explicit DexHiddenAccessFlags(uint32_t access_flags) : access_flags_(access_flags) {} |
| 113 | |
| 114 | ALWAYS_INLINE uint32_t GetSecondFlag() { |
| 115 | return ((access_flags_ & kAccNative) != 0) ? kAccDexHiddenBitNative : kAccDexHiddenBit; |
| 116 | } |
| 117 | |
| 118 | ALWAYS_INLINE bool IsFirstBitSet() { |
| 119 | static_assert(IsPowerOfTwo(0u), "Following statement checks if *at most* one bit is set"); |
| 120 | return !IsPowerOfTwo(access_flags_ & kAccVisibilityFlags); |
| 121 | } |
| 122 | |
| 123 | ALWAYS_INLINE void SetFirstBit(bool value) { |
| 124 | if (IsFirstBitSet() != value) { |
| 125 | access_flags_ ^= kAccVisibilityFlags; |
| 126 | } |
| 127 | } |
| 128 | |
| 129 | ALWAYS_INLINE bool IsSecondBitSet() { |
| 130 | return (access_flags_ & GetSecondFlag()) != 0; |
| 131 | } |
| 132 | |
| 133 | ALWAYS_INLINE void SetSecondBit(bool value) { |
| 134 | if (value) { |
| 135 | access_flags_ |= GetSecondFlag(); |
| 136 | } else { |
| 137 | access_flags_ &= ~GetSecondFlag(); |
| 138 | } |
| 139 | } |
| 140 | |
| 141 | ALWAYS_INLINE uint32_t GetEncoding() const { |
| 142 | return access_flags_; |
| 143 | } |
| 144 | |
| 145 | uint32_t access_flags_; |
| 146 | }; |
| 147 | }; |
| 148 | |
David Brazdil | 068d68d | 2018-02-12 13:04:17 -0800 | [diff] [blame^] | 149 | inline std::ostream& operator<<(std::ostream& os, HiddenApiAccessFlags::ApiList value) { |
| 150 | switch (value) { |
| 151 | case HiddenApiAccessFlags::kWhitelist: |
| 152 | os << "whitelist"; |
| 153 | break; |
| 154 | case HiddenApiAccessFlags::kLightGreylist: |
| 155 | os << "light greylist"; |
| 156 | break; |
| 157 | case HiddenApiAccessFlags::kDarkGreylist: |
| 158 | os << "dark greylist"; |
| 159 | break; |
| 160 | case HiddenApiAccessFlags::kBlacklist: |
| 161 | os << "blacklist"; |
| 162 | break; |
| 163 | } |
| 164 | return os; |
| 165 | } |
| 166 | |
David Brazdil | f6a8a55 | 2018-01-15 18:10:50 +0000 | [diff] [blame] | 167 | } // namespace art |
| 168 | |
| 169 | |
| 170 | #endif // ART_RUNTIME_HIDDEN_API_ACCESS_FLAGS_H_ |