1 //===-- chunk.h -------------------------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef SCUDO_CHUNK_H_ 10 #define SCUDO_CHUNK_H_ 11 12 #include "platform.h" 13 14 #include "atomic_helpers.h" 15 #include "checksum.h" 16 #include "common.h" 17 #include "report.h" 18 19 namespace scudo { 20 21 extern Checksum HashAlgorithm; 22 23 inline u16 computeChecksum(u32 Seed, uptr Value, uptr *Array, uptr ArraySize) { 24 // If the hardware CRC32 feature is defined here, it was enabled everywhere, 25 // as opposed to only for crc32_hw.cpp. This means that other hardware 26 // specific instructions were likely emitted at other places, and as a result 27 // there is no reason to not use it here. 28 #if defined(__CRC32__) || defined(__SSE4_2__) || defined(__ARM_FEATURE_CRC32) 29 u32 Crc = static_cast<u32>(CRC32_INTRINSIC(Seed, Value)); 30 for (uptr I = 0; I < ArraySize; I++) 31 Crc = static_cast<u32>(CRC32_INTRINSIC(Crc, Array[I])); 32 return static_cast<u16>(Crc ^ (Crc >> 16)); 33 #else 34 if (HashAlgorithm == Checksum::HardwareCRC32) { 35 u32 Crc = computeHardwareCRC32(Seed, Value); 36 for (uptr I = 0; I < ArraySize; I++) 37 Crc = computeHardwareCRC32(Crc, Array[I]); 38 return static_cast<u16>(Crc ^ (Crc >> 16)); 39 } else { 40 u16 Checksum = computeBSDChecksum(static_cast<u16>(Seed), Value); 41 for (uptr I = 0; I < ArraySize; I++) 42 Checksum = computeBSDChecksum(Checksum, Array[I]); 43 return Checksum; 44 } 45 #endif // defined(__CRC32__) || defined(__SSE4_2__) || defined(__ARM_FEATURE_CRC32) 46 } 47 48 namespace Chunk { 49 50 // Note that in an ideal world, `State` and `Origin` should be `enum class`, and 51 // the associated `UnpackedHeader` fields of their respective enum class type 52 // but https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414 prevents it from 53 // happening, as it will error, complaining the number of bits is not enough. 54 enum Origin : u8 { 55 Malloc = 0, 56 New = 1, 57 NewArray = 2, 58 Memalign = 3, 59 }; 60 61 enum State : u8 { Available = 0, Allocated = 1, Quarantined = 2 }; 62 63 typedef u64 PackedHeader; 64 // Update the 'Mask' constants to reflect changes in this structure. 65 struct UnpackedHeader { 66 uptr ClassId : 8; 67 u8 State : 2; 68 // Origin if State == Allocated, or WasZeroed otherwise. 69 u8 OriginOrWasZeroed : 2; 70 uptr SizeOrUnusedBytes : 20; 71 uptr Offset : 16; 72 uptr Checksum : 16; 73 }; 74 typedef atomic_u64 AtomicPackedHeader; 75 static_assert(sizeof(UnpackedHeader) == sizeof(PackedHeader), ""); 76 77 // Those constants are required to silence some -Werror=conversion errors when 78 // assigning values to the related bitfield variables. 79 constexpr uptr ClassIdMask = (1UL << 8) - 1; 80 constexpr u8 StateMask = (1U << 2) - 1; 81 constexpr u8 OriginMask = (1U << 2) - 1; 82 constexpr uptr SizeOrUnusedBytesMask = (1UL << 20) - 1; 83 constexpr uptr OffsetMask = (1UL << 16) - 1; 84 constexpr uptr ChecksumMask = (1UL << 16) - 1; 85 86 constexpr uptr getHeaderSize() { 87 return roundUpTo(sizeof(PackedHeader), 1U << SCUDO_MIN_ALIGNMENT_LOG); 88 } 89 90 inline AtomicPackedHeader *getAtomicHeader(void *Ptr) { 91 return reinterpret_cast<AtomicPackedHeader *>(reinterpret_cast<uptr>(Ptr) - 92 getHeaderSize()); 93 } 94 95 inline const AtomicPackedHeader *getConstAtomicHeader(const void *Ptr) { 96 return reinterpret_cast<const AtomicPackedHeader *>( 97 reinterpret_cast<uptr>(Ptr) - getHeaderSize()); 98 } 99 100 // We do not need a cryptographically strong hash for the checksum, but a CRC 101 // type function that can alert us in the event a header is invalid or 102 // corrupted. Ideally slightly better than a simple xor of all fields. 103 static inline u16 computeHeaderChecksum(u32 Cookie, const void *Ptr, 104 UnpackedHeader *Header) { 105 UnpackedHeader ZeroChecksumHeader = *Header; 106 ZeroChecksumHeader.Checksum = 0; 107 uptr HeaderHolder[sizeof(UnpackedHeader) / sizeof(uptr)]; 108 memcpy(&HeaderHolder, &ZeroChecksumHeader, sizeof(HeaderHolder)); 109 return computeChecksum(Cookie, reinterpret_cast<uptr>(Ptr), HeaderHolder, 110 ARRAY_SIZE(HeaderHolder)); 111 } 112 113 inline void storeHeader(u32 Cookie, void *Ptr, 114 UnpackedHeader *NewUnpackedHeader) { 115 NewUnpackedHeader->Checksum = 116 computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader); 117 PackedHeader NewPackedHeader = bit_cast<PackedHeader>(*NewUnpackedHeader); 118 atomic_store_relaxed(getAtomicHeader(Ptr), NewPackedHeader); 119 } 120 121 inline void loadHeader(u32 Cookie, const void *Ptr, 122 UnpackedHeader *NewUnpackedHeader) { 123 PackedHeader NewPackedHeader = atomic_load_relaxed(getConstAtomicHeader(Ptr)); 124 *NewUnpackedHeader = bit_cast<UnpackedHeader>(NewPackedHeader); 125 if (UNLIKELY(NewUnpackedHeader->Checksum != 126 computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader))) 127 reportHeaderCorruption(const_cast<void *>(Ptr)); 128 } 129 130 inline void compareExchangeHeader(u32 Cookie, void *Ptr, 131 UnpackedHeader *NewUnpackedHeader, 132 UnpackedHeader *OldUnpackedHeader) { 133 NewUnpackedHeader->Checksum = 134 computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader); 135 PackedHeader NewPackedHeader = bit_cast<PackedHeader>(*NewUnpackedHeader); 136 PackedHeader OldPackedHeader = bit_cast<PackedHeader>(*OldUnpackedHeader); 137 if (UNLIKELY(!atomic_compare_exchange_strong( 138 getAtomicHeader(Ptr), &OldPackedHeader, NewPackedHeader, 139 memory_order_relaxed))) 140 reportHeaderRace(Ptr); 141 } 142 143 inline bool isValid(u32 Cookie, const void *Ptr, 144 UnpackedHeader *NewUnpackedHeader) { 145 PackedHeader NewPackedHeader = atomic_load_relaxed(getConstAtomicHeader(Ptr)); 146 *NewUnpackedHeader = bit_cast<UnpackedHeader>(NewPackedHeader); 147 return NewUnpackedHeader->Checksum == 148 computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader); 149 } 150 151 } // namespace Chunk 152 153 } // namespace scudo 154 155 #endif // SCUDO_CHUNK_H_ 156