1 //===-- chunk.h -------------------------------------------------*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
10 #define SCUDO_CHUNK_H_
14 #include "atomic_helpers.h"
21 extern Checksum HashAlgorithm;
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.cc. This means that other hardware specific
26 // instructions were likely emitted at other places, and as a result there is
27 // no reason to not use it here.
28 #if 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 & 0xffff) ^ (Crc >> 16));
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 & 0xffff) ^ (Crc >> 16));
40 u16 Checksum = computeBSDChecksum(static_cast<u16>(Seed & 0xffff), Value);
41 for (uptr I = 0; I < ArraySize; I++)
42 Checksum = computeBSDChecksum(Checksum, Array[I]);
45 #endif // defined(__SSE4_2__) || defined(__ARM_FEATURE_CRC32)
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.
61 enum State : u8 { Available = 0, Allocated = 1, Quarantined = 2 };
63 typedef u64 PackedHeader;
64 // Update the 'Mask' constants to reflect changes in this structure.
65 struct UnpackedHeader {
68 u64 SizeOrUnusedBytes : 20;
73 typedef atomic_u64 AtomicPackedHeader;
74 COMPILER_CHECK(sizeof(UnpackedHeader) == sizeof(PackedHeader));
76 // Those constants are required to silence some -Werror=conversion errors when
77 // assigning values to the related bitfield variables.
78 constexpr uptr ChecksumMask = (1UL << 16) - 1;
79 constexpr uptr ClassIdMask = (1UL << 8) - 1;
80 constexpr uptr SizeOrUnusedBytesMask = (1UL << 20) - 1;
81 constexpr uptr StateMask = (1UL << 2) - 1;
82 constexpr uptr OriginMask = (1UL << 2) - 1;
83 constexpr uptr OffsetMask = (1UL << 16) - 1;
85 constexpr uptr getHeaderSize() {
86 return roundUpTo(sizeof(PackedHeader), 1U << SCUDO_MIN_ALIGNMENT_LOG);
89 INLINE AtomicPackedHeader *getAtomicHeader(void *Ptr) {
90 return reinterpret_cast<AtomicPackedHeader *>(reinterpret_cast<uptr>(Ptr) -
95 const AtomicPackedHeader *getConstAtomicHeader(const void *Ptr) {
96 return reinterpret_cast<const AtomicPackedHeader *>(
97 reinterpret_cast<uptr>(Ptr) - getHeaderSize());
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));
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);
122 void loadHeader(u32 Cookie, const void *Ptr,
123 UnpackedHeader *NewUnpackedHeader) {
124 PackedHeader NewPackedHeader = atomic_load_relaxed(getConstAtomicHeader(Ptr));
125 *NewUnpackedHeader = bit_cast<UnpackedHeader>(NewPackedHeader);
126 if (UNLIKELY(NewUnpackedHeader->Checksum !=
127 computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader)))
128 reportHeaderCorruption(const_cast<void *>(Ptr));
131 INLINE void compareExchangeHeader(u32 Cookie, void *Ptr,
132 UnpackedHeader *NewUnpackedHeader,
133 UnpackedHeader *OldUnpackedHeader) {
134 NewUnpackedHeader->Checksum =
135 computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader);
136 PackedHeader NewPackedHeader = bit_cast<PackedHeader>(*NewUnpackedHeader);
137 PackedHeader OldPackedHeader = bit_cast<PackedHeader>(*OldUnpackedHeader);
138 if (UNLIKELY(!atomic_compare_exchange_strong(
139 getAtomicHeader(Ptr), &OldPackedHeader, NewPackedHeader,
140 memory_order_relaxed)))
141 reportHeaderRace(Ptr);
145 bool isValid(u32 Cookie, const void *Ptr, UnpackedHeader *NewUnpackedHeader) {
146 PackedHeader NewPackedHeader = atomic_load_relaxed(getConstAtomicHeader(Ptr));
147 *NewUnpackedHeader = bit_cast<UnpackedHeader>(NewPackedHeader);
148 return NewUnpackedHeader->Checksum ==
149 computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader);
156 #endif // SCUDO_CHUNK_H_