compiler-rt/lib/scudo/standalone/chunk.h

   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__) ||
  46        // defined(__ARM_FEATURE_CRC32)
  47 }
  48
  49 namespace Chunk {
  50
  51 // Note that in an ideal world, `State` and `Origin` should be `enum class`, and
  52 // the associated `UnpackedHeader` fields of their respective enum class type
  53 // but https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414 prevents it from
  54 // happening, as it will error, complaining the number of bits is not enough.
  55 enum Origin : u8 {
  56   Malloc = 0,
  57   New = 1,
  58   NewArray = 2,
  59   Memalign = 3,
  60 };
  61
  62 enum State : u8 { Available = 0, Allocated = 1, Quarantined = 2 };
  63
  64 typedef u64 PackedHeader;
  65 // Update the 'Mask' constants to reflect changes in this structure.
  66 struct UnpackedHeader {
  67   uptr ClassId : 8;
  68   u8 State : 2;
  69   // Origin if State == Allocated, or WasZeroed otherwise.
  70   u8 OriginOrWasZeroed : 2;
  71   uptr SizeOrUnusedBytes : 20;
  72   uptr Offset : 16;
  73   uptr Checksum : 16;
  74 };
  75 typedef atomic_u64 AtomicPackedHeader;
  76 static_assert(sizeof(UnpackedHeader) == sizeof(PackedHeader), "");
  77
  78 // Those constants are required to silence some -Werror=conversion errors when
  79 // assigning values to the related bitfield variables.
  80 constexpr uptr ClassIdMask = (1UL << 8) - 1;
  81 constexpr u8 StateMask = (1U << 2) - 1;
  82 constexpr u8 OriginMask = (1U << 2) - 1;
  83 constexpr uptr SizeOrUnusedBytesMask = (1UL << 20) - 1;
  84 constexpr uptr OffsetMask = (1UL << 16) - 1;
  85 constexpr uptr ChecksumMask = (1UL << 16) - 1;
  86
  87 constexpr uptr getHeaderSize() {
  88   return roundUp(sizeof(PackedHeader), 1U << SCUDO_MIN_ALIGNMENT_LOG);
  89 }
  90
  91 inline AtomicPackedHeader *getAtomicHeader(void *Ptr) {
  92   return reinterpret_cast<AtomicPackedHeader *>(reinterpret_cast<uptr>(Ptr) -
  93                                                 getHeaderSize());
  94 }
  95
  96 inline const AtomicPackedHeader *getConstAtomicHeader(const void *Ptr) {
  97   return reinterpret_cast<const AtomicPackedHeader *>(
  98       reinterpret_cast<uptr>(Ptr) - getHeaderSize());
  99 }
 100
 101 // We do not need a cryptographically strong hash for the checksum, but a CRC
 102 // type function that can alert us in the event a header is invalid or
 103 // corrupted. Ideally slightly better than a simple xor of all fields.
 104 static inline u16 computeHeaderChecksum(u32 Cookie, const void *Ptr,
 105                                         UnpackedHeader *Header) {
 106   UnpackedHeader ZeroChecksumHeader = *Header;
 107   ZeroChecksumHeader.Checksum = 0;
 108   uptr HeaderHolder[sizeof(UnpackedHeader) / sizeof(uptr)];
 109   memcpy(&HeaderHolder, &ZeroChecksumHeader, sizeof(HeaderHolder));
 110   return computeChecksum(Cookie, reinterpret_cast<uptr>(Ptr), HeaderHolder,
 111                          ARRAY_SIZE(HeaderHolder));
 112 }
 113
 114 inline void storeHeader(u32 Cookie, void *Ptr,
 115                         UnpackedHeader *NewUnpackedHeader) {
 116   NewUnpackedHeader->Checksum =
 117       computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader);
 118   PackedHeader NewPackedHeader = bit_cast<PackedHeader>(*NewUnpackedHeader);
 119   atomic_store_relaxed(getAtomicHeader(Ptr), NewPackedHeader);
 120 }
 121
 122 inline 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));
 129 }
 130
 131 inline bool isValid(u32 Cookie, const void *Ptr,
 132                     UnpackedHeader *NewUnpackedHeader) {
 133   PackedHeader NewPackedHeader = atomic_load_relaxed(getConstAtomicHeader(Ptr));
 134   *NewUnpackedHeader = bit_cast<UnpackedHeader>(NewPackedHeader);
 135   return NewUnpackedHeader->Checksum ==
 136          computeHeaderChecksum(Cookie, Ptr, NewUnpackedHeader);
 137 }
 138
 139 } // namespace Chunk
 140
 141 } // namespace scudo
 142
 143 #endif // SCUDO_CHUNK_H_