libsanitizer/ubsan/ubsan_type_hash.h

   1 //===-- ubsan_type_hash.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 // Hashing of types for Clang's undefined behavior checker.
  10 //
  11 //===----------------------------------------------------------------------===//
  12 #ifndef UBSAN_TYPE_HASH_H
  13 #define UBSAN_TYPE_HASH_H
  14
  15 #include "sanitizer_common/sanitizer_common.h"
  16
  17 namespace __ubsan {
  18
  19 typedef uptr HashValue;
  20
  21 /// \brief Information about the dynamic type of an object (extracted from its
  22 /// vptr).
  23 class DynamicTypeInfo {
  24   const char *MostDerivedTypeName;
  25   sptr Offset;
  26   const char *SubobjectTypeName;
  27
  28 public:
  29   DynamicTypeInfo(const char *MDTN, sptr Offset, const char *STN)
  30     : MostDerivedTypeName(MDTN), Offset(Offset), SubobjectTypeName(STN) {}
  31
  32   /// Determine whether the object had a valid dynamic type.
  33   bool isValid() const { return MostDerivedTypeName; }
  34   /// Get the name of the most-derived type of the object.
  35   const char *getMostDerivedTypeName() const { return MostDerivedTypeName; }
  36   /// Get the offset from the most-derived type to this base class.
  37   sptr getOffset() const { return Offset; }
  38   /// Get the name of the most-derived type at the specified offset.
  39   const char *getSubobjectTypeName() const { return SubobjectTypeName; }
  40 };
  41
  42 /// \brief Get information about the dynamic type of an object.
  43 DynamicTypeInfo getDynamicTypeInfoFromObject(void *Object);
  44
  45 /// \brief Get information about the dynamic type of an object from its vtable.
  46 DynamicTypeInfo getDynamicTypeInfoFromVtable(void *Vtable);
  47
  48 /// \brief Check whether the dynamic type of \p Object has a \p Type subobject
  49 /// at offset 0.
  50 /// \return \c true if the type matches, \c false if not.
  51 bool checkDynamicType(void *Object, void *Type, HashValue Hash);
  52
  53 const unsigned VptrTypeCacheSize = 128;
  54
  55 /// A sanity check for Vtable. Offsets to top must be reasonably small
  56 /// numbers (by absolute value). It's a weak check for Vtable corruption.
  57 const int VptrMaxOffsetToTop = 1<<20;
  58
  59 /// \brief A cache of the results of checkDynamicType. \c checkDynamicType would
  60 /// return \c true (modulo hash collisions) if
  61 /// \code
  62 ///   __ubsan_vptr_type_cache[Hash % VptrTypeCacheSize] == Hash
  63 /// \endcode
  64 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
  65 HashValue __ubsan_vptr_type_cache[VptrTypeCacheSize];
  66
  67 /// \brief Do whatever is required by the ABI to check for std::type_info
  68 /// equivalence beyond simple pointer comparison.
  69 bool checkTypeInfoEquality(const void *TypeInfo1, const void *TypeInfo2);
  70
  71 } // namespace __ubsan
  72
  73 #endif // UBSAN_TYPE_HASH_H