libsanitizer/ubsan/ubsan_type_hash.h

   1 //===-- ubsan_type_hash.h ---------------------------------------*- C++ -*-===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // Hashing of types for Clang's undefined behavior checker.
   9 //
  10 //===----------------------------------------------------------------------===//
  11 #ifndef UBSAN_TYPE_HASH_H
  12 #define UBSAN_TYPE_HASH_H
  13
  14 #include "sanitizer_common/sanitizer_common.h"
  15
  16 namespace __ubsan {
  17
  18 typedef uptr HashValue;
  19
  20 /// \brief Information about the dynamic type of an object (extracted from its
  21 /// vptr).
  22 class DynamicTypeInfo {
  23   const char *MostDerivedTypeName;
  24   sptr Offset;
  25   const char *SubobjectTypeName;
  26
  27 public:
  28   DynamicTypeInfo(const char *MDTN, sptr Offset, const char *STN)
  29     : MostDerivedTypeName(MDTN), Offset(Offset), SubobjectTypeName(STN) {}
  30
  31   /// Determine whether the object had a valid dynamic type.
  32   bool isValid() const { return MostDerivedTypeName; }
  33   /// Get the name of the most-derived type of the object.
  34   const char *getMostDerivedTypeName() const { return MostDerivedTypeName; }
  35   /// Get the offset from the most-derived type to this base class.
  36   sptr getOffset() const { return Offset; }
  37   /// Get the name of the most-derived type at the specified offset.
  38   const char *getSubobjectTypeName() const { return SubobjectTypeName; }
  39 };
  40
  41 /// \brief Get information about the dynamic type of an object.
  42 DynamicTypeInfo getDynamicTypeInfoFromObject(void *Object);
  43
  44 /// \brief Get information about the dynamic type of an object from its vtable.
  45 DynamicTypeInfo getDynamicTypeInfoFromVtable(void *Vtable);
  46
  47 /// \brief Check whether the dynamic type of \p Object has a \p Type subobject
  48 /// at offset 0.
  49 /// \return \c true if the type matches, \c false if not.
  50 bool checkDynamicType(void *Object, void *Type, HashValue Hash);
  51
  52 const unsigned VptrTypeCacheSize = 128;
  53
  54 /// A sanity check for Vtable. Offsets to top must be reasonably small
  55 /// numbers (by absolute value). It's a weak check for Vtable corruption.
  56 const int VptrMaxOffsetToTop = 1<<20;
  57
  58 /// \brief A cache of the results of checkDynamicType. \c checkDynamicType would
  59 /// return \c true (modulo hash collisions) if
  60 /// \code
  61 ///   __ubsan_vptr_type_cache[Hash % VptrTypeCacheSize] == Hash
  62 /// \endcode
  63 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
  64 HashValue __ubsan_vptr_type_cache[VptrTypeCacheSize];
  65
  66 } // namespace __ubsan
  67
  68 #endif // UBSAN_TYPE_HASH_H