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: DynamicTypeInfo(const char * MDTN,sptr Offset,const char * STN)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. isValid()33 bool isValid() const { return MostDerivedTypeName; } 34 /// Get the name of the most-derived type of the object. getMostDerivedTypeName()35 const char *getMostDerivedTypeName() const { return MostDerivedTypeName; } 36 /// Get the offset from the most-derived type to this base class. getOffset()37 sptr getOffset() const { return Offset; } 38 /// Get the name of the most-derived type at the specified offset. getSubobjectTypeName()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 74