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
74