1 //===- DWARFAbbreviationDeclaration.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 LLVM_DEBUGINFO_DWARFABBREVIATIONDECLARATION_H
10 #define LLVM_DEBUGINFO_DWARFABBREVIATIONDECLARATION_H
11 
12 #include "llvm/ADT/Optional.h"
13 #include "llvm/ADT/SmallVector.h"
14 #include "llvm/ADT/iterator_range.h"
15 #include "llvm/BinaryFormat/Dwarf.h"
16 #include "llvm/Support/DataExtractor.h"
17 #include <cassert>
18 #include <cstddef>
19 #include <cstdint>
20 
21 namespace llvm {
22 
23 class DWARFFormValue;
24 class DWARFUnit;
25 class raw_ostream;
26 
27 class DWARFAbbreviationDeclaration {
28 public:
29   struct AttributeSpec {
30     AttributeSpec(dwarf::Attribute A, dwarf::Form F, int64_t Value)
31         : Attr(A), Form(F), Value(Value) {
32       assert(isImplicitConst());
33     }
34     AttributeSpec(dwarf::Attribute A, dwarf::Form F, Optional<uint8_t> ByteSize)
35         : Attr(A), Form(F) {
36       assert(!isImplicitConst());
37       this->ByteSize.HasByteSize = ByteSize.hasValue();
38       if (this->ByteSize.HasByteSize)
39         this->ByteSize.ByteSize = *ByteSize;
40     }
41 
42     dwarf::Attribute Attr;
43     dwarf::Form Form;
44 
45   private:
46     /// The following field is used for ByteSize for non-implicit_const
47     /// attributes and as value for implicit_const ones, indicated by
48     /// Form == DW_FORM_implicit_const.
49     /// The following cases are distinguished:
50     /// * Form != DW_FORM_implicit_const and HasByteSize is true:
51     ///     ByteSize contains the fixed size in bytes for the Form in this
52     ///     object.
53     /// * Form != DW_FORM_implicit_const and HasByteSize is false:
54     ///     byte size of Form either varies according to the DWARFUnit
55     ///     that it is contained in or the value size varies and must be
56     ///     decoded from the debug information in order to determine its size.
57     /// * Form == DW_FORM_implicit_const:
58     ///     Value contains value for the implicit_const attribute.
59     struct ByteSizeStorage {
60       bool HasByteSize;
61       uint8_t ByteSize;
62     };
63     union {
64       ByteSizeStorage ByteSize;
65       int64_t Value;
66     };
67 
68   public:
69     bool isImplicitConst() const {
70       return Form == dwarf::DW_FORM_implicit_const;
71     }
72 
73     int64_t getImplicitConstValue() const {
74       assert(isImplicitConst());
75       return Value;
76     }
77 
78     /// Get the fixed byte size of this Form if possible. This function might
79     /// use the DWARFUnit to calculate the size of the Form, like for
80     /// DW_AT_address and DW_AT_ref_addr, so this isn't just an accessor for
81     /// the ByteSize member.
82     Optional<int64_t> getByteSize(const DWARFUnit &U) const;
83   };
84   using AttributeSpecVector = SmallVector<AttributeSpec, 8>;
85 
86   DWARFAbbreviationDeclaration();
87 
88   uint32_t getCode() const { return Code; }
89   uint8_t getCodeByteSize() const { return CodeByteSize; }
90   dwarf::Tag getTag() const { return Tag; }
91   bool hasChildren() const { return HasChildren; }
92 
93   using attr_iterator_range =
94       iterator_range<AttributeSpecVector::const_iterator>;
95 
96   attr_iterator_range attributes() const {
97     return attr_iterator_range(AttributeSpecs.begin(), AttributeSpecs.end());
98   }
99 
100   dwarf::Form getFormByIndex(uint32_t idx) const {
101     assert(idx < AttributeSpecs.size());
102     return AttributeSpecs[idx].Form;
103   }
104 
105   size_t getNumAttributes() const {
106     return AttributeSpecs.size();
107   }
108 
109   dwarf::Attribute getAttrByIndex(uint32_t idx) const {
110     assert(idx < AttributeSpecs.size());
111     return AttributeSpecs[idx].Attr;
112   }
113 
114   bool getAttrIsImplicitConstByIndex(uint32_t idx) const {
115     assert(idx < AttributeSpecs.size());
116     return AttributeSpecs[idx].isImplicitConst();
117   }
118 
119   int64_t getAttrImplicitConstValueByIndex(uint32_t idx) const {
120     assert(idx < AttributeSpecs.size());
121     return AttributeSpecs[idx].getImplicitConstValue();
122   }
123 
124   /// Get the index of the specified attribute.
125   ///
126   /// Searches the this abbreviation declaration for the index of the specified
127   /// attribute.
128   ///
129   /// \param attr DWARF attribute to search for.
130   /// \returns Optional index of the attribute if found, None otherwise.
131   Optional<uint32_t> findAttributeIndex(dwarf::Attribute attr) const;
132 
133   /// Extract a DWARF form value from a DIE specified by DIE offset.
134   ///
135   /// Extract an attribute value for a DWARFUnit given the DIE offset and the
136   /// attribute.
137   ///
138   /// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation
139   /// code in the .debug_info data.
140   /// \param Attr DWARF attribute to search for.
141   /// \param U the DWARFUnit the contains the DIE.
142   /// \returns Optional DWARF form value if the attribute was extracted.
143   Optional<DWARFFormValue> getAttributeValue(const uint64_t DIEOffset,
144                                              const dwarf::Attribute Attr,
145                                              const DWARFUnit &U) const;
146 
147   bool extract(DataExtractor Data, uint64_t* OffsetPtr);
148   void dump(raw_ostream &OS) const;
149 
150   // Return an optional byte size of all attribute data in this abbreviation
151   // if a constant byte size can be calculated given a DWARFUnit. This allows
152   // DWARF parsing to be faster as many DWARF DIEs have a fixed byte size.
153   Optional<size_t> getFixedAttributesByteSize(const DWARFUnit &U) const;
154 
155 private:
156   void clear();
157 
158   /// A helper structure that can quickly determine the size in bytes of an
159   /// abbreviation declaration.
160   struct FixedSizeInfo {
161     /// The fixed byte size for fixed size forms.
162     uint16_t NumBytes = 0;
163     /// Number of DW_FORM_address forms in this abbrevation declaration.
164     uint8_t NumAddrs = 0;
165     /// Number of DW_FORM_ref_addr forms in this abbrevation declaration.
166     uint8_t NumRefAddrs = 0;
167     /// Number of 4 byte in DWARF32 and 8 byte in DWARF64 forms.
168     uint8_t NumDwarfOffsets = 0;
169 
170     FixedSizeInfo() = default;
171 
172     /// Calculate the fixed size in bytes given a DWARFUnit.
173     ///
174     /// \param U the DWARFUnit to use when determing the byte size.
175     /// \returns the size in bytes for all attribute data in this abbreviation.
176     /// The returned size does not include bytes for the  ULEB128 abbreviation
177     /// code
178     size_t getByteSize(const DWARFUnit &U) const;
179   };
180 
181   uint32_t Code;
182   dwarf::Tag Tag;
183   uint8_t CodeByteSize;
184   bool HasChildren;
185   AttributeSpecVector AttributeSpecs;
186   /// If this abbreviation has a fixed byte size then FixedAttributeSize member
187   /// variable below will have a value.
188   Optional<FixedSizeInfo> FixedAttributeSize;
189 };
190 
191 } // end namespace llvm
192 
193 #endif // LLVM_DEBUGINFO_DWARFABBREVIATIONDECLARATION_H
194