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_DWARF_DWARFABBREVIATIONDECLARATION_H
10 #define LLVM_DEBUGINFO_DWARF_DWARFABBREVIATIONDECLARATION_H
11 
12 #include "llvm/ADT/SmallVector.h"
13 #include "llvm/ADT/iterator_range.h"
14 #include "llvm/BinaryFormat/Dwarf.h"
15 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
16 #include <cassert>
17 #include <cstddef>
18 #include <cstdint>
19 
20 namespace llvm {
21 
22 class DataExtractor;
23 class DWARFUnit;
24 class raw_ostream;
25 
26 class DWARFAbbreviationDeclaration {
27 public:
28   enum class ExtractState { Complete, MoreItems };
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,
35                   std::optional<uint8_t> ByteSize)
36         : Attr(A), Form(F) {
37       assert(!isImplicitConst());
38       this->ByteSize.HasByteSize = ByteSize.has_value();
39       if (this->ByteSize.HasByteSize)
40         this->ByteSize.ByteSize = *ByteSize;
41     }
42 
43     DWARFFormValue getFormValue() const {
44       if (Form == dwarf::DW_FORM_implicit_const)
45         return DWARFFormValue::createFromSValue(Form, getImplicitConstValue());
46 
47       return DWARFFormValue(Form);
48     }
49 
50     dwarf::Attribute Attr;
51     dwarf::Form Form;
52 
53   private:
54     /// The following field is used for ByteSize for non-implicit_const
55     /// attributes and as value for implicit_const ones, indicated by
56     /// Form == DW_FORM_implicit_const.
57     /// The following cases are distinguished:
58     /// * Form != DW_FORM_implicit_const and HasByteSize is true:
59     ///     ByteSize contains the fixed size in bytes for the Form in this
60     ///     object.
61     /// * Form != DW_FORM_implicit_const and HasByteSize is false:
62     ///     byte size of Form either varies according to the DWARFUnit
63     ///     that it is contained in or the value size varies and must be
64     ///     decoded from the debug information in order to determine its size.
65     /// * Form == DW_FORM_implicit_const:
66     ///     Value contains value for the implicit_const attribute.
67     struct ByteSizeStorage {
68       bool HasByteSize;
69       uint8_t ByteSize;
70     };
71     union {
72       ByteSizeStorage ByteSize;
73       int64_t Value;
74     };
75 
76   public:
77     bool isImplicitConst() const {
78       return Form == dwarf::DW_FORM_implicit_const;
79     }
80 
81     int64_t getImplicitConstValue() const {
82       assert(isImplicitConst());
83       return Value;
84     }
85 
86     /// Get the fixed byte size of this Form if possible. This function might
87     /// use the DWARFUnit to calculate the size of the Form, like for
88     /// DW_AT_address and DW_AT_ref_addr, so this isn't just an accessor for
89     /// the ByteSize member.
90     std::optional<int64_t> getByteSize(const DWARFUnit &U) const;
91   };
92   using AttributeSpecVector = SmallVector<AttributeSpec, 8>;
93 
94   DWARFAbbreviationDeclaration();
95 
96   uint32_t getCode() const { return Code; }
97   uint8_t getCodeByteSize() const { return CodeByteSize; }
98   dwarf::Tag getTag() const { return Tag; }
99   bool hasChildren() const { return HasChildren; }
100 
101   using attr_iterator_range =
102       iterator_range<AttributeSpecVector::const_iterator>;
103 
104   attr_iterator_range attributes() const {
105     return attr_iterator_range(AttributeSpecs.begin(), AttributeSpecs.end());
106   }
107 
108   dwarf::Form getFormByIndex(uint32_t idx) const {
109     assert(idx < AttributeSpecs.size());
110     return AttributeSpecs[idx].Form;
111   }
112 
113   size_t getNumAttributes() const {
114     return AttributeSpecs.size();
115   }
116 
117   dwarf::Attribute getAttrByIndex(uint32_t idx) const {
118     assert(idx < AttributeSpecs.size());
119     return AttributeSpecs[idx].Attr;
120   }
121 
122   bool getAttrIsImplicitConstByIndex(uint32_t idx) const {
123     assert(idx < AttributeSpecs.size());
124     return AttributeSpecs[idx].isImplicitConst();
125   }
126 
127   int64_t getAttrImplicitConstValueByIndex(uint32_t idx) const {
128     assert(idx < AttributeSpecs.size());
129     return AttributeSpecs[idx].getImplicitConstValue();
130   }
131 
132   /// Get the index of the specified attribute.
133   ///
134   /// Searches the this abbreviation declaration for the index of the specified
135   /// attribute.
136   ///
137   /// \param attr DWARF attribute to search for.
138   /// \returns Optional index of the attribute if found, std::nullopt otherwise.
139   std::optional<uint32_t> findAttributeIndex(dwarf::Attribute attr) const;
140 
141   /// Extract a DWARF form value from a DIE specified by DIE offset.
142   ///
143   /// Extract an attribute value for a DWARFUnit given the DIE offset and the
144   /// attribute.
145   ///
146   /// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation
147   /// code in the .debug_info data.
148   /// \param Attr DWARF attribute to search for.
149   /// \param U the DWARFUnit the contains the DIE.
150   /// \returns Optional DWARF form value if the attribute was extracted.
151   std::optional<DWARFFormValue> getAttributeValue(const uint64_t DIEOffset,
152                                                   const dwarf::Attribute Attr,
153                                                   const DWARFUnit &U) const;
154 
155   /// Compute an offset from a DIE specified by DIE offset and attribute index.
156   ///
157   /// \param AttrIndex an index of DWARF attribute.
158   /// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation
159   /// code in the .debug_info data.
160   /// \param U the DWARFUnit the contains the DIE.
161   /// \returns an offset of the attribute.
162   uint64_t getAttributeOffsetFromIndex(uint32_t AttrIndex, uint64_t DIEOffset,
163                                        const DWARFUnit &U) const;
164 
165   /// Extract a DWARF form value from a DIE speccified by attribute index and
166   /// its offset.
167   ///
168   /// \param AttrIndex an index of DWARF attribute.
169   /// \param Offset offset of the attribute.
170   /// \param U the DWARFUnit the contains the DIE.
171   /// \returns Optional DWARF form value if the attribute was extracted.
172   std::optional<DWARFFormValue>
173   getAttributeValueFromOffset(uint32_t AttrIndex, uint64_t Offset,
174                               const DWARFUnit &U) const;
175 
176   llvm::Expected<ExtractState> extract(DataExtractor Data, uint64_t *OffsetPtr);
177   void dump(raw_ostream &OS) const;
178 
179   // Return an optional byte size of all attribute data in this abbreviation
180   // if a constant byte size can be calculated given a DWARFUnit. This allows
181   // DWARF parsing to be faster as many DWARF DIEs have a fixed byte size.
182   std::optional<size_t> getFixedAttributesByteSize(const DWARFUnit &U) const;
183 
184 private:
185   void clear();
186 
187   /// A helper structure that can quickly determine the size in bytes of an
188   /// abbreviation declaration.
189   struct FixedSizeInfo {
190     /// The fixed byte size for fixed size forms.
191     uint16_t NumBytes = 0;
192     /// Number of DW_FORM_address forms in this abbrevation declaration.
193     uint8_t NumAddrs = 0;
194     /// Number of DW_FORM_ref_addr forms in this abbrevation declaration.
195     uint8_t NumRefAddrs = 0;
196     /// Number of 4 byte in DWARF32 and 8 byte in DWARF64 forms.
197     uint8_t NumDwarfOffsets = 0;
198 
199     FixedSizeInfo() = default;
200 
201     /// Calculate the fixed size in bytes given a DWARFUnit.
202     ///
203     /// \param U the DWARFUnit to use when determing the byte size.
204     /// \returns the size in bytes for all attribute data in this abbreviation.
205     /// The returned size does not include bytes for the  ULEB128 abbreviation
206     /// code
207     size_t getByteSize(const DWARFUnit &U) const;
208   };
209 
210   uint32_t Code;
211   dwarf::Tag Tag;
212   uint8_t CodeByteSize;
213   bool HasChildren;
214   AttributeSpecVector AttributeSpecs;
215   /// If this abbreviation has a fixed byte size then FixedAttributeSize member
216   /// variable below will have a value.
217   std::optional<FixedSizeInfo> FixedAttributeSize;
218 };
219 
220 } // end namespace llvm
221 
222 #endif // LLVM_DEBUGINFO_DWARF_DWARFABBREVIATIONDECLARATION_H
223