1//===-- ValueObjectVTable.cpp ---------------------------------------------===//
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#include "lldb/Core/ValueObjectVTable.h"
10#include "lldb/Core/Module.h"
11#include "lldb/Core/ValueObjectChild.h"
12#include "lldb/Symbol/Function.h"
13#include "lldb/Target/Language.h"
14#include "lldb/Target/LanguageRuntime.h"
15#include "lldb/lldb-defines.h"
16#include "lldb/lldb-enumerations.h"
17#include "lldb/lldb-forward.h"
18#include "lldb/lldb-private-enumerations.h"
19
20using namespace lldb;
21using namespace lldb_private;
22
23class ValueObjectVTableChild : public ValueObject {
24public:
25 ValueObjectVTableChild(ValueObject &parent, uint32_t func_idx,
26 uint64_t addr_size)
27 : ValueObject(parent), m_func_idx(func_idx), m_addr_size(addr_size) {
28 SetFormat(eFormatPointer);
29 SetName(ConstString(llvm::formatv(Fmt: "[{0}]", Vals&: func_idx).str()));
30 }
31
32 ~ValueObjectVTableChild() override = default;
33
34 std::optional<uint64_t> GetByteSize() override { return m_addr_size; };
35
36 llvm::Expected<uint32_t> CalculateNumChildren(uint32_t max) override {
37 return 0;
38 };
39
40 ValueType GetValueType() const override { return eValueTypeVTableEntry; };
41
42 bool IsInScope() override {
43 if (ValueObject *parent = GetParent())
44 return parent->IsInScope();
45 return false;
46 };
47
48protected:
49 bool UpdateValue() override {
50 SetValueIsValid(false);
51 m_value.Clear();
52 ValueObject *parent = GetParent();
53 if (!parent) {
54 m_error.SetErrorString("owning vtable object not valid");
55 return false;
56 }
57
58 addr_t parent_addr = parent->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
59 if (parent_addr == LLDB_INVALID_ADDRESS) {
60 m_error.SetErrorString("invalid vtable address");
61 return false;
62 }
63
64 ProcessSP process_sp = GetProcessSP();
65 if (!process_sp) {
66 m_error.SetErrorString("no process");
67 return false;
68 }
69
70 TargetSP target_sp = GetTargetSP();
71 if (!target_sp) {
72 m_error.SetErrorString("no target");
73 return false;
74 }
75
76 // Each `vtable_entry_addr` points to the function pointer.
77 addr_t vtable_entry_addr = parent_addr + m_func_idx * m_addr_size;
78 addr_t vfunc_ptr =
79 process_sp->ReadPointerFromMemory(vm_addr: vtable_entry_addr, error&: m_error);
80 if (m_error.Fail()) {
81 m_error.SetErrorStringWithFormat(
82 "failed to read virtual function entry 0x%16.16" PRIx64,
83 vtable_entry_addr);
84 return false;
85 }
86
87
88 // Set our value to be the load address of the function pointer in memory
89 // and our type to be the function pointer type.
90 m_value.SetValueType(Value::ValueType::LoadAddress);
91 m_value.GetScalar() = vtable_entry_addr;
92
93 // See if our resolved address points to a function in the debug info. If
94 // it does, then we can report the type as a function prototype for this
95 // function.
96 Function *function = nullptr;
97 Address resolved_vfunc_ptr_address;
98 target_sp->ResolveLoadAddress(load_addr: vfunc_ptr, so_addr&: resolved_vfunc_ptr_address);
99 if (resolved_vfunc_ptr_address.IsValid())
100 function = resolved_vfunc_ptr_address.CalculateSymbolContextFunction();
101 if (function) {
102 m_value.SetCompilerType(function->GetCompilerType().GetPointerType());
103 } else {
104 // Set our value's compiler type to a generic function protoype so that
105 // it displays as a hex function pointer for the value and the summary
106 // will display the address description.
107
108 // Get the original type that this vtable is based off of so we can get
109 // the language from it correctly.
110 ValueObject *val = parent->GetParent();
111 auto type_system = target_sp->GetScratchTypeSystemForLanguage(
112 language: val ? val->GetObjectRuntimeLanguage() : eLanguageTypeC_plus_plus);
113 if (type_system) {
114 m_value.SetCompilerType(
115 (*type_system)->CreateGenericFunctionPrototype().GetPointerType());
116 } else {
117 consumeError(Err: type_system.takeError());
118 }
119 }
120
121 // Now read our value into m_data so that our we can use the default
122 // summary provider for C++ for function pointers which will get the
123 // address description for our function pointer.
124 if (m_error.Success()) {
125 const bool thread_and_frame_only_if_stopped = true;
126 ExecutionContext exe_ctx(
127 GetExecutionContextRef().Lock(thread_and_frame_only_if_stopped));
128 m_error = m_value.GetValueAsData(exe_ctx: &exe_ctx, data&: m_data, module: GetModule().get());
129 }
130 SetValueDidChange(true);
131 SetValueIsValid(true);
132 return true;
133 };
134
135 CompilerType GetCompilerTypeImpl() override {
136 return m_value.GetCompilerType();
137 };
138
139 const uint32_t m_func_idx;
140 const uint64_t m_addr_size;
141
142private:
143 // For ValueObject only
144 ValueObjectVTableChild(const ValueObjectVTableChild &) = delete;
145 const ValueObjectVTableChild &
146 operator=(const ValueObjectVTableChild &) = delete;
147};
148
149ValueObjectSP ValueObjectVTable::Create(ValueObject &parent) {
150 return (new ValueObjectVTable(parent))->GetSP();
151}
152
153ValueObjectVTable::ValueObjectVTable(ValueObject &parent)
154 : ValueObject(parent) {
155 SetFormat(eFormatPointer);
156}
157
158std::optional<uint64_t> ValueObjectVTable::GetByteSize() {
159 if (m_vtable_symbol)
160 return m_vtable_symbol->GetByteSize();
161 return std::nullopt;
162}
163
164llvm::Expected<uint32_t> ValueObjectVTable::CalculateNumChildren(uint32_t max) {
165 if (UpdateValueIfNeeded(update_format: false))
166 return m_num_vtable_entries <= max ? m_num_vtable_entries : max;
167 return 0;
168}
169
170ValueType ValueObjectVTable::GetValueType() const { return eValueTypeVTable; }
171
172ConstString ValueObjectVTable::GetTypeName() {
173 if (m_vtable_symbol)
174 return m_vtable_symbol->GetName();
175 return ConstString();
176}
177
178ConstString ValueObjectVTable::GetQualifiedTypeName() { return GetTypeName(); }
179
180ConstString ValueObjectVTable::GetDisplayTypeName() {
181 if (m_vtable_symbol)
182 return m_vtable_symbol->GetDisplayName();
183 return ConstString();
184}
185
186bool ValueObjectVTable::IsInScope() { return GetParent()->IsInScope(); }
187
188ValueObject *ValueObjectVTable::CreateChildAtIndex(size_t idx,
189 bool synthetic_array_member,
190 int32_t synthetic_index) {
191 if (synthetic_array_member)
192 return nullptr;
193 return new ValueObjectVTableChild(*this, idx, m_addr_size);
194}
195
196bool ValueObjectVTable::UpdateValue() {
197 m_error.Clear();
198 m_flags.m_children_count_valid = false;
199 SetValueIsValid(false);
200 m_num_vtable_entries = 0;
201 ValueObject *parent = GetParent();
202 if (!parent) {
203 m_error.SetErrorString("no parent object");
204 return false;
205 }
206
207 ProcessSP process_sp = GetProcessSP();
208 if (!process_sp) {
209 m_error.SetErrorString("no process");
210 return false;
211 }
212
213 const LanguageType language = parent->GetObjectRuntimeLanguage();
214 LanguageRuntime *language_runtime = process_sp->GetLanguageRuntime(language);
215
216 if (language_runtime == nullptr) {
217 m_error.SetErrorStringWithFormat(
218 "no language runtime support for the language \"%s\"",
219 Language::GetNameForLanguageType(language));
220 return false;
221 }
222
223 // Get the vtable information from the language runtime.
224 llvm::Expected<LanguageRuntime::VTableInfo> vtable_info_or_err =
225 language_runtime->GetVTableInfo(in_value&: *parent, /*check_type=*/true);
226 if (!vtable_info_or_err) {
227 m_error = vtable_info_or_err.takeError();
228 return false;
229 }
230
231 TargetSP target_sp = GetTargetSP();
232 const addr_t vtable_start_addr =
233 vtable_info_or_err->addr.GetLoadAddress(target: target_sp.get());
234
235 m_vtable_symbol = vtable_info_or_err->symbol;
236 if (!m_vtable_symbol) {
237 m_error.SetErrorStringWithFormat(
238 "no vtable symbol found containing 0x%" PRIx64, vtable_start_addr);
239 return false;
240 }
241
242 // Now that we know it's a vtable, we update the object's state.
243 SetName(GetTypeName());
244
245 // Calculate the number of entries
246 if (!m_vtable_symbol->GetByteSizeIsValid()) {
247 m_error.SetErrorStringWithFormat(
248 "vtable symbol \"%s\" doesn't have a valid size",
249 m_vtable_symbol->GetMangled().GetDemangledName().GetCString());
250 return false;
251 }
252
253 m_addr_size = process_sp->GetAddressByteSize();
254 const addr_t vtable_end_addr =
255 m_vtable_symbol->GetLoadAddress(target: target_sp.get()) +
256 m_vtable_symbol->GetByteSize();
257 m_num_vtable_entries = (vtable_end_addr - vtable_start_addr) / m_addr_size;
258
259 m_value.SetValueType(Value::ValueType::LoadAddress);
260 m_value.GetScalar() = parent->GetAddressOf();
261 auto type_system_or_err =
262 target_sp->GetScratchTypeSystemForLanguage(language: eLanguageTypeC_plus_plus);
263 if (type_system_or_err) {
264 m_value.SetCompilerType(
265 (*type_system_or_err)->GetBasicTypeFromAST(basic_type: eBasicTypeUnsignedLong));
266 } else {
267 consumeError(Err: type_system_or_err.takeError());
268 }
269 SetValueDidChange(true);
270 SetValueIsValid(true);
271 return true;
272}
273
274CompilerType ValueObjectVTable::GetCompilerTypeImpl() { return CompilerType(); }
275
276ValueObjectVTable::~ValueObjectVTable() = default;
277

source code of lldb/source/Core/ValueObjectVTable.cpp