1//===-- ValueObjectVariable.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/ValueObjectVariable.h"
10
11#include "lldb/Core/Address.h"
12#include "lldb/Core/AddressRange.h"
13#include "lldb/Core/Declaration.h"
14#include "lldb/Core/Module.h"
15#include "lldb/Core/Value.h"
16#include "lldb/Expression/DWARFExpressionList.h"
17#include "lldb/Symbol/Function.h"
18#include "lldb/Symbol/ObjectFile.h"
19#include "lldb/Symbol/SymbolContext.h"
20#include "lldb/Symbol/SymbolContextScope.h"
21#include "lldb/Symbol/Type.h"
22#include "lldb/Symbol/Variable.h"
23#include "lldb/Target/ExecutionContext.h"
24#include "lldb/Target/Process.h"
25#include "lldb/Target/RegisterContext.h"
26#include "lldb/Target/Target.h"
27#include "lldb/Utility/DataExtractor.h"
28#include "lldb/Utility/RegisterValue.h"
29#include "lldb/Utility/Scalar.h"
30#include "lldb/Utility/Status.h"
31#include "lldb/lldb-private-enumerations.h"
32#include "lldb/lldb-types.h"
33
34#include "llvm/ADT/StringRef.h"
35
36#include <cassert>
37#include <memory>
38
39namespace lldb_private {
40class ExecutionContextScope;
41}
42namespace lldb_private {
43class StackFrame;
44}
45namespace lldb_private {
46struct RegisterInfo;
47}
48using namespace lldb_private;
49
50lldb::ValueObjectSP
51ValueObjectVariable::Create(ExecutionContextScope *exe_scope,
52 const lldb::VariableSP &var_sp) {
53 auto manager_sp = ValueObjectManager::Create();
54 return (new ValueObjectVariable(exe_scope, *manager_sp, var_sp))->GetSP();
55}
56
57ValueObjectVariable::ValueObjectVariable(ExecutionContextScope *exe_scope,
58 ValueObjectManager &manager,
59 const lldb::VariableSP &var_sp)
60 : ValueObject(exe_scope, manager), m_variable_sp(var_sp) {
61 // Do not attempt to construct one of these objects with no variable!
62 assert(m_variable_sp.get() != nullptr);
63 m_name = var_sp->GetName();
64}
65
66ValueObjectVariable::~ValueObjectVariable() = default;
67
68CompilerType ValueObjectVariable::GetCompilerTypeImpl() {
69 Type *var_type = m_variable_sp->GetType();
70 if (var_type)
71 return var_type->GetForwardCompilerType();
72 return CompilerType();
73}
74
75ConstString ValueObjectVariable::GetTypeName() {
76 Type *var_type = m_variable_sp->GetType();
77 if (var_type)
78 return var_type->GetName();
79 return ConstString();
80}
81
82ConstString ValueObjectVariable::GetDisplayTypeName() {
83 Type *var_type = m_variable_sp->GetType();
84 if (var_type)
85 return var_type->GetForwardCompilerType().GetDisplayTypeName();
86 return ConstString();
87}
88
89ConstString ValueObjectVariable::GetQualifiedTypeName() {
90 Type *var_type = m_variable_sp->GetType();
91 if (var_type)
92 return var_type->GetQualifiedName();
93 return ConstString();
94}
95
96size_t ValueObjectVariable::CalculateNumChildren(uint32_t max) {
97 CompilerType type(GetCompilerType());
98
99 if (!type.IsValid())
100 return 0;
101
102 ExecutionContext exe_ctx(GetExecutionContextRef());
103 const bool omit_empty_base_classes = true;
104 auto child_count = type.GetNumChildren(omit_empty_base_classes, &exe_ctx);
105 return child_count <= max ? child_count : max;
106}
107
108llvm::Optional<uint64_t> ValueObjectVariable::GetByteSize() {
109 ExecutionContext exe_ctx(GetExecutionContextRef());
110
111 CompilerType type(GetCompilerType());
112
113 if (!type.IsValid())
114 return {};
115
116 return type.GetByteSize(exe_ctx.GetBestExecutionContextScope());
117}
118
119lldb::ValueType ValueObjectVariable::GetValueType() const {
120 if (m_variable_sp)
121 return m_variable_sp->GetScope();
122 return lldb::eValueTypeInvalid;
123}
124
125bool ValueObjectVariable::UpdateValue() {
126 SetValueIsValid(false);
127 m_error.Clear();
128
129 Variable *variable = m_variable_sp.get();
130 DWARFExpressionList &expr_list = variable->LocationExpressionList();
131
132 if (variable->GetLocationIsConstantValueData()) {
133 // expr doesn't contain DWARF bytes, it contains the constant variable
134 // value bytes themselves...
135 if (expr_list.GetExpressionData(m_data)) {
136 if (m_data.GetDataStart() && m_data.GetByteSize())
137 m_value.SetBytes(m_data.GetDataStart(), m_data.GetByteSize());
138 m_value.SetContext(Value::ContextType::Variable, variable);
139 } else
140 m_error.SetErrorString("empty constant data");
141 // constant bytes can't be edited - sorry
142 m_resolved_value.SetContext(Value::ContextType::Invalid, nullptr);
143 } else {
144 lldb::addr_t loclist_base_load_addr = LLDB_INVALID_ADDRESS;
145 ExecutionContext exe_ctx(GetExecutionContextRef());
146
147 Target *target = exe_ctx.GetTargetPtr();
148 if (target) {
149 m_data.SetByteOrder(target->GetArchitecture().GetByteOrder());
150 m_data.SetAddressByteSize(target->GetArchitecture().GetAddressByteSize());
151 }
152
153 if (!expr_list.IsAlwaysValidSingleExpr()) {
154 SymbolContext sc;
155 variable->CalculateSymbolContext(&sc);
156 if (sc.function)
157 loclist_base_load_addr =
158 sc.function->GetAddressRange().GetBaseAddress().GetLoadAddress(
159 target);
160 }
161 Value old_value(m_value);
162 if (expr_list.Evaluate(&exe_ctx, nullptr, loclist_base_load_addr, nullptr,
163 nullptr, m_value, &m_error)) {
164 m_resolved_value = m_value;
165 m_value.SetContext(Value::ContextType::Variable, variable);
166
167 CompilerType compiler_type = GetCompilerType();
168 if (compiler_type.IsValid())
169 m_value.SetCompilerType(compiler_type);
170
171 Value::ValueType value_type = m_value.GetValueType();
172
173 // The size of the buffer within m_value can be less than the size
174 // prescribed by its type. E.g. this can happen when an expression only
175 // partially describes an object (say, because it contains DW_OP_piece).
176 //
177 // In this case, grow m_value to the expected size. An alternative way to
178 // handle this is to teach Value::GetValueAsData() and ValueObjectChild
179 // not to read past the end of a host buffer, but this gets impractically
180 // complicated as a Value's host buffer may be shared with a distant
181 // ancestor or sibling in the ValueObject hierarchy.
182 //
183 // FIXME: When we grow m_value, we should represent the added bits as
184 // undefined somehow instead of as 0's.
185 if (value_type == Value::ValueType::HostAddress &&
186 compiler_type.IsValid()) {
187 if (size_t value_buf_size = m_value.GetBuffer().GetByteSize()) {
188 size_t value_size = m_value.GetValueByteSize(&m_error, &exe_ctx);
189 if (m_error.Success() && value_buf_size < value_size)
190 m_value.ResizeData(value_size);
191 }
192 }
193
194 Process *process = exe_ctx.GetProcessPtr();
195 const bool process_is_alive = process && process->IsAlive();
196
197 switch (value_type) {
198 case Value::ValueType::Invalid:
199 m_error.SetErrorString("invalid value");
200 break;
201 case Value::ValueType::Scalar:
202 // The variable value is in the Scalar value inside the m_value. We can
203 // point our m_data right to it.
204 m_error =
205 m_value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
206 break;
207
208 case Value::ValueType::FileAddress:
209 case Value::ValueType::LoadAddress:
210 case Value::ValueType::HostAddress:
211 // The DWARF expression result was an address in the inferior process.
212 // If this variable is an aggregate type, we just need the address as
213 // the main value as all child variable objects will rely upon this
214 // location and add an offset and then read their own values as needed.
215 // If this variable is a simple type, we read all data for it into
216 // m_data. Make sure this type has a value before we try and read it
217
218 // If we have a file address, convert it to a load address if we can.
219 if (value_type == Value::ValueType::FileAddress && process_is_alive)
220 m_value.ConvertToLoadAddress(GetModule().get(), target);
221
222 if (!CanProvideValue()) {
223 // this value object represents an aggregate type whose children have
224 // values, but this object does not. So we say we are changed if our
225 // location has changed.
226 SetValueDidChange(value_type != old_value.GetValueType() ||
227 m_value.GetScalar() != old_value.GetScalar());
228 } else {
229 // Copy the Value and set the context to use our Variable so it can
230 // extract read its value into m_data appropriately
231 Value value(m_value);
232 value.SetContext(Value::ContextType::Variable, variable);
233 m_error =
234 value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
235
236 SetValueDidChange(value_type != old_value.GetValueType() ||
237 m_value.GetScalar() != old_value.GetScalar());
238 }
239 break;
240 }
241
242 SetValueIsValid(m_error.Success());
243 } else {
244 // could not find location, won't allow editing
245 m_resolved_value.SetContext(Value::ContextType::Invalid, nullptr);
246 }
247 }
248
249 return m_error.Success();
250}
251
252void ValueObjectVariable::DoUpdateChildrenAddressType(ValueObject &valobj) {
253 Value::ValueType value_type = valobj.GetValue().GetValueType();
254 ExecutionContext exe_ctx(GetExecutionContextRef());
255 Process *process = exe_ctx.GetProcessPtr();
256 const bool process_is_alive = process && process->IsAlive();
257 const uint32_t type_info = valobj.GetCompilerType().GetTypeInfo();
258 const bool is_pointer_or_ref =
259 (type_info & (lldb::eTypeIsPointer | lldb::eTypeIsReference)) != 0;
260
261 switch (value_type) {
262 case Value::ValueType::Invalid:
263 break;
264 case Value::ValueType::FileAddress:
265 // If this type is a pointer, then its children will be considered load
266 // addresses if the pointer or reference is dereferenced, but only if
267 // the process is alive.
268 //
269 // There could be global variables like in the following code:
270 // struct LinkedListNode { Foo* foo; LinkedListNode* next; };
271 // Foo g_foo1;
272 // Foo g_foo2;
273 // LinkedListNode g_second_node = { &g_foo2, NULL };
274 // LinkedListNode g_first_node = { &g_foo1, &g_second_node };
275 //
276 // When we aren't running, we should be able to look at these variables
277 // using the "target variable" command. Children of the "g_first_node"
278 // always will be of the same address type as the parent. But children
279 // of the "next" member of LinkedListNode will become load addresses if
280 // we have a live process, or remain a file address if it was a file
281 // address.
282 if (process_is_alive && is_pointer_or_ref)
283 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
284 else
285 valobj.SetAddressTypeOfChildren(eAddressTypeFile);
286 break;
287 case Value::ValueType::HostAddress:
288 // Same as above for load addresses, except children of pointer or refs
289 // are always load addresses. Host addresses are used to store freeze
290 // dried variables. If this type is a struct, the entire struct
291 // contents will be copied into the heap of the
292 // LLDB process, but we do not currently follow any pointers.
293 if (is_pointer_or_ref)
294 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
295 else
296 valobj.SetAddressTypeOfChildren(eAddressTypeHost);
297 break;
298 case Value::ValueType::LoadAddress:
299 case Value::ValueType::Scalar:
300 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
301 break;
302 }
303}
304
305
306
307bool ValueObjectVariable::IsInScope() {
308 const ExecutionContextRef &exe_ctx_ref = GetExecutionContextRef();
309 if (exe_ctx_ref.HasFrameRef()) {
310 ExecutionContext exe_ctx(exe_ctx_ref);
311 StackFrame *frame = exe_ctx.GetFramePtr();
312 if (frame) {
313 return m_variable_sp->IsInScope(frame);
314 } else {
315 // This ValueObject had a frame at one time, but now we can't locate it,
316 // so return false since we probably aren't in scope.
317 return false;
318 }
319 }
320 // We have a variable that wasn't tied to a frame, which means it is a global
321 // and is always in scope.
322 return true;
323}
324
325lldb::ModuleSP ValueObjectVariable::GetModule() {
326 if (m_variable_sp) {
327 SymbolContextScope *sc_scope = m_variable_sp->GetSymbolContextScope();
328 if (sc_scope) {
329 return sc_scope->CalculateSymbolContextModule();
330 }
331 }
332 return lldb::ModuleSP();
333}
334
335SymbolContextScope *ValueObjectVariable::GetSymbolContextScope() {
336 if (m_variable_sp)
337 return m_variable_sp->GetSymbolContextScope();
338 return nullptr;
339}
340
341bool ValueObjectVariable::GetDeclaration(Declaration &decl) {
342 if (m_variable_sp) {
343 decl = m_variable_sp->GetDeclaration();
344 return true;
345 }
346 return false;
347}
348
349const char *ValueObjectVariable::GetLocationAsCString() {
350 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo)
351 return GetLocationAsCStringImpl(m_resolved_value, m_data);
352 else
353 return ValueObject::GetLocationAsCString();
354}
355
356bool ValueObjectVariable::SetValueFromCString(const char *value_str,
357 Status &error) {
358 if (!UpdateValueIfNeeded()) {
359 error.SetErrorString("unable to update value before writing");
360 return false;
361 }
362
363 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo) {
364 RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
365 ExecutionContext exe_ctx(GetExecutionContextRef());
366 RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
367 RegisterValue reg_value;
368 if (!reg_info || !reg_ctx) {
369 error.SetErrorString("unable to retrieve register info");
370 return false;
371 }
372 error = reg_value.SetValueFromString(reg_info, llvm::StringRef(value_str));
373 if (error.Fail())
374 return false;
375 if (reg_ctx->WriteRegister(reg_info, reg_value)) {
376 SetNeedsUpdate();
377 return true;
378 } else {
379 error.SetErrorString("unable to write back to register");
380 return false;
381 }
382 } else
383 return ValueObject::SetValueFromCString(value_str, error);
384}
385
386bool ValueObjectVariable::SetData(DataExtractor &data, Status &error) {
387 if (!UpdateValueIfNeeded()) {
388 error.SetErrorString("unable to update value before writing");
389 return false;
390 }
391
392 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo) {
393 RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
394 ExecutionContext exe_ctx(GetExecutionContextRef());
395 RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
396 RegisterValue reg_value;
397 if (!reg_info || !reg_ctx) {
398 error.SetErrorString("unable to retrieve register info");
399 return false;
400 }
401 error = reg_value.SetValueFromData(reg_info, data, 0, true);
402 if (error.Fail())
403 return false;
404 if (reg_ctx->WriteRegister(reg_info, reg_value)) {
405 SetNeedsUpdate();
406 return true;
407 } else {
408 error.SetErrorString("unable to write back to register");
409 return false;
410 }
411 } else
412 return ValueObject::SetData(data, error);
413}
414

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