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 #include <optional>
39
40 namespace lldb_private {
41 class ExecutionContextScope;
42 }
43 namespace lldb_private {
44 class StackFrame;
45 }
46 namespace lldb_private {
47 struct RegisterInfo;
48 }
49 using namespace lldb_private;
50
51 lldb::ValueObjectSP
Create(ExecutionContextScope * exe_scope,const lldb::VariableSP & var_sp)52 ValueObjectVariable::Create(ExecutionContextScope *exe_scope,
53 const lldb::VariableSP &var_sp) {
54 auto manager_sp = ValueObjectManager::Create();
55 return (new ValueObjectVariable(exe_scope, *manager_sp, var_sp))->GetSP();
56 }
57
ValueObjectVariable(ExecutionContextScope * exe_scope,ValueObjectManager & manager,const lldb::VariableSP & var_sp)58 ValueObjectVariable::ValueObjectVariable(ExecutionContextScope *exe_scope,
59 ValueObjectManager &manager,
60 const lldb::VariableSP &var_sp)
61 : ValueObject(exe_scope, manager), m_variable_sp(var_sp) {
62 // Do not attempt to construct one of these objects with no variable!
63 assert(m_variable_sp.get() != nullptr);
64 m_name = var_sp->GetName();
65 }
66
67 ValueObjectVariable::~ValueObjectVariable() = default;
68
GetCompilerTypeImpl()69 CompilerType ValueObjectVariable::GetCompilerTypeImpl() {
70 Type *var_type = m_variable_sp->GetType();
71 if (var_type)
72 return var_type->GetForwardCompilerType();
73 return CompilerType();
74 }
75
GetTypeName()76 ConstString ValueObjectVariable::GetTypeName() {
77 Type *var_type = m_variable_sp->GetType();
78 if (var_type)
79 return var_type->GetName();
80 return ConstString();
81 }
82
GetDisplayTypeName()83 ConstString ValueObjectVariable::GetDisplayTypeName() {
84 Type *var_type = m_variable_sp->GetType();
85 if (var_type)
86 return var_type->GetForwardCompilerType().GetDisplayTypeName();
87 return ConstString();
88 }
89
GetQualifiedTypeName()90 ConstString ValueObjectVariable::GetQualifiedTypeName() {
91 Type *var_type = m_variable_sp->GetType();
92 if (var_type)
93 return var_type->GetQualifiedName();
94 return ConstString();
95 }
96
97 llvm::Expected<uint32_t>
CalculateNumChildren(uint32_t max)98 ValueObjectVariable::CalculateNumChildren(uint32_t max) {
99 CompilerType type(GetCompilerType());
100
101 if (!type.IsValid())
102 return llvm::make_error<llvm::StringError>("invalid type",
103 llvm::inconvertibleErrorCode());
104
105 ExecutionContext exe_ctx(GetExecutionContextRef());
106 const bool omit_empty_base_classes = true;
107 auto child_count = type.GetNumChildren(omit_empty_base_classes, &exe_ctx);
108 if (!child_count)
109 return child_count;
110 return *child_count <= max ? *child_count : max;
111 }
112
GetByteSize()113 std::optional<uint64_t> ValueObjectVariable::GetByteSize() {
114 ExecutionContext exe_ctx(GetExecutionContextRef());
115
116 CompilerType type(GetCompilerType());
117
118 if (!type.IsValid())
119 return {};
120
121 return type.GetByteSize(exe_ctx.GetBestExecutionContextScope());
122 }
123
GetValueType() const124 lldb::ValueType ValueObjectVariable::GetValueType() const {
125 if (m_variable_sp)
126 return m_variable_sp->GetScope();
127 return lldb::eValueTypeInvalid;
128 }
129
UpdateValue()130 bool ValueObjectVariable::UpdateValue() {
131 SetValueIsValid(false);
132 m_error.Clear();
133
134 Variable *variable = m_variable_sp.get();
135 DWARFExpressionList &expr_list = variable->LocationExpressionList();
136
137 if (variable->GetLocationIsConstantValueData()) {
138 // expr doesn't contain DWARF bytes, it contains the constant variable
139 // value bytes themselves...
140 if (expr_list.GetExpressionData(m_data)) {
141 if (m_data.GetDataStart() && m_data.GetByteSize())
142 m_value.SetBytes(m_data.GetDataStart(), m_data.GetByteSize());
143 m_value.SetContext(Value::ContextType::Variable, variable);
144 } else
145 m_error.SetErrorString("empty constant data");
146 // constant bytes can't be edited - sorry
147 m_resolved_value.SetContext(Value::ContextType::Invalid, nullptr);
148 } else {
149 lldb::addr_t loclist_base_load_addr = LLDB_INVALID_ADDRESS;
150 ExecutionContext exe_ctx(GetExecutionContextRef());
151
152 Target *target = exe_ctx.GetTargetPtr();
153 if (target) {
154 m_data.SetByteOrder(target->GetArchitecture().GetByteOrder());
155 m_data.SetAddressByteSize(target->GetArchitecture().GetAddressByteSize());
156 }
157
158 if (!expr_list.IsAlwaysValidSingleExpr()) {
159 SymbolContext sc;
160 variable->CalculateSymbolContext(&sc);
161 if (sc.function)
162 loclist_base_load_addr =
163 sc.function->GetAddressRange().GetBaseAddress().GetLoadAddress(
164 target);
165 }
166 Value old_value(m_value);
167 llvm::Expected<Value> maybe_value = expr_list.Evaluate(
168 &exe_ctx, nullptr, loclist_base_load_addr, nullptr, nullptr);
169
170 if (maybe_value) {
171 m_value = *maybe_value;
172 m_resolved_value = m_value;
173 m_value.SetContext(Value::ContextType::Variable, variable);
174
175 CompilerType compiler_type = GetCompilerType();
176 if (compiler_type.IsValid())
177 m_value.SetCompilerType(compiler_type);
178
179 Value::ValueType value_type = m_value.GetValueType();
180
181 // The size of the buffer within m_value can be less than the size
182 // prescribed by its type. E.g. this can happen when an expression only
183 // partially describes an object (say, because it contains DW_OP_piece).
184 //
185 // In this case, grow m_value to the expected size. An alternative way to
186 // handle this is to teach Value::GetValueAsData() and ValueObjectChild
187 // not to read past the end of a host buffer, but this gets impractically
188 // complicated as a Value's host buffer may be shared with a distant
189 // ancestor or sibling in the ValueObject hierarchy.
190 //
191 // FIXME: When we grow m_value, we should represent the added bits as
192 // undefined somehow instead of as 0's.
193 if (value_type == Value::ValueType::HostAddress &&
194 compiler_type.IsValid()) {
195 if (size_t value_buf_size = m_value.GetBuffer().GetByteSize()) {
196 size_t value_size = m_value.GetValueByteSize(&m_error, &exe_ctx);
197 if (m_error.Success() && value_buf_size < value_size)
198 m_value.ResizeData(value_size);
199 }
200 }
201
202 Process *process = exe_ctx.GetProcessPtr();
203 const bool process_is_alive = process && process->IsAlive();
204
205 switch (value_type) {
206 case Value::ValueType::Invalid:
207 m_error.SetErrorString("invalid value");
208 break;
209 case Value::ValueType::Scalar:
210 // The variable value is in the Scalar value inside the m_value. We can
211 // point our m_data right to it.
212 m_error =
213 m_value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
214 break;
215
216 case Value::ValueType::FileAddress:
217 case Value::ValueType::LoadAddress:
218 case Value::ValueType::HostAddress:
219 // The DWARF expression result was an address in the inferior process.
220 // If this variable is an aggregate type, we just need the address as
221 // the main value as all child variable objects will rely upon this
222 // location and add an offset and then read their own values as needed.
223 // If this variable is a simple type, we read all data for it into
224 // m_data. Make sure this type has a value before we try and read it
225
226 // If we have a file address, convert it to a load address if we can.
227 if (value_type == Value::ValueType::FileAddress && process_is_alive)
228 m_value.ConvertToLoadAddress(GetModule().get(), target);
229
230 if (!CanProvideValue()) {
231 // this value object represents an aggregate type whose children have
232 // values, but this object does not. So we say we are changed if our
233 // location has changed.
234 SetValueDidChange(value_type != old_value.GetValueType() ||
235 m_value.GetScalar() != old_value.GetScalar());
236 } else {
237 // Copy the Value and set the context to use our Variable so it can
238 // extract read its value into m_data appropriately
239 Value value(m_value);
240 value.SetContext(Value::ContextType::Variable, variable);
241 m_error =
242 value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
243
244 SetValueDidChange(value_type != old_value.GetValueType() ||
245 m_value.GetScalar() != old_value.GetScalar());
246 }
247 break;
248 }
249
250 SetValueIsValid(m_error.Success());
251 } else {
252 m_error = maybe_value.takeError();
253 // could not find location, won't allow editing
254 m_resolved_value.SetContext(Value::ContextType::Invalid, nullptr);
255 }
256 }
257
258 return m_error.Success();
259 }
260
DoUpdateChildrenAddressType(ValueObject & valobj)261 void ValueObjectVariable::DoUpdateChildrenAddressType(ValueObject &valobj) {
262 Value::ValueType value_type = valobj.GetValue().GetValueType();
263 ExecutionContext exe_ctx(GetExecutionContextRef());
264 Process *process = exe_ctx.GetProcessPtr();
265 const bool process_is_alive = process && process->IsAlive();
266 const uint32_t type_info = valobj.GetCompilerType().GetTypeInfo();
267 const bool is_pointer_or_ref =
268 (type_info & (lldb::eTypeIsPointer | lldb::eTypeIsReference)) != 0;
269
270 switch (value_type) {
271 case Value::ValueType::Invalid:
272 break;
273 case Value::ValueType::FileAddress:
274 // If this type is a pointer, then its children will be considered load
275 // addresses if the pointer or reference is dereferenced, but only if
276 // the process is alive.
277 //
278 // There could be global variables like in the following code:
279 // struct LinkedListNode { Foo* foo; LinkedListNode* next; };
280 // Foo g_foo1;
281 // Foo g_foo2;
282 // LinkedListNode g_second_node = { &g_foo2, NULL };
283 // LinkedListNode g_first_node = { &g_foo1, &g_second_node };
284 //
285 // When we aren't running, we should be able to look at these variables
286 // using the "target variable" command. Children of the "g_first_node"
287 // always will be of the same address type as the parent. But children
288 // of the "next" member of LinkedListNode will become load addresses if
289 // we have a live process, or remain a file address if it was a file
290 // address.
291 if (process_is_alive && is_pointer_or_ref)
292 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
293 else
294 valobj.SetAddressTypeOfChildren(eAddressTypeFile);
295 break;
296 case Value::ValueType::HostAddress:
297 // Same as above for load addresses, except children of pointer or refs
298 // are always load addresses. Host addresses are used to store freeze
299 // dried variables. If this type is a struct, the entire struct
300 // contents will be copied into the heap of the
301 // LLDB process, but we do not currently follow any pointers.
302 if (is_pointer_or_ref)
303 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
304 else
305 valobj.SetAddressTypeOfChildren(eAddressTypeHost);
306 break;
307 case Value::ValueType::LoadAddress:
308 case Value::ValueType::Scalar:
309 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
310 break;
311 }
312 }
313
314
315
IsInScope()316 bool ValueObjectVariable::IsInScope() {
317 const ExecutionContextRef &exe_ctx_ref = GetExecutionContextRef();
318 if (exe_ctx_ref.HasFrameRef()) {
319 ExecutionContext exe_ctx(exe_ctx_ref);
320 StackFrame *frame = exe_ctx.GetFramePtr();
321 if (frame) {
322 return m_variable_sp->IsInScope(frame);
323 } else {
324 // This ValueObject had a frame at one time, but now we can't locate it,
325 // so return false since we probably aren't in scope.
326 return false;
327 }
328 }
329 // We have a variable that wasn't tied to a frame, which means it is a global
330 // and is always in scope.
331 return true;
332 }
333
GetModule()334 lldb::ModuleSP ValueObjectVariable::GetModule() {
335 if (m_variable_sp) {
336 SymbolContextScope *sc_scope = m_variable_sp->GetSymbolContextScope();
337 if (sc_scope) {
338 return sc_scope->CalculateSymbolContextModule();
339 }
340 }
341 return lldb::ModuleSP();
342 }
343
GetSymbolContextScope()344 SymbolContextScope *ValueObjectVariable::GetSymbolContextScope() {
345 if (m_variable_sp)
346 return m_variable_sp->GetSymbolContextScope();
347 return nullptr;
348 }
349
GetDeclaration(Declaration & decl)350 bool ValueObjectVariable::GetDeclaration(Declaration &decl) {
351 if (m_variable_sp) {
352 decl = m_variable_sp->GetDeclaration();
353 return true;
354 }
355 return false;
356 }
357
GetLocationAsCString()358 const char *ValueObjectVariable::GetLocationAsCString() {
359 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo)
360 return GetLocationAsCStringImpl(m_resolved_value, m_data);
361 else
362 return ValueObject::GetLocationAsCString();
363 }
364
SetValueFromCString(const char * value_str,Status & error)365 bool ValueObjectVariable::SetValueFromCString(const char *value_str,
366 Status &error) {
367 if (!UpdateValueIfNeeded()) {
368 error.SetErrorString("unable to update value before writing");
369 return false;
370 }
371
372 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo) {
373 RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
374 ExecutionContext exe_ctx(GetExecutionContextRef());
375 RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
376 RegisterValue reg_value;
377 if (!reg_info || !reg_ctx) {
378 error.SetErrorString("unable to retrieve register info");
379 return false;
380 }
381 error = reg_value.SetValueFromString(reg_info, llvm::StringRef(value_str));
382 if (error.Fail())
383 return false;
384 if (reg_ctx->WriteRegister(reg_info, reg_value)) {
385 SetNeedsUpdate();
386 return true;
387 } else {
388 error.SetErrorString("unable to write back to register");
389 return false;
390 }
391 } else
392 return ValueObject::SetValueFromCString(value_str, error);
393 }
394
SetData(DataExtractor & data,Status & error)395 bool ValueObjectVariable::SetData(DataExtractor &data, Status &error) {
396 if (!UpdateValueIfNeeded()) {
397 error.SetErrorString("unable to update value before writing");
398 return false;
399 }
400
401 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo) {
402 RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
403 ExecutionContext exe_ctx(GetExecutionContextRef());
404 RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
405 RegisterValue reg_value;
406 if (!reg_info || !reg_ctx) {
407 error.SetErrorString("unable to retrieve register info");
408 return false;
409 }
410 error = reg_value.SetValueFromData(*reg_info, data, 0, true);
411 if (error.Fail())
412 return false;
413 if (reg_ctx->WriteRegister(reg_info, reg_value)) {
414 SetNeedsUpdate();
415 return true;
416 } else {
417 error.SetErrorString("unable to write back to register");
418 return false;
419 }
420 } else
421 return ValueObject::SetData(data, error);
422 }
423