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/DWARFExpression.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 <assert.h>
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() {}
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 DWARFExpression &expr = variable->LocationExpression();
131
132 if (variable->GetLocationIsConstantValueData()) {
133 // expr doesn't contain DWARF bytes, it contains the constant variable
134 // value bytes themselves...
135 if (expr.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 }
140 else
141 m_error.SetErrorString("empty constant data");
142 // constant bytes can't be edited - sorry
143 m_resolved_value.SetContext(Value::ContextType::Invalid, nullptr);
144 } else {
145 lldb::addr_t loclist_base_load_addr = LLDB_INVALID_ADDRESS;
146 ExecutionContext exe_ctx(GetExecutionContextRef());
147
148 Target *target = exe_ctx.GetTargetPtr();
149 if (target) {
150 m_data.SetByteOrder(target->GetArchitecture().GetByteOrder());
151 m_data.SetAddressByteSize(target->GetArchitecture().GetAddressByteSize());
152 }
153
154 if (expr.IsLocationList()) {
155 SymbolContext sc;
156 variable->CalculateSymbolContext(&sc);
157 if (sc.function)
158 loclist_base_load_addr =
159 sc.function->GetAddressRange().GetBaseAddress().GetLoadAddress(
160 target);
161 }
162 Value old_value(m_value);
163 if (expr.Evaluate(&exe_ctx, nullptr, loclist_base_load_addr, nullptr,
164 nullptr, m_value, &m_error)) {
165 m_resolved_value = m_value;
166 m_value.SetContext(Value::ContextType::Variable, variable);
167
168 CompilerType compiler_type = GetCompilerType();
169 if (compiler_type.IsValid())
170 m_value.SetCompilerType(compiler_type);
171
172 Value::ValueType value_type = m_value.GetValueType();
173
174 // The size of the buffer within m_value can be less than the size
175 // prescribed by its type. E.g. this can happen when an expression only
176 // partially describes an object (say, because it contains DW_OP_piece).
177 //
178 // In this case, grow m_value to the expected size. An alternative way to
179 // handle this is to teach Value::GetValueAsData() and ValueObjectChild
180 // not to read past the end of a host buffer, but this gets impractically
181 // complicated as a Value's host buffer may be shared with a distant
182 // ancestor or sibling in the ValueObject hierarchy.
183 //
184 // FIXME: When we grow m_value, we should represent the added bits as
185 // undefined somehow instead of as 0's.
186 if (value_type == Value::ValueType::HostAddress &&
187 compiler_type.IsValid()) {
188 if (size_t value_buf_size = m_value.GetBuffer().GetByteSize()) {
189 size_t value_size = m_value.GetValueByteSize(&m_error, &exe_ctx);
190 if (m_error.Success() && value_buf_size < value_size)
191 m_value.ResizeData(value_size);
192 }
193 }
194
195 Process *process = exe_ctx.GetProcessPtr();
196 const bool process_is_alive = process && process->IsAlive();
197
198 switch (value_type) {
199 case Value::ValueType::Invalid:
200 m_error.SetErrorString("invalid value");
201 break;
202 case Value::ValueType::Scalar:
203 // The variable value is in the Scalar value inside the m_value. We can
204 // point our m_data right to it.
205 m_error =
206 m_value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
207 break;
208
209 case Value::ValueType::FileAddress:
210 case Value::ValueType::LoadAddress:
211 case Value::ValueType::HostAddress:
212 // The DWARF expression result was an address in the inferior process.
213 // If this variable is an aggregate type, we just need the address as
214 // the main value as all child variable objects will rely upon this
215 // location and add an offset and then read their own values as needed.
216 // If this variable is a simple type, we read all data for it into
217 // m_data. Make sure this type has a value before we try and read it
218
219 // If we have a file address, convert it to a load address if we can.
220 if (value_type == Value::ValueType::FileAddress && process_is_alive)
221 m_value.ConvertToLoadAddress(GetModule().get(), target);
222
223 if (!CanProvideValue()) {
224 // this value object represents an aggregate type whose children have
225 // values, but this object does not. So we say we are changed if our
226 // location has changed.
227 SetValueDidChange(value_type != old_value.GetValueType() ||
228 m_value.GetScalar() != old_value.GetScalar());
229 } else {
230 // Copy the Value and set the context to use our Variable so it can
231 // extract read its value into m_data appropriately
232 Value value(m_value);
233 value.SetContext(Value::ContextType::Variable, variable);
234 m_error =
235 value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
236
237 SetValueDidChange(value_type != old_value.GetValueType() ||
238 m_value.GetScalar() != old_value.GetScalar());
239 }
240 break;
241 }
242
243 SetValueIsValid(m_error.Success());
244 } else {
245 // could not find location, won't allow editing
246 m_resolved_value.SetContext(Value::ContextType::Invalid, nullptr);
247 }
248 }
249
250 return m_error.Success();
251}
252
253void ValueObjectVariable::DoUpdateChildrenAddressType(ValueObject &valobj) {
254 Value::ValueType value_type = valobj.GetValue().GetValueType();
255 ExecutionContext exe_ctx(GetExecutionContextRef());
256 Process *process = exe_ctx.GetProcessPtr();
257 const bool process_is_alive = process && process->IsAlive();
258 const uint32_t type_info = valobj.GetCompilerType().GetTypeInfo();
259 const bool is_pointer_or_ref =
260 (type_info & (lldb::eTypeIsPointer | lldb::eTypeIsReference)) != 0;
261
262 switch (value_type) {
263 case Value::ValueType::Invalid:
264 break;
265 case Value::ValueType::FileAddress:
266 // If this type is a pointer, then its children will be considered load
267 // addresses if the pointer or reference is dereferenced, but only if
268 // the process is alive.
269 //
270 // There could be global variables like in the following code:
271 // struct LinkedListNode { Foo* foo; LinkedListNode* next; };
272 // Foo g_foo1;
273 // Foo g_foo2;
274 // LinkedListNode g_second_node = { &g_foo2, NULL };
275 // LinkedListNode g_first_node = { &g_foo1, &g_second_node };
276 //
277 // When we aren't running, we should be able to look at these variables
278 // using the "target variable" command. Children of the "g_first_node"
279 // always will be of the same address type as the parent. But children
280 // of the "next" member of LinkedListNode will become load addresses if
281 // we have a live process, or remain a file address if it was a file
282 // address.
283 if (process_is_alive && is_pointer_or_ref)
284 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
285 else
286 valobj.SetAddressTypeOfChildren(eAddressTypeFile);
287 break;
288 case Value::ValueType::HostAddress:
289 // Same as above for load addresses, except children of pointer or refs
290 // are always load addresses. Host addresses are used to store freeze
291 // dried variables. If this type is a struct, the entire struct
292 // contents will be copied into the heap of the
293 // LLDB process, but we do not currently follow any pointers.
294 if (is_pointer_or_ref)
295 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
296 else
297 valobj.SetAddressTypeOfChildren(eAddressTypeHost);
298 break;
299 case Value::ValueType::LoadAddress:
300 case Value::ValueType::Scalar:
301 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
302 break;
303 }
304}
305
306
307
308bool ValueObjectVariable::IsInScope() {
309 const ExecutionContextRef &exe_ctx_ref = GetExecutionContextRef();
310 if (exe_ctx_ref.HasFrameRef()) {
311 ExecutionContext exe_ctx(exe_ctx_ref);
312 StackFrame *frame = exe_ctx.GetFramePtr();
313 if (frame) {
314 return m_variable_sp->IsInScope(frame);
315 } else {
316 // This ValueObject had a frame at one time, but now we can't locate it,
317 // so return false since we probably aren't in scope.
318 return false;
319 }
320 }
321 // We have a variable that wasn't tied to a frame, which means it is a global
322 // and is always in scope.
323 return true;
324}
325
326lldb::ModuleSP ValueObjectVariable::GetModule() {
327 if (m_variable_sp) {
328 SymbolContextScope *sc_scope = m_variable_sp->GetSymbolContextScope();
329 if (sc_scope) {
330 return sc_scope->CalculateSymbolContextModule();
331 }
332 }
333 return lldb::ModuleSP();
334}
335
336SymbolContextScope *ValueObjectVariable::GetSymbolContextScope() {
337 if (m_variable_sp)
338 return m_variable_sp->GetSymbolContextScope();
339 return nullptr;
340}
341
342bool ValueObjectVariable::GetDeclaration(Declaration &decl) {
343 if (m_variable_sp) {
344 decl = m_variable_sp->GetDeclaration();
345 return true;
346 }
347 return false;
348}
349
350const char *ValueObjectVariable::GetLocationAsCString() {
351 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo)
352 return GetLocationAsCStringImpl(m_resolved_value, m_data);
353 else
354 return ValueObject::GetLocationAsCString();
355}
356
357bool ValueObjectVariable::SetValueFromCString(const char *value_str,
358 Status &error) {
359 if (!UpdateValueIfNeeded()) {
360 error.SetErrorString("unable to update value before writing");
361 return false;
362 }
363
364 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo) {
365 RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
366 ExecutionContext exe_ctx(GetExecutionContextRef());
367 RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
368 RegisterValue reg_value;
369 if (!reg_info || !reg_ctx) {
370 error.SetErrorString("unable to retrieve register info");
371 return false;
372 }
373 error = reg_value.SetValueFromString(reg_info, llvm::StringRef(value_str));
374 if (error.Fail())
375 return false;
376 if (reg_ctx->WriteRegister(reg_info, reg_value)) {
377 SetNeedsUpdate();
378 return true;
379 } else {
380 error.SetErrorString("unable to write back to register");
381 return false;
382 }
383 } else
384 return ValueObject::SetValueFromCString(value_str, error);
385}
386
387bool ValueObjectVariable::SetData(DataExtractor &data, Status &error) {
388 if (!UpdateValueIfNeeded()) {
389 error.SetErrorString("unable to update value before writing");
390 return false;
391 }
392
393 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo) {
394 RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
395 ExecutionContext exe_ctx(GetExecutionContextRef());
396 RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
397 RegisterValue reg_value;
398 if (!reg_info || !reg_ctx) {
399 error.SetErrorString("unable to retrieve register info");
400 return false;
401 }
402 error = reg_value.SetValueFromData(reg_info, data, 0, true);
403 if (error.Fail())
404 return false;
405 if (reg_ctx->WriteRegister(reg_info, reg_value)) {
406 SetNeedsUpdate();
407 return true;
408 } else {
409 error.SetErrorString("unable to write back to register");
410 return false;
411 }
412 } else
413 return ValueObject::SetData(data, error);
414}
415