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