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/Module.h"
14 #include "lldb/Core/Value.h"
15 #include "lldb/Expression/DWARFExpression.h"
16 #include "lldb/Symbol/Declaration.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 
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() {}
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   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::eContextTypeVariable, 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::eContextTypeInvalid, 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::eContextTypeVariable, 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::eValueTypeHostAddress &&
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::eValueTypeScalar:
200         // The variable value is in the Scalar value inside the m_value. We can
201         // point our m_data right to it.
202         m_error =
203             m_value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
204         break;
205 
206       case Value::eValueTypeFileAddress:
207       case Value::eValueTypeLoadAddress:
208       case Value::eValueTypeHostAddress:
209         // The DWARF expression result was an address in the inferior process.
210         // If this variable is an aggregate type, we just need the address as
211         // the main value as all child variable objects will rely upon this
212         // location and add an offset and then read their own values as needed.
213         // If this variable is a simple type, we read all data for it into
214         // m_data. Make sure this type has a value before we try and read it
215 
216         // If we have a file address, convert it to a load address if we can.
217         if (value_type == Value::eValueTypeFileAddress && process_is_alive)
218           m_value.ConvertToLoadAddress(GetModule().get(), target);
219 
220         if (!CanProvideValue()) {
221           // this value object represents an aggregate type whose children have
222           // values, but this object does not. So we say we are changed if our
223           // location has changed.
224           SetValueDidChange(value_type != old_value.GetValueType() ||
225                             m_value.GetScalar() != old_value.GetScalar());
226         } else {
227           // Copy the Value and set the context to use our Variable so it can
228           // extract read its value into m_data appropriately
229           Value value(m_value);
230           value.SetContext(Value::eContextTypeVariable, variable);
231           m_error =
232               value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
233 
234           SetValueDidChange(value_type != old_value.GetValueType() ||
235                             m_value.GetScalar() != old_value.GetScalar());
236         }
237         break;
238       }
239 
240       SetValueIsValid(m_error.Success());
241     } else {
242       // could not find location, won't allow editing
243       m_resolved_value.SetContext(Value::eContextTypeInvalid, nullptr);
244     }
245   }
246 
247   return m_error.Success();
248 }
249 
250 void ValueObjectVariable::DoUpdateChildrenAddressType(ValueObject &valobj) {
251   Value::ValueType value_type = valobj.GetValue().GetValueType();
252   ExecutionContext exe_ctx(GetExecutionContextRef());
253   Process *process = exe_ctx.GetProcessPtr();
254   const bool process_is_alive = process && process->IsAlive();
255   const uint32_t type_info = valobj.GetCompilerType().GetTypeInfo();
256   const bool is_pointer_or_ref =
257       (type_info & (lldb::eTypeIsPointer | lldb::eTypeIsReference)) != 0;
258 
259   switch (value_type) {
260   case Value::eValueTypeFileAddress:
261     // If this type is a pointer, then its children will be considered load
262     // addresses if the pointer or reference is dereferenced, but only if
263     // the process is alive.
264     //
265     // There could be global variables like in the following code:
266     // struct LinkedListNode { Foo* foo; LinkedListNode* next; };
267     // Foo g_foo1;
268     // Foo g_foo2;
269     // LinkedListNode g_second_node = { &g_foo2, NULL };
270     // LinkedListNode g_first_node = { &g_foo1, &g_second_node };
271     //
272     // When we aren't running, we should be able to look at these variables
273     // using the "target variable" command. Children of the "g_first_node"
274     // always will be of the same address type as the parent. But children
275     // of the "next" member of LinkedListNode will become load addresses if
276     // we have a live process, or remain a file address if it was a file
277     // address.
278     if (process_is_alive && is_pointer_or_ref)
279       valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
280     else
281       valobj.SetAddressTypeOfChildren(eAddressTypeFile);
282     break;
283   case Value::eValueTypeHostAddress:
284     // Same as above for load addresses, except children of pointer or refs
285     // are always load addresses. Host addresses are used to store freeze
286     // dried variables. If this type is a struct, the entire struct
287     // contents will be copied into the heap of the
288     // LLDB process, but we do not currently follow any pointers.
289     if (is_pointer_or_ref)
290       valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
291     else
292       valobj.SetAddressTypeOfChildren(eAddressTypeHost);
293     break;
294   case Value::eValueTypeLoadAddress:
295   case Value::eValueTypeScalar:
296     valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
297     break;
298   }
299 }
300 
301 
302 
303 bool ValueObjectVariable::IsInScope() {
304   const ExecutionContextRef &exe_ctx_ref = GetExecutionContextRef();
305   if (exe_ctx_ref.HasFrameRef()) {
306     ExecutionContext exe_ctx(exe_ctx_ref);
307     StackFrame *frame = exe_ctx.GetFramePtr();
308     if (frame) {
309       return m_variable_sp->IsInScope(frame);
310     } else {
311       // This ValueObject had a frame at one time, but now we can't locate it,
312       // so return false since we probably aren't in scope.
313       return false;
314     }
315   }
316   // We have a variable that wasn't tied to a frame, which means it is a global
317   // and is always in scope.
318   return true;
319 }
320 
321 lldb::ModuleSP ValueObjectVariable::GetModule() {
322   if (m_variable_sp) {
323     SymbolContextScope *sc_scope = m_variable_sp->GetSymbolContextScope();
324     if (sc_scope) {
325       return sc_scope->CalculateSymbolContextModule();
326     }
327   }
328   return lldb::ModuleSP();
329 }
330 
331 SymbolContextScope *ValueObjectVariable::GetSymbolContextScope() {
332   if (m_variable_sp)
333     return m_variable_sp->GetSymbolContextScope();
334   return nullptr;
335 }
336 
337 bool ValueObjectVariable::GetDeclaration(Declaration &decl) {
338   if (m_variable_sp) {
339     decl = m_variable_sp->GetDeclaration();
340     return true;
341   }
342   return false;
343 }
344 
345 const char *ValueObjectVariable::GetLocationAsCString() {
346   if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo)
347     return GetLocationAsCStringImpl(m_resolved_value, m_data);
348   else
349     return ValueObject::GetLocationAsCString();
350 }
351 
352 bool ValueObjectVariable::SetValueFromCString(const char *value_str,
353                                               Status &error) {
354   if (!UpdateValueIfNeeded()) {
355     error.SetErrorString("unable to update value before writing");
356     return false;
357   }
358 
359   if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo) {
360     RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
361     ExecutionContext exe_ctx(GetExecutionContextRef());
362     RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
363     RegisterValue reg_value;
364     if (!reg_info || !reg_ctx) {
365       error.SetErrorString("unable to retrieve register info");
366       return false;
367     }
368     error = reg_value.SetValueFromString(reg_info, llvm::StringRef(value_str));
369     if (error.Fail())
370       return false;
371     if (reg_ctx->WriteRegister(reg_info, reg_value)) {
372       SetNeedsUpdate();
373       return true;
374     } else {
375       error.SetErrorString("unable to write back to register");
376       return false;
377     }
378   } else
379     return ValueObject::SetValueFromCString(value_str, error);
380 }
381 
382 bool ValueObjectVariable::SetData(DataExtractor &data, Status &error) {
383   if (!UpdateValueIfNeeded()) {
384     error.SetErrorString("unable to update value before writing");
385     return false;
386   }
387 
388   if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo) {
389     RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
390     ExecutionContext exe_ctx(GetExecutionContextRef());
391     RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
392     RegisterValue reg_value;
393     if (!reg_info || !reg_ctx) {
394       error.SetErrorString("unable to retrieve register info");
395       return false;
396     }
397     error = reg_value.SetValueFromData(reg_info, data, 0, true);
398     if (error.Fail())
399       return false;
400     if (reg_ctx->WriteRegister(reg_info, reg_value)) {
401       SetNeedsUpdate();
402       return true;
403     } else {
404       error.SetErrorString("unable to write back to register");
405       return false;
406     }
407   } else
408     return ValueObject::SetData(data, error);
409 }
410