1 //===-- ValueObjectVariable.cpp ---------------------------------*- C++ -*-===//
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   return (new ValueObjectVariable(exe_scope, var_sp))->GetSP();
54 }
55 
56 ValueObjectVariable::ValueObjectVariable(ExecutionContextScope *exe_scope,
57                                          const lldb::VariableSP &var_sp)
58     : ValueObject(exe_scope), m_variable_sp(var_sp) {
59   // Do not attempt to construct one of these objects with no variable!
60   assert(m_variable_sp.get() != nullptr);
61   m_name = var_sp->GetName();
62 }
63 
64 ValueObjectVariable::~ValueObjectVariable() {}
65 
66 CompilerType ValueObjectVariable::GetCompilerTypeImpl() {
67   Type *var_type = m_variable_sp->GetType();
68   if (var_type)
69     return var_type->GetForwardCompilerType();
70   return CompilerType();
71 }
72 
73 ConstString ValueObjectVariable::GetTypeName() {
74   Type *var_type = m_variable_sp->GetType();
75   if (var_type)
76     return var_type->GetName();
77   return ConstString();
78 }
79 
80 ConstString ValueObjectVariable::GetDisplayTypeName() {
81   Type *var_type = m_variable_sp->GetType();
82   if (var_type)
83     return var_type->GetForwardCompilerType().GetDisplayTypeName();
84   return ConstString();
85 }
86 
87 ConstString ValueObjectVariable::GetQualifiedTypeName() {
88   Type *var_type = m_variable_sp->GetType();
89   if (var_type)
90     return var_type->GetQualifiedName();
91   return ConstString();
92 }
93 
94 size_t ValueObjectVariable::CalculateNumChildren(uint32_t max) {
95   CompilerType type(GetCompilerType());
96 
97   if (!type.IsValid())
98     return 0;
99 
100   ExecutionContext exe_ctx(GetExecutionContextRef());
101   const bool omit_empty_base_classes = true;
102   auto child_count = type.GetNumChildren(omit_empty_base_classes, &exe_ctx);
103   return child_count <= max ? child_count : max;
104 }
105 
106 uint64_t ValueObjectVariable::GetByteSize() {
107   ExecutionContext exe_ctx(GetExecutionContextRef());
108 
109   CompilerType type(GetCompilerType());
110 
111   if (!type.IsValid())
112     return 0;
113 
114   return type.GetByteSize(exe_ctx.GetBestExecutionContextScope()).getValueOr(0);
115 }
116 
117 lldb::ValueType ValueObjectVariable::GetValueType() const {
118   if (m_variable_sp)
119     return m_variable_sp->GetScope();
120   return lldb::eValueTypeInvalid;
121 }
122 
123 bool ValueObjectVariable::UpdateValue() {
124   SetValueIsValid(false);
125   m_error.Clear();
126 
127   Variable *variable = m_variable_sp.get();
128   DWARFExpression &expr = variable->LocationExpression();
129 
130   if (variable->GetLocationIsConstantValueData()) {
131     // expr doesn't contain DWARF bytes, it contains the constant variable
132     // value bytes themselves...
133     if (expr.GetExpressionData(m_data))
134       m_value.SetContext(Value::eContextTypeVariable, variable);
135     else
136       m_error.SetErrorString("empty constant data");
137     // constant bytes can't be edited - sorry
138     m_resolved_value.SetContext(Value::eContextTypeInvalid, nullptr);
139   } else {
140     lldb::addr_t loclist_base_load_addr = LLDB_INVALID_ADDRESS;
141     ExecutionContext exe_ctx(GetExecutionContextRef());
142 
143     Target *target = exe_ctx.GetTargetPtr();
144     if (target) {
145       m_data.SetByteOrder(target->GetArchitecture().GetByteOrder());
146       m_data.SetAddressByteSize(target->GetArchitecture().GetAddressByteSize());
147     }
148 
149     if (expr.IsLocationList()) {
150       SymbolContext sc;
151       variable->CalculateSymbolContext(&sc);
152       if (sc.function)
153         loclist_base_load_addr =
154             sc.function->GetAddressRange().GetBaseAddress().GetLoadAddress(
155                 target);
156     }
157     Value old_value(m_value);
158     if (expr.Evaluate(&exe_ctx, nullptr, loclist_base_load_addr, nullptr,
159                       nullptr, m_value, &m_error)) {
160       m_resolved_value = m_value;
161       m_value.SetContext(Value::eContextTypeVariable, variable);
162 
163       CompilerType compiler_type = GetCompilerType();
164       if (compiler_type.IsValid())
165         m_value.SetCompilerType(compiler_type);
166 
167       Value::ValueType value_type = m_value.GetValueType();
168 
169       Process *process = exe_ctx.GetProcessPtr();
170       const bool process_is_alive = process && process->IsAlive();
171 
172       switch (value_type) {
173       case Value::eValueTypeVector:
174       // fall through
175       case Value::eValueTypeScalar:
176         // The variable value is in the Scalar value inside the m_value. We can
177         // point our m_data right to it.
178         m_error =
179             m_value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
180         break;
181 
182       case Value::eValueTypeFileAddress:
183       case Value::eValueTypeLoadAddress:
184       case Value::eValueTypeHostAddress:
185         // The DWARF expression result was an address in the inferior process.
186         // If this variable is an aggregate type, we just need the address as
187         // the main value as all child variable objects will rely upon this
188         // location and add an offset and then read their own values as needed.
189         // If this variable is a simple type, we read all data for it into
190         // m_data. Make sure this type has a value before we try and read it
191 
192         // If we have a file address, convert it to a load address if we can.
193         if (value_type == Value::eValueTypeFileAddress && process_is_alive)
194           m_value.ConvertToLoadAddress(GetModule().get(), target);
195 
196         if (!CanProvideValue()) {
197           // this value object represents an aggregate type whose children have
198           // values, but this object does not. So we say we are changed if our
199           // location has changed.
200           SetValueDidChange(value_type != old_value.GetValueType() ||
201                             m_value.GetScalar() != old_value.GetScalar());
202         } else {
203           // Copy the Value and set the context to use our Variable so it can
204           // extract read its value into m_data appropriately
205           Value value(m_value);
206           value.SetContext(Value::eContextTypeVariable, variable);
207           m_error =
208               value.GetValueAsData(&exe_ctx, m_data, GetModule().get());
209 
210           SetValueDidChange(value_type != old_value.GetValueType() ||
211                             m_value.GetScalar() != old_value.GetScalar());
212         }
213         break;
214       }
215 
216       SetValueIsValid(m_error.Success());
217     } else {
218       // could not find location, won't allow editing
219       m_resolved_value.SetContext(Value::eContextTypeInvalid, nullptr);
220     }
221   }
222   return m_error.Success();
223 }
224 
225 bool ValueObjectVariable::IsInScope() {
226   const ExecutionContextRef &exe_ctx_ref = GetExecutionContextRef();
227   if (exe_ctx_ref.HasFrameRef()) {
228     ExecutionContext exe_ctx(exe_ctx_ref);
229     StackFrame *frame = exe_ctx.GetFramePtr();
230     if (frame) {
231       return m_variable_sp->IsInScope(frame);
232     } else {
233       // This ValueObject had a frame at one time, but now we can't locate it,
234       // so return false since we probably aren't in scope.
235       return false;
236     }
237   }
238   // We have a variable that wasn't tied to a frame, which means it is a global
239   // and is always in scope.
240   return true;
241 }
242 
243 lldb::ModuleSP ValueObjectVariable::GetModule() {
244   if (m_variable_sp) {
245     SymbolContextScope *sc_scope = m_variable_sp->GetSymbolContextScope();
246     if (sc_scope) {
247       return sc_scope->CalculateSymbolContextModule();
248     }
249   }
250   return lldb::ModuleSP();
251 }
252 
253 SymbolContextScope *ValueObjectVariable::GetSymbolContextScope() {
254   if (m_variable_sp)
255     return m_variable_sp->GetSymbolContextScope();
256   return nullptr;
257 }
258 
259 bool ValueObjectVariable::GetDeclaration(Declaration &decl) {
260   if (m_variable_sp) {
261     decl = m_variable_sp->GetDeclaration();
262     return true;
263   }
264   return false;
265 }
266 
267 const char *ValueObjectVariable::GetLocationAsCString() {
268   if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo)
269     return GetLocationAsCStringImpl(m_resolved_value, m_data);
270   else
271     return ValueObject::GetLocationAsCString();
272 }
273 
274 bool ValueObjectVariable::SetValueFromCString(const char *value_str,
275                                               Status &error) {
276   if (!UpdateValueIfNeeded()) {
277     error.SetErrorString("unable to update value before writing");
278     return false;
279   }
280 
281   if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo) {
282     RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
283     ExecutionContext exe_ctx(GetExecutionContextRef());
284     RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
285     RegisterValue reg_value;
286     if (!reg_info || !reg_ctx) {
287       error.SetErrorString("unable to retrieve register info");
288       return false;
289     }
290     error = reg_value.SetValueFromString(reg_info, llvm::StringRef(value_str));
291     if (error.Fail())
292       return false;
293     if (reg_ctx->WriteRegister(reg_info, reg_value)) {
294       SetNeedsUpdate();
295       return true;
296     } else {
297       error.SetErrorString("unable to write back to register");
298       return false;
299     }
300   } else
301     return ValueObject::SetValueFromCString(value_str, error);
302 }
303 
304 bool ValueObjectVariable::SetData(DataExtractor &data, Status &error) {
305   if (!UpdateValueIfNeeded()) {
306     error.SetErrorString("unable to update value before writing");
307     return false;
308   }
309 
310   if (m_resolved_value.GetContextType() == Value::eContextTypeRegisterInfo) {
311     RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
312     ExecutionContext exe_ctx(GetExecutionContextRef());
313     RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
314     RegisterValue reg_value;
315     if (!reg_info || !reg_ctx) {
316       error.SetErrorString("unable to retrieve register info");
317       return false;
318     }
319     error = reg_value.SetValueFromData(reg_info, data, 0, true);
320     if (error.Fail())
321       return false;
322     if (reg_ctx->WriteRegister(reg_info, reg_value)) {
323       SetNeedsUpdate();
324       return true;
325     } else {
326       error.SetErrorString("unable to write back to register");
327       return false;
328     }
329   } else
330     return ValueObject::SetData(data, error);
331 }
332