1 //===-- CPPLanguageRuntime.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 <cstring>
10 
11 #include <memory>
12 
13 #include "CPPLanguageRuntime.h"
14 
15 #include "llvm/ADT/StringRef.h"
16 
17 #include "lldb/Symbol/Block.h"
18 #include "lldb/Symbol/Variable.h"
19 #include "lldb/Symbol/VariableList.h"
20 
21 #include "lldb/Core/PluginManager.h"
22 #include "lldb/Core/UniqueCStringMap.h"
23 #include "lldb/Symbol/CompileUnit.h"
24 #include "lldb/Target/ABI.h"
25 #include "lldb/Target/ExecutionContext.h"
26 #include "lldb/Target/RegisterContext.h"
27 #include "lldb/Target/SectionLoadList.h"
28 #include "lldb/Target/StackFrame.h"
29 #include "lldb/Target/ThreadPlanRunToAddress.h"
30 #include "lldb/Target/ThreadPlanStepInRange.h"
31 #include "lldb/Utility/Timer.h"
32 
33 using namespace lldb;
34 using namespace lldb_private;
35 
36 static ConstString g_this = ConstString("this");
37 
38 char CPPLanguageRuntime::ID = 0;
39 
40 CPPLanguageRuntime::CPPLanguageRuntime(Process *process)
41     : LanguageRuntime(process) {}
42 
43 bool CPPLanguageRuntime::IsAllowedRuntimeValue(ConstString name) {
44   return name == g_this;
45 }
46 
47 bool CPPLanguageRuntime::GetObjectDescription(Stream &str,
48                                               ValueObject &object) {
49   // C++ has no generic way to do this.
50   return false;
51 }
52 
53 bool CPPLanguageRuntime::GetObjectDescription(
54     Stream &str, Value &value, ExecutionContextScope *exe_scope) {
55   // C++ has no generic way to do this.
56   return false;
57 }
58 
59 bool contains_lambda_identifier(llvm::StringRef &str_ref) {
60   return str_ref.contains("$_") || str_ref.contains("'lambda'");
61 }
62 
63 CPPLanguageRuntime::LibCppStdFunctionCallableInfo
64 line_entry_helper(Target &target, const SymbolContext &sc, Symbol *symbol,
65                   llvm::StringRef first_template_param_sref,
66                   bool has___invoke) {
67 
68   CPPLanguageRuntime::LibCppStdFunctionCallableInfo optional_info;
69 
70   AddressRange range;
71   sc.GetAddressRange(eSymbolContextEverything, 0, false, range);
72 
73   Address address = range.GetBaseAddress();
74 
75   Address addr;
76   if (target.ResolveLoadAddress(address.GetCallableLoadAddress(&target),
77                                 addr)) {
78     LineEntry line_entry;
79     addr.CalculateSymbolContextLineEntry(line_entry);
80 
81     if (contains_lambda_identifier(first_template_param_sref) || has___invoke) {
82       // Case 1 and 2
83       optional_info.callable_case = lldb_private::CPPLanguageRuntime::
84           LibCppStdFunctionCallableCase::Lambda;
85     } else {
86       // Case 3
87       optional_info.callable_case = lldb_private::CPPLanguageRuntime::
88           LibCppStdFunctionCallableCase::CallableObject;
89     }
90 
91     optional_info.callable_symbol = *symbol;
92     optional_info.callable_line_entry = line_entry;
93     optional_info.callable_address = addr;
94   }
95 
96   return optional_info;
97 }
98 
99 CPPLanguageRuntime::LibCppStdFunctionCallableInfo
100 CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
101     lldb::ValueObjectSP &valobj_sp) {
102   LLDB_SCOPED_TIMER();
103 
104   LibCppStdFunctionCallableInfo optional_info;
105 
106   if (!valobj_sp)
107     return optional_info;
108 
109   // Member __f_ has type __base*, the contents of which will hold:
110   // 1) a vtable entry which may hold type information needed to discover the
111   //    lambda being called
112   // 2) possibly hold a pointer to the callable object
113   // e.g.
114   //
115   // (lldb) frame var -R  f_display
116   // (std::__1::function<void (int)>) f_display = {
117   //  __buf_ = {
118   //  …
119   // }
120   //  __f_ = 0x00007ffeefbffa00
121   // }
122   // (lldb) memory read -fA 0x00007ffeefbffa00
123   // 0x7ffeefbffa00: ... `vtable for std::__1::__function::__func<void (*) ...
124   // 0x7ffeefbffa08: ... `print_num(int) at std_function_cppreference_exam ...
125   //
126   // We will be handling five cases below, std::function is wrapping:
127   //
128   // 1) a lambda we know at compile time. We will obtain the name of the lambda
129   //    from the first template pameter from __func's vtable. We will look up
130   //    the lambda's operator()() and obtain the line table entry.
131   // 2) a lambda we know at runtime. A pointer to the lambdas __invoke method
132   //    will be stored after the vtable. We will obtain the lambdas name from
133   //    this entry and lookup operator()() and obtain the line table entry.
134   // 3) a callable object via operator()(). We will obtain the name of the
135   //    object from the first template parameter from __func's vtable. We will
136   //    look up the objects operator()() and obtain the line table entry.
137   // 4) a member function. A pointer to the function will stored after the
138   //    we will obtain the name from this pointer.
139   // 5) a free function. A pointer to the function will stored after the vtable
140   //    we will obtain the name from this pointer.
141   ValueObjectSP member__f_(
142       valobj_sp->GetChildMemberWithName(ConstString("__f_"), true));
143 
144   if (member__f_) {
145     ValueObjectSP sub_member__f_(
146        member__f_->GetChildMemberWithName(ConstString("__f_"), true));
147 
148     if (sub_member__f_)
149         member__f_ = sub_member__f_;
150   }
151 
152   if (!member__f_)
153     return optional_info;
154 
155   lldb::addr_t member__f_pointer_value = member__f_->GetValueAsUnsigned(0);
156 
157   optional_info.member__f_pointer_value = member__f_pointer_value;
158 
159   if (!member__f_pointer_value)
160     return optional_info;
161 
162   ExecutionContext exe_ctx(valobj_sp->GetExecutionContextRef());
163   Process *process = exe_ctx.GetProcessPtr();
164 
165   if (process == nullptr)
166     return optional_info;
167 
168   uint32_t address_size = process->GetAddressByteSize();
169   Status status;
170 
171   // First item pointed to by __f_ should be the pointer to the vtable for
172   // a __base object.
173   lldb::addr_t vtable_address =
174       process->ReadPointerFromMemory(member__f_pointer_value, status);
175 
176   if (status.Fail())
177     return optional_info;
178 
179   lldb::addr_t vtable_address_first_entry =
180       process->ReadPointerFromMemory(vtable_address + address_size, status);
181 
182   if (status.Fail())
183     return optional_info;
184 
185   lldb::addr_t address_after_vtable = member__f_pointer_value + address_size;
186   // As commented above we may not have a function pointer but if we do we will
187   // need it.
188   lldb::addr_t possible_function_address =
189       process->ReadPointerFromMemory(address_after_vtable, status);
190 
191   if (status.Fail())
192     return optional_info;
193 
194   Target &target = process->GetTarget();
195 
196   if (target.GetSectionLoadList().IsEmpty())
197     return optional_info;
198 
199   Address vtable_first_entry_resolved;
200 
201   if (!target.GetSectionLoadList().ResolveLoadAddress(
202           vtable_address_first_entry, vtable_first_entry_resolved))
203     return optional_info;
204 
205   Address vtable_addr_resolved;
206   SymbolContext sc;
207   Symbol *symbol = nullptr;
208 
209   if (!target.GetSectionLoadList().ResolveLoadAddress(vtable_address,
210                                                       vtable_addr_resolved))
211     return optional_info;
212 
213   target.GetImages().ResolveSymbolContextForAddress(
214       vtable_addr_resolved, eSymbolContextEverything, sc);
215   symbol = sc.symbol;
216 
217   if (symbol == nullptr)
218     return optional_info;
219 
220   llvm::StringRef vtable_name(symbol->GetName().GetStringRef());
221   bool found_expected_start_string =
222       vtable_name.startswith("vtable for std::__1::__function::__func<");
223 
224   if (!found_expected_start_string)
225     return optional_info;
226 
227   // Given case 1 or 3 we have a vtable name, we are want to extract the first
228   // template parameter
229   //
230   //  ... __func<main::$_0, std::__1::allocator<main::$_0> ...
231   //             ^^^^^^^^^
232   //
233   // We could see names such as:
234   //    main::$_0
235   //    Bar::add_num2(int)::'lambda'(int)
236   //    Bar
237   //
238   // We do this by find the first < and , and extracting in between.
239   //
240   // This covers the case of the lambda known at compile time.
241   size_t first_open_angle_bracket = vtable_name.find('<') + 1;
242   size_t first_comma = vtable_name.find(',');
243 
244   llvm::StringRef first_template_parameter =
245       vtable_name.slice(first_open_angle_bracket, first_comma);
246 
247   Address function_address_resolved;
248 
249   // Setup for cases 2, 4 and 5 we have a pointer to a function after the
250   // vtable. We will use a process of elimination to drop through each case
251   // and obtain the data we need.
252   if (target.GetSectionLoadList().ResolveLoadAddress(
253           possible_function_address, function_address_resolved)) {
254     target.GetImages().ResolveSymbolContextForAddress(
255         function_address_resolved, eSymbolContextEverything, sc);
256     symbol = sc.symbol;
257   }
258 
259   // These conditions are used several times to simplify statements later on.
260   bool has___invoke =
261       (symbol ? symbol->GetName().GetStringRef().contains("__invoke") : false);
262   auto calculate_symbol_context_helper = [](auto &t,
263                                             SymbolContextList &sc_list) {
264     SymbolContext sc;
265     t->CalculateSymbolContext(&sc);
266     sc_list.Append(sc);
267   };
268 
269   // Case 2
270   if (has___invoke) {
271     SymbolContextList scl;
272     calculate_symbol_context_helper(symbol, scl);
273 
274     return line_entry_helper(target, scl[0], symbol, first_template_parameter,
275                              has___invoke);
276   }
277 
278   // Case 4 or 5
279   if (symbol && !symbol->GetName().GetStringRef().startswith("vtable for") &&
280       !contains_lambda_identifier(first_template_parameter) && !has___invoke) {
281     optional_info.callable_case =
282         LibCppStdFunctionCallableCase::FreeOrMemberFunction;
283     optional_info.callable_address = function_address_resolved;
284     optional_info.callable_symbol = *symbol;
285 
286     return optional_info;
287   }
288 
289   std::string func_to_match = first_template_parameter.str();
290 
291   auto it = CallableLookupCache.find(func_to_match);
292   if (it != CallableLookupCache.end())
293     return it->second;
294 
295   SymbolContextList scl;
296 
297   CompileUnit *vtable_cu =
298       vtable_first_entry_resolved.CalculateSymbolContextCompileUnit();
299   llvm::StringRef name_to_use = func_to_match;
300 
301   // Case 3, we have a callable object instead of a lambda
302   //
303   // TODO
304   // We currently don't support this case a callable object may have multiple
305   // operator()() varying on const/non-const and number of arguments and we
306   // don't have a way to currently distinguish them so we will bail out now.
307   if (!contains_lambda_identifier(name_to_use))
308     return optional_info;
309 
310   if (vtable_cu && !has___invoke) {
311     lldb::FunctionSP func_sp =
312         vtable_cu->FindFunction([name_to_use](const FunctionSP &f) {
313           auto name = f->GetName().GetStringRef();
314           if (name.startswith(name_to_use) && name.contains("operator"))
315             return true;
316 
317           return false;
318         });
319 
320     if (func_sp) {
321       calculate_symbol_context_helper(func_sp, scl);
322     }
323   }
324 
325   if (symbol == nullptr)
326     return optional_info;
327 
328   // Case 1 or 3
329   if (scl.GetSize() >= 1) {
330     optional_info = line_entry_helper(target, scl[0], symbol,
331                                       first_template_parameter, has___invoke);
332   }
333 
334   CallableLookupCache[func_to_match] = optional_info;
335 
336   return optional_info;
337 }
338 
339 lldb::ThreadPlanSP
340 CPPLanguageRuntime::GetStepThroughTrampolinePlan(Thread &thread,
341                                                  bool stop_others) {
342   ThreadPlanSP ret_plan_sp;
343 
344   lldb::addr_t curr_pc = thread.GetRegisterContext()->GetPC();
345 
346   TargetSP target_sp(thread.CalculateTarget());
347 
348   if (target_sp->GetSectionLoadList().IsEmpty())
349     return ret_plan_sp;
350 
351   Address pc_addr_resolved;
352   SymbolContext sc;
353   Symbol *symbol;
354 
355   if (!target_sp->GetSectionLoadList().ResolveLoadAddress(curr_pc,
356                                                           pc_addr_resolved))
357     return ret_plan_sp;
358 
359   target_sp->GetImages().ResolveSymbolContextForAddress(
360       pc_addr_resolved, eSymbolContextEverything, sc);
361   symbol = sc.symbol;
362 
363   if (symbol == nullptr)
364     return ret_plan_sp;
365 
366   llvm::StringRef function_name(symbol->GetName().GetCString());
367 
368   // Handling the case where we are attempting to step into std::function.
369   // The behavior will be that we will attempt to obtain the wrapped
370   // callable via FindLibCppStdFunctionCallableInfo() and if we find it we
371   // will return a ThreadPlanRunToAddress to the callable. Therefore we will
372   // step into the wrapped callable.
373   //
374   bool found_expected_start_string =
375       function_name.startswith("std::__1::function<");
376 
377   if (!found_expected_start_string)
378     return ret_plan_sp;
379 
380   AddressRange range_of_curr_func;
381   sc.GetAddressRange(eSymbolContextEverything, 0, false, range_of_curr_func);
382 
383   StackFrameSP frame = thread.GetStackFrameAtIndex(0);
384 
385   if (frame) {
386     ValueObjectSP value_sp = frame->FindVariable(g_this);
387 
388     CPPLanguageRuntime::LibCppStdFunctionCallableInfo callable_info =
389         FindLibCppStdFunctionCallableInfo(value_sp);
390 
391     if (callable_info.callable_case != LibCppStdFunctionCallableCase::Invalid &&
392         value_sp->GetValueIsValid()) {
393       // We found the std::function wrapped callable and we have its address.
394       // We now create a ThreadPlan to run to the callable.
395       ret_plan_sp = std::make_shared<ThreadPlanRunToAddress>(
396           thread, callable_info.callable_address, stop_others);
397       return ret_plan_sp;
398     } else {
399       // We are in std::function but we could not obtain the callable.
400       // We create a ThreadPlan to keep stepping through using the address range
401       // of the current function.
402       ret_plan_sp = std::make_shared<ThreadPlanStepInRange>(
403           thread, range_of_curr_func, sc, nullptr, eOnlyThisThread,
404           eLazyBoolYes, eLazyBoolYes);
405       return ret_plan_sp;
406     }
407   }
408 
409   return ret_plan_sp;
410 }
411