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 // Artificial coroutine-related variables emitted by clang.
38 static ConstString g_promise = ConstString("__promise");
39 static ConstString g_coro_frame = ConstString("__coro_frame");
40
41 char CPPLanguageRuntime::ID = 0;
42
CPPLanguageRuntime(Process * process)43 CPPLanguageRuntime::CPPLanguageRuntime(Process *process)
44 : LanguageRuntime(process) {}
45
IsAllowedRuntimeValue(ConstString name)46 bool CPPLanguageRuntime::IsAllowedRuntimeValue(ConstString name) {
47 return name == g_this || name == g_promise || name == g_coro_frame;
48 }
49
GetObjectDescription(Stream & str,ValueObject & object)50 llvm::Error CPPLanguageRuntime::GetObjectDescription(Stream &str,
51 ValueObject &object) {
52 // C++ has no generic way to do this.
53 return llvm::createStringError("C++ does not support object descriptions");
54 }
55
56 llvm::Error
GetObjectDescription(Stream & str,Value & value,ExecutionContextScope * exe_scope)57 CPPLanguageRuntime::GetObjectDescription(Stream &str, Value &value,
58 ExecutionContextScope *exe_scope) {
59 // C++ has no generic way to do this.
60 return llvm::createStringError("C++ does not support object descriptions");
61 }
62
contains_lambda_identifier(llvm::StringRef & str_ref)63 bool contains_lambda_identifier(llvm::StringRef &str_ref) {
64 return str_ref.contains("$_") || str_ref.contains("'lambda'");
65 }
66
67 CPPLanguageRuntime::LibCppStdFunctionCallableInfo
line_entry_helper(Target & target,const SymbolContext & sc,Symbol * symbol,llvm::StringRef first_template_param_sref,bool has_invoke)68 line_entry_helper(Target &target, const SymbolContext &sc, Symbol *symbol,
69 llvm::StringRef first_template_param_sref,
70 bool has_invoke) {
71
72 CPPLanguageRuntime::LibCppStdFunctionCallableInfo optional_info;
73
74 AddressRange range;
75 sc.GetAddressRange(eSymbolContextEverything, 0, false, range);
76
77 Address address = range.GetBaseAddress();
78
79 Address addr;
80 if (target.ResolveLoadAddress(address.GetCallableLoadAddress(&target),
81 addr)) {
82 LineEntry line_entry;
83 addr.CalculateSymbolContextLineEntry(line_entry);
84
85 if (contains_lambda_identifier(first_template_param_sref) || has_invoke) {
86 // Case 1 and 2
87 optional_info.callable_case = lldb_private::CPPLanguageRuntime::
88 LibCppStdFunctionCallableCase::Lambda;
89 } else {
90 // Case 3
91 optional_info.callable_case = lldb_private::CPPLanguageRuntime::
92 LibCppStdFunctionCallableCase::CallableObject;
93 }
94
95 optional_info.callable_symbol = *symbol;
96 optional_info.callable_line_entry = line_entry;
97 optional_info.callable_address = addr;
98 }
99
100 return optional_info;
101 }
102
103 CPPLanguageRuntime::LibCppStdFunctionCallableInfo
FindLibCppStdFunctionCallableInfo(lldb::ValueObjectSP & valobj_sp)104 CPPLanguageRuntime::FindLibCppStdFunctionCallableInfo(
105 lldb::ValueObjectSP &valobj_sp) {
106 LLDB_SCOPED_TIMER();
107
108 LibCppStdFunctionCallableInfo optional_info;
109
110 if (!valobj_sp)
111 return optional_info;
112
113 // Member __f_ has type __base*, the contents of which will hold:
114 // 1) a vtable entry which may hold type information needed to discover the
115 // lambda being called
116 // 2) possibly hold a pointer to the callable object
117 // e.g.
118 //
119 // (lldb) frame var -R f_display
120 // (std::__1::function<void (int)>) f_display = {
121 // __buf_ = {
122 // …
123 // }
124 // __f_ = 0x00007ffeefbffa00
125 // }
126 // (lldb) memory read -fA 0x00007ffeefbffa00
127 // 0x7ffeefbffa00: ... `vtable for std::__1::__function::__func<void (*) ...
128 // 0x7ffeefbffa08: ... `print_num(int) at std_function_cppreference_exam ...
129 //
130 // We will be handling five cases below, std::function is wrapping:
131 //
132 // 1) a lambda we know at compile time. We will obtain the name of the lambda
133 // from the first template pameter from __func's vtable. We will look up
134 // the lambda's operator()() and obtain the line table entry.
135 // 2) a lambda we know at runtime. A pointer to the lambdas __invoke method
136 // will be stored after the vtable. We will obtain the lambdas name from
137 // this entry and lookup operator()() and obtain the line table entry.
138 // 3) a callable object via operator()(). We will obtain the name of the
139 // object from the first template parameter from __func's vtable. We will
140 // look up the objects operator()() and obtain the line table entry.
141 // 4) a member function. A pointer to the function will stored after the
142 // we will obtain the name from this pointer.
143 // 5) a free function. A pointer to the function will stored after the vtable
144 // we will obtain the name from this pointer.
145 ValueObjectSP member_f_(valobj_sp->GetChildMemberWithName("__f_"));
146
147 if (member_f_) {
148 ValueObjectSP sub_member_f_(member_f_->GetChildMemberWithName("__f_"));
149
150 if (sub_member_f_)
151 member_f_ = sub_member_f_;
152 }
153
154 if (!member_f_)
155 return optional_info;
156
157 lldb::addr_t member_f_pointer_value = member_f_->GetValueAsUnsigned(0);
158
159 optional_info.member_f_pointer_value = member_f_pointer_value;
160
161 if (!member_f_pointer_value)
162 return optional_info;
163
164 ExecutionContext exe_ctx(valobj_sp->GetExecutionContextRef());
165 Process *process = exe_ctx.GetProcessPtr();
166
167 if (process == nullptr)
168 return optional_info;
169
170 uint32_t address_size = process->GetAddressByteSize();
171 Status status;
172
173 // First item pointed to by __f_ should be the pointer to the vtable for
174 // a __base object.
175 lldb::addr_t vtable_address =
176 process->ReadPointerFromMemory(member_f_pointer_value, status);
177
178 if (status.Fail())
179 return optional_info;
180
181 lldb::addr_t vtable_address_first_entry =
182 process->ReadPointerFromMemory(vtable_address + address_size, status);
183
184 if (status.Fail())
185 return optional_info;
186
187 lldb::addr_t address_after_vtable = member_f_pointer_value + address_size;
188 // As commented above we may not have a function pointer but if we do we will
189 // need it.
190 lldb::addr_t possible_function_address =
191 process->ReadPointerFromMemory(address_after_vtable, status);
192
193 if (status.Fail())
194 return optional_info;
195
196 Target &target = process->GetTarget();
197
198 if (target.GetSectionLoadList().IsEmpty())
199 return optional_info;
200
201 Address vtable_first_entry_resolved;
202
203 if (!target.GetSectionLoadList().ResolveLoadAddress(
204 vtable_address_first_entry, vtable_first_entry_resolved))
205 return optional_info;
206
207 Address vtable_addr_resolved;
208 SymbolContext sc;
209 Symbol *symbol = nullptr;
210
211 if (!target.GetSectionLoadList().ResolveLoadAddress(vtable_address,
212 vtable_addr_resolved))
213 return optional_info;
214
215 target.GetImages().ResolveSymbolContextForAddress(
216 vtable_addr_resolved, eSymbolContextEverything, sc);
217 symbol = sc.symbol;
218
219 if (symbol == nullptr)
220 return optional_info;
221
222 llvm::StringRef vtable_name(symbol->GetName().GetStringRef());
223 bool found_expected_start_string =
224 vtable_name.starts_with("vtable for std::__1::__function::__func<");
225
226 if (!found_expected_start_string)
227 return optional_info;
228
229 // Given case 1 or 3 we have a vtable name, we are want to extract the first
230 // template parameter
231 //
232 // ... __func<main::$_0, std::__1::allocator<main::$_0> ...
233 // ^^^^^^^^^
234 //
235 // We could see names such as:
236 // main::$_0
237 // Bar::add_num2(int)::'lambda'(int)
238 // Bar
239 //
240 // We do this by find the first < and , and extracting in between.
241 //
242 // This covers the case of the lambda known at compile time.
243 size_t first_open_angle_bracket = vtable_name.find('<') + 1;
244 size_t first_comma = vtable_name.find(',');
245
246 llvm::StringRef first_template_parameter =
247 vtable_name.slice(first_open_angle_bracket, first_comma);
248
249 Address function_address_resolved;
250
251 // Setup for cases 2, 4 and 5 we have a pointer to a function after the
252 // vtable. We will use a process of elimination to drop through each case
253 // and obtain the data we need.
254 if (target.GetSectionLoadList().ResolveLoadAddress(
255 possible_function_address, function_address_resolved)) {
256 target.GetImages().ResolveSymbolContextForAddress(
257 function_address_resolved, eSymbolContextEverything, sc);
258 symbol = sc.symbol;
259 }
260
261 // These conditions are used several times to simplify statements later on.
262 bool has_invoke =
263 (symbol ? symbol->GetName().GetStringRef().contains("__invoke") : false);
264 auto calculate_symbol_context_helper = [](auto &t,
265 SymbolContextList &sc_list) {
266 SymbolContext sc;
267 t->CalculateSymbolContext(&sc);
268 sc_list.Append(sc);
269 };
270
271 // Case 2
272 if (has_invoke) {
273 SymbolContextList scl;
274 calculate_symbol_context_helper(symbol, scl);
275
276 return line_entry_helper(target, scl[0], symbol, first_template_parameter,
277 has_invoke);
278 }
279
280 // Case 4 or 5
281 if (symbol && !symbol->GetName().GetStringRef().starts_with("vtable for") &&
282 !contains_lambda_identifier(first_template_parameter) && !has_invoke) {
283 optional_info.callable_case =
284 LibCppStdFunctionCallableCase::FreeOrMemberFunction;
285 optional_info.callable_address = function_address_resolved;
286 optional_info.callable_symbol = *symbol;
287
288 return optional_info;
289 }
290
291 std::string func_to_match = first_template_parameter.str();
292
293 auto it = CallableLookupCache.find(func_to_match);
294 if (it != CallableLookupCache.end())
295 return it->second;
296
297 SymbolContextList scl;
298
299 CompileUnit *vtable_cu =
300 vtable_first_entry_resolved.CalculateSymbolContextCompileUnit();
301 llvm::StringRef name_to_use = func_to_match;
302
303 // Case 3, we have a callable object instead of a lambda
304 //
305 // TODO
306 // We currently don't support this case a callable object may have multiple
307 // operator()() varying on const/non-const and number of arguments and we
308 // don't have a way to currently distinguish them so we will bail out now.
309 if (!contains_lambda_identifier(name_to_use))
310 return optional_info;
311
312 if (vtable_cu && !has_invoke) {
313 lldb::FunctionSP func_sp =
314 vtable_cu->FindFunction([name_to_use](const FunctionSP &f) {
315 auto name = f->GetName().GetStringRef();
316 if (name.starts_with(name_to_use) && name.contains("operator"))
317 return true;
318
319 return false;
320 });
321
322 if (func_sp) {
323 calculate_symbol_context_helper(func_sp, scl);
324 }
325 }
326
327 if (symbol == nullptr)
328 return optional_info;
329
330 // Case 1 or 3
331 if (scl.GetSize() >= 1) {
332 optional_info = line_entry_helper(target, scl[0], symbol,
333 first_template_parameter, has_invoke);
334 }
335
336 CallableLookupCache[func_to_match] = optional_info;
337
338 return optional_info;
339 }
340
341 lldb::ThreadPlanSP
GetStepThroughTrampolinePlan(Thread & thread,bool stop_others)342 CPPLanguageRuntime::GetStepThroughTrampolinePlan(Thread &thread,
343 bool stop_others) {
344 ThreadPlanSP ret_plan_sp;
345
346 lldb::addr_t curr_pc = thread.GetRegisterContext()->GetPC();
347
348 TargetSP target_sp(thread.CalculateTarget());
349
350 if (target_sp->GetSectionLoadList().IsEmpty())
351 return ret_plan_sp;
352
353 Address pc_addr_resolved;
354 SymbolContext sc;
355 Symbol *symbol;
356
357 if (!target_sp->GetSectionLoadList().ResolveLoadAddress(curr_pc,
358 pc_addr_resolved))
359 return ret_plan_sp;
360
361 target_sp->GetImages().ResolveSymbolContextForAddress(
362 pc_addr_resolved, eSymbolContextEverything, sc);
363 symbol = sc.symbol;
364
365 if (symbol == nullptr)
366 return ret_plan_sp;
367
368 llvm::StringRef function_name(symbol->GetName().GetCString());
369
370 // Handling the case where we are attempting to step into std::function.
371 // The behavior will be that we will attempt to obtain the wrapped
372 // callable via FindLibCppStdFunctionCallableInfo() and if we find it we
373 // will return a ThreadPlanRunToAddress to the callable. Therefore we will
374 // step into the wrapped callable.
375 //
376 bool found_expected_start_string =
377 function_name.starts_with("std::__1::function<");
378
379 if (!found_expected_start_string)
380 return ret_plan_sp;
381
382 AddressRange range_of_curr_func;
383 sc.GetAddressRange(eSymbolContextEverything, 0, false, range_of_curr_func);
384
385 StackFrameSP frame = thread.GetStackFrameAtIndex(0);
386
387 if (frame) {
388 ValueObjectSP value_sp = frame->FindVariable(g_this);
389
390 CPPLanguageRuntime::LibCppStdFunctionCallableInfo callable_info =
391 FindLibCppStdFunctionCallableInfo(value_sp);
392
393 if (callable_info.callable_case != LibCppStdFunctionCallableCase::Invalid &&
394 value_sp->GetValueIsValid()) {
395 // We found the std::function wrapped callable and we have its address.
396 // We now create a ThreadPlan to run to the callable.
397 ret_plan_sp = std::make_shared<ThreadPlanRunToAddress>(
398 thread, callable_info.callable_address, stop_others);
399 return ret_plan_sp;
400 } else {
401 // We are in std::function but we could not obtain the callable.
402 // We create a ThreadPlan to keep stepping through using the address range
403 // of the current function.
404 ret_plan_sp = std::make_shared<ThreadPlanStepInRange>(
405 thread, range_of_curr_func, sc, nullptr, eOnlyThisThread,
406 eLazyBoolYes, eLazyBoolYes);
407 return ret_plan_sp;
408 }
409 }
410
411 return ret_plan_sp;
412 }
413