1 //===-- AppleObjCTrampolineHandler.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 "AppleObjCTrampolineHandler.h"
10 #include "AppleThreadPlanStepThroughObjCTrampoline.h"
11
12 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
13 #include "lldb/Breakpoint/StoppointCallbackContext.h"
14 #include "lldb/Core/Debugger.h"
15 #include "lldb/Core/Module.h"
16 #include "lldb/Core/StreamFile.h"
17 #include "lldb/Core/Value.h"
18 #include "lldb/Expression/DiagnosticManager.h"
19 #include "lldb/Expression/FunctionCaller.h"
20 #include "lldb/Expression/UserExpression.h"
21 #include "lldb/Expression/UtilityFunction.h"
22 #include "lldb/Symbol/Symbol.h"
23 #include "lldb/Target/ABI.h"
24 #include "lldb/Target/ExecutionContext.h"
25 #include "lldb/Target/Process.h"
26 #include "lldb/Target/RegisterContext.h"
27 #include "lldb/Target/Target.h"
28 #include "lldb/Target/Thread.h"
29 #include "lldb/Target/ThreadPlanRunToAddress.h"
30 #include "lldb/Utility/ConstString.h"
31 #include "lldb/Utility/FileSpec.h"
32 #include "lldb/Utility/LLDBLog.h"
33 #include "lldb/Utility/Log.h"
34
35 #include "llvm/ADT/STLExtras.h"
36 #include "llvm/ADT/ScopeExit.h"
37
38 #include "Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h"
39
40 #include <memory>
41
42 using namespace lldb;
43 using namespace lldb_private;
44
45 const char *AppleObjCTrampolineHandler::g_lookup_implementation_function_name =
46 "__lldb_objc_find_implementation_for_selector";
47 const char *AppleObjCTrampolineHandler::
48 g_lookup_implementation_with_stret_function_code =
49 R"(
50 if (is_stret) {
51 return_struct.impl_addr =
52 class_getMethodImplementation_stret (return_struct.class_addr,
53 return_struct.sel_addr);
54 } else {
55 return_struct.impl_addr =
56 class_getMethodImplementation (return_struct.class_addr,
57 return_struct.sel_addr);
58 }
59 if (debug)
60 printf ("\n*** Returning implementation: %p.\n",
61 return_struct.impl_addr);
62
63 return return_struct.impl_addr;
64 }
65 )";
66 const char *
67 AppleObjCTrampolineHandler::g_lookup_implementation_no_stret_function_code =
68 R"(
69 return_struct.impl_addr =
70 class_getMethodImplementation (return_struct.class_addr,
71 return_struct.sel_addr);
72 if (debug)
73 printf ("\n*** getMethodImpletation for addr: 0x%p sel: 0x%p result: 0x%p.\n",
74 return_struct.class_addr, return_struct.sel_addr, return_struct.impl_addr);
75
76 return return_struct.impl_addr;
77 }
78 )";
79
80 const char
81 *AppleObjCTrampolineHandler::g_lookup_implementation_function_common_code =
82 R"(
83 extern "C"
84 {
85 extern void *class_getMethodImplementation(void *objc_class, void *sel);
86 extern void *class_getMethodImplementation_stret(void *objc_class, void *sel);
87 extern void * object_getClass (id object);
88 extern void * sel_getUid(char *name);
89 extern int printf(const char *format, ...);
90 }
91 extern "C" void *
92 __lldb_objc_find_implementation_for_selector (void *object,
93 void *sel,
94 int is_str_ptr,
95 int is_stret,
96 int is_super,
97 int is_super2,
98 int is_fixup,
99 int is_fixed,
100 int debug)
101 {
102 struct __lldb_imp_return_struct {
103 void *class_addr;
104 void *sel_addr;
105 void *impl_addr;
106 };
107
108 struct __lldb_objc_class {
109 void *isa;
110 void *super_ptr;
111 };
112 struct __lldb_objc_super {
113 void *receiver;
114 struct __lldb_objc_class *class_ptr;
115 };
116 struct __lldb_msg_ref {
117 void *dont_know;
118 void *sel;
119 };
120
121 struct __lldb_imp_return_struct return_struct;
122
123 if (debug)
124 printf ("\n*** Called with obj: %p sel: %p is_str_ptr: %d "
125 "is_stret: %d is_super: %d, "
126 "is_super2: %d, is_fixup: %d, is_fixed: %d\n",
127 object, sel, is_str_ptr, is_stret,
128 is_super, is_super2, is_fixup, is_fixed);
129
130 if (is_str_ptr) {
131 if (debug)
132 printf("*** Turning string: '%s'", sel);
133 sel = sel_getUid((char *)sel);
134 if (debug)
135 printf("*** into sel to %p", sel);
136 }
137 if (is_super) {
138 if (is_super2) {
139 return_struct.class_addr
140 = ((__lldb_objc_super *) object)->class_ptr->super_ptr;
141 } else {
142 return_struct.class_addr = ((__lldb_objc_super *) object)->class_ptr;
143 }
144 if (debug)
145 printf("*** Super, class addr: %p\n", return_struct.class_addr);
146 } else {
147 // This code seems a little funny, but has its reasons...
148 // The call to [object class] is here because if this is a class, and has
149 // not been called into yet, we need to do something to force the class to
150 // initialize itself.
151 // Then the call to object_getClass will actually return the correct class,
152 // either the class if object is a class instance, or the meta-class if it
153 // is a class pointer.
154 void *class_ptr = (void *) [(id) object class];
155 return_struct.class_addr = (id) object_getClass((id) object);
156 if (debug) {
157 if (class_ptr == object) {
158 printf ("Found a class object, need to return the meta class %p -> %p\n",
159 class_ptr, return_struct.class_addr);
160 } else {
161 printf ("[object class] returned: %p object_getClass: %p.\n",
162 class_ptr, return_struct.class_addr);
163 }
164 }
165 }
166
167 if (is_fixup) {
168 if (is_fixed) {
169 return_struct.sel_addr = ((__lldb_msg_ref *) sel)->sel;
170 } else {
171 char *sel_name = (char *) ((__lldb_msg_ref *) sel)->sel;
172 return_struct.sel_addr = sel_getUid (sel_name);
173 if (debug)
174 printf ("\n*** Got fixed up selector: %p for name %s.\n",
175 return_struct.sel_addr, sel_name);
176 }
177 } else {
178 return_struct.sel_addr = sel;
179 }
180 )";
181
VTableRegion(AppleObjCVTables * owner,lldb::addr_t header_addr)182 AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::VTableRegion(
183 AppleObjCVTables *owner, lldb::addr_t header_addr)
184 : m_valid(true), m_owner(owner), m_header_addr(header_addr) {
185 SetUpRegion();
186 }
187
188 AppleObjCTrampolineHandler::~AppleObjCTrampolineHandler() = default;
189
SetUpRegion()190 void AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::SetUpRegion() {
191 // The header looks like:
192 //
193 // uint16_t headerSize
194 // uint16_t descSize
195 // uint32_t descCount
196 // void * next
197 //
198 // First read in the header:
199
200 char memory_buffer[16];
201 ProcessSP process_sp = m_owner->GetProcessSP();
202 if (!process_sp)
203 return;
204 DataExtractor data(memory_buffer, sizeof(memory_buffer),
205 process_sp->GetByteOrder(),
206 process_sp->GetAddressByteSize());
207 size_t actual_size = 8 + process_sp->GetAddressByteSize();
208 Status error;
209 size_t bytes_read =
210 process_sp->ReadMemory(m_header_addr, memory_buffer, actual_size, error);
211 if (bytes_read != actual_size) {
212 m_valid = false;
213 return;
214 }
215
216 lldb::offset_t offset = 0;
217 const uint16_t header_size = data.GetU16(&offset);
218 const uint16_t descriptor_size = data.GetU16(&offset);
219 const size_t num_descriptors = data.GetU32(&offset);
220
221 m_next_region = data.GetAddress(&offset);
222
223 // If the header size is 0, that means we've come in too early before this
224 // data is set up.
225 // Set ourselves as not valid, and continue.
226 if (header_size == 0 || num_descriptors == 0) {
227 m_valid = false;
228 return;
229 }
230
231 // Now read in all the descriptors:
232 // The descriptor looks like:
233 //
234 // uint32_t offset
235 // uint32_t flags
236 //
237 // Where offset is either 0 - in which case it is unused, or it is
238 // the offset of the vtable code from the beginning of the
239 // descriptor record. Below, we'll convert that into an absolute
240 // code address, since I don't want to have to compute it over and
241 // over.
242
243 // Ingest the whole descriptor array:
244 const lldb::addr_t desc_ptr = m_header_addr + header_size;
245 const size_t desc_array_size = num_descriptors * descriptor_size;
246 WritableDataBufferSP data_sp(new DataBufferHeap(desc_array_size, '\0'));
247 uint8_t *dst = (uint8_t *)data_sp->GetBytes();
248
249 DataExtractor desc_extractor(dst, desc_array_size, process_sp->GetByteOrder(),
250 process_sp->GetAddressByteSize());
251 bytes_read = process_sp->ReadMemory(desc_ptr, dst, desc_array_size, error);
252 if (bytes_read != desc_array_size) {
253 m_valid = false;
254 return;
255 }
256
257 // The actual code for the vtables will be laid out consecutively, so I also
258 // compute the start and end of the whole code block.
259
260 offset = 0;
261 m_code_start_addr = 0;
262 m_code_end_addr = 0;
263
264 for (size_t i = 0; i < num_descriptors; i++) {
265 lldb::addr_t start_offset = offset;
266 uint32_t voffset = desc_extractor.GetU32(&offset);
267 uint32_t flags = desc_extractor.GetU32(&offset);
268 lldb::addr_t code_addr = desc_ptr + start_offset + voffset;
269 m_descriptors.push_back(VTableDescriptor(flags, code_addr));
270
271 if (m_code_start_addr == 0 || code_addr < m_code_start_addr)
272 m_code_start_addr = code_addr;
273 if (code_addr > m_code_end_addr)
274 m_code_end_addr = code_addr;
275
276 offset = start_offset + descriptor_size;
277 }
278 // Finally, a little bird told me that all the vtable code blocks
279 // are the same size. Let's compute the blocks and if they are all
280 // the same add the size to the code end address:
281 lldb::addr_t code_size = 0;
282 bool all_the_same = true;
283 for (size_t i = 0; i < num_descriptors - 1; i++) {
284 lldb::addr_t this_size =
285 m_descriptors[i + 1].code_start - m_descriptors[i].code_start;
286 if (code_size == 0)
287 code_size = this_size;
288 else {
289 if (this_size != code_size)
290 all_the_same = false;
291 if (this_size > code_size)
292 code_size = this_size;
293 }
294 }
295 if (all_the_same)
296 m_code_end_addr += code_size;
297 }
298
299 bool AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::
AddressInRegion(lldb::addr_t addr,uint32_t & flags)300 AddressInRegion(lldb::addr_t addr, uint32_t &flags) {
301 if (!IsValid())
302 return false;
303
304 if (addr < m_code_start_addr || addr > m_code_end_addr)
305 return false;
306
307 std::vector<VTableDescriptor>::iterator pos, end = m_descriptors.end();
308 for (pos = m_descriptors.begin(); pos != end; pos++) {
309 if (addr <= (*pos).code_start) {
310 flags = (*pos).flags;
311 return true;
312 }
313 }
314 return false;
315 }
316
Dump(Stream & s)317 void AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::Dump(
318 Stream &s) {
319 s.Printf("Header addr: 0x%" PRIx64 " Code start: 0x%" PRIx64
320 " Code End: 0x%" PRIx64 " Next: 0x%" PRIx64 "\n",
321 m_header_addr, m_code_start_addr, m_code_end_addr, m_next_region);
322 size_t num_elements = m_descriptors.size();
323 for (size_t i = 0; i < num_elements; i++) {
324 s.Indent();
325 s.Printf("Code start: 0x%" PRIx64 " Flags: %d\n",
326 m_descriptors[i].code_start, m_descriptors[i].flags);
327 }
328 }
329
AppleObjCVTables(const ProcessSP & process_sp,const ModuleSP & objc_module_sp)330 AppleObjCTrampolineHandler::AppleObjCVTables::AppleObjCVTables(
331 const ProcessSP &process_sp, const ModuleSP &objc_module_sp)
332 : m_process_wp(), m_trampoline_header(LLDB_INVALID_ADDRESS),
333 m_trampolines_changed_bp_id(LLDB_INVALID_BREAK_ID),
334 m_objc_module_sp(objc_module_sp) {
335 if (process_sp)
336 m_process_wp = process_sp;
337 }
338
~AppleObjCVTables()339 AppleObjCTrampolineHandler::AppleObjCVTables::~AppleObjCVTables() {
340 ProcessSP process_sp = GetProcessSP();
341 if (process_sp) {
342 if (m_trampolines_changed_bp_id != LLDB_INVALID_BREAK_ID)
343 process_sp->GetTarget().RemoveBreakpointByID(m_trampolines_changed_bp_id);
344 }
345 }
346
InitializeVTableSymbols()347 bool AppleObjCTrampolineHandler::AppleObjCVTables::InitializeVTableSymbols() {
348 if (m_trampoline_header != LLDB_INVALID_ADDRESS)
349 return true;
350
351 ProcessSP process_sp = GetProcessSP();
352 if (process_sp) {
353 Target &target = process_sp->GetTarget();
354
355 if (!m_objc_module_sp) {
356 for (ModuleSP module_sp : target.GetImages().Modules()) {
357 if (ObjCLanguageRuntime::Get(*process_sp)
358 ->IsModuleObjCLibrary(module_sp)) {
359 m_objc_module_sp = module_sp;
360 break;
361 }
362 }
363 }
364
365 if (m_objc_module_sp) {
366 ConstString trampoline_name("gdb_objc_trampolines");
367 const Symbol *trampoline_symbol =
368 m_objc_module_sp->FindFirstSymbolWithNameAndType(trampoline_name,
369 eSymbolTypeData);
370 if (trampoline_symbol != nullptr) {
371 m_trampoline_header = trampoline_symbol->GetLoadAddress(&target);
372 if (m_trampoline_header == LLDB_INVALID_ADDRESS)
373 return false;
374
375 // Next look up the "changed" symbol and set a breakpoint on that...
376 ConstString changed_name("gdb_objc_trampolines_changed");
377 const Symbol *changed_symbol =
378 m_objc_module_sp->FindFirstSymbolWithNameAndType(changed_name,
379 eSymbolTypeCode);
380 if (changed_symbol != nullptr) {
381 const Address changed_symbol_addr = changed_symbol->GetAddress();
382 if (!changed_symbol_addr.IsValid())
383 return false;
384
385 lldb::addr_t changed_addr =
386 changed_symbol_addr.GetOpcodeLoadAddress(&target);
387 if (changed_addr != LLDB_INVALID_ADDRESS) {
388 BreakpointSP trampolines_changed_bp_sp =
389 target.CreateBreakpoint(changed_addr, true, false);
390 if (trampolines_changed_bp_sp) {
391 m_trampolines_changed_bp_id = trampolines_changed_bp_sp->GetID();
392 trampolines_changed_bp_sp->SetCallback(RefreshTrampolines, this,
393 true);
394 trampolines_changed_bp_sp->SetBreakpointKind(
395 "objc-trampolines-changed");
396 return true;
397 }
398 }
399 }
400 }
401 }
402 }
403 return false;
404 }
405
RefreshTrampolines(void * baton,StoppointCallbackContext * context,lldb::user_id_t break_id,lldb::user_id_t break_loc_id)406 bool AppleObjCTrampolineHandler::AppleObjCVTables::RefreshTrampolines(
407 void *baton, StoppointCallbackContext *context, lldb::user_id_t break_id,
408 lldb::user_id_t break_loc_id) {
409 AppleObjCVTables *vtable_handler = (AppleObjCVTables *)baton;
410 if (vtable_handler->InitializeVTableSymbols()) {
411 // The Update function is called with the address of an added region. So we
412 // grab that address, and
413 // feed it into ReadRegions. Of course, our friend the ABI will get the
414 // values for us.
415 ExecutionContext exe_ctx(context->exe_ctx_ref);
416 Process *process = exe_ctx.GetProcessPtr();
417 const ABI *abi = process->GetABI().get();
418
419 TypeSystemClangSP scratch_ts_sp =
420 ScratchTypeSystemClang::GetForTarget(process->GetTarget());
421 if (!scratch_ts_sp)
422 return false;
423
424 ValueList argument_values;
425 Value input_value;
426 CompilerType clang_void_ptr_type =
427 scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();
428
429 input_value.SetValueType(Value::ValueType::Scalar);
430 // input_value.SetContext (Value::eContextTypeClangType,
431 // clang_void_ptr_type);
432 input_value.SetCompilerType(clang_void_ptr_type);
433 argument_values.PushValue(input_value);
434
435 bool success =
436 abi->GetArgumentValues(exe_ctx.GetThreadRef(), argument_values);
437 if (!success)
438 return false;
439
440 // Now get a pointer value from the zeroth argument.
441 Status error;
442 DataExtractor data;
443 error = argument_values.GetValueAtIndex(0)->GetValueAsData(&exe_ctx, data,
444 nullptr);
445 lldb::offset_t offset = 0;
446 lldb::addr_t region_addr = data.GetAddress(&offset);
447
448 if (region_addr != 0)
449 vtable_handler->ReadRegions(region_addr);
450 }
451 return false;
452 }
453
ReadRegions()454 bool AppleObjCTrampolineHandler::AppleObjCVTables::ReadRegions() {
455 // The no argument version reads the start region from the value of
456 // the gdb_regions_header, and gets started from there.
457
458 m_regions.clear();
459 if (!InitializeVTableSymbols())
460 return false;
461 Status error;
462 ProcessSP process_sp = GetProcessSP();
463 if (process_sp) {
464 lldb::addr_t region_addr =
465 process_sp->ReadPointerFromMemory(m_trampoline_header, error);
466 if (error.Success())
467 return ReadRegions(region_addr);
468 }
469 return false;
470 }
471
ReadRegions(lldb::addr_t region_addr)472 bool AppleObjCTrampolineHandler::AppleObjCVTables::ReadRegions(
473 lldb::addr_t region_addr) {
474 ProcessSP process_sp = GetProcessSP();
475 if (!process_sp)
476 return false;
477
478 Log *log = GetLog(LLDBLog::Step);
479
480 // We aren't starting at the trampoline symbol.
481 InitializeVTableSymbols();
482 lldb::addr_t next_region = region_addr;
483
484 // Read in the sizes of the headers.
485 while (next_region != 0) {
486 m_regions.push_back(VTableRegion(this, next_region));
487 if (!m_regions.back().IsValid()) {
488 m_regions.clear();
489 return false;
490 }
491 if (log) {
492 StreamString s;
493 m_regions.back().Dump(s);
494 LLDB_LOGF(log, "Read vtable region: \n%s", s.GetData());
495 }
496
497 next_region = m_regions.back().GetNextRegionAddr();
498 }
499
500 return true;
501 }
502
IsAddressInVTables(lldb::addr_t addr,uint32_t & flags)503 bool AppleObjCTrampolineHandler::AppleObjCVTables::IsAddressInVTables(
504 lldb::addr_t addr, uint32_t &flags) {
505 region_collection::iterator pos, end = m_regions.end();
506 for (pos = m_regions.begin(); pos != end; pos++) {
507 if ((*pos).AddressInRegion(addr, flags))
508 return true;
509 }
510 return false;
511 }
512
513 const AppleObjCTrampolineHandler::DispatchFunction
514 AppleObjCTrampolineHandler::g_dispatch_functions[] = {
515 // NAME STRET SUPER SUPER2 FIXUP TYPE
516 {"objc_msgSend", false, false, false, DispatchFunction::eFixUpNone},
517 {"objc_msgSend_fixup", false, false, false,
518 DispatchFunction::eFixUpToFix},
519 {"objc_msgSend_fixedup", false, false, false,
520 DispatchFunction::eFixUpFixed},
521 {"objc_msgSend_stret", true, false, false,
522 DispatchFunction::eFixUpNone},
523 {"objc_msgSend_stret_fixup", true, false, false,
524 DispatchFunction::eFixUpToFix},
525 {"objc_msgSend_stret_fixedup", true, false, false,
526 DispatchFunction::eFixUpFixed},
527 {"objc_msgSend_fpret", false, false, false,
528 DispatchFunction::eFixUpNone},
529 {"objc_msgSend_fpret_fixup", false, false, false,
530 DispatchFunction::eFixUpToFix},
531 {"objc_msgSend_fpret_fixedup", false, false, false,
532 DispatchFunction::eFixUpFixed},
533 {"objc_msgSend_fp2ret", false, false, true,
534 DispatchFunction::eFixUpNone},
535 {"objc_msgSend_fp2ret_fixup", false, false, true,
536 DispatchFunction::eFixUpToFix},
537 {"objc_msgSend_fp2ret_fixedup", false, false, true,
538 DispatchFunction::eFixUpFixed},
539 {"objc_msgSendSuper", false, true, false, DispatchFunction::eFixUpNone},
540 {"objc_msgSendSuper_stret", true, true, false,
541 DispatchFunction::eFixUpNone},
542 {"objc_msgSendSuper2", false, true, true, DispatchFunction::eFixUpNone},
543 {"objc_msgSendSuper2_fixup", false, true, true,
544 DispatchFunction::eFixUpToFix},
545 {"objc_msgSendSuper2_fixedup", false, true, true,
546 DispatchFunction::eFixUpFixed},
547 {"objc_msgSendSuper2_stret", true, true, true,
548 DispatchFunction::eFixUpNone},
549 {"objc_msgSendSuper2_stret_fixup", true, true, true,
550 DispatchFunction::eFixUpToFix},
551 {"objc_msgSendSuper2_stret_fixedup", true, true, true,
552 DispatchFunction::eFixUpFixed},
553 };
554
555 // This is the table of ObjC "accelerated dispatch" functions. They are a set
556 // of objc methods that are "seldom overridden" and so the compiler replaces the
557 // objc_msgSend with a call to one of the dispatch functions. That will check
558 // whether the method has been overridden, and directly call the Foundation
559 // implementation if not.
560 // This table is supposed to be complete. If ones get added in the future, we
561 // will have to add them to the table.
562 const char *AppleObjCTrampolineHandler::g_opt_dispatch_names[] = {
563 "objc_alloc",
564 "objc_autorelease",
565 "objc_release",
566 "objc_retain",
567 "objc_alloc_init",
568 "objc_allocWithZone",
569 "objc_opt_class",
570 "objc_opt_isKindOfClass",
571 "objc_opt_new",
572 "objc_opt_respondsToSelector",
573 "objc_opt_self",
574 };
575
AppleObjCTrampolineHandler(const ProcessSP & process_sp,const ModuleSP & objc_module_sp)576 AppleObjCTrampolineHandler::AppleObjCTrampolineHandler(
577 const ProcessSP &process_sp, const ModuleSP &objc_module_sp)
578 : m_process_wp(), m_objc_module_sp(objc_module_sp),
579 m_impl_fn_addr(LLDB_INVALID_ADDRESS),
580 m_impl_stret_fn_addr(LLDB_INVALID_ADDRESS),
581 m_msg_forward_addr(LLDB_INVALID_ADDRESS),
582 m_msg_forward_stret_addr(LLDB_INVALID_ADDRESS) {
583 if (process_sp)
584 m_process_wp = process_sp;
585 // Look up the known resolution functions:
586
587 ConstString get_impl_name("class_getMethodImplementation");
588 ConstString get_impl_stret_name("class_getMethodImplementation_stret");
589 ConstString msg_forward_name("_objc_msgForward");
590 ConstString msg_forward_stret_name("_objc_msgForward_stret");
591
592 Target *target = process_sp ? &process_sp->GetTarget() : nullptr;
593 const Symbol *class_getMethodImplementation =
594 m_objc_module_sp->FindFirstSymbolWithNameAndType(get_impl_name,
595 eSymbolTypeCode);
596 const Symbol *class_getMethodImplementation_stret =
597 m_objc_module_sp->FindFirstSymbolWithNameAndType(get_impl_stret_name,
598 eSymbolTypeCode);
599 const Symbol *msg_forward = m_objc_module_sp->FindFirstSymbolWithNameAndType(
600 msg_forward_name, eSymbolTypeCode);
601 const Symbol *msg_forward_stret =
602 m_objc_module_sp->FindFirstSymbolWithNameAndType(msg_forward_stret_name,
603 eSymbolTypeCode);
604
605 if (class_getMethodImplementation)
606 m_impl_fn_addr =
607 class_getMethodImplementation->GetAddress().GetOpcodeLoadAddress(
608 target);
609 if (class_getMethodImplementation_stret)
610 m_impl_stret_fn_addr =
611 class_getMethodImplementation_stret->GetAddress().GetOpcodeLoadAddress(
612 target);
613 if (msg_forward)
614 m_msg_forward_addr = msg_forward->GetAddress().GetOpcodeLoadAddress(target);
615 if (msg_forward_stret)
616 m_msg_forward_stret_addr =
617 msg_forward_stret->GetAddress().GetOpcodeLoadAddress(target);
618
619 // FIXME: Do some kind of logging here.
620 if (m_impl_fn_addr == LLDB_INVALID_ADDRESS) {
621 // If we can't even find the ordinary get method implementation function,
622 // then we aren't going to be able to
623 // step through any method dispatches. Warn to that effect and get out of
624 // here.
625 if (process_sp->CanJIT()) {
626 process_sp->GetTarget().GetDebugger().GetErrorStream().Printf(
627 "Could not find implementation lookup function \"%s\""
628 " step in through ObjC method dispatch will not work.\n",
629 get_impl_name.AsCString());
630 }
631 return;
632 }
633
634 // We will either set the implementation to the _stret or non_stret version,
635 // so either way it's safe to start filling the m_lookup_..._code here.
636 m_lookup_implementation_function_code.assign(
637 g_lookup_implementation_function_common_code);
638
639 if (m_impl_stret_fn_addr == LLDB_INVALID_ADDRESS) {
640 // It there is no stret return lookup function, assume that it is the same
641 // as the straight lookup:
642 m_impl_stret_fn_addr = m_impl_fn_addr;
643 // Also we will use the version of the lookup code that doesn't rely on the
644 // stret version of the function.
645 m_lookup_implementation_function_code.append(
646 g_lookup_implementation_no_stret_function_code);
647 } else {
648 m_lookup_implementation_function_code.append(
649 g_lookup_implementation_with_stret_function_code);
650 }
651
652 // Look up the addresses for the objc dispatch functions and cache
653 // them. For now I'm inspecting the symbol names dynamically to
654 // figure out how to dispatch to them. If it becomes more
655 // complicated than this we can turn the g_dispatch_functions char *
656 // array into a template table, and populate the DispatchFunction
657 // map from there.
658
659 for (size_t i = 0; i != std::size(g_dispatch_functions); i++) {
660 ConstString name_const_str(g_dispatch_functions[i].name);
661 const Symbol *msgSend_symbol =
662 m_objc_module_sp->FindFirstSymbolWithNameAndType(name_const_str,
663 eSymbolTypeCode);
664 if (msgSend_symbol && msgSend_symbol->ValueIsAddress()) {
665 // FIXME: Make g_dispatch_functions static table of
666 // DispatchFunctions, and have the map be address->index.
667 // Problem is we also need to lookup the dispatch function. For
668 // now we could have a side table of stret & non-stret dispatch
669 // functions. If that's as complex as it gets, we're fine.
670
671 lldb::addr_t sym_addr =
672 msgSend_symbol->GetAddressRef().GetOpcodeLoadAddress(target);
673
674 m_msgSend_map.insert(std::pair<lldb::addr_t, int>(sym_addr, i));
675 }
676 }
677
678 // Similarly, cache the addresses of the "optimized dispatch" function.
679 for (size_t i = 0; i != std::size(g_opt_dispatch_names); i++) {
680 ConstString name_const_str(g_opt_dispatch_names[i]);
681 const Symbol *msgSend_symbol =
682 m_objc_module_sp->FindFirstSymbolWithNameAndType(name_const_str,
683 eSymbolTypeCode);
684 if (msgSend_symbol && msgSend_symbol->ValueIsAddress()) {
685 lldb::addr_t sym_addr =
686 msgSend_symbol->GetAddressRef().GetOpcodeLoadAddress(target);
687
688 m_opt_dispatch_map.emplace(sym_addr, i);
689 }
690 }
691
692 // Build our vtable dispatch handler here:
693 m_vtables_up =
694 std::make_unique<AppleObjCVTables>(process_sp, m_objc_module_sp);
695 if (m_vtables_up)
696 m_vtables_up->ReadRegions();
697 }
698
699 lldb::addr_t
SetupDispatchFunction(Thread & thread,ValueList & dispatch_values)700 AppleObjCTrampolineHandler::SetupDispatchFunction(Thread &thread,
701 ValueList &dispatch_values) {
702 ThreadSP thread_sp(thread.shared_from_this());
703 ExecutionContext exe_ctx(thread_sp);
704 Log *log = GetLog(LLDBLog::Step);
705
706 lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
707 FunctionCaller *impl_function_caller = nullptr;
708
709 // Scope for mutex locker:
710 {
711 std::lock_guard<std::mutex> guard(m_impl_function_mutex);
712
713 // First stage is to make the ClangUtility to hold our injected function:
714
715 if (!m_impl_code) {
716 if (!m_lookup_implementation_function_code.empty()) {
717 auto utility_fn_or_error = exe_ctx.GetTargetRef().CreateUtilityFunction(
718 m_lookup_implementation_function_code,
719 g_lookup_implementation_function_name, eLanguageTypeC, exe_ctx);
720 if (!utility_fn_or_error) {
721 LLDB_LOG_ERROR(
722 log, utility_fn_or_error.takeError(),
723 "Failed to get Utility Function for implementation lookup: {0}.");
724 return args_addr;
725 }
726 m_impl_code = std::move(*utility_fn_or_error);
727 } else {
728 LLDB_LOGF(log, "No method lookup implementation code.");
729 return LLDB_INVALID_ADDRESS;
730 }
731
732 // Next make the runner function for our implementation utility function.
733 TypeSystemClangSP scratch_ts_sp = ScratchTypeSystemClang::GetForTarget(
734 thread.GetProcess()->GetTarget());
735 if (!scratch_ts_sp)
736 return LLDB_INVALID_ADDRESS;
737
738 CompilerType clang_void_ptr_type =
739 scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();
740 Status error;
741
742 impl_function_caller = m_impl_code->MakeFunctionCaller(
743 clang_void_ptr_type, dispatch_values, thread_sp, error);
744 if (error.Fail()) {
745 LLDB_LOGF(log,
746 "Error getting function caller for dispatch lookup: \"%s\".",
747 error.AsCString());
748 return args_addr;
749 }
750 } else {
751 impl_function_caller = m_impl_code->GetFunctionCaller();
752 }
753 }
754
755 // Now write down the argument values for this particular call.
756 // This looks like it might be a race condition if other threads
757 // were calling into here, but actually it isn't because we allocate
758 // a new args structure for this call by passing args_addr =
759 // LLDB_INVALID_ADDRESS...
760
761 DiagnosticManager diagnostics;
762 if (!impl_function_caller->WriteFunctionArguments(
763 exe_ctx, args_addr, dispatch_values, diagnostics)) {
764 if (log) {
765 LLDB_LOGF(log, "Error writing function arguments.");
766 diagnostics.Dump(log);
767 }
768 return args_addr;
769 }
770
771 return args_addr;
772 }
773
774 const AppleObjCTrampolineHandler::DispatchFunction *
FindDispatchFunction(lldb::addr_t addr)775 AppleObjCTrampolineHandler::FindDispatchFunction(lldb::addr_t addr) {
776 MsgsendMap::iterator pos;
777 pos = m_msgSend_map.find(addr);
778 if (pos != m_msgSend_map.end()) {
779 return &g_dispatch_functions[(*pos).second];
780 }
781 return nullptr;
782 }
783
ForEachDispatchFunction(std::function<void (lldb::addr_t,const DispatchFunction &)> callback)784 void AppleObjCTrampolineHandler::ForEachDispatchFunction(
785 std::function<void(lldb::addr_t, const DispatchFunction &)> callback) {
786 for (auto elem : m_msgSend_map) {
787 callback(elem.first, g_dispatch_functions[elem.second]);
788 }
789 }
790
791 ThreadPlanSP
GetStepThroughDispatchPlan(Thread & thread,bool stop_others)792 AppleObjCTrampolineHandler::GetStepThroughDispatchPlan(Thread &thread,
793 bool stop_others) {
794 ThreadPlanSP ret_plan_sp;
795 lldb::addr_t curr_pc = thread.GetRegisterContext()->GetPC();
796
797 DispatchFunction vtable_dispatch = {"vtable", false, false, false,
798 DispatchFunction::eFixUpFixed};
799 // The selector specific stubs are a wrapper for objc_msgSend. They don't get
800 // passed a SEL, but instead the selector string is encoded in the stub
801 // name, in the form:
802 // objc_msgSend$SelectorName
803 // and the stub figures out the uniqued selector. If we find ourselves in
804 // one of these stubs, we strip off the selector string and pass that to the
805 // implementation finder function, which looks up the SEL (you have to do this
806 // in process) and passes that to the runtime lookup function.
807 DispatchFunction sel_stub_dispatch = {"sel-specific-stub", false, false,
808 false, DispatchFunction::eFixUpNone};
809
810 // First step is to see if we're in a selector-specific dispatch stub.
811 // Those are of the form _objc_msgSend$<SELECTOR>, so see if the current
812 // function has that name:
813 Address func_addr;
814 Target &target = thread.GetProcess()->GetTarget();
815 llvm::StringRef sym_name;
816 const DispatchFunction *this_dispatch = nullptr;
817
818 if (target.ResolveLoadAddress(curr_pc, func_addr)) {
819 Symbol *curr_sym = func_addr.CalculateSymbolContextSymbol();
820 if (curr_sym)
821 sym_name = curr_sym->GetName().GetStringRef();
822
823 if (!sym_name.empty() && !sym_name.consume_front("objc_msgSend$"))
824 sym_name = {};
825 else
826 this_dispatch = &sel_stub_dispatch;
827 }
828 bool in_selector_stub = !sym_name.empty();
829 // Second step is to look and see if we are in one of the known ObjC
830 // dispatch functions. We've already compiled a table of same, so
831 // consult it.
832
833 if (!in_selector_stub)
834 this_dispatch = FindDispatchFunction(curr_pc);
835
836 // Next check to see if we are in a vtable region:
837
838 if (!this_dispatch && m_vtables_up) {
839 uint32_t flags;
840 if (m_vtables_up->IsAddressInVTables(curr_pc, flags)) {
841 vtable_dispatch.stret_return =
842 (flags & AppleObjCVTables::eOBJC_TRAMPOLINE_STRET) ==
843 AppleObjCVTables::eOBJC_TRAMPOLINE_STRET;
844 this_dispatch = &vtable_dispatch;
845 }
846 }
847
848 // Since we set this_dispatch in both the vtable & sel specific stub cases
849 // this if will be used for all three of those cases.
850 if (this_dispatch) {
851 Log *log = GetLog(LLDBLog::Step);
852
853 // We are decoding a method dispatch. First job is to pull the
854 // arguments out. If we are in a regular stub, we get self & selector,
855 // but if we are in a selector-specific stub, we'll have to get that from
856 // the string sym_name.
857
858 lldb::StackFrameSP thread_cur_frame = thread.GetStackFrameAtIndex(0);
859
860 const ABI *abi = nullptr;
861 ProcessSP process_sp(thread.CalculateProcess());
862 if (process_sp)
863 abi = process_sp->GetABI().get();
864 if (abi == nullptr)
865 return ret_plan_sp;
866
867 TargetSP target_sp(thread.CalculateTarget());
868
869 TypeSystemClangSP scratch_ts_sp =
870 ScratchTypeSystemClang::GetForTarget(*target_sp);
871 if (!scratch_ts_sp)
872 return ret_plan_sp;
873
874 ValueList argument_values;
875 Value void_ptr_value;
876 CompilerType clang_void_ptr_type =
877 scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();
878 void_ptr_value.SetValueType(Value::ValueType::Scalar);
879 // void_ptr_value.SetContext (Value::eContextTypeClangType,
880 // clang_void_ptr_type);
881 void_ptr_value.SetCompilerType(clang_void_ptr_type);
882
883 int obj_index;
884 int sel_index;
885
886 // If this is a selector-specific stub then just push one value, 'cause
887 // we only get the object.
888 // If this is a struct return dispatch, then the first argument is
889 // the return struct pointer, and the object is the second, and
890 // the selector is the third.
891 // Otherwise the object is the first and the selector the second.
892 if (in_selector_stub) {
893 obj_index = 0;
894 sel_index = 1;
895 argument_values.PushValue(void_ptr_value);
896 } else if (this_dispatch->stret_return) {
897 obj_index = 1;
898 sel_index = 2;
899 argument_values.PushValue(void_ptr_value);
900 argument_values.PushValue(void_ptr_value);
901 argument_values.PushValue(void_ptr_value);
902 } else {
903 obj_index = 0;
904 sel_index = 1;
905 argument_values.PushValue(void_ptr_value);
906 argument_values.PushValue(void_ptr_value);
907 }
908
909 bool success = abi->GetArgumentValues(thread, argument_values);
910 if (!success)
911 return ret_plan_sp;
912
913 lldb::addr_t obj_addr =
914 argument_values.GetValueAtIndex(obj_index)->GetScalar().ULongLong();
915 if (obj_addr == 0x0) {
916 LLDB_LOGF(
917 log,
918 "Asked to step to dispatch to nil object, returning empty plan.");
919 return ret_plan_sp;
920 }
921
922 ExecutionContext exe_ctx(thread.shared_from_this());
923 // isa_addr will store the class pointer that the method is being
924 // dispatched to - so either the class directly or the super class
925 // if this is one of the objc_msgSendSuper flavors. That's mostly
926 // used to look up the class/selector pair in our cache.
927
928 lldb::addr_t isa_addr = LLDB_INVALID_ADDRESS;
929 lldb::addr_t sel_addr = LLDB_INVALID_ADDRESS;
930 // If we are not in a selector stub, get the sel address from the arguments.
931 if (!in_selector_stub)
932 sel_addr =
933 argument_values.GetValueAtIndex(sel_index)->GetScalar().ULongLong();
934
935 // Figure out the class this is being dispatched to and see if
936 // we've already cached this method call, If so we can push a
937 // run-to-address plan directly. Otherwise we have to figure out
938 // where the implementation lives.
939
940 if (this_dispatch->is_super) {
941 if (this_dispatch->is_super2) {
942 // In the objc_msgSendSuper2 case, we don't get the object
943 // directly, we get a structure containing the object and the
944 // class to which the super message is being sent. So we need
945 // to dig the super out of the class and use that.
946
947 Value super_value(*(argument_values.GetValueAtIndex(obj_index)));
948 super_value.GetScalar() += process_sp->GetAddressByteSize();
949 super_value.ResolveValue(&exe_ctx);
950
951 if (super_value.GetScalar().IsValid()) {
952
953 // isa_value now holds the class pointer. The second word of the
954 // class pointer is the super-class pointer:
955 super_value.GetScalar() += process_sp->GetAddressByteSize();
956 super_value.ResolveValue(&exe_ctx);
957 if (super_value.GetScalar().IsValid())
958 isa_addr = super_value.GetScalar().ULongLong();
959 else {
960 LLDB_LOGF(log, "Failed to extract the super class value from the "
961 "class in objc_super.");
962 }
963 } else {
964 LLDB_LOGF(log, "Failed to extract the class value from objc_super.");
965 }
966 } else {
967 // In the objc_msgSendSuper case, we don't get the object
968 // directly, we get a two element structure containing the
969 // object and the super class to which the super message is
970 // being sent. So the class we want is the second element of
971 // this structure.
972
973 Value super_value(*(argument_values.GetValueAtIndex(obj_index)));
974 super_value.GetScalar() += process_sp->GetAddressByteSize();
975 super_value.ResolveValue(&exe_ctx);
976
977 if (super_value.GetScalar().IsValid()) {
978 isa_addr = super_value.GetScalar().ULongLong();
979 } else {
980 LLDB_LOGF(log, "Failed to extract the class value from objc_super.");
981 }
982 }
983 } else {
984 // In the direct dispatch case, the object->isa is the class pointer we
985 // want.
986
987 // This is a little cheesy, but since object->isa is the first field,
988 // making the object value a load address value and resolving it will get
989 // the pointer sized data pointed to by that value...
990
991 // Note, it isn't a fatal error not to be able to get the
992 // address from the object, since this might be a "tagged
993 // pointer" which isn't a real object, but rather some word
994 // length encoded dingus.
995
996 Value isa_value(*(argument_values.GetValueAtIndex(obj_index)));
997
998 isa_value.SetValueType(Value::ValueType::LoadAddress);
999 isa_value.ResolveValue(&exe_ctx);
1000 if (isa_value.GetScalar().IsValid()) {
1001 isa_addr = isa_value.GetScalar().ULongLong();
1002 } else {
1003 LLDB_LOGF(log, "Failed to extract the isa value from object.");
1004 }
1005 }
1006
1007 // Okay, we've got the address of the class for which we're resolving this,
1008 // let's see if it's in our cache:
1009 lldb::addr_t impl_addr = LLDB_INVALID_ADDRESS;
1010 // If this is a regular dispatch, look up the sel in our addr to sel cache:
1011 if (isa_addr != LLDB_INVALID_ADDRESS) {
1012 ObjCLanguageRuntime *objc_runtime =
1013 ObjCLanguageRuntime::Get(*thread.GetProcess());
1014 assert(objc_runtime != nullptr);
1015 if (!in_selector_stub) {
1016 LLDB_LOG(log, "Resolving call for class - {0} and selector - {1}",
1017 isa_addr, sel_addr);
1018 impl_addr = objc_runtime->LookupInMethodCache(isa_addr, sel_addr);
1019 } else {
1020 LLDB_LOG(log, "Resolving call for class - {0} and selector - {1}",
1021 isa_addr, sym_name);
1022 impl_addr = objc_runtime->LookupInMethodCache(isa_addr, sym_name);
1023 }
1024 }
1025 // If it is a selector-specific stub dispatch, look in the string cache:
1026
1027 if (impl_addr != LLDB_INVALID_ADDRESS) {
1028 // Yup, it was in the cache, so we can run to that address directly.
1029
1030 LLDB_LOGF(log, "Found implementation address in cache: 0x%" PRIx64,
1031 impl_addr);
1032
1033 ret_plan_sp = std::make_shared<ThreadPlanRunToAddress>(thread, impl_addr,
1034 stop_others);
1035 } else {
1036 // We haven't seen this class/selector pair yet. Look it up.
1037 StreamString errors;
1038 Address impl_code_address;
1039
1040 ValueList dispatch_values;
1041
1042 // We've will inject a little function in the target that takes the
1043 // object, selector/selector string and some flags,
1044 // and figures out the implementation. Looks like:
1045 // void *__lldb_objc_find_implementation_for_selector (void *object,
1046 // void *sel,
1047 // int
1048 // is_str_ptr,
1049 // int is_stret,
1050 // int is_super,
1051 // int is_super2,
1052 // int is_fixup,
1053 // int is_fixed,
1054 // int debug)
1055 // If we don't have an actual SEL, but rather a string version of the
1056 // selector WE injected, set is_str_ptr to true, and sel to the address
1057 // of the string.
1058 // So set up the arguments for that call.
1059
1060 dispatch_values.PushValue(*(argument_values.GetValueAtIndex(obj_index)));
1061 lldb::addr_t sel_str_addr = LLDB_INVALID_ADDRESS;
1062 if (!in_selector_stub) {
1063 // If we don't have a selector string, push the selector from arguments.
1064 dispatch_values.PushValue(
1065 *(argument_values.GetValueAtIndex(sel_index)));
1066 } else {
1067 // Otherwise, inject the string into the target, and push that value for
1068 // the sel argument.
1069 Status error;
1070 sel_str_addr = process_sp->AllocateMemory(
1071 sym_name.size() + 1, ePermissionsReadable | ePermissionsWritable,
1072 error);
1073 if (sel_str_addr == LLDB_INVALID_ADDRESS || error.Fail()) {
1074 LLDB_LOG(log,
1075 "Could not allocate memory for selector string {0}: {1}",
1076 sym_name, error);
1077 return ret_plan_sp;
1078 }
1079 process_sp->WriteMemory(sel_str_addr, sym_name.str().c_str(),
1080 sym_name.size() + 1, error);
1081 if (error.Fail()) {
1082 LLDB_LOG(log, "Could not write string to address {0}", sel_str_addr);
1083 return ret_plan_sp;
1084 }
1085 Value sel_ptr_value(void_ptr_value);
1086 sel_ptr_value.GetScalar() = sel_str_addr;
1087 dispatch_values.PushValue(sel_ptr_value);
1088 }
1089
1090 Value flag_value;
1091 CompilerType clang_int_type =
1092 scratch_ts_sp->GetBuiltinTypeForEncodingAndBitSize(
1093 lldb::eEncodingSint, 32);
1094 flag_value.SetValueType(Value::ValueType::Scalar);
1095 // flag_value.SetContext (Value::eContextTypeClangType, clang_int_type);
1096 flag_value.SetCompilerType(clang_int_type);
1097
1098 if (in_selector_stub)
1099 flag_value.GetScalar() = 1;
1100 else
1101 flag_value.GetScalar() = 0;
1102 dispatch_values.PushValue(flag_value);
1103
1104 if (this_dispatch->stret_return)
1105 flag_value.GetScalar() = 1;
1106 else
1107 flag_value.GetScalar() = 0;
1108 dispatch_values.PushValue(flag_value);
1109
1110 if (this_dispatch->is_super)
1111 flag_value.GetScalar() = 1;
1112 else
1113 flag_value.GetScalar() = 0;
1114 dispatch_values.PushValue(flag_value);
1115
1116 if (this_dispatch->is_super2)
1117 flag_value.GetScalar() = 1;
1118 else
1119 flag_value.GetScalar() = 0;
1120 dispatch_values.PushValue(flag_value);
1121
1122 switch (this_dispatch->fixedup) {
1123 case DispatchFunction::eFixUpNone:
1124 flag_value.GetScalar() = 0;
1125 dispatch_values.PushValue(flag_value);
1126 dispatch_values.PushValue(flag_value);
1127 break;
1128 case DispatchFunction::eFixUpFixed:
1129 flag_value.GetScalar() = 1;
1130 dispatch_values.PushValue(flag_value);
1131 flag_value.GetScalar() = 1;
1132 dispatch_values.PushValue(flag_value);
1133 break;
1134 case DispatchFunction::eFixUpToFix:
1135 flag_value.GetScalar() = 1;
1136 dispatch_values.PushValue(flag_value);
1137 flag_value.GetScalar() = 0;
1138 dispatch_values.PushValue(flag_value);
1139 break;
1140 }
1141 if (log && log->GetVerbose())
1142 flag_value.GetScalar() = 1;
1143 else
1144 flag_value.GetScalar() = 0; // FIXME - Set to 0 when debugging is done.
1145 dispatch_values.PushValue(flag_value);
1146
1147 ret_plan_sp = std::make_shared<AppleThreadPlanStepThroughObjCTrampoline>(
1148 thread, *this, dispatch_values, isa_addr, sel_addr, sel_str_addr,
1149 sym_name);
1150 if (log) {
1151 StreamString s;
1152 ret_plan_sp->GetDescription(&s, eDescriptionLevelFull);
1153 LLDB_LOGF(log, "Using ObjC step plan: %s.\n", s.GetData());
1154 }
1155 }
1156 }
1157
1158 // Finally, check if we have hit an "optimized dispatch" function. This will
1159 // either directly call the base implementation or dispatch an objc_msgSend
1160 // if the method has been overridden. So we just do a "step in/step out",
1161 // setting a breakpoint on objc_msgSend, and if we hit the msgSend, we
1162 // will automatically step in again. That's the job of the
1163 // AppleThreadPlanStepThroughDirectDispatch.
1164 if (!this_dispatch && !ret_plan_sp) {
1165 MsgsendMap::iterator pos;
1166 pos = m_opt_dispatch_map.find(curr_pc);
1167 if (pos != m_opt_dispatch_map.end()) {
1168 const char *opt_name = g_opt_dispatch_names[(*pos).second];
1169 ret_plan_sp = std::make_shared<AppleThreadPlanStepThroughDirectDispatch>(
1170 thread, *this, opt_name);
1171 }
1172 }
1173
1174 return ret_plan_sp;
1175 }
1176
1177 FunctionCaller *
GetLookupImplementationFunctionCaller()1178 AppleObjCTrampolineHandler::GetLookupImplementationFunctionCaller() {
1179 return m_impl_code->GetFunctionCaller();
1180 }
1181