1 //===-- AppleObjCTrampolineHandler.cpp ------------------------------------===//
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
7 //===----------------------------------------------------------------------===//
9 #include "AppleObjCTrampolineHandler.h"
10 #include "AppleThreadPlanStepThroughObjCTrampoline.h"
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/Log.h"
34 #include "llvm/ADT/STLExtras.h"
36 #include "Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h"
41 using namespace lldb_private;
43 const char *AppleObjCTrampolineHandler::g_lookup_implementation_function_name =
44 "__lldb_objc_find_implementation_for_selector";
45 const char *AppleObjCTrampolineHandler::
46 g_lookup_implementation_with_stret_function_code =
50 extern void *class_getMethodImplementation(void *objc_class, void *sel); \n\
51 extern void *class_getMethodImplementation_stret(void *objc_class, \n\
53 extern void * object_getClass (id object); \n\
54 extern void * sel_getUid(char *name); \n\
55 extern int printf(const char *format, ...); \n\
57 extern \"C\" void * __lldb_objc_find_implementation_for_selector ( \n\
67 struct __lldb_imp_return_struct \n\
74 struct __lldb_objc_class { \n\
78 struct __lldb_objc_super { \n\
80 struct __lldb_objc_class *class_ptr; \n\
82 struct __lldb_msg_ref { \n\
87 struct __lldb_imp_return_struct return_struct; \n\
90 printf (\"\\n*** Called with obj: 0x%p sel: 0x%p is_stret: %d is_super: %d, \"\n\
91 \"is_super2: %d, is_fixup: %d, is_fixed: %d\\n\", \n\
92 object, sel, is_stret, is_super, is_super2, is_fixup, is_fixed);\n\
97 return_struct.class_addr = ((__lldb_objc_super *) object)->class_ptr->super_ptr;\n\
101 return_struct.class_addr = ((__lldb_objc_super *) object)->class_ptr;\n\
106 // This code seems a little funny, but has its reasons... \n\
108 // The call to [object class] is here because if this is a \n\
109 // class, and has not been called into yet, we need to do \n\
110 // something to force the class to initialize itself. \n\
111 // Then the call to object_getClass will actually return the \n\
112 // correct class, either the class if object is a class \n\
113 // instance, or the meta-class if it is a class pointer. \n\
114 void *class_ptr = (void *) [(id) object class]; \n\
115 return_struct.class_addr = (id) object_getClass((id) object); \n\
118 if (class_ptr == object) \n\
120 printf (\"Found a class object, need to use the meta class %p -> %p\\n\",\n\
121 class_ptr, return_struct.class_addr); \n\
125 printf (\"[object class] returned: %p object_getClass: %p.\\n\", \n\
126 class_ptr, return_struct.class_addr); \n\
135 return_struct.sel_addr = ((__lldb_msg_ref *) sel)->sel; \n\
139 char *sel_name = (char *) ((__lldb_msg_ref *) sel)->sel; \n\
140 return_struct.sel_addr = sel_getUid (sel_name); \n\
142 printf (\"\\n*** Got fixed up selector: %p for name %s.\\n\",\n\
143 return_struct.sel_addr, sel_name); \n\
148 return_struct.sel_addr = sel; \n\
153 return_struct.impl_addr = \n\
154 class_getMethodImplementation_stret (return_struct.class_addr, \n\
155 return_struct.sel_addr); \n\
159 return_struct.impl_addr = \n\
160 class_getMethodImplementation (return_struct.class_addr, \n\
161 return_struct.sel_addr); \n\
164 printf (\"\\n*** Returning implementation: %p.\\n\", \n\
165 return_struct.impl_addr); \n\
167 return return_struct.impl_addr; \n\
171 AppleObjCTrampolineHandler::g_lookup_implementation_no_stret_function_code =
175 extern void *class_getMethodImplementation(void *objc_class, void *sel); \n\
176 extern void * object_getClass (id object); \n\
177 extern void * sel_getUid(char *name); \n\
178 extern int printf(const char *format, ...); \n\
180 extern \"C\" void * __lldb_objc_find_implementation_for_selector (void *object, \n\
189 struct __lldb_imp_return_struct \n\
191 void *class_addr; \n\
196 struct __lldb_objc_class { \n\
200 struct __lldb_objc_super { \n\
202 struct __lldb_objc_class *class_ptr; \n\
204 struct __lldb_msg_ref { \n\
209 struct __lldb_imp_return_struct return_struct; \n\
212 printf (\"\\n*** Called with obj: 0x%p sel: 0x%p is_stret: %d is_super: %d, \" \n\
213 \"is_super2: %d, is_fixup: %d, is_fixed: %d\\n\", \n\
214 object, sel, is_stret, is_super, is_super2, is_fixup, is_fixed); \n\
219 return_struct.class_addr = ((__lldb_objc_super *) object)->class_ptr->super_ptr; \n\
223 return_struct.class_addr = ((__lldb_objc_super *) object)->class_ptr; \n\
228 // This code seems a little funny, but has its reasons... \n\
229 // The call to [object class] is here because if this is a class, and has not been called into \n\
230 // yet, we need to do something to force the class to initialize itself. \n\
231 // Then the call to object_getClass will actually return the correct class, either the class \n\
232 // if object is a class instance, or the meta-class if it is a class pointer. \n\
233 void *class_ptr = (void *) [(id) object class]; \n\
234 return_struct.class_addr = (id) object_getClass((id) object); \n\
237 if (class_ptr == object) \n\
239 printf (\"Found a class object, need to return the meta class %p -> %p\\n\", \n\
240 class_ptr, return_struct.class_addr); \n\
244 printf (\"[object class] returned: %p object_getClass: %p.\\n\", \n\
245 class_ptr, return_struct.class_addr); \n\
254 return_struct.sel_addr = ((__lldb_msg_ref *) sel)->sel; \n\
258 char *sel_name = (char *) ((__lldb_msg_ref *) sel)->sel; \n\
259 return_struct.sel_addr = sel_getUid (sel_name); \n\
261 printf (\"\\n*** Got fixed up selector: %p for name %s.\\n\",\n\
262 return_struct.sel_addr, sel_name); \n\
267 return_struct.sel_addr = sel; \n\
270 return_struct.impl_addr = \n\
271 class_getMethodImplementation (return_struct.class_addr, \n\
272 return_struct.sel_addr); \n\
274 printf (\"\\n*** Returning implementation: 0x%p.\\n\", \n\
275 return_struct.impl_addr); \n\
277 return return_struct.impl_addr; \n\
281 AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::VTableRegion(
282 AppleObjCVTables *owner, lldb::addr_t header_addr)
283 : m_valid(true), m_owner(owner), m_header_addr(header_addr),
284 m_code_start_addr(0), m_code_end_addr(0), m_next_region(0) {
288 AppleObjCTrampolineHandler::~AppleObjCTrampolineHandler() = default;
290 void AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::SetUpRegion() {
291 // The header looks like:
293 // uint16_t headerSize
295 // uint32_t descCount
298 // First read in the header:
300 char memory_buffer[16];
301 ProcessSP process_sp = m_owner->GetProcessSP();
304 DataExtractor data(memory_buffer, sizeof(memory_buffer),
305 process_sp->GetByteOrder(),
306 process_sp->GetAddressByteSize());
307 size_t actual_size = 8 + process_sp->GetAddressByteSize();
310 process_sp->ReadMemory(m_header_addr, memory_buffer, actual_size, error);
311 if (bytes_read != actual_size) {
316 lldb::offset_t offset = 0;
317 const uint16_t header_size = data.GetU16(&offset);
318 const uint16_t descriptor_size = data.GetU16(&offset);
319 const size_t num_descriptors = data.GetU32(&offset);
321 m_next_region = data.GetAddress(&offset);
323 // If the header size is 0, that means we've come in too early before this
325 // Set ourselves as not valid, and continue.
326 if (header_size == 0 || num_descriptors == 0) {
331 // Now read in all the descriptors:
332 // The descriptor looks like:
337 // Where offset is either 0 - in which case it is unused, or it is
338 // the offset of the vtable code from the beginning of the
339 // descriptor record. Below, we'll convert that into an absolute
340 // code address, since I don't want to have to compute it over and
343 // Ingest the whole descriptor array:
344 const lldb::addr_t desc_ptr = m_header_addr + header_size;
345 const size_t desc_array_size = num_descriptors * descriptor_size;
346 DataBufferSP data_sp(new DataBufferHeap(desc_array_size, '\0'));
347 uint8_t *dst = (uint8_t *)data_sp->GetBytes();
349 DataExtractor desc_extractor(dst, desc_array_size, process_sp->GetByteOrder(),
350 process_sp->GetAddressByteSize());
351 bytes_read = process_sp->ReadMemory(desc_ptr, dst, desc_array_size, error);
352 if (bytes_read != desc_array_size) {
357 // The actual code for the vtables will be laid out consecutively, so I also
358 // compute the start and end of the whole code block.
361 m_code_start_addr = 0;
364 for (size_t i = 0; i < num_descriptors; i++) {
365 lldb::addr_t start_offset = offset;
366 uint32_t voffset = desc_extractor.GetU32(&offset);
367 uint32_t flags = desc_extractor.GetU32(&offset);
368 lldb::addr_t code_addr = desc_ptr + start_offset + voffset;
369 m_descriptors.push_back(VTableDescriptor(flags, code_addr));
371 if (m_code_start_addr == 0 || code_addr < m_code_start_addr)
372 m_code_start_addr = code_addr;
373 if (code_addr > m_code_end_addr)
374 m_code_end_addr = code_addr;
376 offset = start_offset + descriptor_size;
378 // Finally, a little bird told me that all the vtable code blocks
379 // are the same size. Let's compute the blocks and if they are all
380 // the same add the size to the code end address:
381 lldb::addr_t code_size = 0;
382 bool all_the_same = true;
383 for (size_t i = 0; i < num_descriptors - 1; i++) {
384 lldb::addr_t this_size =
385 m_descriptors[i + 1].code_start - m_descriptors[i].code_start;
387 code_size = this_size;
389 if (this_size != code_size)
390 all_the_same = false;
391 if (this_size > code_size)
392 code_size = this_size;
396 m_code_end_addr += code_size;
399 bool AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::
400 AddressInRegion(lldb::addr_t addr, uint32_t &flags) {
404 if (addr < m_code_start_addr || addr > m_code_end_addr)
407 std::vector<VTableDescriptor>::iterator pos, end = m_descriptors.end();
408 for (pos = m_descriptors.begin(); pos != end; pos++) {
409 if (addr <= (*pos).code_start) {
410 flags = (*pos).flags;
417 void AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::Dump(
419 s.Printf("Header addr: 0x%" PRIx64 " Code start: 0x%" PRIx64
420 " Code End: 0x%" PRIx64 " Next: 0x%" PRIx64 "\n",
421 m_header_addr, m_code_start_addr, m_code_end_addr, m_next_region);
422 size_t num_elements = m_descriptors.size();
423 for (size_t i = 0; i < num_elements; i++) {
425 s.Printf("Code start: 0x%" PRIx64 " Flags: %d\n",
426 m_descriptors[i].code_start, m_descriptors[i].flags);
430 AppleObjCTrampolineHandler::AppleObjCVTables::AppleObjCVTables(
431 const ProcessSP &process_sp, const ModuleSP &objc_module_sp)
432 : m_process_wp(), m_trampoline_header(LLDB_INVALID_ADDRESS),
433 m_trampolines_changed_bp_id(LLDB_INVALID_BREAK_ID),
434 m_objc_module_sp(objc_module_sp) {
436 m_process_wp = process_sp;
439 AppleObjCTrampolineHandler::AppleObjCVTables::~AppleObjCVTables() {
440 ProcessSP process_sp = GetProcessSP();
442 if (m_trampolines_changed_bp_id != LLDB_INVALID_BREAK_ID)
443 process_sp->GetTarget().RemoveBreakpointByID(m_trampolines_changed_bp_id);
447 bool AppleObjCTrampolineHandler::AppleObjCVTables::InitializeVTableSymbols() {
448 if (m_trampoline_header != LLDB_INVALID_ADDRESS)
451 ProcessSP process_sp = GetProcessSP();
453 Target &target = process_sp->GetTarget();
455 if (!m_objc_module_sp) {
456 for (ModuleSP module_sp : target.GetImages().Modules()) {
457 if (ObjCLanguageRuntime::Get(*process_sp)
458 ->IsModuleObjCLibrary(module_sp)) {
459 m_objc_module_sp = module_sp;
465 if (m_objc_module_sp) {
466 ConstString trampoline_name("gdb_objc_trampolines");
467 const Symbol *trampoline_symbol =
468 m_objc_module_sp->FindFirstSymbolWithNameAndType(trampoline_name,
470 if (trampoline_symbol != nullptr) {
471 m_trampoline_header = trampoline_symbol->GetLoadAddress(&target);
472 if (m_trampoline_header == LLDB_INVALID_ADDRESS)
475 // Next look up the "changed" symbol and set a breakpoint on that...
476 ConstString changed_name("gdb_objc_trampolines_changed");
477 const Symbol *changed_symbol =
478 m_objc_module_sp->FindFirstSymbolWithNameAndType(changed_name,
480 if (changed_symbol != nullptr) {
481 const Address changed_symbol_addr = changed_symbol->GetAddress();
482 if (!changed_symbol_addr.IsValid())
485 lldb::addr_t changed_addr =
486 changed_symbol_addr.GetOpcodeLoadAddress(&target);
487 if (changed_addr != LLDB_INVALID_ADDRESS) {
488 BreakpointSP trampolines_changed_bp_sp =
489 target.CreateBreakpoint(changed_addr, true, false);
490 if (trampolines_changed_bp_sp) {
491 m_trampolines_changed_bp_id = trampolines_changed_bp_sp->GetID();
492 trampolines_changed_bp_sp->SetCallback(RefreshTrampolines, this,
494 trampolines_changed_bp_sp->SetBreakpointKind(
495 "objc-trampolines-changed");
506 bool AppleObjCTrampolineHandler::AppleObjCVTables::RefreshTrampolines(
507 void *baton, StoppointCallbackContext *context, lldb::user_id_t break_id,
508 lldb::user_id_t break_loc_id) {
509 AppleObjCVTables *vtable_handler = (AppleObjCVTables *)baton;
510 if (vtable_handler->InitializeVTableSymbols()) {
511 // The Update function is called with the address of an added region. So we
512 // grab that address, and
513 // feed it into ReadRegions. Of course, our friend the ABI will get the
515 ExecutionContext exe_ctx(context->exe_ctx_ref);
516 Process *process = exe_ctx.GetProcessPtr();
517 const ABI *abi = process->GetABI().get();
519 TypeSystemClang *clang_ast_context =
520 ScratchTypeSystemClang::GetForTarget(process->GetTarget());
521 if (!clang_ast_context)
524 ValueList argument_values;
526 CompilerType clang_void_ptr_type =
527 clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
529 input_value.SetValueType(Value::ValueType::Scalar);
530 // input_value.SetContext (Value::eContextTypeClangType,
531 // clang_void_ptr_type);
532 input_value.SetCompilerType(clang_void_ptr_type);
533 argument_values.PushValue(input_value);
536 abi->GetArgumentValues(exe_ctx.GetThreadRef(), argument_values);
540 // Now get a pointer value from the zeroth argument.
543 error = argument_values.GetValueAtIndex(0)->GetValueAsData(&exe_ctx, data,
545 lldb::offset_t offset = 0;
546 lldb::addr_t region_addr = data.GetAddress(&offset);
548 if (region_addr != 0)
549 vtable_handler->ReadRegions(region_addr);
554 bool AppleObjCTrampolineHandler::AppleObjCVTables::ReadRegions() {
555 // The no argument version reads the start region from the value of
556 // the gdb_regions_header, and gets started from there.
559 if (!InitializeVTableSymbols())
562 ProcessSP process_sp = GetProcessSP();
564 lldb::addr_t region_addr =
565 process_sp->ReadPointerFromMemory(m_trampoline_header, error);
567 return ReadRegions(region_addr);
572 bool AppleObjCTrampolineHandler::AppleObjCVTables::ReadRegions(
573 lldb::addr_t region_addr) {
574 ProcessSP process_sp = GetProcessSP();
578 Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
580 // We aren't starting at the trampoline symbol.
581 InitializeVTableSymbols();
582 lldb::addr_t next_region = region_addr;
584 // Read in the sizes of the headers.
585 while (next_region != 0) {
586 m_regions.push_back(VTableRegion(this, next_region));
587 if (!m_regions.back().IsValid()) {
593 m_regions.back().Dump(s);
594 LLDB_LOGF(log, "Read vtable region: \n%s", s.GetData());
597 next_region = m_regions.back().GetNextRegionAddr();
603 bool AppleObjCTrampolineHandler::AppleObjCVTables::IsAddressInVTables(
604 lldb::addr_t addr, uint32_t &flags) {
605 region_collection::iterator pos, end = m_regions.end();
606 for (pos = m_regions.begin(); pos != end; pos++) {
607 if ((*pos).AddressInRegion(addr, flags))
613 const AppleObjCTrampolineHandler::DispatchFunction
614 AppleObjCTrampolineHandler::g_dispatch_functions[] = {
615 // NAME STRET SUPER SUPER2 FIXUP TYPE
616 {"objc_msgSend", false, false, false, DispatchFunction::eFixUpNone},
617 {"objc_msgSend_fixup", false, false, false,
618 DispatchFunction::eFixUpToFix},
619 {"objc_msgSend_fixedup", false, false, false,
620 DispatchFunction::eFixUpFixed},
621 {"objc_msgSend_stret", true, false, false,
622 DispatchFunction::eFixUpNone},
623 {"objc_msgSend_stret_fixup", true, false, false,
624 DispatchFunction::eFixUpToFix},
625 {"objc_msgSend_stret_fixedup", true, false, false,
626 DispatchFunction::eFixUpFixed},
627 {"objc_msgSend_fpret", false, false, false,
628 DispatchFunction::eFixUpNone},
629 {"objc_msgSend_fpret_fixup", false, false, false,
630 DispatchFunction::eFixUpToFix},
631 {"objc_msgSend_fpret_fixedup", false, false, false,
632 DispatchFunction::eFixUpFixed},
633 {"objc_msgSend_fp2ret", false, false, true,
634 DispatchFunction::eFixUpNone},
635 {"objc_msgSend_fp2ret_fixup", false, false, true,
636 DispatchFunction::eFixUpToFix},
637 {"objc_msgSend_fp2ret_fixedup", false, false, true,
638 DispatchFunction::eFixUpFixed},
639 {"objc_msgSendSuper", false, true, false, DispatchFunction::eFixUpNone},
640 {"objc_msgSendSuper_stret", true, true, false,
641 DispatchFunction::eFixUpNone},
642 {"objc_msgSendSuper2", false, true, true, DispatchFunction::eFixUpNone},
643 {"objc_msgSendSuper2_fixup", false, true, true,
644 DispatchFunction::eFixUpToFix},
645 {"objc_msgSendSuper2_fixedup", false, true, true,
646 DispatchFunction::eFixUpFixed},
647 {"objc_msgSendSuper2_stret", true, true, true,
648 DispatchFunction::eFixUpNone},
649 {"objc_msgSendSuper2_stret_fixup", true, true, true,
650 DispatchFunction::eFixUpToFix},
651 {"objc_msgSendSuper2_stret_fixedup", true, true, true,
652 DispatchFunction::eFixUpFixed},
655 // This is the table of ObjC "accelerated dispatch" functions. They are a set
656 // of objc methods that are "seldom overridden" and so the compiler replaces the
657 // objc_msgSend with a call to one of the dispatch functions. That will check
658 // whether the method has been overridden, and directly call the Foundation
659 // implementation if not.
660 // This table is supposed to be complete. If ones get added in the future, we
661 // will have to add them to the table.
662 const char *AppleObjCTrampolineHandler::g_opt_dispatch_names[] = {
668 "objc_allocWithZone",
670 "objc_opt_isKindOfClass",
672 "objc_opt_respondsToSelector",
676 AppleObjCTrampolineHandler::AppleObjCTrampolineHandler(
677 const ProcessSP &process_sp, const ModuleSP &objc_module_sp)
678 : m_process_wp(), m_objc_module_sp(objc_module_sp),
679 m_lookup_implementation_function_code(nullptr),
680 m_impl_fn_addr(LLDB_INVALID_ADDRESS),
681 m_impl_stret_fn_addr(LLDB_INVALID_ADDRESS),
682 m_msg_forward_addr(LLDB_INVALID_ADDRESS) {
684 m_process_wp = process_sp;
685 // Look up the known resolution functions:
687 ConstString get_impl_name("class_getMethodImplementation");
688 ConstString get_impl_stret_name("class_getMethodImplementation_stret");
689 ConstString msg_forward_name("_objc_msgForward");
690 ConstString msg_forward_stret_name("_objc_msgForward_stret");
692 Target *target = process_sp ? &process_sp->GetTarget() : nullptr;
693 const Symbol *class_getMethodImplementation =
694 m_objc_module_sp->FindFirstSymbolWithNameAndType(get_impl_name,
696 const Symbol *class_getMethodImplementation_stret =
697 m_objc_module_sp->FindFirstSymbolWithNameAndType(get_impl_stret_name,
699 const Symbol *msg_forward = m_objc_module_sp->FindFirstSymbolWithNameAndType(
700 msg_forward_name, eSymbolTypeCode);
701 const Symbol *msg_forward_stret =
702 m_objc_module_sp->FindFirstSymbolWithNameAndType(msg_forward_stret_name,
705 if (class_getMethodImplementation)
707 class_getMethodImplementation->GetAddress().GetOpcodeLoadAddress(
709 if (class_getMethodImplementation_stret)
710 m_impl_stret_fn_addr =
711 class_getMethodImplementation_stret->GetAddress().GetOpcodeLoadAddress(
714 m_msg_forward_addr = msg_forward->GetAddress().GetOpcodeLoadAddress(target);
715 if (msg_forward_stret)
716 m_msg_forward_stret_addr =
717 msg_forward_stret->GetAddress().GetOpcodeLoadAddress(target);
719 // FIXME: Do some kind of logging here.
720 if (m_impl_fn_addr == LLDB_INVALID_ADDRESS) {
721 // If we can't even find the ordinary get method implementation function,
722 // then we aren't going to be able to
723 // step through any method dispatches. Warn to that effect and get out of
725 if (process_sp->CanJIT()) {
726 process_sp->GetTarget().GetDebugger().GetErrorStream().Printf(
727 "Could not find implementation lookup function \"%s\""
728 " step in through ObjC method dispatch will not work.\n",
729 get_impl_name.AsCString());
732 } else if (m_impl_stret_fn_addr == LLDB_INVALID_ADDRESS) {
733 // It there is no stret return lookup function, assume that it is the same
734 // as the straight lookup:
735 m_impl_stret_fn_addr = m_impl_fn_addr;
736 // Also we will use the version of the lookup code that doesn't rely on the
737 // stret version of the function.
738 m_lookup_implementation_function_code =
739 g_lookup_implementation_no_stret_function_code;
741 m_lookup_implementation_function_code =
742 g_lookup_implementation_with_stret_function_code;
745 // Look up the addresses for the objc dispatch functions and cache
746 // them. For now I'm inspecting the symbol names dynamically to
747 // figure out how to dispatch to them. If it becomes more
748 // complicated than this we can turn the g_dispatch_functions char *
749 // array into a template table, and populate the DispatchFunction
752 for (size_t i = 0; i != llvm::array_lengthof(g_dispatch_functions); i++) {
753 ConstString name_const_str(g_dispatch_functions[i].name);
754 const Symbol *msgSend_symbol =
755 m_objc_module_sp->FindFirstSymbolWithNameAndType(name_const_str,
757 if (msgSend_symbol && msgSend_symbol->ValueIsAddress()) {
758 // FIXME: Make g_dispatch_functions static table of
759 // DispatchFunctions, and have the map be address->index.
760 // Problem is we also need to lookup the dispatch function. For
761 // now we could have a side table of stret & non-stret dispatch
762 // functions. If that's as complex as it gets, we're fine.
764 lldb::addr_t sym_addr =
765 msgSend_symbol->GetAddressRef().GetOpcodeLoadAddress(target);
767 m_msgSend_map.insert(std::pair<lldb::addr_t, int>(sym_addr, i));
771 // Similarly, cache the addresses of the "optimized dispatch" function.
772 for (size_t i = 0; i != llvm::array_lengthof(g_opt_dispatch_names); i++) {
773 ConstString name_const_str(g_opt_dispatch_names[i]);
774 const Symbol *msgSend_symbol =
775 m_objc_module_sp->FindFirstSymbolWithNameAndType(name_const_str,
777 if (msgSend_symbol && msgSend_symbol->ValueIsAddress()) {
778 lldb::addr_t sym_addr =
779 msgSend_symbol->GetAddressRef().GetOpcodeLoadAddress(target);
781 m_opt_dispatch_map.emplace(sym_addr, i);
785 // Build our vtable dispatch handler here:
787 std::make_unique<AppleObjCVTables>(process_sp, m_objc_module_sp);
789 m_vtables_up->ReadRegions();
793 AppleObjCTrampolineHandler::SetupDispatchFunction(Thread &thread,
794 ValueList &dispatch_values) {
795 ThreadSP thread_sp(thread.shared_from_this());
796 ExecutionContext exe_ctx(thread_sp);
797 Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
799 lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
800 FunctionCaller *impl_function_caller = nullptr;
802 // Scope for mutex locker:
804 std::lock_guard<std::mutex> guard(m_impl_function_mutex);
806 // First stage is to make the ClangUtility to hold our injected function:
809 if (m_lookup_implementation_function_code != nullptr) {
810 auto utility_fn_or_error = exe_ctx.GetTargetRef().CreateUtilityFunction(
811 m_lookup_implementation_function_code,
812 g_lookup_implementation_function_name, eLanguageTypeC, exe_ctx);
813 if (!utility_fn_or_error) {
815 log, utility_fn_or_error.takeError(),
816 "Failed to get Utility Function for implementation lookup: {0}.");
819 m_impl_code = std::move(*utility_fn_or_error);
821 LLDB_LOGF(log, "No method lookup implementation code.");
822 return LLDB_INVALID_ADDRESS;
825 // Next make the runner function for our implementation utility function.
826 TypeSystemClang *clang_ast_context = ScratchTypeSystemClang::GetForTarget(
827 thread.GetProcess()->GetTarget());
828 if (!clang_ast_context)
829 return LLDB_INVALID_ADDRESS;
831 CompilerType clang_void_ptr_type =
832 clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
835 impl_function_caller = m_impl_code->MakeFunctionCaller(
836 clang_void_ptr_type, dispatch_values, thread_sp, error);
839 "Error getting function caller for dispatch lookup: \"%s\".",
844 impl_function_caller = m_impl_code->GetFunctionCaller();
848 // Now write down the argument values for this particular call.
849 // This looks like it might be a race condition if other threads
850 // were calling into here, but actually it isn't because we allocate
851 // a new args structure for this call by passing args_addr =
852 // LLDB_INVALID_ADDRESS...
854 DiagnosticManager diagnostics;
855 if (!impl_function_caller->WriteFunctionArguments(
856 exe_ctx, args_addr, dispatch_values, diagnostics)) {
858 LLDB_LOGF(log, "Error writing function arguments.");
859 diagnostics.Dump(log);
867 const AppleObjCTrampolineHandler::DispatchFunction *
868 AppleObjCTrampolineHandler::FindDispatchFunction(lldb::addr_t addr) {
869 MsgsendMap::iterator pos;
870 pos = m_msgSend_map.find(addr);
871 if (pos != m_msgSend_map.end()) {
872 return &g_dispatch_functions[(*pos).second];
878 AppleObjCTrampolineHandler::ForEachDispatchFunction(
879 std::function<void(lldb::addr_t,
880 const DispatchFunction &)> callback) {
881 for (auto elem : m_msgSend_map) {
882 callback(elem.first, g_dispatch_functions[elem.second]);
887 AppleObjCTrampolineHandler::GetStepThroughDispatchPlan(Thread &thread,
889 ThreadPlanSP ret_plan_sp;
890 lldb::addr_t curr_pc = thread.GetRegisterContext()->GetPC();
892 DispatchFunction vtable_dispatch
893 = {"vtable", 0, false, false, DispatchFunction::eFixUpFixed};
895 // First step is to look and see if we are in one of the known ObjC
896 // dispatch functions. We've already compiled a table of same, so
899 const DispatchFunction *this_dispatch = FindDispatchFunction(curr_pc);
901 // Next check to see if we are in a vtable region:
903 if (!this_dispatch && m_vtables_up) {
905 if (m_vtables_up->IsAddressInVTables(curr_pc, flags)) {
906 vtable_dispatch.stret_return =
907 (flags & AppleObjCVTables::eOBJC_TRAMPOLINE_STRET) ==
908 AppleObjCVTables::eOBJC_TRAMPOLINE_STRET;
909 this_dispatch = &vtable_dispatch;
914 Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
916 // We are decoding a method dispatch. First job is to pull the
919 lldb::StackFrameSP thread_cur_frame = thread.GetStackFrameAtIndex(0);
921 const ABI *abi = nullptr;
922 ProcessSP process_sp(thread.CalculateProcess());
924 abi = process_sp->GetABI().get();
928 TargetSP target_sp(thread.CalculateTarget());
930 TypeSystemClang *clang_ast_context =
931 ScratchTypeSystemClang::GetForTarget(*target_sp);
932 if (!clang_ast_context)
935 ValueList argument_values;
936 Value void_ptr_value;
937 CompilerType clang_void_ptr_type =
938 clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
939 void_ptr_value.SetValueType(Value::ValueType::Scalar);
940 // void_ptr_value.SetContext (Value::eContextTypeClangType,
941 // clang_void_ptr_type);
942 void_ptr_value.SetCompilerType(clang_void_ptr_type);
947 // If this is a struct return dispatch, then the first argument is
948 // the return struct pointer, and the object is the second, and
949 // the selector is the third. Otherwise the object is the first
950 // and the selector the second.
951 if (this_dispatch->stret_return) {
954 argument_values.PushValue(void_ptr_value);
955 argument_values.PushValue(void_ptr_value);
956 argument_values.PushValue(void_ptr_value);
960 argument_values.PushValue(void_ptr_value);
961 argument_values.PushValue(void_ptr_value);
964 bool success = abi->GetArgumentValues(thread, argument_values);
968 lldb::addr_t obj_addr =
969 argument_values.GetValueAtIndex(obj_index)->GetScalar().ULongLong();
970 if (obj_addr == 0x0) {
973 "Asked to step to dispatch to nil object, returning empty plan.");
977 ExecutionContext exe_ctx(thread.shared_from_this());
978 Process *process = exe_ctx.GetProcessPtr();
979 // isa_addr will store the class pointer that the method is being
980 // dispatched to - so either the class directly or the super class
981 // if this is one of the objc_msgSendSuper flavors. That's mostly
982 // used to look up the class/selector pair in our cache.
984 lldb::addr_t isa_addr = LLDB_INVALID_ADDRESS;
985 lldb::addr_t sel_addr =
986 argument_values.GetValueAtIndex(sel_index)->GetScalar().ULongLong();
988 // Figure out the class this is being dispatched to and see if
989 // we've already cached this method call, If so we can push a
990 // run-to-address plan directly. Otherwise we have to figure out
991 // where the implementation lives.
993 if (this_dispatch->is_super) {
994 if (this_dispatch->is_super2) {
995 // In the objc_msgSendSuper2 case, we don't get the object
996 // directly, we get a structure containing the object and the
997 // class to which the super message is being sent. So we need
998 // to dig the super out of the class and use that.
1000 Value super_value(*(argument_values.GetValueAtIndex(obj_index)));
1001 super_value.GetScalar() += process->GetAddressByteSize();
1002 super_value.ResolveValue(&exe_ctx);
1004 if (super_value.GetScalar().IsValid()) {
1006 // isa_value now holds the class pointer. The second word of the
1007 // class pointer is the super-class pointer:
1008 super_value.GetScalar() += process->GetAddressByteSize();
1009 super_value.ResolveValue(&exe_ctx);
1010 if (super_value.GetScalar().IsValid())
1011 isa_addr = super_value.GetScalar().ULongLong();
1013 LLDB_LOGF(log, "Failed to extract the super class value from the "
1014 "class in objc_super.");
1017 LLDB_LOGF(log, "Failed to extract the class value from objc_super.");
1020 // In the objc_msgSendSuper case, we don't get the object
1021 // directly, we get a two element structure containing the
1022 // object and the super class to which the super message is
1023 // being sent. So the class we want is the second element of
1026 Value super_value(*(argument_values.GetValueAtIndex(obj_index)));
1027 super_value.GetScalar() += process->GetAddressByteSize();
1028 super_value.ResolveValue(&exe_ctx);
1030 if (super_value.GetScalar().IsValid()) {
1031 isa_addr = super_value.GetScalar().ULongLong();
1033 LLDB_LOGF(log, "Failed to extract the class value from objc_super.");
1037 // In the direct dispatch case, the object->isa is the class pointer we
1040 // This is a little cheesy, but since object->isa is the first field,
1041 // making the object value a load address value and resolving it will get
1042 // the pointer sized data pointed to by that value...
1044 // Note, it isn't a fatal error not to be able to get the
1045 // address from the object, since this might be a "tagged
1046 // pointer" which isn't a real object, but rather some word
1047 // length encoded dingus.
1049 Value isa_value(*(argument_values.GetValueAtIndex(obj_index)));
1051 isa_value.SetValueType(Value::ValueType::LoadAddress);
1052 isa_value.ResolveValue(&exe_ctx);
1053 if (isa_value.GetScalar().IsValid()) {
1054 isa_addr = isa_value.GetScalar().ULongLong();
1056 LLDB_LOGF(log, "Failed to extract the isa value from object.");
1060 // Okay, we've got the address of the class for which we're resolving this,
1061 // let's see if it's in our cache:
1062 lldb::addr_t impl_addr = LLDB_INVALID_ADDRESS;
1064 if (isa_addr != LLDB_INVALID_ADDRESS) {
1067 "Resolving call for class - 0x%" PRIx64
1068 " and selector - 0x%" PRIx64,
1069 isa_addr, sel_addr);
1071 ObjCLanguageRuntime *objc_runtime =
1072 ObjCLanguageRuntime::Get(*thread.GetProcess());
1073 assert(objc_runtime != nullptr);
1075 impl_addr = objc_runtime->LookupInMethodCache(isa_addr, sel_addr);
1078 if (impl_addr != LLDB_INVALID_ADDRESS) {
1079 // Yup, it was in the cache, so we can run to that address directly.
1081 LLDB_LOGF(log, "Found implementation address in cache: 0x%" PRIx64,
1084 ret_plan_sp = std::make_shared<ThreadPlanRunToAddress>(thread, impl_addr,
1087 // We haven't seen this class/selector pair yet. Look it up.
1088 StreamString errors;
1089 Address impl_code_address;
1091 ValueList dispatch_values;
1093 // We've will inject a little function in the target that takes the
1094 // object, selector and some flags,
1095 // and figures out the implementation. Looks like:
1096 // void *__lldb_objc_find_implementation_for_selector (void *object,
1104 // So set up the arguments for that call.
1106 dispatch_values.PushValue(*(argument_values.GetValueAtIndex(obj_index)));
1107 dispatch_values.PushValue(*(argument_values.GetValueAtIndex(sel_index)));
1110 CompilerType clang_int_type =
1111 clang_ast_context->GetBuiltinTypeForEncodingAndBitSize(
1112 lldb::eEncodingSint, 32);
1113 flag_value.SetValueType(Value::ValueType::Scalar);
1114 // flag_value.SetContext (Value::eContextTypeClangType, clang_int_type);
1115 flag_value.SetCompilerType(clang_int_type);
1117 if (this_dispatch->stret_return)
1118 flag_value.GetScalar() = 1;
1120 flag_value.GetScalar() = 0;
1121 dispatch_values.PushValue(flag_value);
1123 if (this_dispatch->is_super)
1124 flag_value.GetScalar() = 1;
1126 flag_value.GetScalar() = 0;
1127 dispatch_values.PushValue(flag_value);
1129 if (this_dispatch->is_super2)
1130 flag_value.GetScalar() = 1;
1132 flag_value.GetScalar() = 0;
1133 dispatch_values.PushValue(flag_value);
1135 switch (this_dispatch->fixedup) {
1136 case DispatchFunction::eFixUpNone:
1137 flag_value.GetScalar() = 0;
1138 dispatch_values.PushValue(flag_value);
1139 dispatch_values.PushValue(flag_value);
1141 case DispatchFunction::eFixUpFixed:
1142 flag_value.GetScalar() = 1;
1143 dispatch_values.PushValue(flag_value);
1144 flag_value.GetScalar() = 1;
1145 dispatch_values.PushValue(flag_value);
1147 case DispatchFunction::eFixUpToFix:
1148 flag_value.GetScalar() = 1;
1149 dispatch_values.PushValue(flag_value);
1150 flag_value.GetScalar() = 0;
1151 dispatch_values.PushValue(flag_value);
1154 if (log && log->GetVerbose())
1155 flag_value.GetScalar() = 1;
1157 flag_value.GetScalar() = 0; // FIXME - Set to 0 when debugging is done.
1158 dispatch_values.PushValue(flag_value);
1160 ret_plan_sp = std::make_shared<AppleThreadPlanStepThroughObjCTrampoline>(
1161 thread, *this, dispatch_values, isa_addr, sel_addr);
1164 ret_plan_sp->GetDescription(&s, eDescriptionLevelFull);
1165 LLDB_LOGF(log, "Using ObjC step plan: %s.\n", s.GetData());
1170 // Finally, check if we have hit an "optimized dispatch" function. This will
1171 // either directly call the base implementation or dispatch an objc_msgSend
1172 // if the method has been overridden. So we just do a "step in/step out",
1173 // setting a breakpoint on objc_msgSend, and if we hit the msgSend, we
1174 // will automatically step in again. That's the job of the
1175 // AppleThreadPlanStepThroughDirectDispatch.
1176 if (!this_dispatch && !ret_plan_sp) {
1177 MsgsendMap::iterator pos;
1178 pos = m_opt_dispatch_map.find(curr_pc);
1179 if (pos != m_opt_dispatch_map.end()) {
1180 const char *opt_name = g_opt_dispatch_names[(*pos).second];
1181 ret_plan_sp = std::make_shared<AppleThreadPlanStepThroughDirectDispatch>(
1182 thread, *this, opt_name);
1190 AppleObjCTrampolineHandler::GetLookupImplementationFunctionCaller() {
1191 return m_impl_code->GetFunctionCaller();