//===-- AppleObjCTrampolineHandler.cpp ------------------------------------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

#include "AppleObjCTrampolineHandler.h"

#include "AppleThreadPlanStepThroughObjCTrampoline.h"

#include "Plugins/TypeSystem/Clang/TypeSystemClang.h"

#include "lldb/Breakpoint/StoppointCallbackContext.h"

#include "lldb/Core/Debugger.h"

#include "lldb/Core/Module.h"

#include "lldb/Core/Value.h"

#include "lldb/Expression/DiagnosticManager.h"

#include "lldb/Expression/FunctionCaller.h"

#include "lldb/Expression/UserExpression.h"

#include "lldb/Expression/UtilityFunction.h"

#include "lldb/Symbol/Symbol.h"

#include "lldb/Target/ABI.h"

#include "lldb/Target/ExecutionContext.h"

#include "lldb/Target/Process.h"

#include "lldb/Target/RegisterContext.h"

#include "lldb/Target/Target.h"

#include "lldb/Target/Thread.h"

#include "lldb/Target/ThreadPlanRunToAddress.h"

#include "lldb/Utility/ConstString.h"

#include "lldb/Utility/FileSpec.h"

#include "lldb/Utility/LLDBLog.h"

#include "lldb/Utility/Log.h"

#include "llvm/ADT/STLExtras.h"

#include "llvm/ADT/ScopeExit.h"

#include "Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h"

#include <memory>

using namespace lldb;

using namespace lldb_private;

const char *AppleObjCTrampolineHandler::g_lookup_implementation_function_name =

    "__lldb_objc_find_implementation_for_selector";

const char *AppleObjCTrampolineHandler::

    g_lookup_implementation_with_stret_function_code =

        R"(

  if (is_stret) {

    return_struct.impl_addr =

    class_getMethodImplementation_stret (return_struct.class_addr,

                                         return_struct.sel_addr);

  } else {

    return_struct.impl_addr =

        class_getMethodImplementation (return_struct.class_addr,

                                       return_struct.sel_addr);

  }

  if (debug)

    printf ("\n*** Returning implementation: %p.\n",

            return_struct.impl_addr);

  return return_struct.impl_addr;

}

)";

const char *

    AppleObjCTrampolineHandler::g_lookup_implementation_no_stret_function_code =

        R"(

  return_struct.impl_addr =

    class_getMethodImplementation (return_struct.class_addr,

                                   return_struct.sel_addr);

  if (debug)

    printf ("\n*** getMethodImpletation for addr: 0x%p sel: 0x%p result: 0x%p.\n",

            return_struct.class_addr, return_struct.sel_addr, return_struct.impl_addr);

  return return_struct.impl_addr;

}

)";

const char

    *AppleObjCTrampolineHandler::g_lookup_implementation_function_common_code =

        R"(

extern "C"

{

  extern void *class_getMethodImplementation(void *objc_class, void *sel);

  extern void *class_getMethodImplementation_stret(void *objc_class, void *sel);

  extern void * object_getClass (id object);

  extern void * sel_getUid(char *name);

  extern int printf(const char *format, ...);

}

extern "C" void * 

__lldb_objc_find_implementation_for_selector (void *object,

                                              void *sel,

                                              int is_str_ptr,

                                              int is_stret,

                                              int is_super,

                                              int is_super2,

                                              int is_fixup,

                                              int is_fixed,

                                              int debug)

{

  struct __lldb_imp_return_struct {

    void *class_addr;

    void *sel_addr;

    void *impl_addr;

  };

  struct __lldb_objc_class {

    void *isa;

    void *super_ptr;

  };

  struct __lldb_objc_super {

    void *receiver;

    struct __lldb_objc_class *class_ptr;

  };

  struct __lldb_msg_ref {

    void *dont_know;

    void *sel;

  };

  struct __lldb_imp_return_struct return_struct;

  if (debug)

    printf ("\n*** Called with obj: %p sel: %p is_str_ptr: %d "

            "is_stret: %d is_super: %d, "

            "is_super2: %d, is_fixup: %d, is_fixed: %d\n",

             object, sel, is_str_ptr, is_stret,

             is_super, is_super2, is_fixup, is_fixed);

  if (is_str_ptr) {

    if (debug)

      printf("*** Turning string: '%s'", sel);

    sel = sel_getUid((char *)sel);

    if (debug)

      printf("*** into sel to %p", sel);

  }

  if (is_super) {

    if (is_super2) {

      return_struct.class_addr 

          = ((__lldb_objc_super *) object)->class_ptr->super_ptr;

    } else {

      return_struct.class_addr = ((__lldb_objc_super *) object)->class_ptr;

    }

    if (debug)

      printf("*** Super, class addr: %p\n", return_struct.class_addr);

  } else {

    // This code seems a little funny, but has its reasons...

    // The call to [object class] is here because if this is a class, and has 

    // not been called into yet, we need to do something to force the class to 

    // initialize itself.

    // Then the call to object_getClass will actually return the correct class, 

    // either the class if object is a class instance, or the meta-class if it 

    // is a class pointer.

    void *class_ptr = (void *) [(id) object class];

    return_struct.class_addr = (id)  object_getClass((id) object);

    if (debug) {

      if (class_ptr == object) {

        printf ("Found a class object, need to return the meta class %p -> %p\n",

                class_ptr, return_struct.class_addr);

      } else {

         printf ("[object class] returned: %p object_getClass: %p.\n",

                 class_ptr, return_struct.class_addr);

      }

    }

  }

  if (is_fixup) {

    if (is_fixed) {

        return_struct.sel_addr = ((__lldb_msg_ref *) sel)->sel;

    } else {

      char *sel_name = (char *) ((__lldb_msg_ref *) sel)->sel;

      return_struct.sel_addr = sel_getUid (sel_name);

      if (debug)

        printf ("\n*** Got fixed up selector: %p for name %s.\n",

                return_struct.sel_addr, sel_name);

    }

  } else {

    return_struct.sel_addr = sel;

  }

)";

AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::VTableRegion(

    AppleObjCVTables *owner, lldb::addr_t header_addr)

    : m_valid(true), m_owner(owner), m_header_addr(header_addr) {

  SetUpRegion();

}

AppleObjCTrampolineHandler::~AppleObjCTrampolineHandler() = default;

void AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::SetUpRegion() {

  // The header looks like:

  //

  //   uint16_t headerSize

  //   uint16_t descSize

  //   uint32_t descCount

  //   void * next

  //

  // First read in the header:

  char memory_buffer[16];

  ProcessSP process_sp = m_owner->GetProcessSP();

  if (!process_sp)

    return;

  DataExtractor data(memory_buffer, sizeof(memory_buffer),

                     process_sp->GetByteOrder(),

                     process_sp->GetAddressByteSize());

  size_t actual_size = 8 + process_sp->GetAddressByteSize();

  Status error;

  size_t bytes_read =

      process_sp->ReadMemory(m_header_addr, memory_buffer, actual_size, error);

  if (bytes_read != actual_size) {

    m_valid = false;

    return;

  }

  lldb::offset_t offset = 0;

  const uint16_t header_size = data.GetU16(&offset);

  const uint16_t descriptor_size = data.GetU16(&offset);

  const size_t num_descriptors = data.GetU32(&offset);

  m_next_region = data.GetAddress(&offset);

  // If the header size is 0, that means we've come in too early before this

  // data is set up.

  // Set ourselves as not valid, and continue.

  if (header_size == 0 || num_descriptors == 0) {

    m_valid = false;

    return;

  }

  // Now read in all the descriptors:

  // The descriptor looks like:

  //

  // uint32_t offset

  // uint32_t flags

  //

  // Where offset is either 0 - in which case it is unused, or it is

  // the offset of the vtable code from the beginning of the

  // descriptor record.  Below, we'll convert that into an absolute

  // code address, since I don't want to have to compute it over and

  // over.

  // Ingest the whole descriptor array:

  const lldb::addr_t desc_ptr = m_header_addr + header_size;

  const size_t desc_array_size = num_descriptors * descriptor_size;

  WritableDataBufferSP data_sp(new DataBufferHeap(desc_array_size, '\0'));

  uint8_t *dst = (uint8_t *)data_sp->GetBytes();

  DataExtractor desc_extractor(dst, desc_array_size, process_sp->GetByteOrder(),

                               process_sp->GetAddressByteSize());

  bytes_read = process_sp->ReadMemory(desc_ptr, dst, desc_array_size, error);

  if (bytes_read != desc_array_size) {

    m_valid = false;

    return;

  }

  // The actual code for the vtables will be laid out consecutively, so I also

  // compute the start and end of the whole code block.

  offset = 0;

  m_code_start_addr = 0;

  m_code_end_addr = 0;

  for (size_t i = 0; i < num_descriptors; i++) {

    lldb::addr_t start_offset = offset;

    uint32_t voffset = desc_extractor.GetU32(&offset);

    uint32_t flags = desc_extractor.GetU32(&offset);

    lldb::addr_t code_addr = desc_ptr + start_offset + voffset;

    m_descriptors.push_back(VTableDescriptor(flags, code_addr));

    if (m_code_start_addr == 0 || code_addr < m_code_start_addr)

      m_code_start_addr = code_addr;

    if (code_addr > m_code_end_addr)

      m_code_end_addr = code_addr;

    offset = start_offset + descriptor_size;

  }

  // Finally, a little bird told me that all the vtable code blocks

  // are the same size.  Let's compute the blocks and if they are all

  // the same add the size to the code end address:

  lldb::addr_t code_size = 0;

  bool all_the_same = true;

  for (size_t i = 0; i < num_descriptors - 1; i++) {

    lldb::addr_t this_size =

        m_descriptors[i + 1].code_start - m_descriptors[i].code_start;

    if (code_size == 0)

      code_size = this_size;

    else {

      if (this_size != code_size)

        all_the_same = false;

      if (this_size > code_size)

        code_size = this_size;

    }

  }

  if (all_the_same)

    m_code_end_addr += code_size;

}

bool AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::

    AddressInRegion(lldb::addr_t addr, uint32_t &flags) {

  if (!IsValid())

    return false;

  if (addr < m_code_start_addr || addr > m_code_end_addr)

    return false;

  std::vector<VTableDescriptor>::iterator pos, end = m_descriptors.end();

  for (pos = m_descriptors.begin(); pos != end; pos++) {

    if (addr <= (*pos).code_start) {

      flags = (*pos).flags;

      return true;

    }

  }

  return false;

}

void AppleObjCTrampolineHandler::AppleObjCVTables::VTableRegion::Dump(

    Stream &s) {

  s.Printf("Header addr: 0x%" PRIx64 " Code start: 0x%" PRIx64

           " Code End: 0x%" PRIx64 " Next: 0x%" PRIx64 "\n",

           m_header_addr, m_code_start_addr, m_code_end_addr, m_next_region);

  size_t num_elements = m_descriptors.size();

  for (size_t i = 0; i < num_elements; i++) {

    s.Indent();

    s.Printf("Code start: 0x%" PRIx64 " Flags: %d\n",

             m_descriptors[i].code_start, m_descriptors[i].flags);

  }

}

AppleObjCTrampolineHandler::AppleObjCVTables::AppleObjCVTables(

    const ProcessSP &process_sp, const ModuleSP &objc_module_sp)

    : m_process_wp(), m_trampoline_header(LLDB_INVALID_ADDRESS),

      m_trampolines_changed_bp_id(LLDB_INVALID_BREAK_ID),

      m_objc_module_sp(objc_module_sp) {

  if (process_sp)

    m_process_wp = process_sp;

}

AppleObjCTrampolineHandler::AppleObjCVTables::~AppleObjCVTables() {

  ProcessSP process_sp = GetProcessSP();

  if (process_sp) {

    if (m_trampolines_changed_bp_id != LLDB_INVALID_BREAK_ID)

      process_sp->GetTarget().RemoveBreakpointByID(m_trampolines_changed_bp_id);

  }

}

bool AppleObjCTrampolineHandler::AppleObjCVTables::InitializeVTableSymbols() {

  if (m_trampoline_header != LLDB_INVALID_ADDRESS)

    return true;

  ProcessSP process_sp = GetProcessSP();

  if (process_sp) {

    Target &target = process_sp->GetTarget();

    if (!m_objc_module_sp) {

      for (ModuleSP module_sp : target.GetImages().Modules()) {

        if (ObjCLanguageRuntime::Get(*process_sp)

                ->IsModuleObjCLibrary(module_sp)) {

          m_objc_module_sp = module_sp;

          break;

        }

      }

    }

    if (m_objc_module_sp) {

      ConstString trampoline_name("gdb_objc_trampolines");

      const Symbol *trampoline_symbol =

          m_objc_module_sp->FindFirstSymbolWithNameAndType(trampoline_name,

                                                           eSymbolTypeData);

      if (trampoline_symbol != nullptr) {

        m_trampoline_header = trampoline_symbol->GetLoadAddress(&target);

        if (m_trampoline_header == LLDB_INVALID_ADDRESS)

          return false;

        // Next look up the "changed" symbol and set a breakpoint on that...

        ConstString changed_name("gdb_objc_trampolines_changed");

        const Symbol *changed_symbol =

            m_objc_module_sp->FindFirstSymbolWithNameAndType(changed_name,

                                                             eSymbolTypeCode);

        if (changed_symbol != nullptr) {

          const Address changed_symbol_addr = changed_symbol->GetAddress();

          if (!changed_symbol_addr.IsValid())

            return false;

          lldb::addr_t changed_addr =

              changed_symbol_addr.GetOpcodeLoadAddress(&target);

          if (changed_addr != LLDB_INVALID_ADDRESS) {

            BreakpointSP trampolines_changed_bp_sp =

                target.CreateBreakpoint(changed_addr, true, false);

            if (trampolines_changed_bp_sp) {

              m_trampolines_changed_bp_id = trampolines_changed_bp_sp->GetID();

              trampolines_changed_bp_sp->SetCallback(RefreshTrampolines, this,

                                                     true);

              trampolines_changed_bp_sp->SetBreakpointKind(

                  "objc-trampolines-changed");

              return true;

            }

          }

        }

      }

    }

  }

  return false;

}

bool AppleObjCTrampolineHandler::AppleObjCVTables::RefreshTrampolines(

    void *baton, StoppointCallbackContext *context, lldb::user_id_t break_id,

    lldb::user_id_t break_loc_id) {

  AppleObjCVTables *vtable_handler = (AppleObjCVTables *)baton;

  if (vtable_handler->InitializeVTableSymbols()) {

    // The Update function is called with the address of an added region.  So we

    // grab that address, and

    // feed it into ReadRegions.  Of course, our friend the ABI will get the

    // values for us.

    ExecutionContext exe_ctx(context->exe_ctx_ref);

    Process *process = exe_ctx.GetProcessPtr();

    const ABI *abi = process->GetABI().get();

    TypeSystemClangSP scratch_ts_sp =

        ScratchTypeSystemClang::GetForTarget(process->GetTarget());

    if (!scratch_ts_sp)

      return false;

    ValueList argument_values;

    Value input_value;

    CompilerType clang_void_ptr_type =

        scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();

    input_value.SetValueType(Value::ValueType::Scalar);

    // input_value.SetContext (Value::eContextTypeClangType,

    // clang_void_ptr_type);

    input_value.SetCompilerType(clang_void_ptr_type);

    argument_values.PushValue(input_value);

    bool success =

        abi->GetArgumentValues(exe_ctx.GetThreadRef(), argument_values);

    if (!success)

      return false;

    // Now get a pointer value from the zeroth argument.

    Status error;

    DataExtractor data;

    error = argument_values.GetValueAtIndex(0)->GetValueAsData(&exe_ctx, data,

                                                               nullptr);

    lldb::offset_t offset = 0;

    lldb::addr_t region_addr = data.GetAddress(&offset);

    if (region_addr != 0)

      vtable_handler->ReadRegions(region_addr);

  }

  return false;

}

bool AppleObjCTrampolineHandler::AppleObjCVTables::ReadRegions() {

  // The no argument version reads the  start region from the value of

  // the gdb_regions_header, and gets started from there.

  m_regions.clear();

  if (!InitializeVTableSymbols())

    return false;

  Status error;

  ProcessSP process_sp = GetProcessSP();

  if (process_sp) {

    lldb::addr_t region_addr =

        process_sp->ReadPointerFromMemory(m_trampoline_header, error);

    if (error.Success())

      return ReadRegions(region_addr);

  }

  return false;

}

bool AppleObjCTrampolineHandler::AppleObjCVTables::ReadRegions(

    lldb::addr_t region_addr) {

  ProcessSP process_sp = GetProcessSP();

  if (!process_sp)

    return false;

  Log *log = GetLog(LLDBLog::Step);

  // We aren't starting at the trampoline symbol.

  InitializeVTableSymbols();

  lldb::addr_t next_region = region_addr;

  // Read in the sizes of the headers.

  while (next_region != 0) {

    m_regions.push_back(VTableRegion(this, next_region));

    if (!m_regions.back().IsValid()) {

      m_regions.clear();

      return false;

    }

    if (log) {

      StreamString s;

      m_regions.back().Dump(s);

      LLDB_LOGF(log, "Read vtable region: \n%s", s.GetData());

    }

    next_region = m_regions.back().GetNextRegionAddr();

  }

  return true;

}

bool AppleObjCTrampolineHandler::AppleObjCVTables::IsAddressInVTables(

    lldb::addr_t addr, uint32_t &flags) {

  region_collection::iterator pos, end = m_regions.end();

  for (pos = m_regions.begin(); pos != end; 
pos++0
) {

    if ((*pos).AddressInRegion(addr, flags))

      return true;

  }

  return false;

}

const AppleObjCTrampolineHandler::DispatchFunction

    AppleObjCTrampolineHandler::g_dispatch_functions[] = {

        // NAME                              STRET  SUPER  SUPER2  FIXUP TYPE

        {"objc_msgSend", false, false, false, DispatchFunction::eFixUpNone},

        {"objc_msgSend_fixup", false, false, false,

         DispatchFunction::eFixUpToFix},

        {"objc_msgSend_fixedup", false, false, false,

         DispatchFunction::eFixUpFixed},

        {"objc_msgSend_stret", true, false, false,

         DispatchFunction::eFixUpNone},

        {"objc_msgSend_stret_fixup", true, false, false,

         DispatchFunction::eFixUpToFix},

        {"objc_msgSend_stret_fixedup", true, false, false,

         DispatchFunction::eFixUpFixed},

        {"objc_msgSend_fpret", false, false, false,

         DispatchFunction::eFixUpNone},

        {"objc_msgSend_fpret_fixup", false, false, false,

         DispatchFunction::eFixUpToFix},

        {"objc_msgSend_fpret_fixedup", false, false, false,

         DispatchFunction::eFixUpFixed},

        {"objc_msgSend_fp2ret", false, false, true,

         DispatchFunction::eFixUpNone},

        {"objc_msgSend_fp2ret_fixup", false, false, true,

         DispatchFunction::eFixUpToFix},

        {"objc_msgSend_fp2ret_fixedup", false, false, true,

         DispatchFunction::eFixUpFixed},

        {"objc_msgSendSuper", false, true, false, DispatchFunction::eFixUpNone},

        {"objc_msgSendSuper_stret", true, true, false,

         DispatchFunction::eFixUpNone},

        {"objc_msgSendSuper2", false, true, true, DispatchFunction::eFixUpNone},

        {"objc_msgSendSuper2_fixup", false, true, true,

         DispatchFunction::eFixUpToFix},

        {"objc_msgSendSuper2_fixedup", false, true, true,

         DispatchFunction::eFixUpFixed},

        {"objc_msgSendSuper2_stret", true, true, true,

         DispatchFunction::eFixUpNone},

        {"objc_msgSendSuper2_stret_fixup", true, true, true,

         DispatchFunction::eFixUpToFix},

        {"objc_msgSendSuper2_stret_fixedup", true, true, true,

         DispatchFunction::eFixUpFixed},

};

// This is the table of ObjC "accelerated dispatch" functions.  They are a set

// of objc methods that are "seldom overridden" and so the compiler replaces the

// objc_msgSend with a call to one of the dispatch functions.  That will check

// whether the method has been overridden, and directly call the Foundation 

// implementation if not.  

// This table is supposed to be complete.  If ones get added in the future, we

// will have to add them to the table.

const char *AppleObjCTrampolineHandler::g_opt_dispatch_names[] = {

    "objc_alloc",

    "objc_autorelease",

    "objc_release",

    "objc_retain",

    "objc_alloc_init",

    "objc_allocWithZone",

    "objc_opt_class",

    "objc_opt_isKindOfClass",

    "objc_opt_new",

    "objc_opt_respondsToSelector",

    "objc_opt_self",

};

AppleObjCTrampolineHandler::AppleObjCTrampolineHandler(

    const ProcessSP &process_sp, const ModuleSP &objc_module_sp)

    : m_process_wp(), m_objc_module_sp(objc_module_sp),

      m_impl_fn_addr(LLDB_INVALID_ADDRESS),

      m_impl_stret_fn_addr(LLDB_INVALID_ADDRESS),

      m_msg_forward_addr(LLDB_INVALID_ADDRESS),

      m_msg_forward_stret_addr(LLDB_INVALID_ADDRESS) {

  if (process_sp)

    m_process_wp = process_sp;

  // Look up the known resolution functions:

  ConstString get_impl_name("class_getMethodImplementation");

  ConstString get_impl_stret_name("class_getMethodImplementation_stret");

  ConstString msg_forward_name("_objc_msgForward");

  ConstString msg_forward_stret_name("_objc_msgForward_stret");

  Target *target = process_sp ? &process_sp->GetTarget() : 
nullptr0
;

  const Symbol *class_getMethodImplementation =

      m_objc_module_sp->FindFirstSymbolWithNameAndType(get_impl_name,

                                                       eSymbolTypeCode);

  const Symbol *class_getMethodImplementation_stret =

      m_objc_module_sp->FindFirstSymbolWithNameAndType(get_impl_stret_name,

                                                       eSymbolTypeCode);

  const Symbol *msg_forward = m_objc_module_sp->FindFirstSymbolWithNameAndType(

      msg_forward_name, eSymbolTypeCode);

  const Symbol *msg_forward_stret =

      m_objc_module_sp->FindFirstSymbolWithNameAndType(msg_forward_stret_name,

                                                       eSymbolTypeCode);

  if (class_getMethodImplementation)

    m_impl_fn_addr =

        class_getMethodImplementation->GetAddress().GetOpcodeLoadAddress(

            target);

  if (class_getMethodImplementation_stret)

    m_impl_stret_fn_addr =

        class_getMethodImplementation_stret->GetAddress().GetOpcodeLoadAddress(

            target);

  if (msg_forward)

    m_msg_forward_addr = msg_forward->GetAddress().GetOpcodeLoadAddress(target);

  if (msg_forward_stret)

    m_msg_forward_stret_addr =

        msg_forward_stret->GetAddress().GetOpcodeLoadAddress(target);

  // FIXME: Do some kind of logging here.

  if (m_impl_fn_addr == LLDB_INVALID_ADDRESS) {

    // If we can't even find the ordinary get method implementation function,

    // then we aren't going to be able to

    // step through any method dispatches.  Warn to that effect and get out of

    // here.

    if (process_sp->CanJIT()) {

      process_sp->GetTarget().GetDebugger().GetErrorStream().Printf(

          "Could not find implementation lookup function \"%s\""

          " step in through ObjC method dispatch will not work.\n",

          get_impl_name.AsCString());

    }

    return;

  }

  // We will either set the implementation to the _stret or non_stret version,

  // so either way it's safe to start filling the m_lookup_..._code here.

  m_lookup_implementation_function_code.assign(

          g_lookup_implementation_function_common_code);

  if (m_impl_stret_fn_addr == LLDB_INVALID_ADDRESS) {

    // It there is no stret return lookup function, assume that it is the same

    // as the straight lookup:

    m_impl_stret_fn_addr = m_impl_fn_addr;

    // Also we will use the version of the lookup code that doesn't rely on the

    // stret version of the function.

    m_lookup_implementation_function_code.append(

        g_lookup_implementation_no_stret_function_code);

  } else {

    m_lookup_implementation_function_code.append(

        g_lookup_implementation_with_stret_function_code);

  }

  // Look up the addresses for the objc dispatch functions and cache

  // them.  For now I'm inspecting the symbol names dynamically to

  // figure out how to dispatch to them.  If it becomes more

  // complicated than this we can turn the g_dispatch_functions char *

  // array into a template table, and populate the DispatchFunction

  // map from there.

  for (size_t i = 0; i != std::size(g_dispatch_functions); 
i++42.2k
) {

    ConstString name_const_str(g_dispatch_functions[i].name);

    const Symbol *msgSend_symbol =

        m_objc_module_sp->FindFirstSymbolWithNameAndType(name_const_str,

                                                         eSymbolTypeCode);

    if (msgSend_symbol && msgSend_symbol->ValueIsAddress()) {

      // FIXME: Make g_dispatch_functions static table of

      // DispatchFunctions, and have the map be address->index.

      // Problem is we also need to lookup the dispatch function.  For

      // now we could have a side table of stret & non-stret dispatch

      // functions.  If that's as complex as it gets, we're fine.

      lldb::addr_t sym_addr =

          msgSend_symbol->GetAddressRef().GetOpcodeLoadAddress(target);

      m_msgSend_map.insert(std::pair<lldb::addr_t, int>(sym_addr, i));

    }

  }

  // Similarly, cache the addresses of the "optimized dispatch" function.

  for (size_t i = 0; i != std::size(g_opt_dispatch_names); 
i++23.2k
) {

    ConstString name_const_str(g_opt_dispatch_names[i]);

    const Symbol *msgSend_symbol =

        m_objc_module_sp->FindFirstSymbolWithNameAndType(name_const_str,

                                                         eSymbolTypeCode);

    if (msgSend_symbol && msgSend_symbol->ValueIsAddress()) {

      lldb::addr_t sym_addr =

          msgSend_symbol->GetAddressRef().GetOpcodeLoadAddress(target);

      m_opt_dispatch_map.emplace(sym_addr, i);

    }

  }

  // Build our vtable dispatch handler here:

  m_vtables_up =

      std::make_unique<AppleObjCVTables>(process_sp, m_objc_module_sp);

  if (m_vtables_up)

    m_vtables_up->ReadRegions();

}

lldb::addr_t

AppleObjCTrampolineHandler::SetupDispatchFunction(Thread &thread,

                                                  ValueList &dispatch_values) {

  ThreadSP thread_sp(thread.shared_from_this());

  ExecutionContext exe_ctx(thread_sp);

  Log *log = GetLog(LLDBLog::Step);

  lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;

  FunctionCaller *impl_function_caller = nullptr;

  // Scope for mutex locker:

  {

    std::lock_guard<std::mutex> guard(m_impl_function_mutex);

    // First stage is to make the ClangUtility to hold our injected function:

    if (!m_impl_code) {

      if (!m_lookup_implementation_function_code.empty()) {

        auto utility_fn_or_error = exe_ctx.GetTargetRef().CreateUtilityFunction(

            m_lookup_implementation_function_code,

            g_lookup_implementation_function_name, eLanguageTypeC, exe_ctx);

        if (!utility_fn_or_error) {

          LLDB_LOG_ERROR(

              log, utility_fn_or_error.takeError(),

              "Failed to get Utility Function for implementation lookup: {0}.");

          return args_addr;

        }

        m_impl_code = std::move(*utility_fn_or_error);

      } else {

        LLDB_LOGF(log, "No method lookup implementation code.");

        return LLDB_INVALID_ADDRESS;

      }

      // Next make the runner function for our implementation utility function.

      TypeSystemClangSP scratch_ts_sp = ScratchTypeSystemClang::GetForTarget(

          thread.GetProcess()->GetTarget());

      if (!scratch_ts_sp)

        return LLDB_INVALID_ADDRESS;

      CompilerType clang_void_ptr_type =

          scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();

      Status error;

      impl_function_caller = m_impl_code->MakeFunctionCaller(

          clang_void_ptr_type, dispatch_values, thread_sp, error);

      if (error.Fail()) {

        LLDB_LOGF(log,

                  "Error getting function caller for dispatch lookup: \"%s\".",

                  error.AsCString());

        return args_addr;

      }

    } else {

      impl_function_caller = m_impl_code->GetFunctionCaller();

    }

  }

  // Now write down the argument values for this particular call.

  // This looks like it might be a race condition if other threads

  // were calling into here, but actually it isn't because we allocate

  // a new args structure for this call by passing args_addr =

  // LLDB_INVALID_ADDRESS...

  DiagnosticManager diagnostics;

  if (!impl_function_caller->WriteFunctionArguments(

          exe_ctx, args_addr, dispatch_values, diagnostics)) {

    if (log) {

      LLDB_LOGF(log, "Error writing function arguments.");

      diagnostics.Dump(log);

    }

    return args_addr;

  }

  return args_addr;

}

const AppleObjCTrampolineHandler::DispatchFunction *

AppleObjCTrampolineHandler::FindDispatchFunction(lldb::addr_t addr) {

  MsgsendMap::iterator pos;

  pos = m_msgSend_map.find(addr);

  if (pos != m_msgSend_map.end()) {

    return &g_dispatch_functions[(*pos).second];

  }

  return nullptr;

}

void AppleObjCTrampolineHandler::ForEachDispatchFunction(

    std::function<void(lldb::addr_t, const DispatchFunction &)> callback) {

  for (auto elem : m_msgSend_map) {

    callback(elem.first, g_dispatch_functions[elem.second]);

  }

}

ThreadPlanSP

AppleObjCTrampolineHandler::GetStepThroughDispatchPlan(Thread &thread,

                                                       bool stop_others) {

  ThreadPlanSP ret_plan_sp;

  lldb::addr_t curr_pc = thread.GetRegisterContext()->GetPC();

  DispatchFunction vtable_dispatch = {"vtable", false, false, false,

                                      DispatchFunction::eFixUpFixed};

  // The selector specific stubs are a wrapper for objc_msgSend.  They don't get

  // passed a SEL, but instead the selector string is encoded in the stub

  // name, in the form:

  //   objc_msgSend$SelectorName

  // and the stub figures out the uniqued selector.  If we find ourselves in

  // one of these stubs, we strip off the selector string and pass that to the

  // implementation finder function, which looks up the SEL (you have to do this

  // in process) and passes that to the runtime lookup function.

  DispatchFunction sel_stub_dispatch = {"sel-specific-stub", false, false,

                                        false, DispatchFunction::eFixUpNone};

  // First step is to see if we're in a selector-specific dispatch stub.

  // Those are of the form _objc_msgSend$<SELECTOR>, so see if the current

  // function has that name:

  Address func_addr;

  Target &target = thread.GetProcess()->GetTarget();

  llvm::StringRef sym_name;

  const DispatchFunction *this_dispatch = nullptr;

  if (target.ResolveLoadAddress(curr_pc, func_addr)) {

    Symbol *curr_sym = func_addr.CalculateSymbolContextSymbol();

    if (curr_sym)

      sym_name = curr_sym->GetName().GetStringRef();

    if (!sym_name.empty() && !sym_name.consume_front("objc_msgSend$"))

      sym_name = {};

    else

      this_dispatch = &sel_stub_dispatch;

  }

  bool in_selector_stub = !sym_name.empty();

  // Second step is to look and see if we are in one of the known ObjC

  // dispatch functions.  We've already compiled a table of same, so

  // consult it.

  if (!in_selector_stub)

    this_dispatch = FindDispatchFunction(curr_pc);

  // Next check to see if we are in a vtable region:

  if (!this_dispatch && 
m_vtables_up363
) {

    uint32_t flags;

    if (m_vtables_up->IsAddressInVTables(curr_pc, flags)) {

      vtable_dispatch.stret_return =

          (flags & AppleObjCVTables::eOBJC_TRAMPOLINE_STRET) ==

          AppleObjCVTables::eOBJC_TRAMPOLINE_STRET;

      this_dispatch = &vtable_dispatch;

    }

  }

  // Since we set this_dispatch in both the vtable & sel specific stub cases

  // this if will be used for all three of those cases.

  if (this_dispatch) {

    Log *log = GetLog(LLDBLog::Step);

    // We are decoding a method dispatch.  First job is to pull the

    // arguments out.  If we are in a regular stub, we get self & selector,

    // but if we are in a selector-specific stub, we'll have to get that from

    // the string sym_name.

    lldb::StackFrameSP thread_cur_frame = thread.GetStackFrameAtIndex(0);

    const ABI *abi = nullptr;

    ProcessSP process_sp(thread.CalculateProcess());

    if (process_sp)

      abi = process_sp->GetABI().get();

    if (abi == nullptr)

      return ret_plan_sp;

    TargetSP target_sp(thread.CalculateTarget());

    TypeSystemClangSP scratch_ts_sp =

        ScratchTypeSystemClang::GetForTarget(*target_sp);

    if (!scratch_ts_sp)

      return ret_plan_sp;

    ValueList argument_values;

    Value void_ptr_value;

    CompilerType clang_void_ptr_type =

        scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();

    void_ptr_value.SetValueType(Value::ValueType::Scalar);

    // void_ptr_value.SetContext (Value::eContextTypeClangType,

    // clang_void_ptr_type);

    void_ptr_value.SetCompilerType(clang_void_ptr_type);

    int obj_index;

    int sel_index;

    // If this is a selector-specific stub then just push one value, 'cause

    // we only get the object.

    // If this is a struct return dispatch, then the first argument is

    // the return struct pointer, and the object is the second, and

    // the selector is the third.

    // Otherwise the object is the first and the selector the second.

    if (in_selector_stub) {

      obj_index = 0;

      sel_index = 1;

      argument_values.PushValue(void_ptr_value);

    } else if (this_dispatch->stret_return) {

      obj_index = 1;

      sel_index = 2;

      argument_values.PushValue(void_ptr_value);

      argument_values.PushValue(void_ptr_value);

      argument_values.PushValue(void_ptr_value);

    } else {

      obj_index = 0;

      sel_index = 1;

      argument_values.PushValue(void_ptr_value);

      argument_values.PushValue(void_ptr_value);

    }

    bool success = abi->GetArgumentValues(thread, argument_values);

    if (!success)

      return ret_plan_sp;

    lldb::addr_t obj_addr =

        argument_values.GetValueAtIndex(obj_index)->GetScalar().ULongLong();

    if (obj_addr == 0x0) {

      LLDB_LOGF(

          log,

          "Asked to step to dispatch to nil object, returning empty plan.");

      return ret_plan_sp;

    }

    ExecutionContext exe_ctx(thread.shared_from_this());

    // isa_addr will store the class pointer that the method is being

    // dispatched to - so either the class directly or the super class

    // if this is one of the objc_msgSendSuper flavors.  That's mostly

    // used to look up the class/selector pair in our cache.

    lldb::addr_t isa_addr = LLDB_INVALID_ADDRESS;

    lldb::addr_t sel_addr = LLDB_INVALID_ADDRESS;

    // If we are not in a selector stub, get the sel address from the arguments.

    if (!in_selector_stub)

      sel_addr =

          argument_values.GetValueAtIndex(sel_index)->GetScalar().ULongLong();

    // Figure out the class this is being dispatched to and see if

    // we've already cached this method call, If so we can push a

    // run-to-address plan directly.  Otherwise we have to figure out

    // where the implementation lives.

    if (this_dispatch->is_super) {

      if (this_dispatch->is_super2) {

        // In the objc_msgSendSuper2 case, we don't get the object

        // directly, we get a structure containing the object and the

        // class to which the super message is being sent.  So we need

        // to dig the super out of the class and use that.

        Value super_value(*(argument_values.GetValueAtIndex(obj_index)));

        super_value.GetScalar() += process_sp->GetAddressByteSize();

        super_value.ResolveValue(&exe_ctx);

        if (super_value.GetScalar().IsValid()) {

          // isa_value now holds the class pointer.  The second word of the

          // class pointer is the super-class pointer:

          super_value.GetScalar() += process_sp->GetAddressByteSize();

          super_value.ResolveValue(&exe_ctx);

          if (super_value.GetScalar().IsValid())

            isa_addr = super_value.GetScalar().ULongLong();

          else {

            LLDB_LOGF(log, "Failed to extract the super class value from the "

                           "class in objc_super.");

          }

        } else {

          LLDB_LOGF(log, "Failed to extract the class value from objc_super.");

        }

      } else {

        // In the objc_msgSendSuper case, we don't get the object

        // directly, we get a two element structure containing the

        // object and the super class to which the super message is

        // being sent.  So the class we want is the second element of

        // this structure.

        Value super_value(*(argument_values.GetValueAtIndex(obj_index)));

        super_value.GetScalar() += process_sp->GetAddressByteSize();

        super_value.ResolveValue(&exe_ctx);

        if (super_value.GetScalar().IsValid()) {

          isa_addr = super_value.GetScalar().ULongLong();

        } else {

          LLDB_LOGF(log, "Failed to extract the class value from objc_super.");

        }

      }

    } else {

      // In the direct dispatch case, the object->isa is the class pointer we

      // want.

      // This is a little cheesy, but since object->isa is the first field,

      // making the object value a load address value and resolving it will get

      // the pointer sized data pointed to by that value...

      // Note, it isn't a fatal error not to be able to get the

      // address from the object, since this might be a "tagged

      // pointer" which isn't a real object, but rather some word

      // length encoded dingus.

      Value isa_value(*(argument_values.GetValueAtIndex(obj_index)));

      isa_value.SetValueType(Value::ValueType::LoadAddress);