diff options
Diffstat (limited to 'contrib/llvm-project/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp')
| -rw-r--r-- | contrib/llvm-project/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp | 1179 |
1 files changed, 1179 insertions, 0 deletions
diff --git a/contrib/llvm-project/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp b/contrib/llvm-project/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp new file mode 100644 index 000000000000..2b8adeae10d1 --- /dev/null +++ b/contrib/llvm-project/lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp @@ -0,0 +1,1179 @@ +//===-- 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++) { + 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() : nullptr; + 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++) { + 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++) { + 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_up) { + 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); + isa_value.ResolveValue(&exe_ctx); + if (isa_value.GetScalar().IsValid()) { + isa_addr = isa_value.GetScalar().ULongLong(); + } else { + LLDB_LOGF(log, "Failed to extract the isa value from object."); + } + } + + // Okay, we've got the address of the class for which we're resolving this, + // let's see if it's in our cache: + lldb::addr_t impl_addr = LLDB_INVALID_ADDRESS; + // If this is a regular dispatch, look up the sel in our addr to sel cache: + if (isa_addr != LLDB_INVALID_ADDRESS) { + ObjCLanguageRuntime *objc_runtime = + ObjCLanguageRuntime::Get(*thread.GetProcess()); + assert(objc_runtime != nullptr); + if (!in_selector_stub) { + LLDB_LOG(log, "Resolving call for class - {0} and selector - {1}", + isa_addr, sel_addr); + impl_addr = objc_runtime->LookupInMethodCache(isa_addr, sel_addr); + } else { + LLDB_LOG(log, "Resolving call for class - {0} and selector - {1}", + isa_addr, sym_name); + impl_addr = objc_runtime->LookupInMethodCache(isa_addr, sym_name); + } + } + // If it is a selector-specific stub dispatch, look in the string cache: + + if (impl_addr != LLDB_INVALID_ADDRESS) { + // Yup, it was in the cache, so we can run to that address directly. + + LLDB_LOGF(log, "Found implementation address in cache: 0x%" PRIx64, + impl_addr); + + ret_plan_sp = std::make_shared<ThreadPlanRunToAddress>(thread, impl_addr, + stop_others); + } else { + // We haven't seen this class/selector pair yet. Look it up. + StreamString errors; + Address impl_code_address; + + ValueList dispatch_values; + + // We've will inject a little function in the target that takes the + // object, selector/selector string and some flags, + // and figures out the implementation. Looks like: + // 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) + // If we don't have an actual SEL, but rather a string version of the + // selector WE injected, set is_str_ptr to true, and sel to the address + // of the string. + // So set up the arguments for that call. + + dispatch_values.PushValue(*(argument_values.GetValueAtIndex(obj_index))); + lldb::addr_t sel_str_addr = LLDB_INVALID_ADDRESS; + if (!in_selector_stub) { + // If we don't have a selector string, push the selector from arguments. + dispatch_values.PushValue( + *(argument_values.GetValueAtIndex(sel_index))); + } else { + // Otherwise, inject the string into the target, and push that value for + // the sel argument. + Status error; + sel_str_addr = process_sp->AllocateMemory( + sym_name.size() + 1, ePermissionsReadable | ePermissionsWritable, + error); + if (sel_str_addr == LLDB_INVALID_ADDRESS || error.Fail()) { + LLDB_LOG(log, + "Could not allocate memory for selector string {0}: {1}", + sym_name, error); + return ret_plan_sp; + } + process_sp->WriteMemory(sel_str_addr, sym_name.str().c_str(), + sym_name.size() + 1, error); + if (error.Fail()) { + LLDB_LOG(log, "Could not write string to address {0}", sel_str_addr); + return ret_plan_sp; + } + Value sel_ptr_value(void_ptr_value); + sel_ptr_value.GetScalar() = sel_str_addr; + dispatch_values.PushValue(sel_ptr_value); + } + + Value flag_value; + CompilerType clang_int_type = + scratch_ts_sp->GetBuiltinTypeForEncodingAndBitSize( + lldb::eEncodingSint, 32); + flag_value.SetValueType(Value::ValueType::Scalar); + // flag_value.SetContext (Value::eContextTypeClangType, clang_int_type); + flag_value.SetCompilerType(clang_int_type); + + if (in_selector_stub) + flag_value.GetScalar() = 1; + else + flag_value.GetScalar() = 0; + dispatch_values.PushValue(flag_value); + + if (this_dispatch->stret_return) + flag_value.GetScalar() = 1; + else + flag_value.GetScalar() = 0; + dispatch_values.PushValue(flag_value); + + if (this_dispatch->is_super) + flag_value.GetScalar() = 1; + else + flag_value.GetScalar() = 0; + dispatch_values.PushValue(flag_value); + + if (this_dispatch->is_super2) + flag_value.GetScalar() = 1; + else + flag_value.GetScalar() = 0; + dispatch_values.PushValue(flag_value); + + switch (this_dispatch->fixedup) { + case DispatchFunction::eFixUpNone: + flag_value.GetScalar() = 0; + dispatch_values.PushValue(flag_value); + dispatch_values.PushValue(flag_value); + break; + case DispatchFunction::eFixUpFixed: + flag_value.GetScalar() = 1; + dispatch_values.PushValue(flag_value); + flag_value.GetScalar() = 1; + dispatch_values.PushValue(flag_value); + break; + case DispatchFunction::eFixUpToFix: + flag_value.GetScalar() = 1; + dispatch_values.PushValue(flag_value); + flag_value.GetScalar() = 0; + dispatch_values.PushValue(flag_value); + break; + } + if (log && log->GetVerbose()) + flag_value.GetScalar() = 1; + else + flag_value.GetScalar() = 0; // FIXME - Set to 0 when debugging is done. + dispatch_values.PushValue(flag_value); + + ret_plan_sp = std::make_shared<AppleThreadPlanStepThroughObjCTrampoline>( + thread, *this, dispatch_values, isa_addr, sel_addr, sel_str_addr, + sym_name); + if (log) { + StreamString s; + ret_plan_sp->GetDescription(&s, eDescriptionLevelFull); + LLDB_LOGF(log, "Using ObjC step plan: %s.\n", s.GetData()); + } + } + } + + // Finally, check if we have hit an "optimized dispatch" function. This will + // either directly call the base implementation or dispatch an objc_msgSend + // if the method has been overridden. So we just do a "step in/step out", + // setting a breakpoint on objc_msgSend, and if we hit the msgSend, we + // will automatically step in again. That's the job of the + // AppleThreadPlanStepThroughDirectDispatch. + if (!this_dispatch && !ret_plan_sp) { + MsgsendMap::iterator pos; + pos = m_opt_dispatch_map.find(curr_pc); + if (pos != m_opt_dispatch_map.end()) { + const char *opt_name = g_opt_dispatch_names[(*pos).second]; + ret_plan_sp = std::make_shared<AppleThreadPlanStepThroughDirectDispatch>( + thread, *this, opt_name); + } + } + + return ret_plan_sp; +} + +FunctionCaller * +AppleObjCTrampolineHandler::GetLookupImplementationFunctionCaller() { + return m_impl_code->GetFunctionCaller(); +} |