lldb/source/Plugins/ExpressionParser/Clang/IRDynamicChecks.cpp

   1 //===-- IRDynamicChecks.cpp -----------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/IR/Constants.h"
  10 #include "llvm/IR/DataLayout.h"
  11 #include "llvm/IR/Function.h"
  12 #include "llvm/IR/Instructions.h"
  13 #include "llvm/IR/Module.h"
  14 #include "llvm/IR/Value.h"
  15 #include "llvm/Support/raw_ostream.h"
  16
  17 #include "IRDynamicChecks.h"
  18
  19 #include "lldb/Expression/UtilityFunction.h"
  20 #include "lldb/Target/ExecutionContext.h"
  21 #include "lldb/Target/Process.h"
  22 #include "lldb/Target/StackFrame.h"
  23 #include "lldb/Target/Target.h"
  24 #include "lldb/Utility/ConstString.h"
  25 #include "lldb/Utility/LLDBLog.h"
  26 #include "lldb/Utility/Log.h"
  27
  28 #include "Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h"
  29
  30 using namespace llvm;
  31 using namespace lldb_private;
  32
  33 static char ID;
  34
  35 #define VALID_POINTER_CHECK_NAME "_$__lldb_valid_pointer_check"
  36 #define VALID_OBJC_OBJECT_CHECK_NAME "$__lldb_objc_object_check"
  37
  38 static const char g_valid_pointer_check_text[] =
  39     "extern \"C\" void\n"
  40     "_$__lldb_valid_pointer_check (unsigned char *$__lldb_arg_ptr)\n"
  41     "{\n"
  42     "    unsigned char $__lldb_local_val = *$__lldb_arg_ptr;\n"
  43     "}";
  44
  45 ClangDynamicCheckerFunctions::ClangDynamicCheckerFunctions()
  46     : DynamicCheckerFunctions(DCF_Clang) {}
  47
  48 ClangDynamicCheckerFunctions::~ClangDynamicCheckerFunctions() = default;
  49
  50 llvm::Error ClangDynamicCheckerFunctions::Install(
  51     DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx) {
  52   Expected<std::unique_ptr<UtilityFunction>> utility_fn =
  53       exe_ctx.GetTargetRef().CreateUtilityFunction(
  54           g_valid_pointer_check_text, VALID_POINTER_CHECK_NAME,
  55           lldb::eLanguageTypeC, exe_ctx);
  56   if (!utility_fn)
  57     return utility_fn.takeError();
  58   m_valid_pointer_check = std::move(*utility_fn);
  59
  60   if (Process *process = exe_ctx.GetProcessPtr()) {
  61     ObjCLanguageRuntime *objc_language_runtime =
  62         ObjCLanguageRuntime::Get(*process);
  63
  64     if (objc_language_runtime) {
  65       Expected<std::unique_ptr<UtilityFunction>> checker_fn =
  66           objc_language_runtime->CreateObjectChecker(VALID_OBJC_OBJECT_CHECK_NAME, exe_ctx);
  67       if (!checker_fn)
  68         return checker_fn.takeError();
  69       m_objc_object_check = std::move(*checker_fn);
  70     }
  71   }
  72
  73   return Error::success();
  74 }
  75
  76 bool ClangDynamicCheckerFunctions::DoCheckersExplainStop(lldb::addr_t addr,
  77                                                          Stream &message) {
  78   // FIXME: We have to get the checkers to know why they scotched the call in
  79   // more detail,
  80   // so we can print a better message here.
  81   if (m_valid_pointer_check && m_valid_pointer_check->ContainsAddress(addr)) {
  82     message.Printf("Attempted to dereference an invalid pointer.");
  83     return true;
  84   } else if (m_objc_object_check &&
  85              m_objc_object_check->ContainsAddress(addr)) {
  86     message.Printf("Attempted to dereference an invalid ObjC Object or send it "
  87                    "an unrecognized selector");
  88     return true;
  89   }
  90   return false;
  91 }
  92
  93 static std::string PrintValue(llvm::Value *V, bool truncate = false) {
  94   std::string s;
  95   raw_string_ostream rso(s);
  96   V->print(rso);
  97   if (truncate)
  98     s.resize(s.length() - 1);
  99   return s;
 100 }
 101
 102 /// \class Instrumenter IRDynamicChecks.cpp
 103 /// Finds and instruments individual LLVM IR instructions
 104 ///
 105 /// When instrumenting LLVM IR, it is frequently desirable to first search for
 106 /// instructions, and then later modify them.  This way iterators remain
 107 /// intact, and multiple passes can look at the same code base without
 108 /// treading on each other's toes.
 109 ///
 110 /// The Instrumenter class implements this functionality.  A client first
 111 /// calls Inspect on a function, which populates a list of instructions to be
 112 /// instrumented.  Then, later, when all passes' Inspect functions have been
 113 /// called, the client calls Instrument, which adds the desired
 114 /// instrumentation.
 115 ///
 116 /// A subclass of Instrumenter must override InstrumentInstruction, which
 117 /// is responsible for adding whatever instrumentation is necessary.
 118 ///
 119 /// A subclass of Instrumenter may override:
 120 ///
 121 /// - InspectInstruction [default: does nothing]
 122 ///
 123 /// - InspectBasicBlock [default: iterates through the instructions in a
 124 ///   basic block calling InspectInstruction]
 125 ///
 126 /// - InspectFunction [default: iterates through the basic blocks in a
 127 ///   function calling InspectBasicBlock]
 128 class Instrumenter {
 129 public:
 130   /// Constructor
 131   ///
 132   /// \param[in] module
 133   ///     The module being instrumented.
 134   Instrumenter(llvm::Module &module,
 135                std::shared_ptr<UtilityFunction> checker_function)
 136       : m_module(module), m_checker_function(checker_function) {}
 137
 138   virtual ~Instrumenter() = default;
 139
 140   /// Inspect a function to find instructions to instrument
 141   ///
 142   /// \param[in] function
 143   ///     The function to inspect.
 144   ///
 145   /// \return
 146   ///     True on success; false on error.
 147   bool Inspect(llvm::Function &function) { return InspectFunction(function); }
 148
 149   /// Instrument all the instructions found by Inspect()
 150   ///
 151   /// \return
 152   ///     True on success; false on error.
 153   bool Instrument() {
 154     for (InstIterator ii = m_to_instrument.begin(),
 155                       last_ii = m_to_instrument.end();
 156          ii != last_ii; ++ii) {
 157       if (!InstrumentInstruction(*ii))
 158         return false;
 159     }
 160
 161     return true;
 162   }
 163
 164 protected:
 165   /// Add instrumentation to a single instruction
 166   ///
 167   /// \param[in] inst
 168   ///     The instruction to be instrumented.
 169   ///
 170   /// \return
 171   ///     True on success; false otherwise.
 172   virtual bool InstrumentInstruction(llvm::Instruction *inst) = 0;
 173
 174   /// Register a single instruction to be instrumented
 175   ///
 176   /// \param[in] inst
 177   ///     The instruction to be instrumented.
 178   void RegisterInstruction(llvm::Instruction &inst) {
 179     m_to_instrument.push_back(&inst);
 180   }
 181
 182   /// Determine whether a single instruction is interesting to instrument,
 183   /// and, if so, call RegisterInstruction
 184   ///
 185   /// \param[in] i
 186   ///     The instruction to be inspected.
 187   ///
 188   /// \return
 189   ///     False if there was an error scanning; true otherwise.
 190   virtual bool InspectInstruction(llvm::Instruction &i) { return true; }
 191
 192   /// Scan a basic block to see if any instructions are interesting
 193   ///
 194   /// \param[in] bb
 195   ///     The basic block to be inspected.
 196   ///
 197   /// \return
 198   ///     False if there was an error scanning; true otherwise.
 199   virtual bool InspectBasicBlock(llvm::BasicBlock &bb) {
 200     for (llvm::BasicBlock::iterator ii = bb.begin(), last_ii = bb.end();
 201          ii != last_ii; ++ii) {
 202       if (!InspectInstruction(*ii))
 203         return false;
 204     }
 205
 206     return true;
 207   }
 208
 209   /// Scan a function to see if any instructions are interesting
 210   ///
 211   /// \param[in] f
 212   ///     The function to be inspected.
 213   ///
 214   /// \return
 215   ///     False if there was an error scanning; true otherwise.
 216   virtual bool InspectFunction(llvm::Function &f) {
 217     for (llvm::Function::iterator bbi = f.begin(), last_bbi = f.end();
 218          bbi != last_bbi; ++bbi) {
 219       if (!InspectBasicBlock(*bbi))
 220         return false;
 221     }
 222
 223     return true;
 224   }
 225
 226   /// Build a function pointer for a function with signature void
 227   /// (*)(uint8_t*) with a given address
 228   ///
 229   /// \param[in] start_address
 230   ///     The address of the function.
 231   ///
 232   /// \return
 233   ///     The function pointer, for use in a CallInst.
 234   llvm::FunctionCallee BuildPointerValidatorFunc(lldb::addr_t start_address) {
 235     llvm::Type *param_array[1];
 236
 237     param_array[0] = const_cast<llvm::PointerType *>(GetI8PtrTy());
 238
 239     ArrayRef<llvm::Type *> params(param_array, 1);
 240
 241     FunctionType *fun_ty = FunctionType::get(
 242         llvm::Type::getVoidTy(m_module.getContext()), params, true);
 243     PointerType *fun_ptr_ty = PointerType::getUnqual(fun_ty);
 244     Constant *fun_addr_int =
 245         ConstantInt::get(GetIntptrTy(), start_address, false);
 246     return {fun_ty, ConstantExpr::getIntToPtr(fun_addr_int, fun_ptr_ty)};
 247   }
 248
 249   /// Build a function pointer for a function with signature void
 250   /// (*)(uint8_t*, uint8_t*) with a given address
 251   ///
 252   /// \param[in] start_address
 253   ///     The address of the function.
 254   ///
 255   /// \return
 256   ///     The function pointer, for use in a CallInst.
 257   llvm::FunctionCallee BuildObjectCheckerFunc(lldb::addr_t start_address) {
 258     llvm::Type *param_array[2];
 259
 260     param_array[0] = const_cast<llvm::PointerType *>(GetI8PtrTy());
 261     param_array[1] = const_cast<llvm::PointerType *>(GetI8PtrTy());
 262
 263     ArrayRef<llvm::Type *> params(param_array, 2);
 264
 265     FunctionType *fun_ty = FunctionType::get(
 266         llvm::Type::getVoidTy(m_module.getContext()), params, true);
 267     PointerType *fun_ptr_ty = PointerType::getUnqual(fun_ty);
 268     Constant *fun_addr_int =
 269         ConstantInt::get(GetIntptrTy(), start_address, false);
 270     return {fun_ty, ConstantExpr::getIntToPtr(fun_addr_int, fun_ptr_ty)};
 271   }
 272
 273   PointerType *GetI8PtrTy() {
 274     if (!m_i8ptr_ty)
 275       m_i8ptr_ty = llvm::PointerType::getUnqual(m_module.getContext());
 276
 277     return m_i8ptr_ty;
 278   }
 279
 280   IntegerType *GetIntptrTy() {
 281     if (!m_intptr_ty) {
 282       m_intptr_ty = llvm::Type::getIntNTy(
 283           m_module.getContext(),
 284           m_module.getDataLayout().getPointerSizeInBits());
 285     }
 286
 287     return m_intptr_ty;
 288   }
 289
 290   typedef std::vector<llvm::Instruction *> InstVector;
 291   typedef InstVector::iterator InstIterator;
 292
 293   InstVector m_to_instrument; ///< List of instructions the inspector found
 294   llvm::Module &m_module;     ///< The module which is being instrumented
 295   std::shared_ptr<UtilityFunction>
 296       m_checker_function; ///< The dynamic checker function for the process
 297
 298 private:
 299   PointerType *m_i8ptr_ty = nullptr;
 300   IntegerType *m_intptr_ty = nullptr;
 301 };
 302
 303 class ValidPointerChecker : public Instrumenter {
 304 public:
 305   ValidPointerChecker(llvm::Module &module,
 306                       std::shared_ptr<UtilityFunction> checker_function)
 307       : Instrumenter(module, checker_function),
 308         m_valid_pointer_check_func(nullptr) {}
 309
 310   ~ValidPointerChecker() override = default;
 311
 312 protected:
 313   bool InstrumentInstruction(llvm::Instruction *inst) override {
 314     Log *log = GetLog(LLDBLog::Expressions);
 315
 316     LLDB_LOGF(log, "Instrumenting load/store instruction: %s\n",
 317               PrintValue(inst).c_str());
 318
 319     if (!m_valid_pointer_check_func)
 320       m_valid_pointer_check_func =
 321           BuildPointerValidatorFunc(m_checker_function->StartAddress());
 322
 323     llvm::Value *dereferenced_ptr = nullptr;
 324
 325     if (llvm::LoadInst *li = dyn_cast<llvm::LoadInst>(inst))
 326       dereferenced_ptr = li->getPointerOperand();
 327     else if (llvm::StoreInst *si = dyn_cast<llvm::StoreInst>(inst))
 328       dereferenced_ptr = si->getPointerOperand();
 329     else
 330       return false;
 331
 332     // Insert an instruction to call the helper with the result
 333     CallInst::Create(m_valid_pointer_check_func, dereferenced_ptr, "",
 334                      inst->getIterator());
 335
 336     return true;
 337   }
 338
 339   bool InspectInstruction(llvm::Instruction &i) override {
 340     if (isa<llvm::LoadInst>(&i) || isa<llvm::StoreInst>(&i))
 341       RegisterInstruction(i);
 342
 343     return true;
 344   }
 345
 346 private:
 347   llvm::FunctionCallee m_valid_pointer_check_func;
 348 };
 349
 350 class ObjcObjectChecker : public Instrumenter {
 351 public:
 352   ObjcObjectChecker(llvm::Module &module,
 353                     std::shared_ptr<UtilityFunction> checker_function)
 354       : Instrumenter(module, checker_function),
 355         m_objc_object_check_func(nullptr) {}
 356
 357   ~ObjcObjectChecker() override = default;
 358
 359   enum msgSend_type {
 360     eMsgSend = 0,
 361     eMsgSendSuper,
 362     eMsgSendSuper_stret,
 363     eMsgSend_fpret,
 364     eMsgSend_stret
 365   };
 366
 367   std::map<llvm::Instruction *, msgSend_type> msgSend_types;
 368
 369 protected:
 370   bool InstrumentInstruction(llvm::Instruction *inst) override {
 371     CallInst *call_inst = dyn_cast<CallInst>(inst);
 372
 373     if (!call_inst)
 374       return false; // call_inst really shouldn't be nullptr, because otherwise
 375                     // InspectInstruction wouldn't have registered it
 376
 377     if (!m_objc_object_check_func)
 378       m_objc_object_check_func =
 379           BuildObjectCheckerFunc(m_checker_function->StartAddress());
 380
 381     // id objc_msgSend(id theReceiver, SEL theSelector, ...)
 382
 383     llvm::Value *target_object;
 384     llvm::Value *selector;
 385
 386     switch (msgSend_types[inst]) {
 387     case eMsgSend:
 388     case eMsgSend_fpret:
 389       // On arm64, clang uses objc_msgSend for scalar and struct return
 390       // calls.  The call instruction will record which was used.
 391       if (call_inst->hasStructRetAttr()) {
 392         target_object = call_inst->getArgOperand(1);
 393         selector = call_inst->getArgOperand(2);
 394       } else {
 395         target_object = call_inst->getArgOperand(0);
 396         selector = call_inst->getArgOperand(1);
 397       }
 398       break;
 399     case eMsgSend_stret:
 400       target_object = call_inst->getArgOperand(1);
 401       selector = call_inst->getArgOperand(2);
 402       break;
 403     case eMsgSendSuper:
 404     case eMsgSendSuper_stret:
 405       return true;
 406     }
 407
 408     // These objects should always be valid according to Sean Calannan
 409     assert(target_object);
 410     assert(selector);
 411
 412     // Insert an instruction to call the helper with the result
 413
 414     llvm::Value *arg_array[2];
 415
 416     arg_array[0] = target_object;
 417     arg_array[1] = selector;
 418
 419     ArrayRef<llvm::Value *> args(arg_array, 2);
 420
 421     CallInst::Create(m_objc_object_check_func, args, "", inst->getIterator());
 422
 423     return true;
 424   }
 425
 426   static llvm::Function *GetFunction(llvm::Value *value) {
 427     if (llvm::Function *function = llvm::dyn_cast<llvm::Function>(value)) {
 428       return function;
 429     }
 430
 431     if (llvm::ConstantExpr *const_expr =
 432             llvm::dyn_cast<llvm::ConstantExpr>(value)) {
 433       switch (const_expr->getOpcode()) {
 434       default:
 435         return nullptr;
 436       case llvm::Instruction::BitCast:
 437         return GetFunction(const_expr->getOperand(0));
 438       }
 439     }
 440
 441     return nullptr;
 442   }
 443
 444   static llvm::Function *GetCalledFunction(llvm::CallInst *inst) {
 445     return GetFunction(inst->getCalledOperand());
 446   }
 447
 448   bool InspectInstruction(llvm::Instruction &i) override {
 449     Log *log = GetLog(LLDBLog::Expressions);
 450
 451     CallInst *call_inst = dyn_cast<CallInst>(&i);
 452
 453     if (call_inst) {
 454       const llvm::Function *called_function = GetCalledFunction(call_inst);
 455
 456       if (!called_function)
 457         return true;
 458
 459       std::string name_str = called_function->getName().str();
 460       const char *name_cstr = name_str.c_str();
 461
 462       LLDB_LOGF(log, "Found call to %s: %s\n", name_cstr,
 463                 PrintValue(call_inst).c_str());
 464
 465       if (name_str.find("objc_msgSend") == std::string::npos)
 466         return true;
 467
 468       if (!strcmp(name_cstr, "objc_msgSend")) {
 469         RegisterInstruction(i);
 470         msgSend_types[&i] = eMsgSend;
 471         return true;
 472       }
 473
 474       if (!strcmp(name_cstr, "objc_msgSend_stret")) {
 475         RegisterInstruction(i);
 476         msgSend_types[&i] = eMsgSend_stret;
 477         return true;
 478       }
 479
 480       if (!strcmp(name_cstr, "objc_msgSend_fpret")) {
 481         RegisterInstruction(i);
 482         msgSend_types[&i] = eMsgSend_fpret;
 483         return true;
 484       }
 485
 486       if (!strcmp(name_cstr, "objc_msgSendSuper")) {
 487         RegisterInstruction(i);
 488         msgSend_types[&i] = eMsgSendSuper;
 489         return true;
 490       }
 491
 492       if (!strcmp(name_cstr, "objc_msgSendSuper_stret")) {
 493         RegisterInstruction(i);
 494         msgSend_types[&i] = eMsgSendSuper_stret;
 495         return true;
 496       }
 497
 498       LLDB_LOGF(log,
 499                 "Function name '%s' contains 'objc_msgSend' but is not handled",
 500                 name_str.c_str());
 501
 502       return true;
 503     }
 504
 505     return true;
 506   }
 507
 508 private:
 509   llvm::FunctionCallee m_objc_object_check_func;
 510 };
 511
 512 IRDynamicChecks::IRDynamicChecks(
 513     ClangDynamicCheckerFunctions &checker_functions, const char *func_name)
 514     : ModulePass(ID), m_func_name(func_name),
 515       m_checker_functions(checker_functions) {}
 516
 517 IRDynamicChecks::~IRDynamicChecks() = default;
 518
 519 bool IRDynamicChecks::runOnModule(llvm::Module &M) {
 520   Log *log = GetLog(LLDBLog::Expressions);
 521
 522   llvm::Function *function = M.getFunction(StringRef(m_func_name));
 523
 524   if (!function) {
 525     LLDB_LOGF(log, "Couldn't find %s() in the module", m_func_name.c_str());
 526
 527     return false;
 528   }
 529
 530   if (m_checker_functions.m_valid_pointer_check) {
 531     ValidPointerChecker vpc(M, m_checker_functions.m_valid_pointer_check);
 532
 533     if (!vpc.Inspect(*function))
 534       return false;
 535
 536     if (!vpc.Instrument())
 537       return false;
 538   }
 539
 540   if (m_checker_functions.m_objc_object_check) {
 541     ObjcObjectChecker ooc(M, m_checker_functions.m_objc_object_check);
 542
 543     if (!ooc.Inspect(*function))
 544       return false;
 545
 546     if (!ooc.Instrument())
 547       return false;
 548   }
 549
 550   if (log && log->GetVerbose()) {
 551     std::string s;
 552     raw_string_ostream oss(s);
 553
 554     M.print(oss, nullptr);
 555
 556     LLDB_LOGF(log, "Module after dynamic checks: \n%s", s.c_str());
 557   }
 558
 559   return true;
 560 }
 561
 562 void IRDynamicChecks::assignPassManager(PMStack &PMS, PassManagerType T) {}
 563
 564 PassManagerType IRDynamicChecks::getPotentialPassManagerType() const {
 565   return PMT_ModulePassManager;
 566 }