LLDB mainline
IRDynamicChecks.cpp
Go to the documentation of this file.
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
21#include "lldb/Target/Process.h"
23#include "lldb/Target/Target.h"
26#include "lldb/Utility/Log.h"
27
29
30using namespace llvm;
31using namespace lldb_private;
32
33static 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
38static 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
46 : DynamicCheckerFunctions(DCF_Clang) {}
47
49
51 DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx) {
52 Expected<std::unique_ptr<UtilityFunction>> utility_fn =
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 =
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
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
93static std::string PrintValue(llvm::Value *V, bool truncate = false) {
94 std::string s;
95 raw_string_ostream rso(s);
96 V->print(rso);
97 rso.flush();
98 if (truncate)
99 s.resize(s.length() - 1);
100 return s;
101}
102
103/// \class Instrumenter IRDynamicChecks.cpp
104/// Finds and instruments individual LLVM IR instructions
105///
106/// When instrumenting LLVM IR, it is frequently desirable to first search for
107/// instructions, and then later modify them. This way iterators remain
108/// intact, and multiple passes can look at the same code base without
109/// treading on each other's toes.
110///
111/// The Instrumenter class implements this functionality. A client first
112/// calls Inspect on a function, which populates a list of instructions to be
113/// instrumented. Then, later, when all passes' Inspect functions have been
114/// called, the client calls Instrument, which adds the desired
115/// instrumentation.
116///
117/// A subclass of Instrumenter must override InstrumentInstruction, which
118/// is responsible for adding whatever instrumentation is necessary.
119///
120/// A subclass of Instrumenter may override:
121///
122/// - InspectInstruction [default: does nothing]
123///
124/// - InspectBasicBlock [default: iterates through the instructions in a
125/// basic block calling InspectInstruction]
126///
127/// - InspectFunction [default: iterates through the basic blocks in a
128/// function calling InspectBasicBlock]
130public:
131 /// Constructor
132 ///
133 /// \param[in] module
134 /// The module being instrumented.
135 Instrumenter(llvm::Module &module,
136 std::shared_ptr<UtilityFunction> checker_function)
137 : m_module(module), m_checker_function(checker_function) {}
138
139 virtual ~Instrumenter() = default;
140
141 /// Inspect a function to find instructions to instrument
142 ///
143 /// \param[in] function
144 /// The function to inspect.
145 ///
146 /// \return
147 /// True on success; false on error.
148 bool Inspect(llvm::Function &function) { return InspectFunction(function); }
149
150 /// Instrument all the instructions found by Inspect()
151 ///
152 /// \return
153 /// True on success; false on error.
154 bool Instrument() {
155 for (InstIterator ii = m_to_instrument.begin(),
156 last_ii = m_to_instrument.end();
157 ii != last_ii; ++ii) {
158 if (!InstrumentInstruction(*ii))
159 return false;
160 }
161
162 return true;
163 }
164
165protected:
166 /// Add instrumentation to a single instruction
167 ///
168 /// \param[in] inst
169 /// The instruction to be instrumented.
170 ///
171 /// \return
172 /// True on success; false otherwise.
173 virtual bool InstrumentInstruction(llvm::Instruction *inst) = 0;
174
175 /// Register a single instruction to be instrumented
176 ///
177 /// \param[in] inst
178 /// The instruction to be instrumented.
179 void RegisterInstruction(llvm::Instruction &inst) {
180 m_to_instrument.push_back(&inst);
181 }
182
183 /// Determine whether a single instruction is interesting to instrument,
184 /// and, if so, call RegisterInstruction
185 ///
186 /// \param[in] i
187 /// The instruction to be inspected.
188 ///
189 /// \return
190 /// False if there was an error scanning; true otherwise.
191 virtual bool InspectInstruction(llvm::Instruction &i) { return true; }
192
193 /// Scan a basic block to see if any instructions are interesting
194 ///
195 /// \param[in] bb
196 /// The basic block to be inspected.
197 ///
198 /// \return
199 /// False if there was an error scanning; true otherwise.
200 virtual bool InspectBasicBlock(llvm::BasicBlock &bb) {
201 for (llvm::BasicBlock::iterator ii = bb.begin(), last_ii = bb.end();
202 ii != last_ii; ++ii) {
203 if (!InspectInstruction(*ii))
204 return false;
205 }
206
207 return true;
208 }
209
210 /// Scan a function to see if any instructions are interesting
211 ///
212 /// \param[in] f
213 /// The function to be inspected.
214 ///
215 /// \return
216 /// False if there was an error scanning; true otherwise.
217 virtual bool InspectFunction(llvm::Function &f) {
218 for (llvm::Function::iterator bbi = f.begin(), last_bbi = f.end();
219 bbi != last_bbi; ++bbi) {
220 if (!InspectBasicBlock(*bbi))
221 return false;
222 }
223
224 return true;
225 }
226
227 /// Build a function pointer for a function with signature void
228 /// (*)(uint8_t*) with a given address
229 ///
230 /// \param[in] start_address
231 /// The address of the function.
232 ///
233 /// \return
234 /// The function pointer, for use in a CallInst.
235 llvm::FunctionCallee BuildPointerValidatorFunc(lldb::addr_t start_address) {
236 llvm::Type *param_array[1];
237
238 param_array[0] = const_cast<llvm::PointerType *>(GetI8PtrTy());
239
240 ArrayRef<llvm::Type *> params(param_array, 1);
241
242 FunctionType *fun_ty = FunctionType::get(
243 llvm::Type::getVoidTy(m_module.getContext()), params, true);
244 PointerType *fun_ptr_ty = PointerType::getUnqual(fun_ty);
245 Constant *fun_addr_int =
246 ConstantInt::get(GetIntptrTy(), start_address, false);
247 return {fun_ty, ConstantExpr::getIntToPtr(fun_addr_int, fun_ptr_ty)};
248 }
249
250 /// Build a function pointer for a function with signature void
251 /// (*)(uint8_t*, uint8_t*) with a given address
252 ///
253 /// \param[in] start_address
254 /// The address of the function.
255 ///
256 /// \return
257 /// The function pointer, for use in a CallInst.
258 llvm::FunctionCallee BuildObjectCheckerFunc(lldb::addr_t start_address) {
259 llvm::Type *param_array[2];
260
261 param_array[0] = const_cast<llvm::PointerType *>(GetI8PtrTy());
262 param_array[1] = const_cast<llvm::PointerType *>(GetI8PtrTy());
263
264 ArrayRef<llvm::Type *> params(param_array, 2);
265
266 FunctionType *fun_ty = FunctionType::get(
267 llvm::Type::getVoidTy(m_module.getContext()), params, true);
268 PointerType *fun_ptr_ty = PointerType::getUnqual(fun_ty);
269 Constant *fun_addr_int =
270 ConstantInt::get(GetIntptrTy(), start_address, false);
271 return {fun_ty, ConstantExpr::getIntToPtr(fun_addr_int, fun_ptr_ty)};
272 }
273
274 PointerType *GetI8PtrTy() {
275 if (!m_i8ptr_ty)
276 m_i8ptr_ty = llvm::PointerType::getUnqual(m_module.getContext());
277
278 return m_i8ptr_ty;
279 }
280
281 IntegerType *GetIntptrTy() {
282 if (!m_intptr_ty) {
283 llvm::DataLayout data_layout(&m_module);
284
285 m_intptr_ty = llvm::Type::getIntNTy(m_module.getContext(),
286 data_layout.getPointerSizeInBits());
287 }
288
289 return m_intptr_ty;
290 }
291
292 typedef std::vector<llvm::Instruction *> InstVector;
293 typedef InstVector::iterator InstIterator;
294
295 InstVector m_to_instrument; ///< List of instructions the inspector found
296 llvm::Module &m_module; ///< The module which is being instrumented
297 std::shared_ptr<UtilityFunction>
298 m_checker_function; ///< The dynamic checker function for the process
299
300private:
301 PointerType *m_i8ptr_ty = nullptr;
302 IntegerType *m_intptr_ty = nullptr;
303};
304
306public:
307 ValidPointerChecker(llvm::Module &module,
308 std::shared_ptr<UtilityFunction> checker_function)
309 : Instrumenter(module, checker_function),
310 m_valid_pointer_check_func(nullptr) {}
311
312 ~ValidPointerChecker() override = default;
313
314protected:
315 bool InstrumentInstruction(llvm::Instruction *inst) override {
316 Log *log = GetLog(LLDBLog::Expressions);
317
318 LLDB_LOGF(log, "Instrumenting load/store instruction: %s\n",
319 PrintValue(inst).c_str());
320
321 if (!m_valid_pointer_check_func)
322 m_valid_pointer_check_func =
323 BuildPointerValidatorFunc(m_checker_function->StartAddress());
324
325 llvm::Value *dereferenced_ptr = nullptr;
326
327 if (llvm::LoadInst *li = dyn_cast<llvm::LoadInst>(inst))
328 dereferenced_ptr = li->getPointerOperand();
329 else if (llvm::StoreInst *si = dyn_cast<llvm::StoreInst>(inst))
330 dereferenced_ptr = si->getPointerOperand();
331 else
332 return false;
333
334 // Insert an instruction to call the helper with the result
335 CallInst::Create(m_valid_pointer_check_func, dereferenced_ptr, "", inst);
336
337 return true;
338 }
339
340 bool InspectInstruction(llvm::Instruction &i) override {
341 if (isa<llvm::LoadInst>(&i) || isa<llvm::StoreInst>(&i))
342 RegisterInstruction(i);
343
344 return true;
345 }
346
347private:
348 llvm::FunctionCallee m_valid_pointer_check_func;
349};
350
352public:
353 ObjcObjectChecker(llvm::Module &module,
354 std::shared_ptr<UtilityFunction> checker_function)
355 : Instrumenter(module, checker_function),
356 m_objc_object_check_func(nullptr) {}
357
358 ~ObjcObjectChecker() override = default;
359
361 eMsgSend = 0,
365 eMsgSend_stret
366 };
367
368 std::map<llvm::Instruction *, msgSend_type> msgSend_types;
369
370protected:
371 bool InstrumentInstruction(llvm::Instruction *inst) override {
372 CallInst *call_inst = dyn_cast<CallInst>(inst);
373
374 if (!call_inst)
375 return false; // call_inst really shouldn't be nullptr, because otherwise
376 // InspectInstruction wouldn't have registered it
377
378 if (!m_objc_object_check_func)
379 m_objc_object_check_func =
380 BuildObjectCheckerFunc(m_checker_function->StartAddress());
381
382 // id objc_msgSend(id theReceiver, SEL theSelector, ...)
383
384 llvm::Value *target_object;
385 llvm::Value *selector;
386
387 switch (msgSend_types[inst]) {
388 case eMsgSend:
389 case eMsgSend_fpret:
390 // On arm64, clang uses objc_msgSend for scalar and struct return
391 // calls. The call instruction will record which was used.
392 if (call_inst->hasStructRetAttr()) {
393 target_object = call_inst->getArgOperand(1);
394 selector = call_inst->getArgOperand(2);
395 } else {
396 target_object = call_inst->getArgOperand(0);
397 selector = call_inst->getArgOperand(1);
398 }
399 break;
400 case eMsgSend_stret:
401 target_object = call_inst->getArgOperand(1);
402 selector = call_inst->getArgOperand(2);
403 break;
404 case eMsgSendSuper:
405 case eMsgSendSuper_stret:
406 return true;
407 }
408
409 // These objects should always be valid according to Sean Calannan
410 assert(target_object);
411 assert(selector);
412
413 // Insert an instruction to call the helper with the result
414
415 llvm::Value *arg_array[2];
416
417 arg_array[0] = target_object;
418 arg_array[1] = selector;
419
420 ArrayRef<llvm::Value *> args(arg_array, 2);
421
422 CallInst::Create(m_objc_object_check_func, args, "", inst);
423
424 return true;
425 }
426
427 static llvm::Function *GetFunction(llvm::Value *value) {
428 if (llvm::Function *function = llvm::dyn_cast<llvm::Function>(value)) {
429 return function;
430 }
431
432 if (llvm::ConstantExpr *const_expr =
433 llvm::dyn_cast<llvm::ConstantExpr>(value)) {
434 switch (const_expr->getOpcode()) {
435 default:
436 return nullptr;
437 case llvm::Instruction::BitCast:
438 return GetFunction(const_expr->getOperand(0));
439 }
440 }
441
442 return nullptr;
443 }
444
445 static llvm::Function *GetCalledFunction(llvm::CallInst *inst) {
446 return GetFunction(inst->getCalledOperand());
447 }
448
449 bool InspectInstruction(llvm::Instruction &i) override {
450 Log *log = GetLog(LLDBLog::Expressions);
451
452 CallInst *call_inst = dyn_cast<CallInst>(&i);
453
454 if (call_inst) {
455 const llvm::Function *called_function = GetCalledFunction(call_inst);
456
457 if (!called_function)
458 return true;
459
460 std::string name_str = called_function->getName().str();
461 const char *name_cstr = name_str.c_str();
462
463 LLDB_LOGF(log, "Found call to %s: %s\n", name_cstr,
464 PrintValue(call_inst).c_str());
465
466 if (name_str.find("objc_msgSend") == std::string::npos)
467 return true;
468
469 if (!strcmp(name_cstr, "objc_msgSend")) {
470 RegisterInstruction(i);
471 msgSend_types[&i] = eMsgSend;
472 return true;
473 }
474
475 if (!strcmp(name_cstr, "objc_msgSend_stret")) {
476 RegisterInstruction(i);
477 msgSend_types[&i] = eMsgSend_stret;
478 return true;
479 }
480
481 if (!strcmp(name_cstr, "objc_msgSend_fpret")) {
482 RegisterInstruction(i);
483 msgSend_types[&i] = eMsgSend_fpret;
484 return true;
485 }
486
487 if (!strcmp(name_cstr, "objc_msgSendSuper")) {
488 RegisterInstruction(i);
489 msgSend_types[&i] = eMsgSendSuper;
490 return true;
491 }
492
493 if (!strcmp(name_cstr, "objc_msgSendSuper_stret")) {
494 RegisterInstruction(i);
495 msgSend_types[&i] = eMsgSendSuper_stret;
496 return true;
497 }
498
499 LLDB_LOGF(log,
500 "Function name '%s' contains 'objc_msgSend' but is not handled",
501 name_str.c_str());
502
503 return true;
504 }
505
506 return true;
507 }
508
509private:
510 llvm::FunctionCallee m_objc_object_check_func;
511};
512
514 ClangDynamicCheckerFunctions &checker_functions, const char *func_name)
515 : ModulePass(ID), m_func_name(func_name),
516 m_checker_functions(checker_functions) {}
517
519
520bool IRDynamicChecks::runOnModule(llvm::Module &M) {
522
523 llvm::Function *function = M.getFunction(StringRef(m_func_name));
524
525 if (!function) {
526 LLDB_LOGF(log, "Couldn't find %s() in the module", m_func_name.c_str());
527
528 return false;
529 }
530
533
534 if (!vpc.Inspect(*function))
535 return false;
536
537 if (!vpc.Instrument())
538 return false;
539 }
540
543
544 if (!ooc.Inspect(*function))
545 return false;
546
547 if (!ooc.Instrument())
548 return false;
549 }
550
551 if (log && log->GetVerbose()) {
552 std::string s;
553 raw_string_ostream oss(s);
554
555 M.print(oss, nullptr);
556
557 oss.flush();
558
559 LLDB_LOGF(log, "Module after dynamic checks: \n%s", s.c_str());
560 }
561
562 return true;
563}
564
565void IRDynamicChecks::assignPassManager(PMStack &PMS, PassManagerType T) {}
566
568 return PMT_ModulePassManager;
569}
static char ID
Definition: HostInfoBase.h:37
#define VALID_OBJC_OBJECT_CHECK_NAME
static char ID
static const char g_valid_pointer_check_text[]
#define VALID_POINTER_CHECK_NAME
static std::string PrintValue(const Value *value, bool truncate=false)
#define LLDB_LOGF(log,...)
Definition: Log.h:366
Finds and instruments individual LLVM IR instructions.
llvm::Module & m_module
The module which is being instrumented.
virtual bool InspectInstruction(llvm::Instruction &i)
Determine whether a single instruction is interesting to instrument, and, if so, call RegisterInstruc...
IntegerType * GetIntptrTy()
virtual bool InstrumentInstruction(llvm::Instruction *inst)=0
Add instrumentation to a single instruction.
std::shared_ptr< UtilityFunction > m_checker_function
The dynamic checker function for the process.
Instrumenter(llvm::Module &module, std::shared_ptr< UtilityFunction > checker_function)
Constructor.
InstVector m_to_instrument
List of instructions the inspector found.
llvm::FunctionCallee BuildPointerValidatorFunc(lldb::addr_t start_address)
Build a function pointer for a function with signature void (*)(uint8_t*) with a given address.
PointerType * GetI8PtrTy()
bool Inspect(llvm::Function &function)
Inspect a function to find instructions to instrument.
virtual ~Instrumenter()=default
std::vector< llvm::Instruction * > InstVector
bool Instrument()
Instrument all the instructions found by Inspect()
virtual bool InspectBasicBlock(llvm::BasicBlock &bb)
Scan a basic block to see if any instructions are interesting.
virtual bool InspectFunction(llvm::Function &f)
Scan a function to see if any instructions are interesting.
void RegisterInstruction(llvm::Instruction &inst)
Register a single instruction to be instrumented.
llvm::FunctionCallee BuildObjectCheckerFunc(lldb::addr_t start_address)
Build a function pointer for a function with signature void (*)(uint8_t*, uint8_t*) with a given addr...
InstVector::iterator InstIterator
std::map< llvm::Instruction *, msgSend_type > msgSend_types
bool InspectInstruction(llvm::Instruction &i) override
Determine whether a single instruction is interesting to instrument, and, if so, call RegisterInstruc...
static llvm::Function * GetCalledFunction(llvm::CallInst *inst)
~ObjcObjectChecker() override=default
llvm::FunctionCallee m_objc_object_check_func
bool InstrumentInstruction(llvm::Instruction *inst) override
Add instrumentation to a single instruction.
static llvm::Function * GetFunction(llvm::Value *value)
ObjcObjectChecker(llvm::Module &module, std::shared_ptr< UtilityFunction > checker_function)
bool InstrumentInstruction(llvm::Instruction *inst) override
Add instrumentation to a single instruction.
ValidPointerChecker(llvm::Module &module, std::shared_ptr< UtilityFunction > checker_function)
llvm::FunctionCallee m_valid_pointer_check_func
bool InspectInstruction(llvm::Instruction &i) override
Determine whether a single instruction is interesting to instrument, and, if so, call RegisterInstruc...
~ValidPointerChecker() override=default
bool DoCheckersExplainStop(lldb::addr_t addr, Stream &message) override
std::shared_ptr< UtilityFunction > m_objc_object_check
llvm::Error Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx) override
Install the utility functions into a process.
std::shared_ptr< UtilityFunction > m_valid_pointer_check
~ClangDynamicCheckerFunctions() override
Destructor.
Encapsulates dynamic check functions used by expressions.
"lldb/Target/ExecutionContext.h" A class that contains an execution context.
Target & GetTargetRef() const
Returns a reference to the target object.
Process * GetProcessPtr() const
Returns a pointer to the process object.
~IRDynamicChecks() override
Destructor.
ClangDynamicCheckerFunctions & m_checker_functions
The checker functions for the process.
bool runOnModule(llvm::Module &M) override
Run this IR transformer on a single module.
std::string m_func_name
The name of the function to add checks to.
IRDynamicChecks(ClangDynamicCheckerFunctions &checker_functions, const char *func_name="$__lldb_expr")
Constructor.
llvm::PassManagerType getPotentialPassManagerType() const override
Returns PMT_ModulePassManager.
void assignPassManager(llvm::PMStack &PMS, llvm::PassManagerType T=llvm::PMT_ModulePassManager) override
Interface stub.
bool GetVerbose() const
Definition: Log.cpp:314
static ObjCLanguageRuntime * Get(Process &process)
virtual llvm::Expected< std::unique_ptr< UtilityFunction > > CreateObjectChecker(std::string name, ExecutionContext &exe_ctx)=0
A plug-in interface definition class for debugging a process.
Definition: Process.h:341
A stream class that can stream formatted output to a file.
Definition: Stream.h:28
size_t Printf(const char *format,...) __attribute__((format(printf
Output printf formatted output to the stream.
Definition: Stream.cpp:134
llvm::Expected< std::unique_ptr< UtilityFunction > > CreateUtilityFunction(std::string expression, std::string name, lldb::LanguageType language, ExecutionContext &exe_ctx)
Creates and installs a UtilityFunction for the given language.
Definition: Target.cpp:2569
A class that represents a running process on the host machine.
Definition: SBAttachInfo.h:14
Log * GetLog(Cat mask)
Retrieve the Log object for the channel associated with the given log enum.
Definition: Log.h:331
@ eLanguageTypeC
Non-standardized C, such as K&R.
uint64_t addr_t
Definition: lldb-types.h:80
Definition: Debugger.h:54