aboutsummaryrefslogtreecommitdiffstats
path: root/source/Expression/IRDynamicChecks.cpp
blob: 64fdb08157aa7e39a799b3ac07ce4bd2dd7605f0 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
//===-- IRDynamicChecks.cpp -------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// C Includes
// C++ Includes
// Other libraries and framework includes
#include "llvm/Support/raw_ostream.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Value.h"

// Project includes
#include "lldb/Expression/IRDynamicChecks.h"

#include "lldb/Core/ConstString.h"
#include "lldb/Core/Log.h"
#include "lldb/Expression/UtilityFunction.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/ObjCLanguageRuntime.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/StackFrame.h"
#include "lldb/Target/Target.h"

using namespace llvm;
using namespace lldb_private;

static char ID;

#define VALID_POINTER_CHECK_NAME "_$__lldb_valid_pointer_check"
#define VALID_OBJC_OBJECT_CHECK_NAME "$__lldb_objc_object_check"

static const char g_valid_pointer_check_text[] =
"extern \"C\" void\n"
"_$__lldb_valid_pointer_check (unsigned char *$__lldb_arg_ptr)\n"
"{\n"
"    unsigned char $__lldb_local_val = *$__lldb_arg_ptr;\n"
"}";

DynamicCheckerFunctions::DynamicCheckerFunctions() = default;

DynamicCheckerFunctions::~DynamicCheckerFunctions() = default;

bool
DynamicCheckerFunctions::Install(Stream &error_stream,
                                 ExecutionContext &exe_ctx)
{
    Error error;
    m_valid_pointer_check.reset(exe_ctx.GetTargetRef().GetUtilityFunctionForLanguage(g_valid_pointer_check_text,
                                                                                     lldb::eLanguageTypeC,
                                                                                     VALID_POINTER_CHECK_NAME,
                                                                                     error));
    if (error.Fail())
        return false;
        
    if (!m_valid_pointer_check->Install(error_stream, exe_ctx))
        return false;

    Process *process = exe_ctx.GetProcessPtr();

    if (process)
    {
        ObjCLanguageRuntime *objc_language_runtime = process->GetObjCLanguageRuntime();

        if (objc_language_runtime)
        {
            m_objc_object_check.reset(objc_language_runtime->CreateObjectChecker(VALID_OBJC_OBJECT_CHECK_NAME));

            if (!m_objc_object_check->Install(error_stream, exe_ctx))
                return false;
        }
    }

    return true;
}

bool
DynamicCheckerFunctions::DoCheckersExplainStop (lldb::addr_t addr, Stream &message)
{
    // FIXME: We have to get the checkers to know why they scotched the call in more detail,
    // so we can print a better message here.
    if (m_valid_pointer_check && m_valid_pointer_check->ContainsAddress(addr))
    {
        message.Printf ("Attempted to dereference an invalid pointer.");
        return true;
    }
    else if (m_objc_object_check && m_objc_object_check->ContainsAddress(addr))
    {
        message.Printf ("Attempted to dereference an invalid ObjC Object or send it an unrecognized selector");
        return true;
    }
    return false;
}

static std::string
PrintValue(llvm::Value *V, bool truncate = false)
{
    std::string s;
    raw_string_ostream rso(s);
    V->print(rso);
    rso.flush();
    if (truncate)
        s.resize(s.length() - 1);
    return s;
}

//----------------------------------------------------------------------
/// @class Instrumenter IRDynamicChecks.cpp
/// @brief Finds and instruments individual LLVM IR instructions
///
/// When instrumenting LLVM IR, it is frequently desirable to first search
/// for instructions, and then later modify them.  This way iterators
/// remain intact, and multiple passes can look at the same code base without
/// treading on each other's toes.
///
/// The Instrumenter class implements this functionality.  A client first
/// calls Inspect on a function, which populates a list of instructions to
/// be instrumented.  Then, later, when all passes' Inspect functions have
/// been called, the client calls Instrument, which adds the desired
/// instrumentation.
///
/// A subclass of Instrumenter must override InstrumentInstruction, which
/// is responsible for adding whatever instrumentation is necessary.
///
/// A subclass of Instrumenter may override:
///
/// - InspectInstruction [default: does nothing]
///
/// - InspectBasicBlock [default: iterates through the instructions in a
///   basic block calling InspectInstruction]
///
/// - InspectFunction [default: iterates through the basic blocks in a
///   function calling InspectBasicBlock]
//----------------------------------------------------------------------
class Instrumenter {
public:
    //------------------------------------------------------------------
    /// Constructor
    ///
    /// @param[in] module
    ///     The module being instrumented.
    //------------------------------------------------------------------
    Instrumenter (llvm::Module &module,
                  DynamicCheckerFunctions &checker_functions) :
        m_module(module),
        m_checker_functions(checker_functions),
        m_i8ptr_ty(nullptr),
        m_intptr_ty(nullptr)
    {
    }

    virtual ~Instrumenter() = default;

    //------------------------------------------------------------------
    /// Inspect a function to find instructions to instrument
    ///
    /// @param[in] function
    ///     The function to inspect.
    ///
    /// @return
    ///     True on success; false on error.
    //------------------------------------------------------------------
    bool Inspect (llvm::Function &function)
    {
        return InspectFunction(function);
    }

    //------------------------------------------------------------------
    /// Instrument all the instructions found by Inspect()
    ///
    /// @return
    ///     True on success; false on error.
    //------------------------------------------------------------------
    bool Instrument ()
    {
        for (InstIterator ii = m_to_instrument.begin(), last_ii = m_to_instrument.end();
             ii != last_ii;
             ++ii)
        {
            if (!InstrumentInstruction(*ii))
                return false;
        }

        return true;
    }

protected:
    //------------------------------------------------------------------
    /// Add instrumentation to a single instruction
    ///
    /// @param[in] inst
    ///     The instruction to be instrumented.
    ///
    /// @return
    ///     True on success; false otherwise.
    //------------------------------------------------------------------
    virtual bool InstrumentInstruction(llvm::Instruction *inst) = 0;

    //------------------------------------------------------------------
    /// Register a single instruction to be instrumented
    ///
    /// @param[in] inst
    ///     The instruction to be instrumented.
    //------------------------------------------------------------------
    void RegisterInstruction(llvm::Instruction &i)
    {
        m_to_instrument.push_back(&i);
    }

    //------------------------------------------------------------------
    /// Determine whether a single instruction is interesting to
    /// instrument, and, if so, call RegisterInstruction
    ///
    /// @param[in] i
    ///     The instruction to be inspected.
    ///
    /// @return
    ///     False if there was an error scanning; true otherwise.
    //------------------------------------------------------------------
    virtual bool InspectInstruction(llvm::Instruction &i)
    {
        return true;
    }

    //------------------------------------------------------------------
    /// Scan a basic block to see if any instructions are interesting
    ///
    /// @param[in] bb
    ///     The basic block to be inspected.
    ///
    /// @return
    ///     False if there was an error scanning; true otherwise.
    //------------------------------------------------------------------
    virtual bool InspectBasicBlock(llvm::BasicBlock &bb)
    {
        for (llvm::BasicBlock::iterator ii = bb.begin(), last_ii = bb.end();
             ii != last_ii;
             ++ii)
        {
            if (!InspectInstruction(*ii))
                return false;
        }

        return true;
    }

    //------------------------------------------------------------------
    /// Scan a function to see if any instructions are interesting
    ///
    /// @param[in] f
    ///     The function to be inspected.
    ///
    /// @return
    ///     False if there was an error scanning; true otherwise.
    //------------------------------------------------------------------
    virtual bool InspectFunction(llvm::Function &f)
    {
        for (llvm::Function::iterator bbi = f.begin(), last_bbi = f.end();
             bbi != last_bbi;
             ++bbi)
        {
            if (!InspectBasicBlock(*bbi))
                return false;
        }

        return true;
    }

    //------------------------------------------------------------------
    /// Build a function pointer for a function with signature
    /// void (*)(uint8_t*) with a given address
    ///
    /// @param[in] start_address
    ///     The address of the function.
    ///
    /// @return
    ///     The function pointer, for use in a CallInst.
    //------------------------------------------------------------------
    llvm::Value *BuildPointerValidatorFunc(lldb::addr_t start_address)
    {
        llvm::Type *param_array[1];

        param_array[0] = const_cast<llvm::PointerType*>(GetI8PtrTy());

        ArrayRef<llvm::Type*> params(param_array, 1);

        FunctionType *fun_ty = FunctionType::get(llvm::Type::getVoidTy(m_module.getContext()), params, true);
        PointerType *fun_ptr_ty = PointerType::getUnqual(fun_ty);
        Constant *fun_addr_int = ConstantInt::get(GetIntptrTy(), start_address, false);
        return ConstantExpr::getIntToPtr(fun_addr_int, fun_ptr_ty);
    }

    //------------------------------------------------------------------
    /// Build a function pointer for a function with signature
    /// void (*)(uint8_t*, uint8_t*) with a given address
    ///
    /// @param[in] start_address
    ///     The address of the function.
    ///
    /// @return
    ///     The function pointer, for use in a CallInst.
    //------------------------------------------------------------------
    llvm::Value *BuildObjectCheckerFunc(lldb::addr_t start_address)
    {
        llvm::Type *param_array[2];

        param_array[0] = const_cast<llvm::PointerType*>(GetI8PtrTy());
        param_array[1] = const_cast<llvm::PointerType*>(GetI8PtrTy());

        ArrayRef<llvm::Type*> params(param_array, 2);

        FunctionType *fun_ty = FunctionType::get(llvm::Type::getVoidTy(m_module.getContext()), params, true);
        PointerType *fun_ptr_ty = PointerType::getUnqual(fun_ty);
        Constant *fun_addr_int = ConstantInt::get(GetIntptrTy(), start_address, false);
        return ConstantExpr::getIntToPtr(fun_addr_int, fun_ptr_ty);
    }

    PointerType *GetI8PtrTy()
    {
        if (!m_i8ptr_ty)
            m_i8ptr_ty = llvm::Type::getInt8PtrTy(m_module.getContext());

        return m_i8ptr_ty;
    }

    IntegerType *GetIntptrTy()
    {
        if (!m_intptr_ty)
        {
            llvm::DataLayout data_layout(&m_module);

            m_intptr_ty = llvm::Type::getIntNTy(m_module.getContext(), data_layout.getPointerSizeInBits());
        }

        return m_intptr_ty;
    }

    typedef std::vector <llvm::Instruction *>   InstVector;
    typedef InstVector::iterator                InstIterator;

    InstVector                  m_to_instrument;        ///< List of instructions the inspector found
    llvm::Module               &m_module;               ///< The module which is being instrumented
    DynamicCheckerFunctions    &m_checker_functions;    ///< The dynamic checker functions for the process

private:
    PointerType                *m_i8ptr_ty;
    IntegerType                *m_intptr_ty;
};

class ValidPointerChecker : public Instrumenter
{
public:
    ValidPointerChecker (llvm::Module &module,
                         DynamicCheckerFunctions &checker_functions) :
        Instrumenter(module, checker_functions),
        m_valid_pointer_check_func(nullptr)
    {
    }

    ~ValidPointerChecker() override = default;

protected:
    bool InstrumentInstruction(llvm::Instruction *inst) override
    {
        Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

        if (log)
            log->Printf("Instrumenting load/store instruction: %s\n",
                        PrintValue(inst).c_str());

        if (!m_valid_pointer_check_func)
            m_valid_pointer_check_func = BuildPointerValidatorFunc(m_checker_functions.m_valid_pointer_check->StartAddress());

        llvm::Value *dereferenced_ptr = nullptr;

        if (llvm::LoadInst *li = dyn_cast<llvm::LoadInst> (inst))
            dereferenced_ptr = li->getPointerOperand();
        else if (llvm::StoreInst *si = dyn_cast<llvm::StoreInst> (inst))
            dereferenced_ptr = si->getPointerOperand();
        else
            return false;

        // Insert an instruction to cast the loaded value to int8_t*

        BitCastInst *bit_cast = new BitCastInst(dereferenced_ptr,
                                                GetI8PtrTy(),
                                                "",
                                                inst);

        // Insert an instruction to call the helper with the result

        llvm::Value *arg_array[1];

        arg_array[0] = bit_cast;

        llvm::ArrayRef<llvm::Value *> args(arg_array, 1);

        CallInst::Create(m_valid_pointer_check_func,
                         args,
                         "",
                         inst);

        return true;
    }

    bool InspectInstruction(llvm::Instruction &i) override
    {
        if (dyn_cast<llvm::LoadInst> (&i) ||
            dyn_cast<llvm::StoreInst> (&i))
            RegisterInstruction(i);

        return true;
    }

private:
    llvm::Value         *m_valid_pointer_check_func;
};

class ObjcObjectChecker : public Instrumenter
{
public:
    ObjcObjectChecker(llvm::Module &module,
                        DynamicCheckerFunctions &checker_functions) :
        Instrumenter(module, checker_functions),
        m_objc_object_check_func(nullptr)
    {
    }

    ~ObjcObjectChecker() override = default;

    enum msgSend_type
    {
        eMsgSend = 0,
        eMsgSendSuper,
        eMsgSendSuper_stret,
        eMsgSend_fpret,
        eMsgSend_stret
    };

    std::map <llvm::Instruction *, msgSend_type> msgSend_types;

protected:
    bool InstrumentInstruction(llvm::Instruction *inst) override
    {
        CallInst *call_inst = dyn_cast<CallInst>(inst);

        if (!call_inst)
            return false; // call_inst really shouldn't be nullptr, because otherwise InspectInstruction wouldn't have registered it

        if (!m_objc_object_check_func)
            m_objc_object_check_func = BuildObjectCheckerFunc(m_checker_functions.m_objc_object_check->StartAddress());

        // id objc_msgSend(id theReceiver, SEL theSelector, ...)

        llvm::Value *target_object;
        llvm::Value *selector;

        switch (msgSend_types[inst])
        {
        case eMsgSend:
        case eMsgSend_fpret:
            target_object = call_inst->getArgOperand(0);
            selector = call_inst->getArgOperand(1);
            break;
        case eMsgSend_stret:
            target_object = call_inst->getArgOperand(1);
            selector = call_inst->getArgOperand(2);
            break;
        case eMsgSendSuper:
        case eMsgSendSuper_stret:
            return true;
        }

        // These objects should always be valid according to Sean Calannan
        assert (target_object);
        assert (selector);

        // Insert an instruction to cast the receiver id to int8_t*

        BitCastInst *bit_cast = new BitCastInst(target_object,
                                                GetI8PtrTy(),
                                                "",
                                                inst);

        // Insert an instruction to call the helper with the result

        llvm::Value *arg_array[2];

        arg_array[0] = bit_cast;
        arg_array[1] = selector;

        ArrayRef<llvm::Value*> args(arg_array, 2);

        CallInst::Create(m_objc_object_check_func,
                         args,
                         "",
                         inst);

        return true;
    }

    bool InspectInstruction(llvm::Instruction &i) override
    {
        Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

        CallInst *call_inst = dyn_cast<CallInst>(&i);

        if (call_inst)
        {
            // This metadata is set by IRForTarget::MaybeHandleCall().

            MDNode *metadata = call_inst->getMetadata("lldb.call.realName");

            if (!metadata)
                return true;

            if (metadata->getNumOperands() != 1)
            {
                if (log)
                    log->Printf("Function call metadata has %d operands for [%p] %s",
                                metadata->getNumOperands(),
                                static_cast<void*>(call_inst),
                                PrintValue(call_inst).c_str());
                return false;
            }

            MDString *real_name = dyn_cast<MDString>(metadata->getOperand(0));

            if (!real_name)
            {
                if (log)
                    log->Printf("Function call metadata is not an MDString for [%p] %s",
                                static_cast<void*>(call_inst),
                                PrintValue(call_inst).c_str());
                return false;
            }

            std::string name_str = real_name->getString();
            const char* name_cstr = name_str.c_str();

            if (log)
                log->Printf("Found call to %s: %s\n", name_cstr, PrintValue(call_inst).c_str());

            if (name_str.find("objc_msgSend") == std::string::npos)
                return true;

            if (!strcmp(name_cstr, "objc_msgSend"))
            {
                RegisterInstruction(i);
                msgSend_types[&i] = eMsgSend;
                return true;
            }

            if (!strcmp(name_cstr, "objc_msgSend_stret"))
            {
                RegisterInstruction(i);
                msgSend_types[&i] = eMsgSend_stret;
                return true;
            }

            if (!strcmp(name_cstr, "objc_msgSend_fpret"))
            {
                RegisterInstruction(i);
                msgSend_types[&i] = eMsgSend_fpret;
                return true;
            }

            if (!strcmp(name_cstr, "objc_msgSendSuper"))
            {
                RegisterInstruction(i);
                msgSend_types[&i] = eMsgSendSuper;
                return true;
            }

            if (!strcmp(name_cstr, "objc_msgSendSuper_stret"))
            {
                RegisterInstruction(i);
                msgSend_types[&i] = eMsgSendSuper_stret;
                return true;
            }

            if (log)
                log->Printf("Function name '%s' contains 'objc_msgSend' but is not handled", name_str.c_str());

            return true;
        }

        return true;
    }

private:
    llvm::Value         *m_objc_object_check_func;
};

IRDynamicChecks::IRDynamicChecks(DynamicCheckerFunctions &checker_functions,
                                 const char *func_name) :
    ModulePass(ID),
    m_func_name(func_name),
    m_checker_functions(checker_functions)
{
}

IRDynamicChecks::~IRDynamicChecks() = default;

bool
IRDynamicChecks::runOnModule(llvm::Module &M)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    llvm::Function* function = M.getFunction(StringRef(m_func_name.c_str()));

    if (!function)
    {
        if (log)
            log->Printf("Couldn't find %s() in the module", m_func_name.c_str());

        return false;
    }

    if (m_checker_functions.m_valid_pointer_check)
    {
        ValidPointerChecker vpc(M, m_checker_functions);

        if (!vpc.Inspect(*function))
            return false;

        if (!vpc.Instrument())
            return false;
    }

    if (m_checker_functions.m_objc_object_check)
    {
        ObjcObjectChecker ooc(M, m_checker_functions);

        if (!ooc.Inspect(*function))
            return false;

        if (!ooc.Instrument())
            return false;
    }

    if (log && log->GetVerbose())
    {
        std::string s;
        raw_string_ostream oss(s);

        M.print(oss, nullptr);

        oss.flush();

        log->Printf ("Module after dynamic checks: \n%s", s.c_str());
    }

    return true;
}

void
IRDynamicChecks::assignPassManager(PMStack &PMS,
                                   PassManagerType T)
{
}

PassManagerType
IRDynamicChecks::getPotentialPassManagerType() const
{
    return PMT_ModulePassManager;
}