about summary refs log tree commit diff homepage
path: root/lib/Solver/Solver.cpp
blob: 43d673ff8d41b8da57e4353ec81c51e3b465048d (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
//===-- Solver.cpp --------------------------------------------------------===//
//
//                     The KLEE Symbolic Virtual Machine
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "klee/Solver.h"
#include "klee/SolverImpl.h"

#include "SolverStats.h"
#include "STPBuilder.h"

#include "klee/Constraints.h"
#include "klee/Expr.h"
#include "klee/TimerStatIncrementer.h"
#include "klee/util/Assignment.h"
#include "klee/util/ExprPPrinter.h"
#include "klee/util/ExprUtil.h"
#include "klee/Internal/Support/Timer.h"

#define vc_bvBoolExtract IAMTHESPAWNOFSATAN

#include <cassert>
#include <map>
#include <vector>

#include <signal.h>
#include <sys/wait.h>
#include <sys/ipc.h>
#include <sys/shm.h>

using namespace klee;

/***/

const char *Solver::validity_to_str(Validity v) {
  switch (v) {
  default:    return "Unknown";
  case True:  return "True";
  case False: return "False";
  }
}

Solver::~Solver() { 
  delete impl; 
}

SolverImpl::~SolverImpl() {
}

bool Solver::evaluate(const Query& query, Validity &result) {
  assert(query.expr.getWidth() == Expr::Bool && "Invalid expression type!");

  // Maintain invariants implementation expect.
  if (query.expr.isConstant()) {
    result = query.expr.getConstantValue() ? True : False;
    return true;
  }

  return impl->computeValidity(query, result);
}

bool SolverImpl::computeValidity(const Query& query, Solver::Validity &result) {
  bool isTrue, isFalse;
  if (!computeTruth(query, isTrue))
    return false;
  if (isTrue) {
    result = Solver::True;
  } else {
    if (!computeTruth(query.negateExpr(), isFalse))
      return false;
    result = isFalse ? Solver::False : Solver::Unknown;
  }
  return true;
}

bool Solver::mustBeTrue(const Query& query, bool &result) {
  assert(query.expr.getWidth() == Expr::Bool && "Invalid expression type!");

  // Maintain invariants implementation expect.
  if (query.expr.isConstant()) {
    result = query.expr.getConstantValue() ? true : false;
    return true;
  }

  return impl->computeTruth(query, result);
}

bool Solver::mustBeFalse(const Query& query, bool &result) {
  return mustBeTrue(query.negateExpr(), result);
}

bool Solver::mayBeTrue(const Query& query, bool &result) {
  bool res;
  if (!mustBeFalse(query, res))
    return false;
  result = !res;
  return true;
}

bool Solver::mayBeFalse(const Query& query, bool &result) {
  bool res;
  if (!mustBeTrue(query, res))
    return false;
  result = !res;
  return true;
}

bool Solver::getValue(const Query& query, ref<Expr> &result) {
  // Maintain invariants implementation expect.
  if (query.expr.isConstant()) {
    result = query.expr;
    return true;
  }

  return impl->computeValue(query, result);
}

bool 
Solver::getInitialValues(const Query& query,
                         const std::vector<const Array*> &objects,
                         std::vector< std::vector<unsigned char> > &values) {
  bool hasSolution;
  bool success =
    impl->computeInitialValues(query, objects, values, hasSolution);
  // FIXME: Propogate this out.
  if (!hasSolution)
    return false;
    
  return success;
}

std::pair< ref<Expr>, ref<Expr> > Solver::getRange(const Query& query) {
  ref<Expr> e = query.expr;
  Expr::Width width = e.getWidth();
  uint64_t min, max;

  if (width==1) {
    Solver::Validity result;
    if (!evaluate(query, result))
      assert(0 && "computeValidity failed");
    switch (result) {
    case Solver::True: 
      min = max = 1; break;
    case Solver::False: 
      min = max = 0; break;
    default:
      min = 0, max = 1; break;
    }
  } else if (e.isConstant()) {
    min = max = e.getConstantValue();
  } else {
    // binary search for # of useful bits
    uint64_t lo=0, hi=width, mid, bits=0;
    while (lo<hi) {
      mid = (lo+hi)/2;
      bool res;
      bool success = 
        mustBeTrue(query.withExpr(
                     EqExpr::create(LShrExpr::create(e,
                                                     ConstantExpr::create(mid, 
                                                                          width)),
                                    ConstantExpr::create(0, width))),
                   res);
      assert(success && "FIXME: Unhandled solver failure");
      if (res) {
        hi = mid;
      } else {
        lo = mid+1;
      }

      bits = lo;
    }
    
    // could binary search for training zeros and offset
    // min max but unlikely to be very useful

    // check common case
    bool res = false;
    bool success = 
      mayBeTrue(query.withExpr(EqExpr::create(e, ConstantExpr::create(0, 
                                                                      width))), 
                res);
    assert(success && "FIXME: Unhandled solver failure");      
    if (res) {
      min = 0;
    } else {
      // binary search for min
      lo=0, hi=bits64::maxValueOfNBits(bits);
      while (lo<hi) {
        mid = (lo+hi)/2;
        bool res = false;
        bool success = 
          mayBeTrue(query.withExpr(UleExpr::create(e, 
                                                   ConstantExpr::create(mid, 
                                                                        width))),
                    res);
        assert(success && "FIXME: Unhandled solver failure");      
        if (res) {
          hi = mid;
        } else {
          lo = mid+1;
        }
      }

      min = lo;
    }

    // binary search for max
    lo=min, hi=bits64::maxValueOfNBits(bits);
    while (lo<hi) {
      mid = (lo+hi)/2;
      bool res;
      bool success = 
        mustBeTrue(query.withExpr(UleExpr::create(e, 
                                                  ConstantExpr::create(mid, 
                                                                       width))),
                   res);
      assert(success && "FIXME: Unhandled solver failure");      
      if (res) {
        hi = mid;
      } else {
        lo = mid+1;
      }
    }

    max = lo;
  }

  return std::make_pair(ConstantExpr::create(min, width),
                        ConstantExpr::create(max, width));
}

/***/

class ValidatingSolver : public SolverImpl {
private:
  Solver *solver, *oracle;

public: 
  ValidatingSolver(Solver *_solver, Solver *_oracle) 
    : solver(_solver), oracle(_oracle) {}
  ~ValidatingSolver() { delete solver; }
  
  bool computeValidity(const Query&, Solver::Validity &result);
  bool computeTruth(const Query&, bool &isValid);
  bool computeValue(const Query&, ref<Expr> &result);
  bool computeInitialValues(const Query&,
                            const std::vector<const Array*> &objects,
                            std::vector< std::vector<unsigned char> > &values,
                            bool &hasSolution);
};

bool ValidatingSolver::computeTruth(const Query& query,
                                    bool &isValid) {
  bool answer;
  
  if (!solver->impl->computeTruth(query, isValid))
    return false;
  if (!oracle->impl->computeTruth(query, answer))
    return false;
  
  if (isValid != answer)
    assert(0 && "invalid solver result (computeTruth)");
  
  return true;
}

bool ValidatingSolver::computeValidity(const Query& query,
                                       Solver::Validity &result) {
  Solver::Validity answer;
  
  if (!solver->impl->computeValidity(query, result))
    return false;
  if (!oracle->impl->computeValidity(query, answer))
    return false;
  
  if (result != answer)
    assert(0 && "invalid solver result (computeValidity)");
  
  return true;
}

bool ValidatingSolver::computeValue(const Query& query,
                                    ref<Expr> &result) {  
  bool answer;

  if (!solver->impl->computeValue(query, result))
    return false;
  // We don't want to compare, but just make sure this is a legal
  // solution.
  if (!oracle->impl->computeTruth(query.withExpr(NeExpr::create(query.expr, 
                                                                result)),
                                  answer))
    return false;

  if (answer)
    assert(0 && "invalid solver result (computeValue)");

  return true;
}

bool 
ValidatingSolver::computeInitialValues(const Query& query,
                                       const std::vector<const Array*>
                                         &objects,
                                       std::vector< std::vector<unsigned char> >
                                         &values,
                                       bool &hasSolution) {
  bool answer;

  if (!solver->impl->computeInitialValues(query, objects, values, 
                                          hasSolution))
    return false;

  if (hasSolution) {
    // Assert the bindings as constraints, and verify that the
    // conjunction of the actual constraints is satisfiable.
    std::vector< ref<Expr> > bindings;
    for (unsigned i = 0; i != values.size(); ++i) {
      const Array *array = objects[i];
      for (unsigned j=0; j<array->size; j++) {
        unsigned char value = values[i][j];
        bindings.push_back(EqExpr::create(ReadExpr::create(UpdateList(array,
                                                                      true, 0),
                                                           ref<Expr>(j, Expr::Int32)),
                                          ref<Expr>(value, Expr::Int8)));
      }
    }
    ConstraintManager tmp(bindings);
    ref<Expr> constraints = Expr::createNot(query.expr);
    for (ConstraintManager::const_iterator it = query.constraints.begin(), 
           ie = query.constraints.end(); it != ie; ++it)
      constraints = AndExpr::create(constraints, *it);
    
    if (!oracle->impl->computeTruth(Query(tmp, constraints), answer))
      return false;
    if (!answer)
      assert(0 && "invalid solver result (computeInitialValues)");
  } else {
    if (!oracle->impl->computeTruth(query, answer))
      return false;
    if (!answer)
      assert(0 && "invalid solver result (computeInitialValues)");    
  }

  return true;
}

Solver *klee::createValidatingSolver(Solver *s, Solver *oracle) {
  return new Solver(new ValidatingSolver(s, oracle));
}

/***/

class STPSolverImpl : public SolverImpl {
private:
  /// The solver we are part of, for access to public information.
  STPSolver *solver;
  VC vc;
  STPBuilder *builder;
  double timeout;
  bool useForkedSTP;

public:
  STPSolverImpl(STPSolver *_solver, bool _useForkedSTP);
  ~STPSolverImpl();

  char *getConstraintLog(const Query&);
  void setTimeout(double _timeout) { timeout = _timeout; }

  bool computeTruth(const Query&, bool &isValid);
  bool computeValue(const Query&, ref<Expr> &result);
  bool computeInitialValues(const Query&,
                            const std::vector<const Array*> &objects,
                            std::vector< std::vector<unsigned char> > &values,
                            bool &hasSolution);
};

static unsigned char *shared_memory_ptr;
static const unsigned shared_memory_size = 1<<20;
static int shared_memory_id;

static void stp_error_handler(const char* err_msg) {
  fprintf(stderr, "error: STP Error: %s\n", err_msg);
  abort();
}

STPSolverImpl::STPSolverImpl(STPSolver *_solver, bool _useForkedSTP) 
  : solver(_solver),
    vc(vc_createValidityChecker()),
    builder(new STPBuilder(vc)),
    timeout(0.0),
    useForkedSTP(_useForkedSTP)
{
  assert(vc && "unable to create validity checker");
  assert(builder && "unable to create STPBuilder");

  vc_registerErrorHandler(::stp_error_handler);

  if (useForkedSTP) {
    shared_memory_id = shmget(IPC_PRIVATE, shared_memory_size, IPC_CREAT | 0700);
    assert(shared_memory_id>=0 && "shmget failed");
    shared_memory_ptr = (unsigned char*) shmat(shared_memory_id, NULL, 0);
    assert(shared_memory_ptr!=(void*)-1 && "shmat failed");
    shmctl(shared_memory_id, IPC_RMID, NULL);
  }
}

STPSolverImpl::~STPSolverImpl() {
  delete builder;

  vc_Destroy(vc);
}

/***/

STPSolver::STPSolver(bool useForkedSTP) 
  : Solver(new STPSolverImpl(this, useForkedSTP))
{
}

char *STPSolver::getConstraintLog(const Query &query) {
  return static_cast<STPSolverImpl*>(impl)->getConstraintLog(query);  
}

void STPSolver::setTimeout(double timeout) {
  static_cast<STPSolverImpl*>(impl)->setTimeout(timeout);
}

/***/

char *STPSolverImpl::getConstraintLog(const Query &query) {
  vc_push(vc);
  for (std::vector< ref<Expr> >::const_iterator it = query.constraints.begin(), 
         ie = query.constraints.end(); it != ie; ++it)
    vc_assertFormula(vc, builder->construct(*it));
  assert(query.expr == ref<Expr>(0, Expr::Bool) &&
         "Unexpected expression in query!");

  char *buffer;
  unsigned long length;
  vc_printQueryStateToBuffer(vc, builder->getFalse(), 
                             &buffer, &length, false);
  vc_pop(vc);

  return buffer;
}

bool STPSolverImpl::computeTruth(const Query& query,
                                 bool &isValid) {
  std::vector<const Array*> objects;
  std::vector< std::vector<unsigned char> > values;
  bool hasSolution;

  if (!computeInitialValues(query, objects, values, hasSolution))
    return false;

  isValid = !hasSolution;
  return true;
}

bool STPSolverImpl::computeValue(const Query& query,
                                 ref<Expr> &result) {
  std::vector<const Array*> objects;
  std::vector< std::vector<unsigned char> > values;
  bool hasSolution;

  // Find the object used in the expression, and compute an assignment
  // for them.
  findSymbolicObjects(query.expr, objects);
  if (!computeInitialValues(query.withFalse(), objects, values, hasSolution))
    return false;
  assert(hasSolution && "state has invalid constraint set");
  
  // Evaluate the expression with the computed assignment.
  Assignment a(objects, values);
  result = a.evaluate(query.expr);

  return true;
}

static void runAndGetCex(::VC vc, STPBuilder *builder, ::VCExpr q,
                   const std::vector<const Array*> &objects,
                   std::vector< std::vector<unsigned char> > &values,
                   bool &hasSolution) {
  // XXX I want to be able to timeout here, safely
  hasSolution = !vc_query(vc, q);

  if (hasSolution) {
    values.reserve(objects.size());
    for (std::vector<const Array*>::const_iterator
           it = objects.begin(), ie = objects.end(); it != ie; ++it) {
      const Array *array = *it;
      std::vector<unsigned char> data;
      
      data.reserve(array->size);
      for (unsigned offset = 0; offset < array->size; offset++) {
        ExprHandle counter = 
          vc_getCounterExample(vc, builder->getInitialRead(array, offset));
        unsigned char val = getBVUnsigned(counter);
        data.push_back(val);
      }
      
      values.push_back(data);
    }
  }
}

static void stpTimeoutHandler(int x) {
  _exit(52);
}

static bool runAndGetCexForked(::VC vc, 
                               STPBuilder *builder,
                               ::VCExpr q,
                               const std::vector<const Array*> &objects,
                               std::vector< std::vector<unsigned char> >
                                 &values,
                               bool &hasSolution,
                               double timeout) {
  unsigned char *pos = shared_memory_ptr;
  unsigned sum = 0;
  for (std::vector<const Array*>::const_iterator
         it = objects.begin(), ie = objects.end(); it != ie; ++it)
    sum += (*it)->size;
  assert(sum<shared_memory_size && "not enough shared memory for counterexample");

  fflush(stdout);
  fflush(stderr);
  int pid = fork();
  if (pid==-1) {
    fprintf(stderr, "error: fork failed (for STP)");
    return false;
  }

  if (pid == 0) {
    if (timeout) {
      ::alarm(0); /* Turn off alarm so we can safely set signal handler */
      ::signal(SIGALRM, stpTimeoutHandler);
      ::alarm(std::max(1, (int)timeout));
    }    
    unsigned res = vc_query(vc, q);
    if (!res) {
      for (std::vector<const Array*>::const_iterator
             it = objects.begin(), ie = objects.end(); it != ie; ++it) {
        const Array *array = *it;
        for (unsigned offset = 0; offset < array->size; offset++) {
          ExprHandle counter = 
            vc_getCounterExample(vc, builder->getInitialRead(array, offset));
          *pos++ = getBVUnsigned(counter);
        }
      }
    }
    _exit(res);
  } else {
    int status;
    int res = waitpid(pid, &status, 0);
    
    if (res<0) {
      fprintf(stderr, "error: waitpid() for STP failed");
      return false;
    }
    
    // From timed_run.py: It appears that linux at least will on
    // "occasion" return a status when the process was terminated by a
    // signal, so test signal first.
    if (WIFSIGNALED(status) || !WIFEXITED(status)) {
      fprintf(stderr, "error: STP did not return successfully");
      return false;
    }

    int exitcode = WEXITSTATUS(status);
    if (exitcode==0) {
      hasSolution = true;
    } else if (exitcode==1) {
      hasSolution = false;
    } else if (exitcode==52) {
      fprintf(stderr, "error: STP timed out");
      return false;
    } else {
      fprintf(stderr, "error: STP did not return a recognized code");
      return false;
    }
    
    if (hasSolution) {
      values = std::vector< std::vector<unsigned char> >(objects.size());
      unsigned i=0;
      for (std::vector<const Array*>::const_iterator
             it = objects.begin(), ie = objects.end(); it != ie; ++it) {
        const Array *array = *it;
        std::vector<unsigned char> &data = values[i++];
        data.insert(data.begin(), pos, pos + array->size);
        pos += array->size;
      }
    }

    return true;
  }
}

bool
STPSolverImpl::computeInitialValues(const Query &query,
                                    const std::vector<const Array*> 
                                      &objects,
                                    std::vector< std::vector<unsigned char> > 
                                      &values,
                                    bool &hasSolution) {
  TimerStatIncrementer t(stats::queryTime);

  vc_push(vc);

  for (ConstraintManager::const_iterator it = query.constraints.begin(), 
         ie = query.constraints.end(); it != ie; ++it)
    vc_assertFormula(vc, builder->construct(*it));
  
  ++stats::queries;
  ++stats::queryCounterexamples;

  ExprHandle stp_e = builder->construct(query.expr);
     
  bool success;
  if (useForkedSTP) {
    success = runAndGetCexForked(vc, builder, stp_e, objects, values, 
                                 hasSolution, timeout);
  } else {
    runAndGetCex(vc, builder, stp_e, objects, values, hasSolution);
    success = true;
  }
  
  if (success) {
    if (hasSolution)
      ++stats::queriesInvalid;
    else
      ++stats::queriesValid;
  }
  
  vc_pop(vc);
  
  return success;
}