about summary refs log tree commit diff homepage
path: root/lib/Solver/Z3Solver.cpp
blob: 1cbca566a37b394604851f0274c2071f0e1c68bf (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
//===-- Z3Solver.cpp -------------------------------------------*- C++ -*-====//
//
//                     The KLEE Symbolic Virtual Machine
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "klee/Config/config.h"
#include "klee/Internal/Support/ErrorHandling.h"
#ifdef ENABLE_Z3
#include "Z3Builder.h"
#include "klee/Constraints.h"
#include "klee/Solver.h"
#include "klee/SolverImpl.h"
#include "klee/util/Assignment.h"
#include "klee/util/ExprUtil.h"

#include "llvm/Support/ErrorHandling.h"

namespace klee {

class Z3SolverImpl : public SolverImpl {
private:
  Z3Builder *builder;
  double timeout;
  SolverRunStatus runStatusCode;
  ::Z3_params solverParameters;
  // Parameter symbols
  ::Z3_symbol timeoutParamStrSymbol;

  bool internalRunSolver(const Query &,
                         const std::vector<const Array *> *objects,
                         std::vector<std::vector<unsigned char> > *values,
                         bool &hasSolution);

public:
  Z3SolverImpl();
  ~Z3SolverImpl();

  char *getConstraintLog(const Query &);
  void setCoreSolverTimeout(double _timeout) {
    assert(_timeout >= 0.0 && "timeout must be >= 0");
    timeout = _timeout;

    unsigned int timeoutInMilliSeconds = (unsigned int)((timeout * 1000) + 0.5);
    if (timeoutInMilliSeconds == 0)
      timeoutInMilliSeconds = UINT_MAX;
    Z3_params_set_uint(builder->ctx, solverParameters, timeoutParamStrSymbol,
                       timeoutInMilliSeconds);
  }

  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);
  SolverRunStatus
  handleSolverResponse(::Z3_solver theSolver, ::Z3_lbool satisfiable,
                       const std::vector<const Array *> *objects,
                       std::vector<std::vector<unsigned char> > *values,
                       bool &hasSolution);
  SolverRunStatus getOperationStatusCode();
};

Z3SolverImpl::Z3SolverImpl()
    : builder(new Z3Builder(/*autoClearConstructCache=*/false)), timeout(0.0),
      runStatusCode(SOLVER_RUN_STATUS_FAILURE) {
  assert(builder && "unable to create Z3Builder");
  solverParameters = Z3_mk_params(builder->ctx);
  Z3_params_inc_ref(builder->ctx, solverParameters);
  timeoutParamStrSymbol = Z3_mk_string_symbol(builder->ctx, "timeout");
  setCoreSolverTimeout(timeout);
}

Z3SolverImpl::~Z3SolverImpl() {
  Z3_params_dec_ref(builder->ctx, solverParameters);
  delete builder;
}

Z3Solver::Z3Solver() : Solver(new Z3SolverImpl()) {}

char *Z3Solver::getConstraintLog(const Query &query) {
  return impl->getConstraintLog(query);
}

void Z3Solver::setCoreSolverTimeout(double timeout) {
  impl->setCoreSolverTimeout(timeout);
}

char *Z3SolverImpl::getConstraintLog(const Query &query) {
  std::vector<Z3ASTHandle> assumptions;
  for (std::vector<ref<Expr> >::const_iterator it = query.constraints.begin(),
                                               ie = query.constraints.end();
       it != ie; ++it) {
    assumptions.push_back(builder->construct(*it));
  }
  ::Z3_ast *assumptionsArray = NULL;
  int numAssumptions = query.constraints.size();
  if (numAssumptions) {
    assumptionsArray = (::Z3_ast *)malloc(sizeof(::Z3_ast) * numAssumptions);
    for (int index = 0; index < numAssumptions; ++index) {
      assumptionsArray[index] = (::Z3_ast)assumptions[index];
    }
  }

  // KLEE Queries are validity queries i.e.
  // ∀ X Constraints(X) → query(X)
  // but Z3 works in terms of satisfiability so instead we ask the
  // the negation of the equivalent i.e.
  // ∃ X Constraints(X) ∧ ¬ query(X)
  Z3ASTHandle formula = Z3ASTHandle(
      Z3_mk_not(builder->ctx, builder->construct(query.expr)), builder->ctx);

  ::Z3_string result = Z3_benchmark_to_smtlib_string(
      builder->ctx,
      /*name=*/"Emited by klee::Z3SolverImpl::getConstraintLog()",
      /*logic=*/"",
      /*status=*/"unknown",
      /*attributes=*/"",
      /*num_assumptions=*/numAssumptions,
      /*assumptions=*/assumptionsArray,
      /*formula=*/formula);

  if (numAssumptions)
    free(assumptionsArray);
  // Client is responsible for freeing the returned C-string
  return strdup(result);
}

bool Z3SolverImpl::computeTruth(const Query &query, bool &isValid) {
  bool hasSolution;
  bool status =
      internalRunSolver(query, /*objects=*/NULL, /*values=*/NULL, hasSolution);
  isValid = !hasSolution;
  return status;
}

bool Z3SolverImpl::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;
}

bool Z3SolverImpl::computeInitialValues(
    const Query &query, const std::vector<const Array *> &objects,
    std::vector<std::vector<unsigned char> > &values, bool &hasSolution) {
  return internalRunSolver(query, &objects, &values, hasSolution);
}

bool Z3SolverImpl::internalRunSolver(
    const Query &query, const std::vector<const Array *> *objects,
    std::vector<std::vector<unsigned char> > *values, bool &hasSolution) {
  TimerStatIncrementer t(stats::queryTime);
  // TODO: Does making a new solver for each query have a performance
  // impact vs making one global solver and using push and pop?
  // TODO: is the "simple_solver" the right solver to use for
  // best performance?
  Z3_solver theSolver = Z3_mk_simple_solver(builder->ctx);
  Z3_solver_inc_ref(builder->ctx, theSolver);
  Z3_solver_set_params(builder->ctx, theSolver, solverParameters);

  runStatusCode = SOLVER_RUN_STATUS_FAILURE;

  for (ConstraintManager::const_iterator it = query.constraints.begin(),
                                         ie = query.constraints.end();
       it != ie; ++it) {
    Z3_solver_assert(builder->ctx, theSolver, builder->construct(*it));
  }
  ++stats::queries;
  if (objects)
    ++stats::queryCounterexamples;

  Z3ASTHandle z3QueryExpr =
      Z3ASTHandle(builder->construct(query.expr), builder->ctx);

  // KLEE Queries are validity queries i.e.
  // ∀ X Constraints(X) → query(X)
  // but Z3 works in terms of satisfiability so instead we ask the
  // negation of the equivalent i.e.
  // ∃ X Constraints(X) ∧ ¬ query(X)
  Z3_solver_assert(
      builder->ctx, theSolver,
      Z3ASTHandle(Z3_mk_not(builder->ctx, z3QueryExpr), builder->ctx));

  ::Z3_lbool satisfiable = Z3_solver_check(builder->ctx, theSolver);
  runStatusCode = handleSolverResponse(theSolver, satisfiable, objects, values,
                                       hasSolution);

  Z3_solver_dec_ref(builder->ctx, theSolver);
  // Clear the builder's cache to prevent memory usage exploding.
  // By using ``autoClearConstructCache=false`` and clearning now
  // we allow Z3_ast expressions to be shared from an entire
  // ``Query`` rather than only sharing within a single call to
  // ``builder->construct()``.
  builder->clearConstructCache();

  if (runStatusCode == SolverImpl::SOLVER_RUN_STATUS_SUCCESS_SOLVABLE ||
      runStatusCode == SolverImpl::SOLVER_RUN_STATUS_SUCCESS_UNSOLVABLE) {
    if (hasSolution) {
      ++stats::queriesInvalid;
    } else {
      ++stats::queriesValid;
    }
    return true; // success
  }
  return false; // failed
}

SolverImpl::SolverRunStatus Z3SolverImpl::handleSolverResponse(
    ::Z3_solver theSolver, ::Z3_lbool satisfiable,
    const std::vector<const Array *> *objects,
    std::vector<std::vector<unsigned char> > *values, bool &hasSolution) {
  switch (satisfiable) {
  case Z3_L_TRUE: {
    hasSolution = true;
    if (!objects) {
      // No assignment is needed
      assert(values == NULL);
      return SolverImpl::SOLVER_RUN_STATUS_SUCCESS_SOLVABLE;
    }
    assert(values && "values cannot be nullptr");
    ::Z3_model theModel = Z3_solver_get_model(builder->ctx, theSolver);
    assert(theModel && "Failed to retrieve model");
    Z3_model_inc_ref(builder->ctx, theModel);
    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++) {
        // We can't use Z3ASTHandle here so have to do ref counting manually
        ::Z3_ast arrayElementExpr;
        Z3ASTHandle initial_read = builder->getInitialRead(array, offset);

        bool successfulEval =
            Z3_model_eval(builder->ctx, theModel, initial_read,
                          /*model_completion=*/Z3_TRUE, &arrayElementExpr);
        assert(successfulEval && "Failed to evaluate model");
        Z3_inc_ref(builder->ctx, arrayElementExpr);
        assert(Z3_get_ast_kind(builder->ctx, arrayElementExpr) ==
                   Z3_NUMERAL_AST &&
               "Evaluated expression has wrong sort");

        int arrayElementValue = 0;
        bool successGet = Z3_get_numeral_int(builder->ctx, arrayElementExpr,
                                             &arrayElementValue);
        assert(successGet && "failed to get value back");
        assert(arrayElementValue >= 0 && arrayElementValue <= 255 &&
               "Integer from model is out of range");
        data.push_back(arrayElementValue);
        Z3_dec_ref(builder->ctx, arrayElementExpr);
      }
      values->push_back(data);
    }

    Z3_model_dec_ref(builder->ctx, theModel);
    return SolverImpl::SOLVER_RUN_STATUS_SUCCESS_SOLVABLE;
  }
  case Z3_L_FALSE:
    hasSolution = false;
    return SolverImpl::SOLVER_RUN_STATUS_SUCCESS_UNSOLVABLE;
  case Z3_L_UNDEF: {
    ::Z3_string reason =
        ::Z3_solver_get_reason_unknown(builder->ctx, theSolver);
    if (strcmp(reason, "timeout") == 0 || strcmp(reason, "canceled") == 0) {
      return SolverImpl::SOLVER_RUN_STATUS_TIMEOUT;
    }
    if (strcmp(reason, "unknown") == 0) {
      return SolverImpl::SOLVER_RUN_STATUS_FAILURE;
    }
    klee_warning("Unexpected solver failure. Reason is \"%s,\"\n", reason);
    abort();
  }
  default:
    llvm_unreachable("unhandled Z3 result");
  }
}

SolverImpl::SolverRunStatus Z3SolverImpl::getOperationStatusCode() {
  return runStatusCode;
}
}
#endif // ENABLE_Z3