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congo.go
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congo.go
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package congo
import (
"bytes"
"go/ast"
"go/format"
"go/token"
"go/types"
"io"
"github.com/ajalab/congo/interp"
"github.com/ajalab/congo/log"
"github.com/ajalab/congo/solver"
"golang.org/x/tools/go/ssa"
"github.com/pkg/errors"
)
// Program is a type that contains information of the target program.
type Program struct {
runnerFile *ast.File
runnerTypesInfo *types.Info
runnerPackage *ssa.Package
targetPackage *ssa.Package
congoSymbolPackage *ssa.Package
}
// ExecuteOption is a type that contains options to perform concolic execution on a target function.
type ExecuteOption struct {
MaxExec uint `key:"maxexec"`
MinCoverage float64 `key:"cover"`
}
var defaultExecuteOption = &ExecuteOption{
MaxExec: 10,
MinCoverage: 1.0,
}
// Fill fills the fields in ExecuteOption with those in src.
func (eo *ExecuteOption) Fill(src *ExecuteOption, overwrite bool) *ExecuteOption {
if eo == nil || src == nil {
return eo
}
if overwrite {
if src.MaxExec != 0 {
eo.MaxExec = src.MaxExec
}
if src.MinCoverage != 0 {
eo.MinCoverage = src.MinCoverage
}
} else {
if eo.MaxExec == 0 {
eo.MaxExec = src.MaxExec
}
if eo.MinCoverage == 0.0 {
eo.MinCoverage = src.MinCoverage
}
}
return eo
}
// Target is a type that contains the single target of concolic testing (function and set of symbols).
type Target struct {
name string
f *ssa.Function
runnerName string
symbols []ssa.Value
*ExecuteOption
}
// Congo is a type that contains the program and dict of targets
// (keys are names of target function).
type Congo struct {
program *Program
targets map[string]*Target
}
// Execute executes concolic execution.
// The iteration time is bounded by maxExec and stopped when minCoverage is accomplished.
func (c *Congo) Execute(funcName string) (*ExecuteResult, error) {
target, ok := c.targets[funcName]
if !ok {
return nil, errors.Errorf("function %s does not exist", funcName)
}
n := len(target.symbols)
solutions := make([]solver.Solution, n)
covered := make(map[*ssa.BasicBlock]struct{})
coverage := 0.0
var runResults []*RunResult
for i, symbol := range target.symbols {
solutions[i] = solver.NewIndefinite(symbol.Type())
}
for i := uint(0); i < target.MaxExec; i++ {
values := make([]interface{}, n)
// Assign a zero value if the concrete value is nil.
for j, sol := range solutions {
values[j] = sol.Concretize(zero)
}
log.Info.Printf("[%d] run: %v", i, values)
// Interpret the program with the current symbol values.
result, err := c.Run(funcName, values)
if err != nil {
log.Info.Printf("[%d] panic", i)
}
// Update the covered blocks.
nNewCoveredBlks := 0
for _, instr := range result.Instrs {
b := instr.Block()
if b.Parent() == target.f {
if _, ok := covered[b]; !ok {
covered[b] = struct{}{}
nNewCoveredBlks++
}
}
}
// Record the concrete values if new blocks are covered.
if nNewCoveredBlks > 0 {
runResults = append(runResults, &RunResult{
symbolValues: values,
returnValues: result.Return,
panicked: result.ExitCode != 0,
})
}
// Compute the coverage and exit if it exceeds the minCoverage.
// Also exit when the execution count minus one is equal to maxExec to avoid unnecessary constraint solver call.
coverage = float64(len(covered)) / float64(len(target.f.Blocks))
log.Info.Printf("[%d] coverage: %.3f", i, coverage)
if coverage >= target.MinCoverage {
log.Info.Printf("[%d] stop because the coverage criteria has been satisfied.", i)
break
}
if i == target.MaxExec-1 {
log.Info.Printf("[%d] stop because the runnign count has reached the limit", i)
}
z3Solver, err := solver.CreateZ3Solver(target.symbols, result.Instrs, result.ExitCode == 0)
if err != nil {
return nil, errors.Wrap(err, "failed to create a solver")
}
branches := z3Solver.Branches()
queue, queueAfter := make([]int, 0), make([]int, 0)
for j := len(branches) - 1; j >= 0; j-- {
branch := branches[j]
switch branch := branch.(type) {
case *solver.BranchIf:
b := branch.Other()
if _, ok := covered[b]; !ok {
queue = append(queue, j)
} else {
queueAfter = append(queueAfter, j)
}
case *solver.BranchDeref:
queue = append(queue, j)
}
}
queue = append(queue, queueAfter...)
for _, j := range queue {
log.Info.Printf("[%d] negate %d", i, j)
solutions, err = z3Solver.Solve(j)
if err == nil {
log.Info.Printf("[%d] sat %d", i, j)
break
} else if _, ok := err.(solver.UnsatError); ok {
log.Info.Printf("[%d] unsat %d", i, j)
} else {
return nil, errors.Wrap(err, "failed to solve assertions")
}
}
z3Solver.Close()
}
symbolTypes := make([]types.Type, n)
for i, symbol := range target.symbols {
symbolTypes[i] = symbol.Type()
}
return &ExecuteResult{
Coverage: coverage,
SymbolTypes: symbolTypes,
RunResults: runResults,
runnerFile: c.program.runnerFile,
runnerTypesInfo: c.program.runnerTypesInfo,
runnerPackage: c.program.runnerPackage.Pkg,
runnerFuncName: target.runnerName,
targetPackage: c.program.targetPackage.Pkg,
congoSymbolPackage: c.program.congoSymbolPackage.Pkg,
targetFuncSig: target.f.Signature,
targetFuncName: funcName,
}, nil
}
// Run runs the program by the interpreter provided by interp module.
func (c *Congo) Run(funcName string, values []interface{}) (*interp.CongoInterpResult, error) {
target, ok := c.targets[funcName]
if !ok {
return nil, errors.Errorf("function %s does not exist", funcName)
}
n := len(values)
symbolValues := make([]interp.SymbolicValue, n)
for i, symbol := range target.symbols {
symbolValues[i] = interp.SymbolicValue{
Value: values[i],
Type: symbol.Type(),
}
}
interp.CapturedOutput = new(bytes.Buffer)
mode := interp.DisableRecover // interp.EnableTracing
return interp.Interpret(
c.program.runnerPackage,
target.f,
target.runnerName,
symbolValues,
mode,
&types.StdSizes{WordSize: 8, MaxAlign: 8},
"",
[]string{},
)
}
// DumpRunnerAST dumps the runner AST file into dest.
func (c *Congo) DumpRunnerAST(dest io.Writer) error {
return format.Node(dest, token.NewFileSet(), c.program.runnerFile)
}
// DumpSSA dumps the SSA-format code into dest.
func (c *Congo) DumpSSA(dest io.Writer) error {
var err error
_, err = c.program.runnerPackage.Func("main").WriteTo(dest)
if err != nil {
return err
}
for _, target := range c.targets {
_, err = target.f.WriteTo(dest)
if err != nil {
break
}
}
return err
}
// Funcs returns the list of function names that Congo loaded as execution target.
func (c *Congo) Funcs() []string {
names := make([]string, len(c.targets))
i := 0
for name := range c.targets {
names[i] = name
i++
}
return names
}
// Target returns the target which has the given name.
func (c *Congo) Target(name string) *Target {
return c.targets[name]
}
// ExecuteResult is a type that contains the result of Execute.
// TODO(ajalab):
// ReturnValues has type []interp.value so it is meaningless to make this property public.
// We use reflection to extract values from interp.value for now.
type ExecuteResult struct {
Coverage float64 // achieved coverage.
SymbolTypes []types.Type
RunResults []*RunResult
runnerFile *ast.File
runnerTypesInfo *types.Info
runnerPackage *types.Package
runnerFuncName string
targetPackage *types.Package
congoSymbolPackage *types.Package
targetFuncSig *types.Signature
targetFuncName string
}
// RunResult is a type that contains the result of Run.
type RunResult struct {
symbolValues []interface{}
returnValues interface{}
panicked bool
}