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//===- FuzzerDataFlowTrace.cpp - DataFlowTrace ---*- C++ -* ===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// fuzzer::DataFlowTrace
//===----------------------------------------------------------------------===//
#include "FuzzerDataFlowTrace.h"
#include "FuzzerIO.h"
#include "FuzzerRandom.h"
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <string>
#include <vector>
namespace fuzzer {
static const char *kFunctionsTxt = "functions.txt";
bool BlockCoverage::AppendCoverage(const std::string &S) {
std::stringstream SS(S);
return AppendCoverage(SS);
}
// Coverage lines have this form:
// CN X Y Z T
// where N is the number of the function, T is the total number of instrumented
// BBs, and X,Y,Z, if present, are the indecies of covered BB.
// BB #0, which is the entry block, is not explicitly listed.
bool BlockCoverage::AppendCoverage(std::istream &IN) {
std::string L;
while (std::getline(IN, L, '\n')) {
if (L.empty() || L[0] != 'C')
continue; // Ignore non-coverage lines.
std::stringstream SS(L.c_str() + 1);
size_t FunctionId = 0;
SS >> FunctionId;
Vector<uint32_t> CoveredBlocks;
while (true) {
uint32_t BB = 0;
SS >> BB;
if (!SS) break;
CoveredBlocks.push_back(BB);
}
if (CoveredBlocks.empty()) return false;
uint32_t NumBlocks = CoveredBlocks.back();
CoveredBlocks.pop_back();
for (auto BB : CoveredBlocks)
if (BB >= NumBlocks) return false;
auto It = Functions.find(FunctionId);
auto &Counters =
It == Functions.end()
? Functions.insert({FunctionId, Vector<uint32_t>(NumBlocks)})
.first->second
: It->second;
if (Counters.size() != NumBlocks) return false; // wrong number of blocks.
Counters[0]++;
for (auto BB : CoveredBlocks)
Counters[BB]++;
}
return true;
}
// Assign weights to each function.
// General principles:
// * any uncovered function gets weight 0.
// * a function with lots of uncovered blocks gets bigger weight.
// * a function with a less frequently executed code gets bigger weight.
Vector<double> BlockCoverage::FunctionWeights(size_t NumFunctions) const {
Vector<double> Res(NumFunctions);
for (auto It : Functions) {
auto FunctionID = It.first;
auto Counters = It.second;
auto &Weight = Res[FunctionID];
Weight = 1000.; // this function is covered.
Weight /= SmallestNonZeroCounter(Counters);
Weight *= NumberOfUncoveredBlocks(Counters) + 1; // make sure it's not 0.
}
return Res;
}
void DataFlowTrace::ReadCoverage(const std::string &DirPath) {
Vector<SizedFile> Files;
GetSizedFilesFromDir(DirPath, &Files);
for (auto &SF : Files) {
auto Name = Basename(SF.File);
if (Name == kFunctionsTxt) continue;
std::ifstream IF(SF.File);
Coverage.AppendCoverage(IF);
}
}
void DataFlowTrace::Init(const std::string &DirPath,
std::string *FocusFunction,
Random &Rand) {
if (DirPath.empty()) return;
Printf("INFO: DataFlowTrace: reading from '%s'\n", DirPath.c_str());
Vector<SizedFile> Files;
GetSizedFilesFromDir(DirPath, &Files);
std::string L;
size_t FocusFuncIdx = SIZE_MAX;
Vector<std::string> FunctionNames;
// Read functions.txt
std::ifstream IF(DirPlusFile(DirPath, kFunctionsTxt));
size_t NumFunctions = 0;
while (std::getline(IF, L, '\n')) {
FunctionNames.push_back(L);
NumFunctions++;
if (*FocusFunction == L)
FocusFuncIdx = NumFunctions - 1;
}
if (*FocusFunction == "auto") {
// AUTOFOCUS works like this:
// * reads the coverage data from the DFT files.
// * assigns weights to functions based on coverage.
// * chooses a random function according to the weights.
ReadCoverage(DirPath);
auto Weights = Coverage.FunctionWeights(NumFunctions);
Vector<double> Intervals(NumFunctions + 1);
std::iota(Intervals.begin(), Intervals.end(), 0);
auto Distribution = std::piecewise_constant_distribution<double>(
Intervals.begin(), Intervals.end(), Weights.begin());
FocusFuncIdx = static_cast<size_t>(Distribution(Rand));
*FocusFunction = FunctionNames[FocusFuncIdx];
assert(FocusFuncIdx < NumFunctions);
Printf("INFO: AUTOFOCUS: %zd %s\n", FocusFuncIdx,
FunctionNames[FocusFuncIdx].c_str());
for (size_t i = 0; i < NumFunctions; i++) {
if (!Weights[i]) continue;
Printf(" [%zd] W %g\tBB-tot %u\tBB-cov %u\tEntryFreq %u:\t%s\n", i,
Weights[i], Coverage.GetNumberOfBlocks(i),
Coverage.GetNumberOfCoveredBlocks(i), Coverage.GetCounter(i, 0),
FunctionNames[i].c_str());
}
}
if (!NumFunctions || FocusFuncIdx == SIZE_MAX || Files.size() <= 1)
return;
// Read traces.
size_t NumTraceFiles = 0;
size_t NumTracesWithFocusFunction = 0;
for (auto &SF : Files) {
auto Name = Basename(SF.File);
if (Name == kFunctionsTxt) continue;
auto ParseError = [&](const char *Err) {
Printf("DataFlowTrace: parse error: %s\n File: %s\n Line: %s\n", Err,
Name.c_str(), L.c_str());
};
NumTraceFiles++;
// Printf("=== %s\n", Name.c_str());
std::ifstream IF(SF.File);
while (std::getline(IF, L, '\n')) {
if (!L.empty() && L[0] == 'C')
continue; // Ignore coverage.
size_t SpacePos = L.find(' ');
if (SpacePos == std::string::npos)
return ParseError("no space in the trace line");
if (L.empty() || L[0] != 'F')
return ParseError("the trace line doesn't start with 'F'");
size_t N = std::atol(L.c_str() + 1);
if (N >= NumFunctions)
return ParseError("N is greater than the number of functions");
if (N == FocusFuncIdx) {
NumTracesWithFocusFunction++;
const char *Beg = L.c_str() + SpacePos + 1;
const char *End = L.c_str() + L.size();
assert(Beg < End);
size_t Len = End - Beg;
Vector<uint8_t> V(Len);
for (size_t I = 0; I < Len; I++) {
if (Beg[I] != '0' && Beg[I] != '1')
ParseError("the trace should contain only 0 or 1");
V[I] = Beg[I] == '1';
}
Traces[Name] = V;
// Print just a few small traces.
if (NumTracesWithFocusFunction <= 3 && Len <= 16)
Printf("%s => |%s|\n", Name.c_str(), L.c_str() + SpacePos + 1);
break; // No need to parse the following lines.
}
}
}
assert(NumTraceFiles == Files.size() - 1);
Printf("INFO: DataFlowTrace: %zd trace files, %zd functions, "
"%zd traces with focus function\n",
NumTraceFiles, NumFunctions, NumTracesWithFocusFunction);
}
int CollectDataFlow(const std::string &DFTBinary, const std::string &DirPath,
const Vector<SizedFile> &CorporaFiles) {
Printf("INFO: collecting data flow for %zd files\n", CorporaFiles.size());
return 0;
}
} // namespace fuzzer
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