path: root/afl-dyninst.cc

// Binary instrumentation tool
//
// SPDX-FileCopyrightText: 2016 Aleksandar Nikolic <anikolich@sourcefire.com>
// SPDX-FileCopyrightText: 2018-2021 Marc "van Hauser" Heuse <vh@thc.org>
// SPDX-License-Identifier: Apache-2.0
//
// SPDX-FileCopyrightText: 2024 Nguyễn Gia Phong <cnx@loang.net>
// SPDX-License-Identifier: AGPL-3.0-or-later

// DyninstAPI includes
#include "BPatch.h"
#include "BPatch_flowGraph.h"
#include "BPatch_point.h"

#include <cstdlib>
#include <fcntl.h>
#include <getopt.h>
#include <iostream>
#include <sstream>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <vector>

using namespace std;
using namespace Dyninst;

// cmd line options
char *entryPointName = NULL;
int verbose = 0;

Dyninst::Address entryPoint;
set<string> todo;
set<string> runtimeLibraries;
set<string> skipAddresses;
set<string> onlyAddresses;
set<unsigned long> exitAddresses;
unsigned int bbMinSize = 10;
int bbSkip = 0, performance = 1;
bool skipMainModule = false, do_bb = true, dynfix = false;
unsigned long int insertions = 0;
uintptr_t mapaddr = 0;

BPatch_function *save_rdi;
BPatch_function *restore_rdi;

const char *functions[] = {"main", "_main", "_initproc", "_init", "start", "_start", NULL};

BPatch_function *findFuncByName(BPatch_image *appImage, char *funcName) {
  BPatch_Vector<BPatch_function *> funcs;

  if (NULL == appImage->findFunction(funcName, funcs) || !funcs.size() || NULL == funcs[0]) {
    cerr << "Failed to find " << funcName << " function." << endl;
    return NULL;
  }

  return funcs[0];
}

// insert callback to initialization function in the instrumentation library
// either at _init or at manualy specified entry point.
bool insertCallToInit(BPatch_addressSpace *appBin, BPatch_function *instIncFunc, BPatch_module *module, BPatch_function *funcInit, bool install_hack) {
  /* Find the instrumentation points */
  vector<BPatch_point *> points;
  vector<BPatch_point *> *funcEntry = funcInit->findPoint(BPatch_entry);
  BPatch_image *appImage = appBin->getImage();
  BPatchSnippetHandle *handle;

  if (NULL == funcEntry) {
    cerr << "Failed to find entry for function. " << endl;
    return false;
  }

  // THIS BLOCK IS DISABLED - dyninst is too volatile for this to work reliably
  // disabled because performance can not be greater than 2
  if (performance >= 3 && install_hack == true) {
    cout << "Inserting global variables" << endl;
    // we set up a fake map so we do not have crashes if the the forkserver
    // is not installed in _init but later for speed reasons.
    // we could also check in the bb() code if map == 0 but that would
    // cost precious instructions.
    BPatch_variableExpr *fakemap = appBin->malloc(65536);
    BPatch_constExpr fakemap_ptr(fakemap->getBaseAddr());
    BPatch_variableExpr *map = appBin->malloc(*(appImage->findType("size_t")), "map");
    BPatch_arithExpr initmap(BPatch_assign, *map, fakemap_ptr);

    appBin->insertSnippet(initmap, *funcEntry, BPatch_firstSnippet);
    BPatch_constExpr map_ptr(map->getBaseAddr());
    BPatch_variableExpr *prev_id = appBin->malloc(*(appImage->findType("size_t")), "prev_id");
    BPatch_arithExpr initprevid(BPatch_assign, *prev_id, BPatch_constExpr(0));

    appBin->insertSnippet(initprevid, *funcEntry);
    BPatch_Vector<BPatch_snippet *> instArgs;
    instArgs.push_back(&map_ptr);
    BPatch_funcCallExpr instIncExpr(*instIncFunc, instArgs);

    handle = appBin->insertSnippet(instIncExpr, *funcEntry, BPatch_callBefore, BPatch_lastSnippet);
  } else {
    BPatch_Vector<BPatch_snippet *> instArgs;
    BPatch_funcCallExpr instIncExpr(*instIncFunc, instArgs);

    handle = appBin->insertSnippet(instIncExpr, *funcEntry, BPatch_callBefore, BPatch_lastSnippet);
  }

  if (!handle) {
    cerr << "Failed to insert init callback." << endl;
    return false;
  }
  return true;
}

// inserts a callback for each basic block assigning it an instrumentation
// time 16bit random ID just as afl
bool insertBBCallback(BPatch_addressSpace *appBin, BPatch_function *curFunc, char *funcName, BPatch_function *instBBIncFunc, int *bbIndex) {
  BPatch_image *appImage = appBin->getImage();
  BPatch_flowGraph *appCFG = curFunc->getCFG();
  unsigned short randID;

  if (!appCFG) {
    cerr << "Failed to find CFG for function " << funcName << endl;
    return false;
  }

  BPatch_Set<BPatch_basicBlock *> allBlocks;
  if (!appCFG->getAllBasicBlocks(allBlocks)) {
    cerr << "Failed to find basic blocks for function " << funcName << endl;
    return false;
  } else if (allBlocks.size() == 0) {
    cerr << "No basic blocks for function " << funcName << endl;
    return false;
  }

  BPatch_Set<BPatch_basicBlock *>::iterator iter;
  for (iter = allBlocks.begin(); iter != allBlocks.end(); iter++) {
    if (*bbIndex < bbSkip || (*iter)->size() < bbMinSize) { // skip over first bbSkip bbs or below minimum size
      (*bbIndex)++;
      continue;
    }

    BPatch_point *bbEntry = (*iter)->findEntryPoint();

    if (performance >= 1) {
      if ((*iter)->isEntryBlock() == false) {
        bool good = false;

        BPatch_Vector<BPatch_basicBlock *> sources;
        (*iter)->getSources(sources);
        for (unsigned int i = 0; i < sources.size() && good == false; i++) {
          BPatch_Vector<BPatch_basicBlock *> targets;
          sources[i]->getTargets(targets);
          if (targets.size() > 1)
            good = true;
        }
        if (good == false)
          continue;
      }
    }

    unsigned long address = (*iter)->getStartAddress();

    randID = rand() % USHRT_MAX;
    if (verbose >= 1) {
      cout << "Instrumenting Basic Block 0x" << hex << address << " of " << funcName << " with size " << dec << (*iter)->size() << " with random id " << randID << "/0x" << hex << randID << endl;
    }

    if (NULL == bbEntry) {
      // warn the user, but continue
      cerr << "Failed to find entry for basic block at 0x" << hex << address << endl;
      (*bbIndex)++;
      continue;
    }

    BPatchSnippetHandle *handle;

    // level 3 is disabled
    if (performance >= 3) {
      // these are dummy instructions we overwrite later
      BPatch_variableExpr *pid = appImage->findVariable("prev_id");
      BPatch_arithExpr new_prev_id(BPatch_assign, *pid, BPatch_arithExpr(BPatch_divide, BPatch_constExpr(8), BPatch_constExpr(2)));

      handle = appBin->insertSnippet(new_prev_id, *bbEntry, BPatch_lastSnippet);
      BPatch_variableExpr *map = appImage->findVariable("map");
      BPatch_variableExpr *pid2 = appImage->findVariable("prev_id");
      BPatch_arithExpr map_idx(BPatch_arithExpr(BPatch_plus, *map, BPatch_arithExpr(BPatch_divide, *pid2, BPatch_constExpr(2))));

      if (mapaddr == 0) {
        printf("Map for AFL is installed at: %p\n", (void *)map->getBaseAddr());
        mapaddr = (uintptr_t)map->getBaseAddr();
      }
      handle = appBin->insertSnippet(map_idx, *bbEntry, BPatch_firstSnippet);
    } else {
      BPatch_Vector<BPatch_snippet *> instArgs1;
      BPatch_Vector<BPatch_snippet *> instArgs;
      BPatch_constExpr bbId(randID);

      instArgs.push_back(&bbId);
      BPatch_funcCallExpr instIncExpr(*instBBIncFunc, instArgs);


      handle = appBin->insertSnippet(instIncExpr, *bbEntry, BPatch_callBefore);
    }

    if (!handle) {
      // warn the user, but continue to next bb
      cerr << "Failed to insert instrumention in basic block at 0x" << hex << address << endl;
      (*bbIndex)++;
      continue;
    } else
      insertions++;

    (*bbIndex)++;
  }

  return true;
}

int main(int argc, char **argv) {
  static const char *const USAGE = "Usage: afl-dyninst"
    " [OPTIONS]... INFILE OUTFILE\n\n"
    "Instrument binary to be fuzzed by AFL.\n\n"
    "Options:\n"
    "  -h, --help               show this help message and exit\n"
    "      --version            show program's version number and exit\n"
    "  -e ADDR, --entry=ADDR    "
    "entry point address to patch (required for stripped binaries)\n"
    "  -E ADDR, --exit=ADDR     force exit(0) at this address (multiple use)\n"
    "  -D                       "
    "instrument only a simple fork server and also forced exit functions\n"
    "  -r PATH, --library=PATH  runtime library to instrument (multiple use)\n"
    "  -I NAME, --include=NAME  "
    "instrument only this function and nothing else (multiple use)\n"
    "  -S NAME, --exclude=NAME  "
    "do not instrument this function (multiple use)\n"
    "  -m N, --min-size=N       "
    "minimum size of a basic bock to instrument (default to 10)\n"
    "  -s N, --skip=N           "
    "number of initial basic blocks to skip in binary\n"
    "  -v, --verbose            enable verbose output (up to 3 levels)\n"
    "  -x                       "
    "experimental performance mode (multiple use, ~25-50% speed improvement)\n";

  int c;
  int option_index = 0;
  const static struct option long_options[] = {
    {"help", no_argument, NULL, 'h'},
    {"entry", required_argument, NULL, 'e'},
    {"exit", required_argument, NULL, 'E'},
    {"library", required_argument, NULL, 'r'},
    {"include", required_argument, NULL, 'I'},
    {"exclude", required_argument, NULL, 'S'},
    {"min-size", required_argument, NULL, 'm'},
    {"skip", required_argument, NULL, 's'},
    {"verbose", no_argument, NULL, 'v'},
    {"version", no_argument, NULL, 0},
    {NULL, 0, NULL, 0},
  };
  while ((c = getopt_long(argc, argv, "he:E:Dr:I:S:m:s:vx",
                          long_options, &option_index)) != -1) {
    switch (c) {
    case 0:
      if (strcmp(long_options[option_index].name, "version") == 0) {
        std::cout << "afl-dyninst " VERSION "\n";
        return EXIT_SUCCESS;
      }
      __builtin_unreachable();
    case 'h':
      std::cout << USAGE;
      return EXIT_SUCCESS;
    case 'e':
      if ((entryPoint = strtoul(optarg, NULL, 16)) < 0x1000)
        entryPointName = optarg;
      break;
    case 'E':
      exitAddresses.insert(strtoul(optarg, NULL, 16));
      break;
    case 'D':
      do_bb = false;
      break;
    case 'r':
      runtimeLibraries.insert(optarg);
      break;
    case 'I':
      onlyAddresses.insert(optarg);
      break;
    case 'S':
      skipAddresses.insert(optarg);
      break;
    case 'm':
      bbMinSize = atoi(optarg);
      break;
    case 's':
      bbSkip = atoi(optarg);
      break;
    case 'v':
      verbose++;
      break;
    case 'x':
      performance++;
      if (performance > 2) {
//#if ( __amd64__ || __x86_64__ )
//        std::cerr << "Warning: performance level 3 is currently totally experimental\n";
//#else
//        std::cerr << "Warning: maximum performance level for non-intelx64 x86 is 2\n";
        performance = 2;
//#endif
      }
      break;
    default:
      return EXIT_FAILURE;
    }
  }
  if (optind >= argc) {
    std::cerr << USAGE;
    return EXIT_FAILURE;
  }
  const char *const originalBinary = argv[optind];
  if (++optind >= argc) {
    std::cerr << USAGE;
    return EXIT_FAILURE;
  }
  const char *const instrumentedBinary = argv[optind];

  BPatch bpatch;

  if (performance >= 2) {
    bpatch.setSaveFPR(false);
    bpatch.setTrampRecursive(true);
  }

  const char *dyninstapi_rt_lib = getenv("DYNINSTAPI_RT_LIB");
  if (setenv("DYNINSTAPI_RT_LIB", DYNINSTAPI_RT_LIB, true) != 0) {
    cerr << "Failed to set DYNINSTAPI_RT_LIB\n"; // TODO: explain
    return EXIT_FAILURE;
  }
  BPatch_addressSpace *appBin = bpatch.openBinary(originalBinary, false);
  if (dyninstapi_rt_lib == NULL)
    unsetenv("DYNINSTAPI_RT_LIB");
  else
    setenv("DYNINSTAPI_RT_LIB", dyninstapi_rt_lib, true);
  if (appBin == NULL) {
    cerr << "Failed to open binary" << endl;
    return EXIT_FAILURE;
  }

  BPatch_image *appImage = appBin->getImage();

  // get and iterate over all modules, instrumenting only the default and manually specified ones
  vector<BPatch_module *> *modules = appImage->getModules();
  vector<BPatch_module *>::iterator moduleIter;
  vector<BPatch_function *> *funcsInModule;
  BPatch_module *defaultModule = NULL, *firstModule = NULL;
  string defaultModuleName;

  // look for _init
  char *func2patch = NULL;
  if (defaultModuleName.empty()) {
    for (unsigned loop = 0; functions[loop] != NULL && func2patch == NULL; loop++) {
      for (moduleIter = modules->begin(); moduleIter != modules->end(); ++moduleIter) {
        vector<BPatch_function *>::iterator funcsIterator;
        char moduleName[1024];

        if (firstModule == NULL)
          firstModule = (*moduleIter);
        (*moduleIter)->getName(moduleName, 1024);
        funcsInModule = (*moduleIter)->getProcedures();
        if (verbose >= 2)
          cout << "Looking for init function " << functions[loop] << " in " << moduleName << endl;
        for (funcsIterator = funcsInModule->begin(); funcsIterator != funcsInModule->end(); ++funcsIterator) {
          char funcName[1024];

          (*funcsIterator)->getName(funcName, 1024);
          if (verbose >= 3 && loop == 0)
            printf("module: %s function: %s\n", moduleName, funcName);
          if (string(funcName) == string(functions[loop])) {
            func2patch = (char *)functions[loop];
            defaultModuleName = string(moduleName);
            defaultModule = (*moduleIter);
            if (verbose >= 1) {
              cout << "Found " << func2patch << " in " << moduleName << endl;
            }
            break;
          }
        }
        if (!defaultModuleName.empty())
          break;
      }
      if (func2patch != NULL)
        break;
    }
  }
  // last resort, by name of the binary
  if (defaultModuleName.empty())
    defaultModuleName = string(originalBinary).substr(string(originalBinary).find_last_of("\\/") + 1);
  if (defaultModule == NULL)
    defaultModule = firstModule;

  if (!appBin->loadLibrary(AFL_DYNINST_LIB)) {
    cerr << "Failed to open instrumentation library " << AFL_DYNINST_LIB << endl;
    cerr << "It needs to be located in the current working directory." << endl;
    return EXIT_FAILURE;
  }

  /* Find code coverage functions in the instrumentation library */
  BPatch_function *initAflForkServer;

  BPatch_function *bbCallback = findFuncByName(appImage, (char *)"bbCallback");
  BPatch_function *forceCleanExit = findFuncByName(appImage, (char *)"forceCleanExit");

  if (do_bb == true) {
    if (performance >= 3)
      initAflForkServer = findFuncByName(appImage, (char *)"initAflForkServerVar");
    else
      initAflForkServer = findFuncByName(appImage, (char *)"initAflForkServer");
  } else
    initAflForkServer = findFuncByName(appImage, (char *)"initOnlyAflForkServer");

  if (!initAflForkServer || !bbCallback || !forceCleanExit) {
    cerr << "Instrumentation library lacks callbacks!" << endl;
    return EXIT_FAILURE;
  }

  int bbIndex = 0;

  // if an entrypoint was set then find function, else find _init
  BPatch_function *funcToPatch = NULL;

  if (entryPoint == 0 && entryPointName == NULL) {
    if (func2patch == NULL) {
      cerr << "Couldn't locate _init, specify entry point manually with -e 0xaddr" << endl;
      return EXIT_FAILURE;
    }
    BPatch_Vector<BPatch_function *> funcs;
    defaultModule->findFunction(func2patch, funcs);
    if (!funcs.size()) {
      cerr << "Couldn't locate _init, specify entry point manually with -e 0xaddr" << endl;
      return EXIT_FAILURE;
    }
    // there should really be only one
    funcToPatch = funcs[0];
  } else {
    if (entryPointName != NULL) {
      for (moduleIter = modules->begin(); moduleIter != modules->end() && funcToPatch == 0; ++moduleIter) {
        BPatch_Vector<BPatch_function *> funcs;
        (*moduleIter)->findFunction(entryPointName, funcs);
        if (funcs.size() > 0) {
          char moduleName[1024];

          funcToPatch = funcs[0];
          defaultModule = (*moduleIter);
          defaultModule->getName(moduleName, 1024);
          defaultModuleName = string(moduleName);
          printf("Found entypoint %s in module %s\n", entryPointName, moduleName);
          break;
        }
      }
    }
    if (!funcToPatch) {
      if (verbose > 1)
        printf("Looking for entrypoint %p\n", (char *)entryPoint);
      funcToPatch = defaultModule->findFunctionByEntry(entryPoint);
      if (!funcToPatch && defaultModule != firstModule) {
        funcToPatch = firstModule->findFunctionByEntry(entryPoint);
        if (funcToPatch)
          defaultModule = firstModule;
      }
      if (!funcToPatch) { // ok lets go hardcore ...
        if (verbose > 1)
          printf("OK we did not find the entrypoint so far, lets dig deeper ...\n");
        for (moduleIter = modules->begin(); moduleIter != modules->end() && funcToPatch != NULL; ++moduleIter) {
          vector<BPatch_function *>::iterator funcsIterator;
          funcToPatch = (*moduleIter)->findFunctionByEntry(entryPoint);
          if (funcToPatch)
            defaultModule = (*moduleIter);
        }
      }
      if (funcToPatch && verbose >= 1) {
        char moduleName[1024];

        defaultModule->getName(moduleName, 1024);
        defaultModuleName = string(moduleName);
        printf("Found entypoint %p in module %s\n", (void *)entryPoint, moduleName);
      }
    }
  }
  if (!funcToPatch) {
    cerr << "Couldn't locate function at given entry point. " << endl;
    cerr << "Try: readelf -ls " << originalBinary << " | egrep 'Entry|FUNC.*GLOBAL.*DEFAULT' | egrep -v '@|UND'" << endl;
    return EXIT_FAILURE;
  }
  if (!insertCallToInit(appBin, initAflForkServer, defaultModule, funcToPatch, true)) {
    cerr << "Could not insert init callback at given entry point." << endl;
    return EXIT_FAILURE;
  }

  for (moduleIter = modules->begin(); moduleIter != modules->end(); ++moduleIter) {
    char moduleName[1024];

    (*moduleIter)->getName(moduleName, 1024);
    if ((*moduleIter)->isSharedLib())
      continue;

    if (string(moduleName).find(defaultModuleName) != string::npos) {
      if (skipMainModule)
        continue;
    }

    if (do_bb == true) {
      cout << "Instrumenting module: " << moduleName << endl;
      vector<BPatch_function *> *allFunctions = (*moduleIter)->getProcedures();
      vector<BPatch_function *>::iterator funcIter;
      // iterate over all functions in the module
      for (funcIter = allFunctions->begin(); funcIter != allFunctions->end(); ++funcIter) {
        BPatch_function *curFunc = *funcIter;
        char funcName[1024];
        int do_patch = 1;

        curFunc->getName(funcName, 1024);
        if (string(funcName) == string("_init") || string(funcName) == string("__libc_csu_init") || string(funcName) == string("_start")) {
          if (verbose)
            cout << "Skipping instrumenting function " << funcName << endl;
          continue; // here's a bug on hlt // XXX: check what happens if removed
        }
        if (!skipAddresses.empty()) {
          set<string>::iterator saiter;
          for (saiter = skipAddresses.begin(); saiter != skipAddresses.end() && do_patch == 1; saiter++)
            if (*saiter == string(funcName))
              do_patch = 0;
          if (do_patch == 0) {
            cout << "Skipping instrumenting function " << funcName << endl;
            continue;
          }
        }
        if (!onlyAddresses.empty()) {
          do_patch = 0;
          set<string>::iterator saiter;
          for (saiter = onlyAddresses.begin(); saiter != onlyAddresses.end() && do_patch == 1; saiter++)
            if (*saiter == string(funcName))
              do_patch = 1;
          if (do_patch == 0) {
            cout << "Skipping instrumenting function " << funcName << endl;
            continue;
          }
        }
        insertBBCallback(appBin, curFunc, funcName, bbCallback, &bbIndex);
      }
    }
  }

  if (!exitAddresses.empty()) {
    cout << "Instrumenting forced exit addresses." << endl;
    set<unsigned long>::iterator uliter;

    for (uliter = exitAddresses.begin(); uliter != exitAddresses.end(); uliter++) {
      if (*uliter > 0 && (signed long)*uliter != -1) {
        funcToPatch = defaultModule->findFunctionByEntry(*uliter);
        if (!funcToPatch) {
          cerr << "Could not find enty point 0x" << hex << *uliter << " (continuing)" << endl;
        } else {
          if (!insertCallToInit(appBin, forceCleanExit, defaultModule, funcToPatch, false))
            cerr << "Could not insert force clean exit callback at 0x" << hex << *uliter << " (continuing)" << endl;
        }
      }
    }
  }

  // Output the instrumented binary
  BPatch_binaryEdit *appBinr = dynamic_cast<BPatch_binaryEdit *>(appBin);

  if (!appBinr->writeFile(instrumentedBinary)) {
    cerr << "Failed to write output file: " << instrumentedBinary << endl;
    return EXIT_FAILURE;
  }
  todo.insert(instrumentedBinary);

  if (!runtimeLibraries.empty()) {
    cout << "Instrumenting runtime libraries." << endl;
    set<string>::iterator rtLibIter;
    for (rtLibIter = runtimeLibraries.begin(); rtLibIter != runtimeLibraries.end(); rtLibIter++) {
      BPatch_addressSpace *libBin = bpatch.openBinary((*rtLibIter).c_str(), false);

      if (libBin == NULL) {
        cerr << "Failed to open binary " << *rtLibIter << endl;
        return EXIT_FAILURE;
      }
      BPatch_image *libImg = libBin->getImage();

      vector<BPatch_module *> *modules = libImg->getModules();
      moduleIter = modules->begin();
      for (; moduleIter != modules->end(); ++moduleIter) {
        char moduleName[1024];

        (*moduleIter)->getName(moduleName, 1024);
        cout << "Instrumenting module: " << moduleName << endl;
        vector<BPatch_function *> *allFunctions = (*moduleIter)->getProcedures();
        vector<BPatch_function *>::iterator funcIter;
        // iterate over all functions in the module
        for (funcIter = allFunctions->begin(); funcIter != allFunctions->end(); ++funcIter) {
          BPatch_function *curFunc = *funcIter;
          char funcName[1024];
          int do_patch = 1;

          curFunc->getName(funcName, 1024);
          if (string(funcName) == string("_init") || string(funcName) == string("__libc_csu_init") || string(funcName) == string("_start"))
            continue;
          if (!skipAddresses.empty()) {
            set<string>::iterator saiter;
            for (saiter = skipAddresses.begin(); saiter != skipAddresses.end() && do_patch == 1; saiter++)
              if (*saiter == string(funcName))
                do_patch = 0;
            if (do_patch == 0) {
              cout << "Skipping instrumenting function " << funcName << endl;
              continue;
            }
          }

          insertBBCallback(libBin, curFunc, funcName, bbCallback, &bbIndex);
        }
      }
      appBinr = dynamic_cast<BPatch_binaryEdit *>(libBin);
      if (!appBinr->writeFile((*rtLibIter + ".ins").c_str())) {
        cerr << "Failed to write output file: " << (*rtLibIter + ".ins").c_str() << endl;
        return EXIT_FAILURE;
      } else {
        cout << "Saved the instrumented library to " << (*rtLibIter + ".ins").c_str() << "." << endl;
        todo.insert(*rtLibIter + ".ins");
      }
    }
  }

  printf("Did a total of %lu basic block insertions\n", insertions);

  if (performance >= 3) {
    int fd;
    struct stat st;
    uint64_t i, found = 0;
    unsigned char *ptr;

    unsigned char snip1[] = {0x00, 0x00, 0x71, 0x00, 0x00, 0x00, 0x00, 0x00};
    unsigned char snip2[] = {0x08, 0x00, 0x71, 0x00, 0x00, 0x00, 0x00, 0x00};
    unsigned char fullsnip[] = {0x53, 0x50, 0x41, 0x52, 0x48, 0xBB, 0x00, 0x00, 0x71, 0x00, 0x00, 0x00, 0x00, 0x00, 0x48, 0x8b, 0x03, 0x48, 0x85, 0xc0, 0x74, 0x28, 0x49, 0xBA, 0x08, 0x00, 0x71, 0x00, 0x00, 0x00, 0x00, 0x00, 0x66, 0x41, 0x8b, 0x1a, 0x66, 0x81, 0xf3, 0x99, 0x99, 0x48, 0x0f, 0xb7, 0xdb, 0x80, 0x04, 0x18, 0x01, 0x66, 0x41, 0x8b, 0x1a, 0x66, 0xd1, 0xfb, 0x66, 0x41, 0x89, 0x1a, 0x41, 0x5a, 0x58, 0x5b, 0x90, 0x90, 0x90, 0x90};
    memcpy(snip1, (char *)&mapaddr, sizeof(mapaddr));
    memcpy(fullsnip + 6, (char *)&mapaddr, sizeof(mapaddr));
    mapaddr += sizeof(mapaddr);
    memcpy(snip2, (char *)&mapaddr, sizeof(mapaddr));
    memcpy(fullsnip + 24, (char *)&mapaddr, sizeof(mapaddr));
    set<string>::iterator fn;
    for (fn = todo.begin(); fn != todo.end(); fn++) {
      cout << "Reinstrumenting " << *fn << " ..." << endl;
      if ((fd = open((const char *)(fn->c_str()), O_RDWR)) == -1 || fstat(fd, &st) != 0) {
        cerr << "Error: file is gone: " << *fn << endl;
        exit(-1);
      }
      if ((size_t)st.st_size < (size_t)sizeof(fullsnip)) {
        cerr << "Error: somethings horrible wrong here with " << *fn << " ..." << endl;
        continue;
      }
      ptr = (unsigned char *)mmap(NULL, st.st_size, PROT_WRITE | PROT_READ, MAP_SHARED, fd, 0);
      for (i = 2; i < (size_t)st.st_size - (size_t)sizeof(fullsnip); i++) {
        if (memcmp(ptr + i, snip1, sizeof(snip1)) == 0 && memcmp(ptr + i + sizeof(snip1) + 4, snip2, sizeof(snip2)) == 0) {
          found++;
          fullsnip[0x27] = rand() % 256;
          fullsnip[0x28] = rand() % 256;
          memcpy(ptr + i - 2, fullsnip, sizeof(fullsnip));
        }
      }
      // printf("found %lu entries, snipsize %u\n", found, (unsigned int)sizeof(fullsnip));
      munmap((void *)ptr, st.st_size);
      close(fd);
    }
    if (found == insertions) {
      printf("SUCCESS! Performance level 3 succeeded :)\n");
    } else {
      fprintf(stderr, "Error: can not complete performance level 3, could not find all insertions (%lu of %lu).\n", found, insertions);
      exit(-1);
    }
  }
  return EXIT_SUCCESS;
}