perfprofd/perfprofdcore.cc

/*
**
** Copyright 2015, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
**     http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/

#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>
#include <string>
#include <sstream>
#include <map>
#include <set>
#include <cctype>

#include <android-base/file.h>
#include <android-base/stringprintf.h>
#include <cutils/properties.h>

#include "perfprofdcore.h"
#include "perfprofdutils.h"
#include "perf_data_converter.h"
#include "cpuconfig.h"
#include "configreader.h"

//
// Perf profiling daemon -- collects system-wide profiles using
//
//       simpleperf record -a
//
// and encodes them so that they can be uploaded by a separate service.
//

//......................................................................

//
// Output file from 'perf record'.
//
#define PERF_OUTPUT "perf.data"

//
// This enum holds the results of the "should we profile" configuration check.
//
typedef enum {

  // All systems go for profile collection.
  DO_COLLECT_PROFILE,

  // The selected configuration directory doesn't exist.
  DONT_PROFILE_MISSING_CONFIG_DIR,

  // Destination directory does not contain the semaphore file that
  // the perf profile uploading service creates when it determines
  // that the user has opted "in" for usage data collection. No
  // semaphore -> no user approval -> no profiling.
  DONT_PROFILE_MISSING_SEMAPHORE,

  // No perf executable present
  DONT_PROFILE_MISSING_PERF_EXECUTABLE,

  // We're running in the emulator, perf won't be able to do much
  DONT_PROFILE_RUNNING_IN_EMULATOR

} CKPROFILE_RESULT;

//
// Are we running in the emulator? If so, stub out profile collection
// Starts as uninitialized (-1), then set to 1 or 0 at init time.
//
static int running_in_emulator = -1;

//
// Is this a debug build ('userdebug' or 'eng')?
// Starts as uninitialized (-1), then set to 1 or 0 at init time.
//
static int is_debug_build = -1;

//
// Random number generator seed (set at startup time).
//
static unsigned short random_seed[3];

//
// SIGHUP handler. Sending SIGHUP to the daemon can be used to break it
// out of a sleep() call so as to trigger a new collection (debugging)
//
static void sig_hup(int /* signum */)
{
  W_ALOGW("SIGHUP received");
}

//
// Parse command line args. Currently you can supply "-c P" to set
// the path of the config file to P.
//
static void parse_args(int argc, char** argv)
{
  int ac;

  for (ac = 1; ac < argc; ++ac) {
    if (!strcmp(argv[ac], "-c")) {
      if (ac >= argc-1) {
        W_ALOGE("malformed command line: -c option requires argument)");
        continue;
      }
      ConfigReader::setConfigFilePath(argv[ac+1]);
      ++ac;
    } else {
      W_ALOGE("malformed command line: unknown option or arg %s)", argv[ac]);
      continue;
    }
  }
}

//
// Convert a CKPROFILE_RESULT to a string
//
const char *ckprofile_result_to_string(CKPROFILE_RESULT result)
{
  switch (result) {
    case DO_COLLECT_PROFILE:
      return "DO_COLLECT_PROFILE";
    case DONT_PROFILE_MISSING_CONFIG_DIR:
      return "missing config directory";
    case DONT_PROFILE_MISSING_SEMAPHORE:
      return "missing semaphore file";
    case DONT_PROFILE_MISSING_PERF_EXECUTABLE:
      return "missing 'perf' executable";
    case DONT_PROFILE_RUNNING_IN_EMULATOR:
      return "running in emulator";
    default: return "unknown";
  }
  return "notreached";
}

//
// Convert a PROFILE_RESULT to a string
//
const char *profile_result_to_string(PROFILE_RESULT result)
{
  switch(result) {
    case OK_PROFILE_COLLECTION:
      return "profile collection succeeded";
    case ERR_FORK_FAILED:
      return "fork() system call failed";
    case ERR_PERF_RECORD_FAILED:
      return "perf record returned bad exit status";
    case ERR_PERF_ENCODE_FAILED:
      return "failure encoding perf.data to protobuf";
    case ERR_OPEN_ENCODED_FILE_FAILED:
      return "failed to open encoded perf file";
    case ERR_WRITE_ENCODED_FILE_FAILED:
      return "write to encoded perf file failed";
    default: return "unknown";
  }
  return "notreached";
}

//
// Check to see whether we should perform a profile collection
//
static CKPROFILE_RESULT check_profiling_enabled(ConfigReader &config)
{
  //
  // Profile collection in the emulator doesn't make sense
  //
  assert(running_in_emulator != -1);
  if (running_in_emulator) {
    return DONT_PROFILE_RUNNING_IN_EMULATOR;
  }

  //
  // Check for existence of semaphore file in config directory
  //
  if (access(config.getStringValue("config_directory").c_str(), F_OK) == -1) {
    W_ALOGW("unable to open config directory %s: (%s)",
            config.getStringValue("config_directory").c_str(), strerror(errno));
    return DONT_PROFILE_MISSING_CONFIG_DIR;
  }


  // Check for existence of semaphore file
  std::string semaphore_filepath = config.getStringValue("config_directory")
                                   + "/" + SEMAPHORE_FILENAME;
  if (access(semaphore_filepath.c_str(), F_OK) == -1) {
    return DONT_PROFILE_MISSING_SEMAPHORE;
  }

  // Check for existence of simpleperf/perf executable
  std::string pp = config.getStringValue("perf_path");
  if (access(pp.c_str(), R_OK|X_OK) == -1) {
    W_ALOGW("unable to access/execute %s", pp.c_str());
    return DONT_PROFILE_MISSING_PERF_EXECUTABLE;
  }

  //
  // We are good to go
  //
  return DO_COLLECT_PROFILE;
}

bool get_booting()
{
  char propBuf[PROPERTY_VALUE_MAX];
  propBuf[0] = '\0';
  property_get("sys.boot_completed", propBuf, "");
  return (propBuf[0] != '1');
}

//
// Constructor takes a timeout (in seconds) and a child pid; If an
// alarm set for the specified number of seconds triggers, then a
// SIGKILL is sent to the child. Destructor resets alarm. Example:
//
//       pid_t child_pid = ...;
//       { AlarmHelper h(10, child_pid);
//         ... = read_from_child(child_pid, ...);
//       }
//
// NB: this helper is not re-entrant-- avoid nested use or
// use by multiple threads
//
class AlarmHelper {
 public:
  AlarmHelper(unsigned num_seconds, pid_t child)
  {
    struct sigaction sigact;
    assert(child);
    assert(child_ == 0);
    memset(&sigact, 0, sizeof(sigact));
    sigact.sa_sigaction = handler;
    sigaction(SIGALRM, &sigact, &oldsigact_);
    child_ = child;
    alarm(num_seconds);
  }
  ~AlarmHelper()
  {
    alarm(0);
    child_ = 0;
    sigaction(SIGALRM, &oldsigact_, NULL);
  }
  static void handler(int, siginfo_t *, void *);

 private:
  struct sigaction oldsigact_;
  static pid_t child_;
};

pid_t AlarmHelper::child_;

void AlarmHelper::handler(int, siginfo_t *, void *)
{
  W_ALOGW("SIGALRM timeout");
  kill(child_, SIGKILL);
}

//
// This implementation invokes "dumpsys media.camera" and inspects the
// output to determine if any camera clients are active. NB: this is
// currently disable (via config option) until the selinux issues can
// be sorted out. Another possible implementation (not yet attempted)
// would be to use the binder to call into the native camera service
// via "ICameraService".
//
bool get_camera_active()
{
  int pipefds[2];
  if (pipe2(pipefds, O_CLOEXEC) != 0) {
    W_ALOGE("pipe2() failed (%s)", strerror(errno));
    return false;
  }
  pid_t pid = fork();
  if (pid == -1) {
    W_ALOGE("fork() failed (%s)", strerror(errno));
    close(pipefds[0]);
    close(pipefds[1]);
    return false;
  } else if (pid == 0) {
    // child
    close(pipefds[0]);
    dup2(pipefds[1], fileno(stderr));
    dup2(pipefds[1], fileno(stdout));
    const char *argv[10];
    unsigned slot = 0;
    argv[slot++] = "/system/bin/dumpsys";
    argv[slot++] = "media.camera";
    argv[slot++] = nullptr;
    execvp(argv[0], (char * const *)argv);
    W_ALOGE("execvp() failed (%s)", strerror(errno));
    return false;
  }
  // parent
  AlarmHelper helper(10, pid);
  close(pipefds[1]);

  // read output
  bool have_cam = false;
  bool have_clients = true;
  std::string dump_output;
  bool result = android::base::ReadFdToString(pipefds[0], &dump_output);
  close(pipefds[0]);
  if (result) {
    std::stringstream ss(dump_output);
    std::string line;
    while (std::getline(ss,line,'\n')) {
      if (line.find("Camera module API version:") !=
          std::string::npos) {
        have_cam = true;
      }
      if (line.find("No camera module available") !=
          std::string::npos ||
          line.find("No active camera clients yet") !=
          std::string::npos) {
        have_clients = false;
      }
    }
  }

  // reap child (no zombies please)
  int st = 0;
  TEMP_FAILURE_RETRY(waitpid(pid, &st, 0));
  return have_cam && have_clients;
}

bool get_charging()
{
  std::string psdir("/sys/class/power_supply");
  DIR* dir = opendir(psdir.c_str());
  if (dir == NULL) {
    W_ALOGE("Failed to open dir %s (%s)", psdir.c_str(), strerror(errno));
    return false;
  }
  struct dirent* e;
  bool result = false;
  while ((e = readdir(dir)) != 0) {
    if (e->d_name[0] != '.') {
      std::string online_path = psdir + "/" + e->d_name + "/online";
      std::string contents;
      int value = 0;
      if (android::base::ReadFileToString(online_path.c_str(), &contents) &&
          sscanf(contents.c_str(), "%d", &value) == 1) {
        if (value) {
          result = true;
          break;
        }
      }
    }
  }
  closedir(dir);
  return result;
}

bool postprocess_proc_stat_contents(const std::string &pscontents,
                                    long unsigned *idleticks,
                                    long unsigned *remainingticks)
{
  long unsigned usertime, nicetime, systime, idletime, iowaittime;
  long unsigned irqtime, softirqtime;

  int rc = sscanf(pscontents.c_str(), "cpu  %lu %lu %lu %lu %lu %lu %lu",
                  &usertime, &nicetime, &systime, &idletime,
                  &iowaittime, &irqtime, &softirqtime);
  if (rc != 7) {
    return false;
  }
  *idleticks = idletime;
  *remainingticks = usertime + nicetime + systime + iowaittime + irqtime + softirqtime;
  return true;
}

unsigned collect_cpu_utilization()
{
  std::string contents;
  long unsigned idle[2];
  long unsigned busy[2];
  for (unsigned iter = 0; iter < 2; ++iter) {
    if (!android::base::ReadFileToString("/proc/stat", &contents)) {
      return 0;
    }
    if (!postprocess_proc_stat_contents(contents, &idle[iter], &busy[iter])) {
      return 0;
    }
    if (iter == 0) {
      sleep(1);
    }
  }
  long unsigned total_delta = (idle[1] + busy[1]) - (idle[0] + busy[0]);
  long unsigned busy_delta = busy[1] - busy[0];
  return busy_delta * 100 / total_delta;
}

static void annotate_encoded_perf_profile(wireless_android_play_playlog::AndroidPerfProfile *profile,
                                          const ConfigReader &config,
                                          unsigned cpu_utilization)
{
  //
  // Incorporate cpu utilization (collected prior to perf run)
  //
  if (config.getUnsignedValue("collect_cpu_utilization")) {
    profile->set_cpu_utilization(cpu_utilization);
  }

  //
  // Load average as reported by the kernel
  //
  std::string load;
  double fload = 0.0;
  if (android::base::ReadFileToString("/proc/loadavg", &load) &&
      sscanf(load.c_str(), "%lf", &fload) == 1) {
    int iload = static_cast<int>(fload * 100.0);
    profile->set_sys_load_average(iload);
  } else {
    W_ALOGE("Failed to read or scan /proc/loadavg (%s)", strerror(errno));
  }

  //
  // Device still booting? Camera in use? Plugged into charger?
  //
  bool is_booting = get_booting();
  if (config.getUnsignedValue("collect_booting")) {
    profile->set_booting(is_booting);
  }
  if (config.getUnsignedValue("collect_camera_active")) {
    profile->set_camera_active(is_booting ? false : get_camera_active());
  }
  if (config.getUnsignedValue("collect_charging_state")) {
    profile->set_on_charger(get_charging());
  }

  //
  // Examine the contents of wake_unlock to determine whether the
  // device display is on or off. NB: is this really the only way to
  // determine this info?
  //
  std::string disp;
  if (android::base::ReadFileToString("/sys/power/wake_unlock", &disp)) {
    bool ison = (strstr(disp.c_str(), "PowerManagerService.Display") == 0);
    profile->set_display_on(ison);
  } else {
    W_ALOGE("Failed to read /sys/power/wake_unlock (%s)", strerror(errno));
  }
}

inline char* string_as_array(std::string* str) {
  return str->empty() ? NULL : &*str->begin();
}

PROFILE_RESULT encode_to_proto(const std::string &data_file_path,
                               const char *encoded_file_path,
                               const ConfigReader &config,
                               unsigned cpu_utilization)
{
  //
  // Open and read perf.data file
  //
  const wireless_android_play_playlog::AndroidPerfProfile &encodedProfile =
      wireless_android_logging_awp::RawPerfDataToAndroidPerfProfile(data_file_path);

  //
  // Issue error if no samples
  //
  if (encodedProfile.programs().size() == 0) {
    return ERR_PERF_ENCODE_FAILED;
  }

  // All of the info in 'encodedProfile' is derived from the perf.data file;
  // here we tack display status, cpu utilization, system load, etc.
  wireless_android_play_playlog::AndroidPerfProfile &prof =
      const_cast<wireless_android_play_playlog::AndroidPerfProfile&>
      (encodedProfile);
  annotate_encoded_perf_profile(&prof, config, cpu_utilization);

  //
  // Serialize protobuf to array
  //
  int size = encodedProfile.ByteSize();
  std::string data;
  data.resize(size);
  ::google::protobuf::uint8* dtarget =
        reinterpret_cast<::google::protobuf::uint8*>(string_as_array(&data));
  encodedProfile.SerializeWithCachedSizesToArray(dtarget);

  //
  // Open file and write encoded data to it
  //
  FILE *fp = fopen(encoded_file_path, "w");
  if (!fp) {
    return ERR_OPEN_ENCODED_FILE_FAILED;
  }
  size_t fsiz = size;
  if (fwrite(dtarget, fsiz, 1, fp) != 1) {
    fclose(fp);
    return ERR_WRITE_ENCODED_FILE_FAILED;
  }
  fclose(fp);
  chmod(encoded_file_path, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH);

  return OK_PROFILE_COLLECTION;
}

//
// Invoke "perf record". Return value is OK_PROFILE_COLLECTION for
// success, or some other error code if something went wrong.
//
static PROFILE_RESULT invoke_perf(const std::string &perf_path,
                                  unsigned sampling_period,
                                  const char *stack_profile_opt,
                                  unsigned duration,
                                  const std::string &data_file_path,
                                  const std::string &perf_stderr_path)
{
  pid_t pid = fork();

  if (pid == -1) {
    return ERR_FORK_FAILED;
  }

  if (pid == 0) {
    // child

    // Open file to receive stderr/stdout from perf
    FILE *efp = fopen(perf_stderr_path.c_str(), "w");
    if (efp) {
      dup2(fileno(efp), STDERR_FILENO);
      dup2(fileno(efp), STDOUT_FILENO);
    } else {
      W_ALOGW("unable to open %s for writing", perf_stderr_path.c_str());
    }

    // marshall arguments
    constexpr unsigned max_args = 13;
    const char *argv[max_args];
    unsigned slot = 0;
    argv[slot++] = perf_path.c_str();
    argv[slot++] = "record";

    // -o perf.data
    argv[slot++] = "-o";
    argv[slot++] = data_file_path.c_str();

    // -c N
    argv[slot++] = "-c";
    std::string p_str = android::base::StringPrintf("%u", sampling_period);
    argv[slot++] = p_str.c_str();

    // -g if desired
    if (stack_profile_opt)
      argv[slot++] = stack_profile_opt;

    // system wide profiling
    argv[slot++] = "-a";

    // no need for kernel symbols
    argv[slot++] = "--no-dump-kernel-symbols";

    // sleep <duration>
    argv[slot++] = "/system/bin/sleep";
    std::string d_str = android::base::StringPrintf("%u", duration);
    argv[slot++] = d_str.c_str();

    // terminator
    argv[slot++] = nullptr;
    assert(slot < max_args);

    // record the final command line in the error output file for
    // posterity/debugging purposes
    fprintf(stderr, "perf invocation (pid=%d):\n", getpid());
    for (unsigned i = 0; argv[i] != nullptr; ++i) {
      fprintf(stderr, "%s%s", i ? " " : "", argv[i]);
    }
    fprintf(stderr, "\n");

    // exec
    execvp(argv[0], (char * const *)argv);
    fprintf(stderr, "exec failed: %s\n", strerror(errno));
    exit(1);

  } else {
    // parent
    int st = 0;
    pid_t reaped = TEMP_FAILURE_RETRY(waitpid(pid, &st, 0));

    if (reaped == -1) {
      W_ALOGW("waitpid failed: %s", strerror(errno));
    } else if (WIFSIGNALED(st)) {
      W_ALOGW("perf killed by signal %d", WTERMSIG(st));
    } else if (WEXITSTATUS(st) != 0) {
      W_ALOGW("perf bad exit status %d", WEXITSTATUS(st));
    } else {
      return OK_PROFILE_COLLECTION;
    }
  }

  return ERR_PERF_RECORD_FAILED;
}

//
// Remove all files in the destination directory during initialization
//
static void cleanup_destination_dir(const ConfigReader &config)
{
  std::string dest_dir = config.getStringValue("destination_directory");
  DIR* dir = opendir(dest_dir.c_str());
  if (dir != NULL) {
    struct dirent* e;
    while ((e = readdir(dir)) != 0) {
      if (e->d_name[0] != '.') {
        std::string file_path = dest_dir + "/" + e->d_name;
        remove(file_path.c_str());
      }
    }
    closedir(dir);
  } else {
    W_ALOGW("unable to open destination dir %s for cleanup",
            dest_dir.c_str());
  }
}

//
// Post-processes after profile is collected and converted to protobuf.
// * GMS core stores processed file sequence numbers in
//   /data/data/com.google.android.gms/files/perfprofd_processed.txt
// * Update /data/misc/perfprofd/perfprofd_produced.txt to remove the sequence
//   numbers that have been processed and append the current seq number
// Returns true if the current_seq should increment.
//
static bool post_process(const ConfigReader &config, int current_seq)
{
  std::string dest_dir = config.getStringValue("destination_directory");
  std::string processed_file_path =
      config.getStringValue("config_directory") + "/" + PROCESSED_FILENAME;
  std::string produced_file_path = dest_dir + "/" + PRODUCED_FILENAME;


  std::set<int> processed;
  FILE *fp = fopen(processed_file_path.c_str(), "r");
  if (fp != NULL) {
    int seq;
    while(fscanf(fp, "%d\n", &seq) > 0) {
      if (remove(android::base::StringPrintf(
          "%s/perf.data.encoded.%d", dest_dir.c_str(),seq).c_str()) == 0) {
        processed.insert(seq);
      }
    }
    fclose(fp);
  }

  std::set<int> produced;
  fp = fopen(produced_file_path.c_str(), "r");
  if (fp != NULL) {
    int seq;
    while(fscanf(fp, "%d\n", &seq) > 0) {
      if (processed.find(seq) == processed.end()) {
        produced.insert(seq);
      }
    }
    fclose(fp);
  }

  unsigned maxLive = config.getUnsignedValue("max_unprocessed_profiles");
  if (produced.size() >= maxLive) {
    return false;
  }

  produced.insert(current_seq);
  fp = fopen(produced_file_path.c_str(), "w");
  if (fp == NULL) {
    W_ALOGW("Cannot write %s", produced_file_path.c_str());
    return false;
  }
  for (std::set<int>::const_iterator iter = produced.begin();
       iter != produced.end(); ++iter) {
    fprintf(fp, "%d\n", *iter);
  }
  fclose(fp);
  chmod(produced_file_path.c_str(),
        S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH);
  return true;
}

//
// Collect a perf profile. Steps for this operation are:
// - kick off 'perf record'
// - read perf.data, convert to protocol buf
//
static PROFILE_RESULT collect_profile(const ConfigReader &config, int seq)
{
  //
  // Collect cpu utilization if enabled
  //
  unsigned cpu_utilization = 0;
  if (config.getUnsignedValue("collect_cpu_utilization")) {
    cpu_utilization = collect_cpu_utilization();
  }

  //
  // Form perf.data file name, perf error output file name
  //
  std::string destdir = config.getStringValue("destination_directory");
  std::string data_file_path(destdir);
  data_file_path += "/";
  data_file_path += PERF_OUTPUT;
  std::string perf_stderr_path(destdir);
  perf_stderr_path += "/perferr.txt";

  //
  // Remove any existing perf.data file -- if we don't do this, perf
  // will rename the old file and we'll have extra cruft lying around.
  //
  struct stat statb;
  if (stat(data_file_path.c_str(), &statb) == 0) { // if file exists...
    if (unlink(data_file_path.c_str())) {          // then try to remove
      W_ALOGW("unable to unlink previous perf.data file");
    }
  }

  //
  // The "mpdecision" daemon can cause problems for profile
  // collection: if it decides to online a CPU partway through the
  // 'perf record' run, the activity on that CPU will be invisible to
  // perf, and if it offlines a CPU during the recording this can
  // sometimes leave the PMU in an unusable state (dmesg errors of the
  // form "perfevents: unable to request IRQXXX for ...").  To avoid
  // these issues, if "mpdecision" is running the helper below will
  // stop the service and then online all available CPUs. The object
  // destructor (invoked when this routine terminates) will then
  // restart the service again when needed.
  //
  unsigned duration = config.getUnsignedValue("sample_duration");
  unsigned hardwire = config.getUnsignedValue("hardwire_cpus");
  unsigned max_duration = config.getUnsignedValue("hardwire_cpus_max_duration");
  bool take_action = (hardwire && duration <= max_duration);
  HardwireCpuHelper helper(take_action);

  //
  // Invoke perf
  //
  const char *stack_profile_opt =
      (config.getUnsignedValue("stack_profile") != 0 ? "-g" : nullptr);
  std::string perf_path = config.getStringValue("perf_path");
  unsigned period = config.getUnsignedValue("sampling_period");

  PROFILE_RESULT ret = invoke_perf(perf_path.c_str(),
                                  period,
                                  stack_profile_opt,
                                  duration,
                                  data_file_path,
                                  perf_stderr_path);
  if (ret != OK_PROFILE_COLLECTION) {
    return ret;
  }

  //
  // Read the resulting perf.data file, encode into protocol buffer, then write
  // the result to the file perf.data.encoded
  //
  std::string path = android::base::StringPrintf(
      "%s.encoded.%d", data_file_path.c_str(), seq);
  return encode_to_proto(data_file_path, path.c_str(), config, cpu_utilization);
}

//
// Assuming that we want to collect a profile every N seconds,
// randomly partition N into two sub-intervals.
//
static void determine_before_after(unsigned &sleep_before_collect,
                                   unsigned &sleep_after_collect,
                                   unsigned collection_interval)
{
  double frac = erand48(random_seed);
  sleep_before_collect = (unsigned) (((double)collection_interval) * frac);
  assert(sleep_before_collect <= collection_interval);
  sleep_after_collect = collection_interval - sleep_before_collect;
}

//
// Set random number generator seed
//
static void set_seed(ConfigReader &config)
{
  unsigned seed = 0;
  unsigned use_fixed_seed = config.getUnsignedValue("use_fixed_seed");
  if (use_fixed_seed) {
    //
    // Use fixed user-specified seed
    //
    seed = use_fixed_seed;
  } else {
    //
    // Randomized seed
    //
    seed = arc4random();
  }
  W_ALOGI("random seed set to %u", seed);
  // Distribute the 32-bit seed into the three 16-bit array
  // elements. The specific values being written do not especially
  // matter as long as we are setting them to something based on the seed.
  random_seed[0] = seed & 0xffff;
  random_seed[1] = (seed >> 16);
  random_seed[2] = (random_seed[0] ^ random_seed[1]);
}

//
// Initialization
//
static void init(ConfigReader &config)
{
  if (!config.readFile()) {
    W_ALOGE("unable to open configuration file %s",
            config.getConfigFilePath());
  }

  // Children of init inherit an artificially low OOM score -- this is not
  // desirable for perfprofd (its OOM score should be on par with
  // other user processes).
  std::stringstream oomscore_path;
  oomscore_path << "/proc/" << getpid() << "/oom_score_adj";
  if (!android::base::WriteStringToFile("0", oomscore_path.str())) {
    W_ALOGE("unable to write to %s", oomscore_path.str().c_str());
  }

  set_seed(config);
  cleanup_destination_dir(config);

  char propBuf[PROPERTY_VALUE_MAX];
  propBuf[0] = '\0';
  property_get("ro.kernel.qemu", propBuf, "");
  running_in_emulator = (propBuf[0] == '1');
  property_get("ro.debuggable", propBuf, "");
  is_debug_build = (propBuf[0] == '1');

  signal(SIGHUP, sig_hup);
}

//
// Main routine:
// 1. parse cmd line args
// 2. read config file
// 3. loop: {
//       sleep for a while
//       perform a profile collection
//    }
//
int perfprofd_main(int argc, char** argv)
{
  ConfigReader config;

  W_ALOGI("starting Android Wide Profiling daemon");

  parse_args(argc, argv);
  init(config);

  // Early exit if we're not supposed to run on this build flavor
  if (is_debug_build != 1 &&
      config.getUnsignedValue("only_debug_build") == 1) {
    W_ALOGI("early exit due to inappropriate build type");
    return 0;
  }

  unsigned iterations = 0;
  int seq = 0;
  while(config.getUnsignedValue("main_loop_iterations") == 0 ||
        iterations < config.getUnsignedValue("main_loop_iterations")) {

    // Figure out where in the collection interval we're going to actually
    // run perf
    unsigned sleep_before_collect = 0;
    unsigned sleep_after_collect = 0;
    determine_before_after(sleep_before_collect, sleep_after_collect,
                           config.getUnsignedValue("collection_interval"));
    perfprofd_sleep(sleep_before_collect);

    // Reread config file -- the uploader may have rewritten it as a result
    // of a gservices change
    config.readFile();

    // Check for profiling enabled...
    CKPROFILE_RESULT ckresult = check_profiling_enabled(config);
    if (ckresult != DO_COLLECT_PROFILE) {
      W_ALOGI("profile collection skipped (%s)",
              ckprofile_result_to_string(ckresult));
    } else {
      // Kick off the profiling run...
      W_ALOGI("initiating profile collection");
      PROFILE_RESULT result = collect_profile(config, seq);
      if (result != OK_PROFILE_COLLECTION) {
        W_ALOGI("profile collection failed (%s)",
                profile_result_to_string(result));
      } else {
        if (post_process(config, seq)) {
          seq++;
        }
        W_ALOGI("profile collection complete");
      }
    }
    perfprofd_sleep(sleep_after_collect);
    iterations += 1;
  }

  W_ALOGI("finishing Android Wide Profiling daemon");
  return 0;
}