components/browser_watcher/watcher_metrics_provider_win.cc

   1 // Copyright (c) 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "components/browser_watcher/watcher_metrics_provider_win.h"
   6
   7 #include <limits>
   8 #include <vector>
   9
  10 #include "base/metrics/sparse_histogram.h"
  11 #include "base/process/process_handle.h"
  12 #include "base/strings/string_number_conversions.h"
  13 #include "base/strings/string_piece.h"
  14 #include "base/strings/utf_string_conversions.h"
  15 #include "base/win/registry.h"
  16
  17 namespace browser_watcher {
  18
  19 namespace {
  20
  21 void CompileAsserts() {
  22   // Process ID APIs on Windows talk in DWORDs, whereas for string formatting
  23   // and parsing, this code uses int. In practice there are no process IDs with
  24   // the high bit set on Windows, so there's no danger of overflow if this is
  25   // done consistently.
  26   static_assert(sizeof(DWORD) == sizeof(int),
  27                 "process ids are expected to be no larger than int");
  28 }
  29
  30 // This function does soft matching on the PID recorded in the key only.
  31 // Due to PID reuse, the possibility exists that the process that's now live
  32 // with the given PID is not the same process the data was recorded for.
  33 // This doesn't matter for the purpose, as eventually the data will be
  34 // scavenged and reported.
  35 bool IsDeadProcess(base::StringPiece16 key_or_value_name) {
  36   // Truncate the input string to the first occurrence of '-', if one exists.
  37   size_t num_end = key_or_value_name.find(L'-');
  38   if (num_end != base::StringPiece16::npos)
  39     key_or_value_name = key_or_value_name.substr(0, num_end);
  40
  41   // Convert to the numeric PID.
  42   int pid = 0;
  43   if (!base::StringToInt(key_or_value_name, &pid) || pid == 0)
  44     return true;
  45
  46   // This is a very inexpensive check for the common case of our own PID.
  47   if (static_cast<base::ProcessId>(pid) == base::GetCurrentProcId())
  48     return false;
  49
  50   // The process is not our own - see whether a process with this PID exists.
  51   // This is more expensive than the above check, but should also be very rare,
  52   // as this only happens more than once for a given PID if a user is running
  53   // multiple Chrome instances concurrently.
  54   base::ProcessHandle process = base::kNullProcessHandle;
  55   if (base::OpenProcessHandle(static_cast<base::ProcessId>(pid), &process)) {
  56     base::CloseProcessHandle(process);
  57
  58     // The fact that it was possible to open the process says it's live.
  59     return false;
  60   }
  61
  62   return true;
  63 }
  64
  65 void RecordExitCodes(const base::string16& registry_path) {
  66   base::win::RegKey regkey(HKEY_CURRENT_USER,
  67                            registry_path.c_str(),
  68                            KEY_QUERY_VALUE | KEY_SET_VALUE);
  69   if (!regkey.Valid())
  70     return;
  71
  72   size_t num = regkey.GetValueCount();
  73   if (num == 0)
  74     return;
  75   std::vector<base::string16> to_delete;
  76
  77   // Record the exit codes in a sparse stability histogram, as the range of
  78   // values used to report failures is large.
  79   base::HistogramBase* exit_code_histogram =
  80       base::SparseHistogram::FactoryGet(
  81           WatcherMetricsProviderWin::kBrowserExitCodeHistogramName,
  82           base::HistogramBase::kUmaStabilityHistogramFlag);
  83
  84   for (size_t i = 0; i < num; ++i) {
  85     base::string16 name;
  86     if (regkey.GetValueNameAt(static_cast<int>(i), &name) == ERROR_SUCCESS) {
  87       DWORD exit_code = 0;
  88       if (regkey.ReadValueDW(name.c_str(), &exit_code) == ERROR_SUCCESS) {
  89         // Do not report exit codes for processes that are still live,
  90         // notably for our own process.
  91         if (exit_code != STILL_ACTIVE || IsDeadProcess(name)) {
  92           to_delete.push_back(name);
  93           exit_code_histogram->Add(exit_code);
  94         }
  95       }
  96     }
  97   }
  98
  99   // Delete the values reported above.
 100   for (size_t i = 0; i < to_delete.size(); ++i)
 101     regkey.DeleteValue(to_delete[i].c_str());
 102 }
 103
 104 void ReadSingleExitFunnel(
 105     base::win::RegKey* parent_key, const base::char16* name,
 106     std::vector<std::pair<base::string16, int64>>* events_out) {
 107   DCHECK(parent_key);
 108   DCHECK(name);
 109   DCHECK(events_out);
 110
 111   base::win::RegKey regkey(parent_key->Handle(), name, KEY_READ | KEY_WRITE);
 112   if (!regkey.Valid())
 113     return;
 114
 115   // Exit early if no work to do.
 116   size_t num = regkey.GetValueCount();
 117   if (num == 0)
 118     return;
 119
 120   // Enumerate the recorded events for this process for processing.
 121   std::vector<std::pair<base::string16, int64>> events;
 122   for (size_t i = 0; i < num; ++i) {
 123     base::string16 event_name;
 124     LONG res = regkey.GetValueNameAt(static_cast<int>(i), &event_name);
 125     if (res == ERROR_SUCCESS) {
 126       int64 event_time = 0;
 127       res = regkey.ReadInt64(event_name.c_str(), &event_time);
 128       if (res == ERROR_SUCCESS)
 129         events.push_back(std::make_pair(event_name, event_time));
 130     }
 131   }
 132
 133   // Attempt to delete the values before reporting anything.
 134   // Exit if this fails to make sure there is no double-reporting on e.g.
 135   // permission problems or other corruption.
 136   for (size_t i = 0; i < events.size(); ++i) {
 137     const base::string16& event_name = events[i].first;
 138     LONG res = regkey.DeleteValue(event_name.c_str());
 139     if (res != ERROR_SUCCESS) {
 140       LOG(ERROR) << "Failed to delete value " << event_name;
 141       return;
 142     }
 143   }
 144
 145   events_out->swap(events);
 146 }
 147
 148 void RecordSingleExitFunnel(base::win::RegKey* parent_key,
 149                             const base::char16* name) {
 150   std::vector<std::pair<base::string16, int64>> events;
 151   ReadSingleExitFunnel(parent_key, name, &events);
 152
 153   // Find the earliest event time.
 154   int64 min_time = std::numeric_limits<int64>::max();
 155   for (size_t i = 0; i < events.size(); ++i)
 156     min_time = std::min(min_time, events[i].second);
 157
 158   // Record the exit funnel event times in a sparse stability histogram.
 159   for (size_t i = 0; i < events.size(); ++i) {
 160     std::string histogram_name(
 161         WatcherMetricsProviderWin::kExitFunnelHistogramPrefix);
 162     histogram_name.append(base::WideToUTF8(events[i].first));
 163     base::TimeDelta event_time =
 164         base::Time::FromInternalValue(events[i].second) -
 165             base::Time::FromInternalValue(min_time);
 166     base::HistogramBase* histogram =
 167         base::SparseHistogram::FactoryGet(
 168             histogram_name.c_str(),
 169             base::HistogramBase::kUmaStabilityHistogramFlag);
 170
 171     // Record the time rounded up to the nearest millisecond.
 172     histogram->Add(event_time.InMillisecondsRoundedUp());
 173   }
 174 }
 175
 176 void RecordExitFunnels(const base::string16& registry_path) {
 177   base::win::RegistryKeyIterator it(HKEY_CURRENT_USER, registry_path.c_str());
 178   if (!it.Valid())
 179     return;
 180
 181   // Exit early if no work to do.
 182   if (it.SubkeyCount() == 0)
 183     return;
 184
 185   // Open the key we use for deletion preemptively to prevent reporting
 186   // multiple times on permission problems.
 187   base::win::RegKey key(HKEY_CURRENT_USER,
 188                         registry_path.c_str(),
 189                         KEY_QUERY_VALUE);
 190   if (!key.Valid()) {
 191     LOG(ERROR) << "Failed to open " << registry_path << " for writing.";
 192     return;
 193   }
 194
 195   std::vector<base::string16> to_delete;
 196   for (; it.Valid(); ++it) {
 197     // Defer reporting on still-live processes.
 198     if (IsDeadProcess(it.Name())) {
 199       RecordSingleExitFunnel(&key, it.Name());
 200       to_delete.push_back(it.Name());
 201     }
 202   }
 203
 204   for (size_t i = 0; i < to_delete.size(); ++i) {
 205     LONG res = key.DeleteEmptyKey(to_delete[i].c_str());
 206     if (res != ERROR_SUCCESS)
 207       LOG(ERROR) << "Failed to delete key " << to_delete[i];
 208   }
 209 }
 210
 211 }  // namespace
 212
 213 const char WatcherMetricsProviderWin::kBrowserExitCodeHistogramName[] =
 214     "Stability.BrowserExitCodes";
 215 const char WatcherMetricsProviderWin::kExitFunnelHistogramPrefix[] =
 216     "Stability.ExitFunnel.";
 217
 218 WatcherMetricsProviderWin::WatcherMetricsProviderWin(
 219     const base::char16* registry_path) : registry_path_(registry_path) {
 220 }
 221
 222 WatcherMetricsProviderWin::~WatcherMetricsProviderWin() {
 223 }
 224
 225 void WatcherMetricsProviderWin::ProvideStabilityMetrics(
 226     metrics::SystemProfileProto* /* system_profile_proto */) {
 227   // Note that if there are multiple instances of Chrome running in the same
 228   // user account, there's a small race that will double-report the exit codes
 229   // from both/multiple instances. This ought to be vanishingly rare and will
 230   // only manifest as low-level "random" noise. To work around this it would be
 231   // necessary to implement some form of global locking, which is not worth it
 232   // here.
 233   RecordExitCodes(registry_path_);
 234   RecordExitFunnels(registry_path_);
 235 }
 236
 237 }  // namespace browser_watcher