1 files changed, 337 insertions, 0 deletions
diff --git a/mozglue/misc/TimeStamp_posix.cpp b/mozglue/misc/TimeStamp_posix.cpp
new file mode 100644
index 0000000000..10c046d046
--- /dev/null
+++ b/mozglue/misc/TimeStamp_posix.cpp
@@ -0,0 +1,337 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//
+// Implement TimeStamp::Now() with POSIX clocks.
+//
+// The "tick" unit for POSIX clocks is simply a nanosecond, as this is
+// the smallest unit of time representable by struct timespec.  That
+// doesn't mean that a nanosecond is the resolution of TimeDurations
+// obtained with this API; see TimeDuration::Resolution;
+//
+
+#include <sys/syscall.h>
+#include <time.h>
+#include <unistd.h>
+#include <string.h>
+
+#if defined(__DragonFly__) || defined(__FreeBSD__) || defined(__NetBSD__) || \
+    defined(__OpenBSD__)
+#  include <sys/param.h>
+#  include <sys/sysctl.h>
+#endif
+
+#if defined(__DragonFly__) || defined(__FreeBSD__)
+#  include <sys/user.h>
+#endif
+
+#if defined(__NetBSD__)
+#  undef KERN_PROC
+#  define KERN_PROC KERN_PROC2
+#  define KINFO_PROC struct kinfo_proc2
+#else
+#  define KINFO_PROC struct kinfo_proc
+#endif
+
+#if defined(__DragonFly__)
+#  define KP_START_SEC kp_start.tv_sec
+#  define KP_START_USEC kp_start.tv_usec
+#elif defined(__FreeBSD__)
+#  define KP_START_SEC ki_start.tv_sec
+#  define KP_START_USEC ki_start.tv_usec
+#else
+#  define KP_START_SEC p_ustart_sec
+#  define KP_START_USEC p_ustart_usec
+#endif
+
+#include "mozilla/Sprintf.h"
+#include "mozilla/TimeStamp.h"
+
+#if !defined(__wasi__)
+#  include <pthread.h>
+#endif
+
+// Estimate of the smallest duration of time we can measure.
+static uint64_t sResolution;
+static uint64_t sResolutionSigDigs;
+
+#if !defined(__wasi__)
+static const uint16_t kNsPerUs = 1000;
+#endif
+
+static const uint64_t kNsPerMs = 1000000;
+static const uint64_t kNsPerSec = 1000000000;
+static const double kNsPerMsd = 1000000.0;
+static const double kNsPerSecd = 1000000000.0;
+
+static uint64_t TimespecToNs(const struct timespec& aTs) {
+  uint64_t baseNs = uint64_t(aTs.tv_sec) * kNsPerSec;
+  return baseNs + uint64_t(aTs.tv_nsec);
+}
+
+static uint64_t ClockTimeNs() {
+  struct timespec ts;
+  // this can't fail: we know &ts is valid, and TimeStamp::Startup()
+  // checks that CLOCK_MONOTONIC is supported (and aborts if not)
+  clock_gettime(CLOCK_MONOTONIC, &ts);
+
+  // tv_sec is defined to be relative to an arbitrary point in time,
+  // but it would be madness for that point in time to be earlier than
+  // the Epoch.  So we can safely assume that even if time_t is 32
+  // bits, tv_sec won't overflow while the browser is open.  Revisit
+  // this argument if we're still building with 32-bit time_t around
+  // the year 2037.
+  return TimespecToNs(ts);
+}
+
+static uint64_t ClockResolutionNs() {
+  // NB: why not rely on clock_getres()?  Two reasons: (i) it might
+  // lie, and (ii) it might return an "ideal" resolution that while
+  // theoretically true, could never be measured in practice.  Since
+  // clock_gettime() likely involves a system call on your platform,
+  // the "actual" timing resolution shouldn't be lower than syscall
+  // overhead.
+
+  uint64_t start = ClockTimeNs();
+  uint64_t end = ClockTimeNs();
+  uint64_t minres = (end - start);
+
+  // 10 total trials is arbitrary: what we're trying to avoid by
+  // looping is getting unlucky and being interrupted by a context
+  // switch or signal, or being bitten by paging/cache effects
+  for (int i = 0; i < 9; ++i) {
+    start = ClockTimeNs();
+    end = ClockTimeNs();
+
+    uint64_t candidate = (start - end);
+    if (candidate < minres) {
+      minres = candidate;
+    }
+  }
+
+  if (0 == minres) {
+    // measurable resolution is either incredibly low, ~1ns, or very
+    // high.  fall back on clock_getres()
+    struct timespec ts;
+    if (0 == clock_getres(CLOCK_MONOTONIC, &ts)) {
+      minres = TimespecToNs(ts);
+    }
+  }
+
+  if (0 == minres) {
+    // clock_getres probably failed.  fall back on NSPR's resolution
+    // assumption
+    minres = 1 * kNsPerMs;
+  }
+
+  return minres;
+}
+
+namespace mozilla {
+
+double BaseTimeDurationPlatformUtils::ToSeconds(int64_t aTicks) {
+  return double(aTicks) / kNsPerSecd;
+}
+
+double BaseTimeDurationPlatformUtils::ToSecondsSigDigits(int64_t aTicks) {
+  // don't report a value < mResolution ...
+  int64_t valueSigDigs = sResolution * (aTicks / sResolution);
+  // and chop off insignificant digits
+  valueSigDigs = sResolutionSigDigs * (valueSigDigs / sResolutionSigDigs);
+  return double(valueSigDigs) / kNsPerSecd;
+}
+
+int64_t BaseTimeDurationPlatformUtils::TicksFromMilliseconds(
+    double aMilliseconds) {
+  double result = aMilliseconds * kNsPerMsd;
+  if (result > double(INT64_MAX)) {
+    return INT64_MAX;
+  }
+  if (result < INT64_MIN) {
+    return INT64_MIN;
+  }
+
+  return result;
+}
+
+int64_t BaseTimeDurationPlatformUtils::ResolutionInTicks() {
+  return static_cast<int64_t>(sResolution);
+}
+
+static bool gInitialized = false;
+
+void TimeStamp::Startup() {
+  if (gInitialized) {
+    return;
+  }
+
+  struct timespec dummy;
+  if (clock_gettime(CLOCK_MONOTONIC, &dummy) != 0) {
+    MOZ_CRASH("CLOCK_MONOTONIC is absent!");
+  }
+
+  sResolution = ClockResolutionNs();
+
+  // find the number of significant digits in sResolution, for the
+  // sake of ToSecondsSigDigits()
+  for (sResolutionSigDigs = 1; !(sResolutionSigDigs == sResolution ||
+                                 10 * sResolutionSigDigs > sResolution);
+       sResolutionSigDigs *= 10)
+    ;
+
+  gInitialized = true;
+}
+
+void TimeStamp::Shutdown() {}
+
+TimeStamp TimeStamp::Now(bool aHighResolution) {
+  return TimeStamp(ClockTimeNs());
+}
+
+#if defined(XP_LINUX) || defined(ANDROID)
+
+// Calculates the amount of jiffies that have elapsed since boot and up to the
+// starttime value of a specific process as found in its /proc/*/stat file.
+// Returns 0 if an error occurred.
+
+static uint64_t JiffiesSinceBoot(const char* aFile) {
+  char stat[512];
+
+  FILE* f = fopen(aFile, "r");
+  if (!f) {
+    return 0;
+  }
+
+  int n = fread(&stat, 1, sizeof(stat) - 1, f);
+
+  fclose(f);
+
+  if (n <= 0) {
+    return 0;
+  }
+
+  stat[n] = 0;
+
+  long long unsigned startTime = 0;  // instead of uint64_t to keep GCC quiet
+  char* s = strrchr(stat, ')');
+
+  if (!s) {
+    return 0;
+  }
+
+  int rv = sscanf(s + 2,
+                  "%*c %*d %*d %*d %*d %*d %*u %*u %*u %*u "
+                  "%*u %*u %*u %*d %*d %*d %*d %*d %*d %llu",
+                  &startTime);
+
+  if (rv != 1 || !startTime) {
+    return 0;
+  }
+
+  return startTime;
+}
+
+// Computes the interval that has elapsed between the thread creation and the
+// process creation by comparing the starttime fields in the respective
+// /proc/*/stat files. The resulting value will be a good approximation of the
+// process uptime. This value will be stored at the address pointed by aTime;
+// if an error occurred 0 will be stored instead.
+
+static void* ComputeProcessUptimeThread(void* aTime) {
+  uint64_t* uptime = static_cast<uint64_t*>(aTime);
+  long hz = sysconf(_SC_CLK_TCK);
+
+  *uptime = 0;
+
+  if (!hz) {
+    return nullptr;
+  }
+
+  char threadStat[40];
+  SprintfLiteral(threadStat, "/proc/self/task/%d/stat",
+                 (pid_t)syscall(__NR_gettid));
+
+  uint64_t threadJiffies = JiffiesSinceBoot(threadStat);
+  uint64_t selfJiffies = JiffiesSinceBoot("/proc/self/stat");
+
+  if (!threadJiffies || !selfJiffies) {
+    return nullptr;
+  }
+
+  *uptime = ((threadJiffies - selfJiffies) * kNsPerSec) / hz;
+  return nullptr;
+}
+
+// Computes and returns the process uptime in us on Linux & its derivatives.
+// Returns 0 if an error was encountered.
+
+uint64_t TimeStamp::ComputeProcessUptime() {
+  uint64_t uptime = 0;
+  pthread_t uptime_pthread;
+
+  if (pthread_create(&uptime_pthread, nullptr, ComputeProcessUptimeThread,
+                     &uptime)) {
+    MOZ_CRASH("Failed to create process uptime thread.");
+    return 0;
+  }
+
+  pthread_join(uptime_pthread, NULL);
+
+  return uptime / kNsPerUs;
+}
+
+#elif defined(__DragonFly__) || defined(__FreeBSD__) || defined(__NetBSD__) || \
+    defined(__OpenBSD__)
+
+// Computes and returns the process uptime in us on various BSD flavors.
+// Returns 0 if an error was encountered.
+
+uint64_t TimeStamp::ComputeProcessUptime() {
+  struct timespec ts;
+  int rv = clock_gettime(CLOCK_REALTIME, &ts);
+
+  if (rv == -1) {
+    return 0;
+  }
+
+  int mib[] = {
+    CTL_KERN,
+    KERN_PROC,
+    KERN_PROC_PID,
+    getpid(),
+#  if defined(__NetBSD__) || defined(__OpenBSD__)
+    sizeof(KINFO_PROC),
+    1,
+#  endif
+  };
+  u_int mibLen = sizeof(mib) / sizeof(mib[0]);
+
+  KINFO_PROC proc;
+  size_t bufferSize = sizeof(proc);
+  rv = sysctl(mib, mibLen, &proc, &bufferSize, nullptr, 0);
+
+  if (rv == -1) {
+    return 0;
+  }
+
+  uint64_t startTime = ((uint64_t)proc.KP_START_SEC * kNsPerSec) +
+                       (proc.KP_START_USEC * kNsPerUs);
+  uint64_t now = ((uint64_t)ts.tv_sec * kNsPerSec) + ts.tv_nsec;
+
+  if (startTime > now) {
+    return 0;
+  }
+
+  return (now - startTime) / kNsPerUs;
+}
+
+#else
+
+uint64_t TimeStamp::ComputeProcessUptime() { return 0; }
+
+#endif
+
+}  // namespace mozilla