Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

23 files changed, 2757 insertions, 0 deletions

diff --git a/toolkit/components/processtools/Cargo.toml b/toolkit/components/processtools/Cargo.toml
new file mode 100644
index 0000000000..bd56de8e63
--- /dev/null
+++ b/toolkit/components/processtools/Cargo.toml
@@ -0,0 +1,15 @@
+[package]
+name = "processtools"
+version = "0.1.0"
+authors = ["David Teller <dteller@mozilla.com>"]
+license = "MPL-2.0"
+
+[dependencies]
+nserror = { path = "../../../xpcom/rust/nserror" }
+xpcom = { path = "../../../xpcom/rust/xpcom" }
+
+[target.'cfg(windows)'.dependencies]
+winapi = "0.3.7"
+
+[target.'cfg(unix)'.dependencies]
+libc = "0.2"
diff --git a/toolkit/components/processtools/ProcInfo.h b/toolkit/components/processtools/ProcInfo.h
new file mode 100644
index 0000000000..ab7fc4de31
--- /dev/null
+++ b/toolkit/components/processtools/ProcInfo.h
@@ -0,0 +1,275 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#ifndef __mozilla_ProcInfo_h
+#define __mozilla_ProcInfo_h
+
+#include <base/process.h>
+#include <stdint.h>
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/ChromeUtilsBinding.h"
+#include "mozilla/dom/ipc/IdType.h"
+#include "mozilla/HashTable.h"
+#include "mozilla/MozPromise.h"
+
+namespace mozilla {
+
+namespace ipc {
+class GeckoChildProcessHost;
+}
+
+/**
+ * Return the number of milliseconds of CPU time used since process start.
+ *
+ * @return NS_OK on success.
+ */
+nsresult GetCpuTimeSinceProcessStartInMs(uint64_t* aResult);
+
+/**
+ * Return the number of milliseconds of GPU time used since process start.
+ *
+ * @return NS_OK on success.
+ */
+nsresult GetGpuTimeSinceProcessStartInMs(uint64_t* aResult);
+
+// Process types. When updating this enum, please make sure to update
+// WebIDLProcType, ChromeUtils::RequestProcInfo and ProcTypeToWebIDL to
+// mirror the changes.
+enum class ProcType {
+  // These must match the ones in RemoteType.h, and E10SUtils.sys.mjs
+  Web,
+  WebIsolated,
+  File,
+  Extension,
+  PrivilegedAbout,
+  PrivilegedMozilla,
+  WebCOOPCOEP,
+  WebServiceWorker,
+// the rest matches GeckoProcessTypes.h
+#define GECKO_PROCESS_TYPE(enum_value, enum_name, string_name, proc_typename, \
+                           process_bin_type, procinfo_typename,               \
+                           webidl_typename, allcaps_name)                     \
+  procinfo_typename,
+#define SKIP_PROCESS_TYPE_CONTENT
+#ifndef MOZ_ENABLE_FORKSERVER
+#  define SKIP_PROCESS_TYPE_FORKSERVER
+#endif  // MOZ_ENABLE_FORKSERVER
+#include "mozilla/GeckoProcessTypes.h"
+#undef SKIP_PROCESS_TYPE_CONTENT
+#ifndef MOZ_ENABLE_FORKSERVER
+#  undef SKIP_PROCESS_TYPE_FORKSERVER
+#endif  // MOZ_ENABLE_FORKSERVER
+#undef GECKO_PROCESS_TYPE
+  Preallocated,
+  // Unknown type of process
+  Unknown,
+  Max = Unknown,
+};
+
+using UtilityActorName = mozilla::dom::WebIDLUtilityActorName;
+
+// String that will be used e.g. to annotate crash reports
+nsCString GetUtilityActorName(const UtilityActorName aActorName);
+
+/* Get the CPU frequency to use to convert cycle time values to actual time.
+ * @returns the TSC (Time Stamp Counter) frequency in MHz, or 0 if converting
+ * cycle time values should not be attempted. */
+int GetCycleTimeFrequencyMHz();
+
+struct ThreadInfo {
+  // Thread Id.
+  base::ProcessId tid = 0;
+  // Thread name, if any.
+  nsString name;
+  // CPU time in ns.
+  uint64_t cpuTime = 0;
+  // CPU time in cycles if available.
+  uint64_t cpuCycleCount = 0;
+};
+
+// Info on a DOM window.
+struct WindowInfo {
+  explicit WindowInfo()
+      : outerWindowId(0),
+        documentURI(nullptr),
+        documentTitle(u""_ns),
+        isProcessRoot(false),
+        isInProcess(false) {}
+  WindowInfo(uint64_t aOuterWindowId, nsIURI* aDocumentURI,
+             nsAString&& aDocumentTitle, bool aIsProcessRoot, bool aIsInProcess)
+      : outerWindowId(aOuterWindowId),
+        documentURI(aDocumentURI),
+        documentTitle(std::move(aDocumentTitle)),
+        isProcessRoot(aIsProcessRoot),
+        isInProcess(aIsInProcess) {}
+
+  // Internal window id.
+  const uint64_t outerWindowId;
+
+  // URI of the document.
+  const nsCOMPtr<nsIURI> documentURI;
+
+  // Title of the document.
+  const nsString documentTitle;
+
+  // True if this is the toplevel window of the process.
+  // Note that this may be an iframe from another process.
+  const bool isProcessRoot;
+
+  const bool isInProcess;
+};
+
+// Info on a Utility process actor
+struct UtilityInfo {
+  explicit UtilityInfo() : actorName(UtilityActorName::Unknown) {}
+  explicit UtilityInfo(UtilityActorName aActorName) : actorName(aActorName) {}
+  const UtilityActorName actorName;
+};
+
+struct ProcInfo {
+  // Process Id
+  base::ProcessId pid = 0;
+  // Child Id as defined by Firefox when a child process is created.
+  dom::ContentParentId childId;
+  // Process type
+  ProcType type;
+  // Origin, if any
+  nsCString origin;
+  // Memory size in bytes.
+  uint64_t memory = 0;
+  // CPU time in ns.
+  uint64_t cpuTime = 0;
+  uint64_t cpuCycleCount = 0;
+  // Threads owned by this process.
+  CopyableTArray<ThreadInfo> threads;
+  // DOM windows represented by this process.
+  CopyableTArray<WindowInfo> windows;
+  // Utility process actors, empty for non Utility process
+  CopyableTArray<UtilityInfo> utilityActors;
+};
+
+typedef MozPromise<mozilla::HashMap<base::ProcessId, ProcInfo>, nsresult, true>
+    ProcInfoPromise;
+
+/**
+ * Data we need to request process info (e.g. CPU usage, memory usage)
+ * from the operating system and populate the resulting `ProcInfo`.
+ *
+ * Note that this structure contains a mix of:
+ * - low-level handles that we need to request low-level process info
+ *    (`aChildTask` on macOS, `aPid` on other platforms); and
+ * - high-level data that we already acquired while looking for
+ * `aPid`/`aChildTask` and that we will need further down the road.
+ */
+struct ProcInfoRequest {
+  ProcInfoRequest(base::ProcessId aPid, ProcType aProcessType,
+                  const nsACString& aOrigin, nsTArray<WindowInfo>&& aWindowInfo,
+                  nsTArray<UtilityInfo>&& aUtilityInfo, uint32_t aChildId = 0
+#ifdef XP_MACOSX
+                  ,
+                  mach_port_t aChildTask = 0
+#endif  // XP_MACOSX
+                  )
+      : pid(aPid),
+        processType(aProcessType),
+        origin(aOrigin),
+        windowInfo(std::move(aWindowInfo)),
+        utilityInfo(std::move(aUtilityInfo)),
+        childId(aChildId)
+#ifdef XP_MACOSX
+        ,
+        childTask(aChildTask)
+#endif  // XP_MACOSX
+  {
+  }
+  const base::ProcessId pid;
+  const ProcType processType;
+  const nsCString origin;
+  const nsTArray<WindowInfo> windowInfo;
+  const nsTArray<UtilityInfo> utilityInfo;
+  // If the process is a child, its child id, otherwise `0`.
+  const int32_t childId;
+#ifdef XP_MACOSX
+  const mach_port_t childTask;
+#endif  // XP_MACOSX
+};
+
+/**
+ * Batch a request for low-level information on Gecko processes.
+ *
+ * # Request
+ *
+ * Argument `aRequests` is a list of processes, along with high-level data
+ * we have already obtained on them and that we need to populate the
+ * resulting array of `ProcInfo`.
+ *
+ * # Result
+ *
+ * This call succeeds (possibly with missing data, see below) unless we
+ * cannot allocate memory.
+ *
+ * # Performance
+ *
+ * - This call is always executed on a background thread.
+ * - This call does NOT wake up children processes.
+ * - This function is sometimes observably slow to resolve, in particular
+ *   under Windows.
+ *
+ * # Error-handling and race conditions
+ *
+ * Requesting low-level information on a process and its threads is inherently
+ * subject to race conditions. Typically, if a process or a thread is killed
+ * while we're preparing to fetch information, we can easily end up with
+ * system/lib calls that return failures.
+ *
+ * For this reason, this API assumes that errors when placing a system/lib call
+ * are likely and normal. When some information cannot be obtained, the API will
+ * simply skip over said information.
+ *
+ * Note that due to different choices by OSes, the exact information we skip may
+ * vary across platforms. For instance, under Unix, failing to access the
+ * threads of a process will cause us to skip all data on the process, while
+ * under Windows, process information will be returned without thread
+ * information.
+ */
+RefPtr<ProcInfoPromise> GetProcInfo(nsTArray<ProcInfoRequest>&& aRequests);
+
+/**
+ * Synchronous version of GetProcInfo.
+ */
+ProcInfoPromise::ResolveOrRejectValue GetProcInfoSync(
+    nsTArray<ProcInfoRequest>&& aRequests);
+
+/**
+ * Utility function: copy data from a `ProcInfo` and into either a
+ * `ParentProcInfoDictionary` or a `ChildProcInfoDictionary`.
+ */
+template <typename T>
+nsresult CopySysProcInfoToDOM(const ProcInfo& source, T* dest) {
+  // Copy system info.
+  dest->mPid = source.pid;
+  dest->mMemory = source.memory;
+  dest->mCpuTime = source.cpuTime;
+  dest->mCpuCycleCount = source.cpuCycleCount;
+
+  // Copy thread info.
+  mozilla::dom::Sequence<mozilla::dom::ThreadInfoDictionary> threads;
+  for (const ThreadInfo& entry : source.threads) {
+    mozilla::dom::ThreadInfoDictionary* thread =
+        threads.AppendElement(fallible);
+    if (NS_WARN_IF(!thread)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+    thread->mCpuTime = entry.cpuTime;
+    thread->mCpuCycleCount = entry.cpuCycleCount;
+    thread->mTid = entry.tid;
+    thread->mName.Assign(entry.name);
+  }
+  dest->mThreads = std::move(threads);
+  return NS_OK;
+}
+
+}  // namespace mozilla
+#endif  // ProcInfo_h
diff --git a/toolkit/components/processtools/ProcInfo.mm b/toolkit/components/processtools/ProcInfo.mm
new file mode 100644
index 0000000000..80804aea42
--- /dev/null
+++ b/toolkit/components/processtools/ProcInfo.mm
@@ -0,0 +1,180 @@
+/* -*- 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/. */
+
+#include "mozilla/ProcInfo.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+
+#include "nsMemoryReporterManager.h"
+
+#include <cstdio>
+#include <cstring>
+#include <unistd.h>
+
+#include <libproc.h>
+#include <sys/sysctl.h>
+#include <mach/mach.h>
+#include <mach/mach_time.h>
+
+static void GetTimeBase(mach_timebase_info_data_t* timebase) {
+  // Expected results are 125/3 on aarch64, and 1/1 on Intel CPUs.
+  if (mach_timebase_info(timebase) != KERN_SUCCESS) {
+    timebase->numer = 1;
+    timebase->denom = 1;
+  }
+}
+
+namespace mozilla {
+
+nsresult GetCpuTimeSinceProcessStartInMs(uint64_t* aResult) {
+  struct proc_taskinfo pti;
+  if ((unsigned long)proc_pidinfo(getpid(), PROC_PIDTASKINFO, 0, &pti, PROC_PIDTASKINFO_SIZE) <
+      PROC_PIDTASKINFO_SIZE) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mach_timebase_info_data_t timebase;
+  GetTimeBase(&timebase);
+
+  *aResult = (pti.pti_total_user + pti.pti_total_system) * timebase.numer / timebase.denom /
+             PR_NSEC_PER_MSEC;
+  return NS_OK;
+}
+
+nsresult GetGpuTimeSinceProcessStartInMs(uint64_t* aResult) {
+  task_power_info_v2_data_t task_power_info;
+  mach_msg_type_number_t count = TASK_POWER_INFO_V2_COUNT;
+  kern_return_t kr =
+      task_info(mach_task_self(), TASK_POWER_INFO_V2, (task_info_t)&task_power_info, &count);
+  if (kr != KERN_SUCCESS) {
+    return NS_ERROR_FAILURE;
+  }
+
+  *aResult = task_power_info.gpu_energy.task_gpu_utilisation / PR_NSEC_PER_MSEC;
+  return NS_OK;
+}
+
+int GetCycleTimeFrequencyMHz() { return 0; }
+
+ProcInfoPromise::ResolveOrRejectValue GetProcInfoSync(nsTArray<ProcInfoRequest>&& aRequests) {
+  ProcInfoPromise::ResolveOrRejectValue result;
+
+  HashMap<base::ProcessId, ProcInfo> gathered;
+  if (!gathered.reserve(aRequests.Length())) {
+    result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+    return result;
+  }
+
+  mach_timebase_info_data_t timebase;
+  GetTimeBase(&timebase);
+
+  for (const auto& request : aRequests) {
+    ProcInfo info;
+    info.pid = request.pid;
+    info.childId = request.childId;
+    info.type = request.processType;
+    info.origin = std::move(request.origin);
+    info.windows = std::move(request.windowInfo);
+    info.utilityActors = std::move(request.utilityInfo);
+
+    struct proc_taskinfo pti;
+    if ((unsigned long)proc_pidinfo(request.pid, PROC_PIDTASKINFO, 0, &pti, PROC_PIDTASKINFO_SIZE) <
+        PROC_PIDTASKINFO_SIZE) {
+      // Can't read data for this process.
+      // Probably either a sandboxing issue or a race condition, e.g.
+      // the process has been just been killed. Regardless, skip process.
+      continue;
+    }
+    info.cpuTime = (pti.pti_total_user + pti.pti_total_system) * timebase.numer / timebase.denom;
+
+    mach_port_t selectedTask;
+    // If we did not get a task from a child process, we use mach_task_self()
+    if (request.childTask == MACH_PORT_NULL) {
+      selectedTask = mach_task_self();
+    } else {
+      selectedTask = request.childTask;
+    }
+
+    // The phys_footprint value (introduced in 10.11) of the TASK_VM_INFO data
+    // matches the value in the 'Memory' column of the Activity Monitor.
+    task_vm_info_data_t task_vm_info;
+    mach_msg_type_number_t count = TASK_VM_INFO_COUNT;
+    kern_return_t kr = task_info(selectedTask, TASK_VM_INFO, (task_info_t)&task_vm_info, &count);
+    info.memory = kr == KERN_SUCCESS ? task_vm_info.phys_footprint : 0;
+
+    // Now getting threads info
+
+    // task_threads() gives us a snapshot of the process threads
+    // but those threads can go away. All the code below makes
+    // the assumption that thread_info() calls may fail, and
+    // these errors will be ignored.
+    thread_act_port_array_t threadList;
+    mach_msg_type_number_t threadCount;
+    kern_return_t kret = task_threads(selectedTask, &threadList, &threadCount);
+    if (kret != KERN_SUCCESS) {
+      // For some reason, we have no data on the threads for this process.
+      // Most likely reason is that we have just lost a race condition and
+      // the process is dead.
+      // Let's stop here and ignore the entire process.
+      continue;
+    }
+
+    // Deallocate the thread list.
+    // Note that this deallocation is entirely undocumented, so the following code is based
+    // on guesswork and random examples found on the web.
+    auto guardThreadCount = MakeScopeExit([&] {
+      if (threadList == nullptr) {
+        return;
+      }
+      // Free each thread to avoid leaks.
+      for (mach_msg_type_number_t i = 0; i < threadCount; i++) {
+        mach_port_deallocate(mach_task_self(), threadList[i]);
+      }
+      vm_deallocate(mach_task_self(), /* address */ (vm_address_t)threadList,
+                    /* size */ sizeof(thread_t) * threadCount);
+    });
+
+    for (mach_msg_type_number_t i = 0; i < threadCount; i++) {
+      // Basic thread info.
+      thread_extended_info_data_t threadInfoData;
+      count = THREAD_EXTENDED_INFO_COUNT;
+      kret =
+          thread_info(threadList[i], THREAD_EXTENDED_INFO, (thread_info_t)&threadInfoData, &count);
+      if (kret != KERN_SUCCESS) {
+        continue;
+      }
+
+      // Getting the thread id.
+      thread_identifier_info identifierInfo;
+      count = THREAD_IDENTIFIER_INFO_COUNT;
+      kret = thread_info(threadList[i], THREAD_IDENTIFIER_INFO, (thread_info_t)&identifierInfo,
+                         &count);
+      if (kret != KERN_SUCCESS) {
+        continue;
+      }
+
+      // The two system calls were successful, let's add that thread
+      ThreadInfo* thread = info.threads.AppendElement(fallible);
+      if (!thread) {
+        result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+        return result;
+      }
+      thread->cpuTime = threadInfoData.pth_user_time + threadInfoData.pth_system_time;
+      thread->name.AssignASCII(threadInfoData.pth_name);
+      thread->tid = identifierInfo.thread_id;
+    }
+
+    if (!gathered.put(request.pid, std::move(info))) {
+      result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+      return result;
+    }
+  }
+
+  result.SetResolve(std::move(gathered));
+  return result;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/components/processtools/ProcInfo_bsd.cpp b/toolkit/components/processtools/ProcInfo_bsd.cpp
new file mode 100644
index 0000000000..a6ff488194
--- /dev/null
+++ b/toolkit/components/processtools/ProcInfo_bsd.cpp
@@ -0,0 +1,115 @@
+/* -*- 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/. */
+
+#include "mozilla/ProcInfo.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/Logging.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "nsMemoryReporterManager.h"
+#include "nsWhitespaceTokenizer.h"
+
+#include <sys/types.h>
+#include <sys/sysctl.h>
+#include <cerrno>
+#include <cstdio>
+#include <cstring>
+#include <unistd.h>
+
+namespace mozilla {
+
+int GetCycleTimeFrequencyMHz() { return 0; }
+
+nsresult GetCpuTimeSinceProcessStartInMs(uint64_t* aResult) {
+  timespec t;
+  if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &t) == 0) {
+    uint64_t cpuTime =
+        uint64_t(t.tv_sec) * 1'000'000'000u + uint64_t(t.tv_nsec);
+    *aResult = cpuTime / PR_NSEC_PER_MSEC;
+    return NS_OK;
+  }
+
+  return NS_ERROR_FAILURE;
+}
+
+nsresult GetGpuTimeSinceProcessStartInMs(uint64_t* aResult) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+ProcInfoPromise::ResolveOrRejectValue GetProcInfoSync(
+    nsTArray<ProcInfoRequest>&& aRequests) {
+  ProcInfoPromise::ResolveOrRejectValue result;
+
+  HashMap<base::ProcessId, ProcInfo> gathered;
+  if (!gathered.reserve(aRequests.Length())) {
+    result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+    return result;
+  }
+  for (const auto& request : aRequests) {
+    size_t size;
+    int mib[6];
+    mib[0] = CTL_KERN;
+    mib[1] = KERN_PROC;
+    mib[2] = KERN_PROC_PID | KERN_PROC_SHOW_THREADS;
+    mib[3] = request.pid;
+    mib[4] = sizeof(kinfo_proc);
+    mib[5] = 0;
+    if (sysctl(mib, 6, nullptr, &size, nullptr, 0) == -1) {
+      // Can't get info for this process. Skip it.
+      continue;
+    }
+
+    mib[5] = size / sizeof(kinfo_proc);
+    auto procs = MakeUniqueFallible<kinfo_proc[]>(mib[5]);
+    if (!procs) {
+      result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+      return result;
+    }
+    if (sysctl(mib, 6, procs.get(), &size, nullptr, 0) == -1 &&
+        errno != ENOMEM) {
+      continue;
+    }
+
+    ProcInfo info;
+    info.pid = request.pid;
+    info.childId = request.childId;
+    info.type = request.processType;
+    info.origin = request.origin;
+    info.windows = std::move(request.windowInfo);
+    info.utilityActors = std::move(request.utilityInfo);
+
+    bool found = false;
+    for (size_t i = 0; i < size / sizeof(kinfo_proc); i++) {
+      const auto& p = procs[i];
+      if (p.p_tid == -1) {
+        // This is the process.
+        found = true;
+        info.cpuTime = uint64_t(p.p_rtime_sec) * 1'000'000'000u +
+                       uint64_t(p.p_rtime_usec) * 1'000u;
+        info.memory =
+            (p.p_vm_tsize + p.p_vm_dsize + p.p_vm_ssize) * getpagesize();
+      } else {
+        // This is one of its threads.
+        ThreadInfo threadInfo;
+        threadInfo.tid = p.p_tid;
+        threadInfo.cpuTime = uint64_t(p.p_rtime_sec) * 1'000'000'000u +
+                             uint64_t(p.p_rtime_usec) * 1'000u;
+        info.threads.AppendElement(threadInfo);
+      }
+    }
+
+    if (found && !gathered.put(request.pid, std::move(info))) {
+      result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+      return result;
+    }
+  }
+
+  // ... and we're done!
+  result.SetResolve(std::move(gathered));
+  return result;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/components/processtools/ProcInfo_common.cpp b/toolkit/components/processtools/ProcInfo_common.cpp
new file mode 100644
index 0000000000..ee64b157e0
--- /dev/null
+++ b/toolkit/components/processtools/ProcInfo_common.cpp
@@ -0,0 +1,65 @@
+/* -*- 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/. */
+
+#include "mozilla/ProcInfo.h"
+
+#include "mozilla/UniquePtr.h"
+#include "nsNetCID.h"
+#include "nsServiceManagerUtils.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla {
+
+RefPtr<ProcInfoPromise> GetProcInfo(nsTArray<ProcInfoRequest>&& aRequests) {
+  auto holder = MakeUnique<MozPromiseHolder<ProcInfoPromise>>();
+  RefPtr<ProcInfoPromise> promise = holder->Ensure(__func__);
+
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsIEventTarget> target =
+      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID, &rv);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Failed to get stream transport service");
+    holder->Reject(rv, __func__);
+    return promise;
+  }
+
+  RefPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      __func__,
+      [holder = std::move(holder),
+       requests = std::move(aRequests)]() mutable -> void {
+        holder->ResolveOrReject(GetProcInfoSync(std::move(requests)), __func__);
+      });
+
+  rv = target->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Failed to dispatch the LoadDataRunnable.");
+  }
+
+  return promise;
+}
+
+nsCString GetUtilityActorName(const UtilityActorName aActorName) {
+  switch (aActorName) {
+    case UtilityActorName::Unknown:
+      return "unknown"_ns;
+    case UtilityActorName::AudioDecoder_Generic:
+      return "audio-decoder-generic"_ns;
+    case UtilityActorName::AudioDecoder_AppleMedia:
+      return "audio-decoder-applemedia"_ns;
+    case UtilityActorName::AudioDecoder_WMF:
+      return "audio-decoder-wmf"_ns;
+    case UtilityActorName::MfMediaEngineCDM:
+      return "mf-media-engine"_ns;
+    case UtilityActorName::JSOracle:
+      return "js-oracle"_ns;
+    case UtilityActorName::WindowsUtils:
+      return "windows-utils"_ns;
+    default:
+      return "unknown"_ns;
+  }
+}
+
+}  // namespace mozilla
diff --git a/toolkit/components/processtools/ProcInfo_linux.cpp b/toolkit/components/processtools/ProcInfo_linux.cpp
new file mode 100644
index 0000000000..51aa35c62e
--- /dev/null
+++ b/toolkit/components/processtools/ProcInfo_linux.cpp
@@ -0,0 +1,344 @@
+/* -*- 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/. */
+
+#include "mozilla/ProcInfo.h"
+#include "mozilla/ProcInfo_linux.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/Logging.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "nsMemoryReporterManager.h"
+#include "nsWhitespaceTokenizer.h"
+
+#include <cstdio>
+#include <cstring>
+#include <unistd.h>
+#include <dirent.h>
+
+#define NANOPERSEC 1000000000.
+
+namespace mozilla {
+
+int GetCycleTimeFrequencyMHz() { return 0; }
+
+// StatReader can parse and tokenize a POSIX stat file.
+// see http://man7.org/linux/man-pages/man5/proc.5.html
+//
+// Its usage is quite simple:
+//
+// StatReader reader(pid);
+// ProcInfo info;
+// rv = reader.ParseProc(info);
+// if (NS_FAILED(rv)) {
+//     // the reading of the file or its parsing failed.
+// }
+//
+class StatReader {
+ public:
+  explicit StatReader(const base::ProcessId aPid)
+      : mPid(aPid), mMaxIndex(15), mTicksPerSec(sysconf(_SC_CLK_TCK)) {}
+
+  nsresult ParseProc(ProcInfo& aInfo) {
+    nsAutoString fileContent;
+    nsresult rv = ReadFile(fileContent);
+    NS_ENSURE_SUCCESS(rv, rv);
+    // We first extract the file or thread name
+    int32_t startPos = fileContent.RFindChar('(');
+    if (startPos == -1) {
+      return NS_ERROR_FAILURE;
+    }
+    int32_t endPos = fileContent.RFindChar(')');
+    if (endPos == -1) {
+      return NS_ERROR_FAILURE;
+    }
+    int32_t len = endPos - (startPos + 1);
+    mName.Assign(Substring(fileContent, startPos + 1, len));
+
+    // now we can use the tokenizer for the rest of the file
+    nsWhitespaceTokenizer tokenizer(Substring(fileContent, endPos + 2));
+    int32_t index = 2;  // starting at third field
+    while (tokenizer.hasMoreTokens() && index < mMaxIndex) {
+      const nsAString& token = tokenizer.nextToken();
+      rv = UseToken(index, token, aInfo);
+      NS_ENSURE_SUCCESS(rv, rv);
+      index++;
+    }
+    return NS_OK;
+  }
+
+ protected:
+  // Called for each token found in the stat file.
+  nsresult UseToken(int32_t aIndex, const nsAString& aToken, ProcInfo& aInfo) {
+    // We're using a subset of what stat has to offer for now.
+    nsresult rv = NS_OK;
+    // see the proc documentation for fields index references.
+    switch (aIndex) {
+      case 13:
+        // Amount of time that this process has been scheduled
+        // in user mode, measured in clock ticks
+        aInfo.cpuTime += GetCPUTime(aToken, &rv);
+        NS_ENSURE_SUCCESS(rv, rv);
+        break;
+      case 14:
+        // Amount of time that this process has been scheduled
+        // in kernel mode, measured in clock ticks
+        aInfo.cpuTime += GetCPUTime(aToken, &rv);
+        NS_ENSURE_SUCCESS(rv, rv);
+        break;
+    }
+    return rv;
+  }
+
+  // Converts a token into a int64_t
+  uint64_t Get64Value(const nsAString& aToken, nsresult* aRv) {
+    // We can't use aToken.ToInteger64() since it returns a signed 64.
+    // and that can result into an overflow.
+    nsresult rv = NS_OK;
+    uint64_t out = 0;
+    if (sscanf(NS_ConvertUTF16toUTF8(aToken).get(), "%" PRIu64, &out) == 0) {
+      rv = NS_ERROR_FAILURE;
+    }
+    *aRv = rv;
+    return out;
+  }
+
+  // Converts a token into CPU time in nanoseconds.
+  uint64_t GetCPUTime(const nsAString& aToken, nsresult* aRv) {
+    nsresult rv;
+    uint64_t value = Get64Value(aToken, &rv);
+    *aRv = rv;
+    if (NS_FAILED(rv)) {
+      return 0;
+    }
+    if (value) {
+      value = (value * NANOPERSEC) / mTicksPerSec;
+    }
+    return value;
+  }
+
+  base::ProcessId mPid;
+  int32_t mMaxIndex;
+  nsCString mFilepath;
+  nsString mName;
+
+ private:
+  // Reads the stat file and puts its content in a nsString.
+  nsresult ReadFile(nsAutoString& aFileContent) {
+    if (mFilepath.IsEmpty()) {
+      if (mPid == 0) {
+        mFilepath.AssignLiteral("/proc/self/stat");
+      } else {
+        mFilepath.AppendPrintf("/proc/%u/stat", unsigned(mPid));
+      }
+    }
+    FILE* fstat = fopen(mFilepath.get(), "r");
+    if (!fstat) {
+      return NS_ERROR_FAILURE;
+    }
+    // /proc is a virtual file system and all files are
+    // of size 0, so GetFileSize() and related functions will
+    // return 0 - so the way to read the file is to fill a buffer
+    // of an arbitrary big size and look for the end of line char.
+    char buffer[2048];
+    char* end;
+    char* start = fgets(buffer, 2048, fstat);
+    fclose(fstat);
+    if (start == nullptr) {
+      return NS_ERROR_FAILURE;
+    }
+    // let's find the end
+    end = strchr(buffer, '\n');
+    if (!end) {
+      return NS_ERROR_FAILURE;
+    }
+    aFileContent.AssignASCII(buffer, size_t(end - start));
+    return NS_OK;
+  }
+
+  int64_t mTicksPerSec;
+};
+
+// Threads have the same stat file. The only difference is its path
+// and we're getting less info in the ThreadInfo structure.
+class ThreadInfoReader final : public StatReader {
+ public:
+  ThreadInfoReader(const base::ProcessId aPid, const base::ProcessId aTid)
+      : StatReader(aPid) {
+    mFilepath.AppendPrintf("/proc/%u/task/%u/stat", unsigned(aPid),
+                           unsigned(aTid));
+  }
+
+  nsresult ParseThread(ThreadInfo& aInfo) {
+    ProcInfo info;
+    nsresult rv = StatReader::ParseProc(info);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Copying over the data we got from StatReader::ParseProc()
+    aInfo.cpuTime = info.cpuTime;
+    aInfo.name.Assign(mName);
+    return NS_OK;
+  }
+};
+
+nsresult GetCpuTimeSinceProcessStartInMs(uint64_t* aResult) {
+  timespec t;
+  if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &t) == 0) {
+    uint64_t cpuTime =
+        uint64_t(t.tv_sec) * 1'000'000'000u + uint64_t(t.tv_nsec);
+    *aResult = cpuTime / PR_NSEC_PER_MSEC;
+    return NS_OK;
+  }
+
+  StatReader reader(0);
+  ProcInfo info;
+  nsresult rv = reader.ParseProc(info);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  *aResult = info.cpuTime / PR_NSEC_PER_MSEC;
+  return NS_OK;
+}
+
+nsresult GetGpuTimeSinceProcessStartInMs(uint64_t* aResult) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+ProcInfoPromise::ResolveOrRejectValue GetProcInfoSync(
+    nsTArray<ProcInfoRequest>&& aRequests) {
+  ProcInfoPromise::ResolveOrRejectValue result;
+
+  HashMap<base::ProcessId, ProcInfo> gathered;
+  if (!gathered.reserve(aRequests.Length())) {
+    result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+    return result;
+  }
+  for (const auto& request : aRequests) {
+    ProcInfo info;
+
+    timespec t;
+    clockid_t clockid = MAKE_PROCESS_CPUCLOCK(request.pid, CPUCLOCK_SCHED);
+    if (clock_gettime(clockid, &t) == 0) {
+      info.cpuTime = uint64_t(t.tv_sec) * 1'000'000'000u + uint64_t(t.tv_nsec);
+    } else {
+      // Fallback to parsing /proc/<pid>/stat
+      StatReader reader(request.pid);
+      nsresult rv = reader.ParseProc(info);
+      if (NS_FAILED(rv)) {
+        // Can't read data for this proc.
+        // Probably either a sandboxing issue or a race condition, e.g.
+        // the process has been just been killed. Regardless, skip process.
+        continue;
+      }
+    }
+
+    // The 'Memory' value displayed in the system monitor is resident -
+    // shared. statm contains more fields, but we're only interested in
+    // the first three.
+    static const int MAX_FIELD = 3;
+    size_t VmSize, resident, shared;
+    info.memory = 0;
+    FILE* f = fopen(nsPrintfCString("/proc/%u/statm", request.pid).get(), "r");
+    if (f) {
+      int nread = fscanf(f, "%zu %zu %zu", &VmSize, &resident, &shared);
+      fclose(f);
+      if (nread == MAX_FIELD) {
+        info.memory = (resident - shared) * getpagesize();
+      }
+    }
+
+    // Extra info
+    info.pid = request.pid;
+    info.childId = request.childId;
+    info.type = request.processType;
+    info.origin = request.origin;
+    info.windows = std::move(request.windowInfo);
+    info.utilityActors = std::move(request.utilityInfo);
+
+    // Let's look at the threads
+    nsCString taskPath;
+    taskPath.AppendPrintf("/proc/%u/task", unsigned(request.pid));
+    DIR* dirHandle = opendir(taskPath.get());
+    if (!dirHandle) {
+      // For some reason, we have no data on the threads for this process.
+      // Most likely reason is that we have just lost a race condition and
+      // the process is dead.
+      // Let's stop here and ignore the entire process.
+      continue;
+    }
+    auto cleanup = mozilla::MakeScopeExit([&] { closedir(dirHandle); });
+
+    // If we can't read some thread info, we ignore that thread.
+    dirent* entry;
+    while ((entry = readdir(dirHandle)) != nullptr) {
+      if (entry->d_name[0] == '.') {
+        continue;
+      }
+      nsAutoCString entryName(entry->d_name);
+      nsresult rv;
+      int32_t tid = entryName.ToInteger(&rv);
+      if (NS_FAILED(rv)) {
+        continue;
+      }
+
+      ThreadInfo threadInfo;
+      threadInfo.tid = tid;
+
+      timespec ts;
+      if (clock_gettime(MAKE_THREAD_CPUCLOCK(tid, CPUCLOCK_SCHED), &ts) == 0) {
+        threadInfo.cpuTime =
+            uint64_t(ts.tv_sec) * 1'000'000'000u + uint64_t(ts.tv_nsec);
+
+        nsCString path;
+        path.AppendPrintf("/proc/%u/task/%u/comm", unsigned(request.pid),
+                          unsigned(tid));
+        FILE* fstat = fopen(path.get(), "r");
+        if (fstat) {
+          // /proc is a virtual file system and all files are
+          // of size 0, so GetFileSize() and related functions will
+          // return 0 - so the way to read the file is to fill a buffer
+          // of an arbitrary big size and look for the end of line char.
+          // The size of the buffer needs to be as least 16, which is the
+          // value of TASK_COMM_LEN in the Linux kernel.
+          char buffer[32];
+          char* start = fgets(buffer, sizeof(buffer), fstat);
+          fclose(fstat);
+          if (start) {
+            // The thread name should always be smaller than our buffer,
+            // so we should find a newline character.
+            char* end = strchr(buffer, '\n');
+            if (end) {
+              threadInfo.name.AssignASCII(buffer, size_t(end - start));
+              info.threads.AppendElement(threadInfo);
+              continue;
+            }
+          }
+        }
+      }
+
+      // Fallback to parsing /proc/<pid>/task/<tid>/stat
+      // This is needed for child processes, as access to the per-thread
+      // CPU clock is restricted to the process owning the thread.
+      ThreadInfoReader reader(request.pid, tid);
+      rv = reader.ParseThread(threadInfo);
+      if (NS_FAILED(rv)) {
+        continue;
+      }
+      info.threads.AppendElement(threadInfo);
+    }
+
+    if (!gathered.put(request.pid, std::move(info))) {
+      result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+      return result;
+    }
+  }
+
+  // ... and we're done!
+  result.SetResolve(std::move(gathered));
+  return result;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/components/processtools/ProcInfo_linux.h b/toolkit/components/processtools/ProcInfo_linux.h
new file mode 100644
index 0000000000..7be1ca5cb7
--- /dev/null
+++ b/toolkit/components/processtools/ProcInfo_linux.h
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#ifndef __mozilla_ProcInfo_linux_h
+#define __mozilla_ProcInfo_linux_h
+
+// The following is directly inspired from kernel:
+// https://github.com/torvalds/linux/blob/v5.16/include/linux/posix-timers.h#L29-L48
+#ifndef CPUCLOCK_SCHED
+#  define CPUCLOCK_SCHED 2
+#endif
+#ifndef CPUCLOCK_PERTHREAD_MASK
+#  define CPUCLOCK_PERTHREAD_MASK 4
+#endif
+#ifndef MAKE_PROCESS_CPUCLOCK
+#  define MAKE_PROCESS_CPUCLOCK(pid, clock) \
+    ((int)(~(unsigned)(pid) << 3) | (int)(clock))
+#endif
+#ifndef MAKE_THREAD_CPUCLOCK
+#  define MAKE_THREAD_CPUCLOCK(tid, clock) \
+    MAKE_PROCESS_CPUCLOCK(tid, (clock) | CPUCLOCK_PERTHREAD_MASK)
+#endif
+
+#endif  // ProcInfo_linux_h
diff --git a/toolkit/components/processtools/ProcInfo_win.cpp b/toolkit/components/processtools/ProcInfo_win.cpp
new file mode 100644
index 0000000000..f290f3d8df
--- /dev/null
+++ b/toolkit/components/processtools/ProcInfo_win.cpp
@@ -0,0 +1,283 @@
+/* -*- 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/. */
+
+#include "mozilla/ProcInfo.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "mozilla/SSE.h"
+#include "gfxWindowsPlatform.h"
+#include "nsMemoryReporterManager.h"
+#include "nsWindowsHelpers.h"
+#include <windows.h>
+#include <psapi.h>
+#include <winternl.h>
+
+#ifndef STATUS_INFO_LENGTH_MISMATCH
+#  define STATUS_INFO_LENGTH_MISMATCH ((NTSTATUS)0xC0000004L)
+#endif
+
+#define PR_USEC_PER_NSEC 1000L
+
+typedef HRESULT(WINAPI* GETTHREADDESCRIPTION)(HANDLE hThread,
+                                              PWSTR* threadDescription);
+
+namespace mozilla {
+
+static uint64_t ToNanoSeconds(const FILETIME& aFileTime) {
+  // FILETIME values are 100-nanoseconds units, converting
+  ULARGE_INTEGER usec = {{aFileTime.dwLowDateTime, aFileTime.dwHighDateTime}};
+  return usec.QuadPart * 100;
+}
+
+int GetCycleTimeFrequencyMHz() {
+  static const int frequency = []() {
+    // Having a constant TSC is required to convert cycle time to actual time.
+    if (!mozilla::has_constant_tsc()) {
+      return 0;
+    }
+
+    // Now get the nominal CPU frequency.
+    HKEY key;
+    static const WCHAR keyName[] =
+        L"HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0";
+
+    if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keyName, 0, KEY_QUERY_VALUE, &key) ==
+        ERROR_SUCCESS) {
+      DWORD data, len;
+      len = sizeof(data);
+
+      if (RegQueryValueEx(key, L"~Mhz", 0, 0, reinterpret_cast<LPBYTE>(&data),
+                          &len) == ERROR_SUCCESS) {
+        return static_cast<int>(data);
+      }
+    }
+
+    return 0;
+  }();
+
+  return frequency;
+}
+
+nsresult GetCpuTimeSinceProcessStartInMs(uint64_t* aResult) {
+  int frequencyInMHz = GetCycleTimeFrequencyMHz();
+  if (frequencyInMHz) {
+    uint64_t cpuCycleCount;
+    if (!QueryProcessCycleTime(::GetCurrentProcess(), &cpuCycleCount)) {
+      return NS_ERROR_FAILURE;
+    }
+    constexpr int HZ_PER_MHZ = 1000000;
+    *aResult =
+        cpuCycleCount / (frequencyInMHz * (HZ_PER_MHZ / PR_MSEC_PER_SEC));
+    return NS_OK;
+  }
+
+  FILETIME createTime, exitTime, kernelTime, userTime;
+  if (!GetProcessTimes(::GetCurrentProcess(), &createTime, &exitTime,
+                       &kernelTime, &userTime)) {
+    return NS_ERROR_FAILURE;
+  }
+  *aResult =
+      (ToNanoSeconds(kernelTime) + ToNanoSeconds(userTime)) / PR_NSEC_PER_MSEC;
+  return NS_OK;
+}
+
+nsresult GetGpuTimeSinceProcessStartInMs(uint64_t* aResult) {
+  return gfxWindowsPlatform::GetGpuTimeSinceProcessStartInMs(aResult);
+}
+
+ProcInfoPromise::ResolveOrRejectValue GetProcInfoSync(
+    nsTArray<ProcInfoRequest>&& aRequests) {
+  ProcInfoPromise::ResolveOrRejectValue result;
+
+  HashMap<base::ProcessId, ProcInfo> gathered;
+  if (!gathered.reserve(aRequests.Length())) {
+    result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+    return result;
+  }
+
+  int frequencyInMHz = GetCycleTimeFrequencyMHz();
+
+  // ---- Copying data on processes (minus threads).
+
+  for (const auto& request : aRequests) {
+    nsAutoHandle handle(OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ,
+                                    FALSE, request.pid));
+
+    if (!handle) {
+      // Ignore process, it may have died.
+      continue;
+    }
+
+    uint64_t cpuCycleTime;
+    if (!QueryProcessCycleTime(handle.get(), &cpuCycleTime)) {
+      // Ignore process, it may have died.
+      continue;
+    }
+
+    uint64_t cpuTime;
+    if (frequencyInMHz) {
+      cpuTime = cpuCycleTime * PR_USEC_PER_NSEC / frequencyInMHz;
+    } else {
+      FILETIME createTime, exitTime, kernelTime, userTime;
+      if (!GetProcessTimes(handle.get(), &createTime, &exitTime, &kernelTime,
+                           &userTime)) {
+        // Ignore process, it may have died.
+        continue;
+      }
+      cpuTime = ToNanoSeconds(kernelTime) + ToNanoSeconds(userTime);
+    }
+
+    PROCESS_MEMORY_COUNTERS_EX memoryCounters;
+    if (!GetProcessMemoryInfo(handle.get(),
+                              (PPROCESS_MEMORY_COUNTERS)&memoryCounters,
+                              sizeof(memoryCounters))) {
+      // Ignore process, it may have died.
+      continue;
+    }
+
+    // Assumption: values of `pid` are distinct between processes,
+    // regardless of any race condition we might have stumbled upon. Even
+    // if it somehow could happen, in the worst case scenario, we might
+    // end up overwriting one process info and we might end up with too
+    // many threads attached to a process, as the data is not crucial, we
+    // do not need to defend against that (unlikely) scenario.
+    ProcInfo info;
+    info.pid = request.pid;
+    info.childId = request.childId;
+    info.type = request.processType;
+    info.origin = request.origin;
+    info.windows = std::move(request.windowInfo);
+    info.utilityActors = std::move(request.utilityInfo);
+    info.cpuTime = cpuTime;
+    info.cpuCycleCount = cpuCycleTime;
+    info.memory = memoryCounters.PrivateUsage;
+
+    if (!gathered.put(request.pid, std::move(info))) {
+      result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+      return result;
+    }
+  }
+
+  // ---- Add thread data to already-copied processes.
+
+  NTSTATUS ntStatus;
+
+  UniquePtr<char[]> buf;
+  ULONG bufLen = 512u * 1024u;
+
+  // We must query for information in a loop, since we are effectively asking
+  // the kernel to take a snapshot of all the processes on the system;
+  // the size of the required buffer may fluctuate between successive calls.
+  do {
+    // These allocations can be hundreds of megabytes on some computers, so
+    // we should use fallible new here.
+    buf = MakeUniqueFallible<char[]>(bufLen);
+    if (!buf) {
+      result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+      return result;
+    }
+
+    ntStatus = ::NtQuerySystemInformation(SystemProcessInformation, buf.get(),
+                                          bufLen, &bufLen);
+    if (ntStatus != STATUS_INFO_LENGTH_MISMATCH) {
+      break;
+    }
+
+    // If we need another NtQuerySystemInformation call, allocate a
+    // slightly larger buffer than what would have been needed this time,
+    // to account for possible process or thread creations that might
+    // happen between our calls.
+    bufLen += 8u * 1024u;
+  } while (true);
+  if (!NT_SUCCESS(ntStatus)) {
+    result.SetReject(NS_ERROR_UNEXPECTED);
+    return result;
+  }
+
+  // `GetThreadDescription` is available as of Windows 10.
+  // We attempt to import it dynamically, knowing that it
+  // may be `nullptr`.
+  auto getThreadDescription =
+      reinterpret_cast<GETTHREADDESCRIPTION>(::GetProcAddress(
+          ::GetModuleHandleW(L"Kernel32.dll"), "GetThreadDescription"));
+
+  PSYSTEM_PROCESS_INFORMATION processInfo;
+  for (ULONG offset = 0;; offset += processInfo->NextEntryOffset) {
+    MOZ_RELEASE_ASSERT(offset < bufLen);
+    processInfo =
+        reinterpret_cast<PSYSTEM_PROCESS_INFORMATION>(buf.get() + offset);
+    ULONG pid = HandleToUlong(processInfo->UniqueProcessId);
+    // Check if we are interested in this process.
+    auto processLookup = gathered.lookup(pid);
+    if (processLookup) {
+      for (ULONG i = 0; i < processInfo->NumberOfThreads; ++i) {
+        // The thread information structs are stored in the buffer right
+        // after the SYSTEM_PROCESS_INFORMATION struct.
+        PSYSTEM_THREAD_INFORMATION thread =
+            reinterpret_cast<PSYSTEM_THREAD_INFORMATION>(
+                buf.get() + offset + sizeof(SYSTEM_PROCESS_INFORMATION) +
+                sizeof(SYSTEM_THREAD_INFORMATION) * i);
+        ULONG tid = HandleToUlong(thread->ClientId.UniqueThread);
+
+        ThreadInfo* threadInfo =
+            processLookup->value().threads.AppendElement(fallible);
+        if (!threadInfo) {
+          result.SetReject(NS_ERROR_OUT_OF_MEMORY);
+          return result;
+        }
+
+        nsAutoHandle hThread(
+            OpenThread(/* dwDesiredAccess = */ THREAD_QUERY_INFORMATION,
+                       /* bInheritHandle = */ FALSE,
+                       /* dwThreadId = */ tid));
+        if (!hThread) {
+          // Cannot open thread. Not sure why, but let's erase this thread
+          // and attempt to find data on other threads.
+          processLookup->value().threads.RemoveLastElement();
+          continue;
+        }
+
+        threadInfo->tid = tid;
+
+        // Attempt to get thread times.
+        // If we fail, continue without this piece of information.
+        if (QueryThreadCycleTime(hThread.get(), &threadInfo->cpuCycleCount) &&
+            frequencyInMHz) {
+          threadInfo->cpuTime =
+              threadInfo->cpuCycleCount * PR_USEC_PER_NSEC / frequencyInMHz;
+        } else {
+          FILETIME createTime, exitTime, kernelTime, userTime;
+          if (GetThreadTimes(hThread.get(), &createTime, &exitTime, &kernelTime,
+                             &userTime)) {
+            threadInfo->cpuTime =
+                ToNanoSeconds(kernelTime) + ToNanoSeconds(userTime);
+          }
+        }
+
+        // Attempt to get thread name.
+        // If we fail, continue without this piece of information.
+        if (getThreadDescription) {
+          PWSTR threadName = nullptr;
+          if (getThreadDescription(hThread.get(), &threadName) && threadName) {
+            threadInfo->name = threadName;
+          }
+          if (threadName) {
+            LocalFree(threadName);
+          }
+        }
+      }
+    }
+
+    if (processInfo->NextEntryOffset == 0) {
+      break;
+    }
+  }
+
+  // ----- We're ready to return.
+  result.SetResolve(std::move(gathered));
+  return result;
+}
+
+}  // namespace mozilla
diff --git a/toolkit/components/processtools/ProcessToolsService.cpp b/toolkit/components/processtools/ProcessToolsService.cpp
new file mode 100644
index 0000000000..3855996fdf
--- /dev/null
+++ b/toolkit/components/processtools/ProcessToolsService.cpp
@@ -0,0 +1,33 @@
+/* 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/. */
+
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/StaticPtr.h"
+#include "nsCOMPtr.h"
+#include "ProcessToolsService.h"
+
+// This anonymous namespace prevents outside C++ code from improperly accessing
+// these implementation details.
+namespace {
+extern "C" {
+// Implemented in Rust.
+void new_process_tools_service(nsIProcessToolsService** result);
+}
+
+static mozilla::StaticRefPtr<nsIProcessToolsService> sProcessToolsService;
+}  // namespace
+
+already_AddRefed<nsIProcessToolsService> GetProcessToolsService() {
+  nsCOMPtr<nsIProcessToolsService> processToolsService;
+
+  if (sProcessToolsService) {
+    processToolsService = sProcessToolsService;
+  } else {
+    new_process_tools_service(getter_AddRefs(processToolsService));
+    sProcessToolsService = processToolsService;
+    mozilla::ClearOnShutdown(&sProcessToolsService);
+  }
+
+  return processToolsService.forget();
+}
diff --git a/toolkit/components/processtools/ProcessToolsService.h b/toolkit/components/processtools/ProcessToolsService.h
new file mode 100644
index 0000000000..932fd5d4eb
--- /dev/null
+++ b/toolkit/components/processtools/ProcessToolsService.h
@@ -0,0 +1,8 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "nsIProcessToolsService.h"
+
+already_AddRefed<nsIProcessToolsService> GetProcessToolsService();
diff --git a/toolkit/components/processtools/components.conf b/toolkit/components/processtools/components.conf
new file mode 100644
index 0000000000..6e7aede0dc
--- /dev/null
+++ b/toolkit/components/processtools/components.conf
@@ -0,0 +1,10 @@
+Classes = [
+    {
+        'cid': '{79A13656-A472-4713-B0E1-AB39A15CF790}',
+        'contract_ids': ["@mozilla.org/processtools-service;1"],
+        'type': 'nsIProcessToolsService',
+        'constructor': 'GetProcessToolsService',
+        'singleton': True,
+        'headers': ['ProcessToolsService.h'],
+    }
+]
diff --git a/toolkit/components/processtools/metrics.yaml b/toolkit/components/processtools/metrics.yaml
new file mode 100644
index 0000000000..6efbd22fa5
--- /dev/null
+++ b/toolkit/components/processtools/metrics.yaml
@@ -0,0 +1,337 @@
+# 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/.
+
+# Adding a new metric? We have docs for that!
+# https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/new_definitions_file.html
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+$tags:
+  - "Core :: DOM: Content Processes"
+
+power:
+  cpu_time_bogus_values:
+    type: counter
+    description: >
+      Impossibly large CPU time values that were discarded.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1755733
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1755733
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    telemetry_mirror: POWER_CPU_TIME_BOGUS_VALUES
+
+  cpu_time_per_process_type_ms:
+    type: labeled_counter
+    description: >
+      CPU time used by each process type in ms.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1747138
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1747138
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    labels: &per_process_type_labels
+      - parent.active
+      - parent.active.playing-audio
+      - parent.active.playing-video
+      - parent.inactive
+      - parent.inactive.playing-audio
+      - parent.inactive.playing-video
+      - prealloc
+      - privilegedabout
+      - rdd
+      - socket
+      - web.background
+      - web.background-perceivable
+      - web.foreground
+      - extension
+      - gpu
+      - gmplugin
+      - utility
+    telemetry_mirror: POWER_CPU_TIME_PER_PROCESS_TYPE_MS
+
+  cpu_time_per_tracker_type_ms:
+    type: labeled_counter
+    description: >
+      CPU time used by content processes used only for tracking resources,
+      labeled by the category of the tracker.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1802361
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1802361
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    labels:
+      - ad
+      - analytics
+      - cryptomining
+      - fingerprinting
+      - social
+      - unknown
+
+  gpu_time_per_process_type_ms:
+    type: labeled_counter
+    description: >
+      GPU time used by each process type in ms.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1747138
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1747138
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    labels: *per_process_type_labels
+    telemetry_mirror: POWER_GPU_TIME_PER_PROCESS_TYPE_MS
+
+  gpu_time_bogus_values:
+    type: counter
+    description: >
+      Impossibly large GPU time values that were discarded.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1755733
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1755733
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    telemetry_mirror: POWER_GPU_TIME_BOGUS_VALUES
+
+  wakeups_per_process_type:
+    type: labeled_counter
+    description: >
+      How many times threads woke up and could have woken up a CPU core.
+      Broken down by process type.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1759535
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1759535
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    labels: *per_process_type_labels
+    telemetry_mirror: POWER_WAKEUPS_PER_PROCESS_TYPE
+
+  total_cpu_time_ms:
+    type: counter
+    description: >
+      Total CPU time used by all processes in ms.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1736040
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1736040
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    telemetry_mirror: POWER_TOTAL_CPU_TIME_MS
+
+  total_gpu_time_ms:
+    type: counter
+    description: >
+      Total GPU time used by all processes in ms.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1743176
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1743176
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    telemetry_mirror: POWER_TOTAL_GPU_TIME_MS
+
+  total_thread_wakeups:
+    type: counter
+    description: >
+      How many times threads woke up and could have woken up a CPU core.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1759535
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1759535
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    telemetry_mirror: POWER_TOTAL_THREAD_WAKEUPS
+
+power.wakeups_per_thread:
+  parent_active: &per_thread_wakeups
+    type: labeled_counter
+    description: >
+      How many times threads woke up and could have woken up a CPU core.
+      Broken down by thread name for a given process type.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1763474
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1763474
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    labels: &per_thread_labels
+      - asynclogger
+      - audioipc
+      - audioipc_callback_rpc
+      - audioipc_client_callback
+      - audioipc_client_rpc
+      - audioipc_devicecollection_rpc
+      - audioipc_server_callback
+      - audioipc_server_rpc
+      - backgroundthreadpool
+      - bgiothreadpool
+      - bgreadurls
+      - bhmgr_monitor
+      - bhmgr_processor
+      - cameras_ipc
+      - capturethread
+      - classifier_update
+      - com_mta
+      - compositor
+      - cookie
+      - cubeboperation
+      - datachannel_io
+      - dns_resolver
+      - dom_worker
+      - domcachethread
+      - extensionprotocolhandler
+      - font_loader
+      - fontenumthread
+      - fs_broker
+      - geckomain
+      - gmpthread
+      - graphrunner
+      - html5_parser
+      - imagebridgechld
+      - imageio
+      - indexeddb
+      - initfontlist
+      - inotifyeventthread
+      - ipc_i_o_child
+      - ipc_i_o_parent
+      - ipc_launch
+      - ipdl_background
+      - js_watchdog
+      - jump_list
+      - libwebrtcmodulethread
+      - link_monitor
+      - ls_thread
+      - mediacache
+      - mediadecoderstatemachine
+      - mediapdecoder
+      - mediasupervisor
+      - mediatimer
+      - mediatrackgrph
+      - memorypoller
+      - mozstorage
+      - mtransport
+      - netlink_monitor
+      - pacerthread
+      - permission
+      - playeventsound
+      - processhangmon
+      - profilerchild
+      - proxyresolution
+      - quotamanager_io
+      - registerfonts
+      - remotebackbuffer
+      - remotelzystream
+      - remvidchild
+      - renderer
+      - sandboxreporter
+      - savescripts
+      - socket_thread
+      - softwarevsyncthread
+      - ssl_cert
+      - startupcache
+      - streamtrans
+      - stylethread
+      - swcomposite
+      - taskcontroller
+      - timer
+      - toastbgthread
+      - trr_background
+      - untrusted_modules
+      - url_classifier
+      - videocapture
+      - vsynciothread
+      - webrtccallthread
+      - webrtcworker
+      - wincompositor
+      - windowsvsyncthread
+      - winwindowocclusioncalc
+      - worker_launcher
+      - wrrenderbackend
+      - wrscenebuilder
+      - wrscenebuilderlp
+      - wrworker
+      - wrworkerlp
+
+  parent_inactive: *per_thread_wakeups
+  content_foreground: *per_thread_wakeups
+  content_background: *per_thread_wakeups
+  gpu_process: *per_thread_wakeups
+
+power.cpu_ms_per_thread:
+  parent_active: &per_thread_cpu_ms
+    type: labeled_counter
+    description: >
+      How many miliseconds of CPU time were used.
+      Broken down by thread name for a given process type.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1763474
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1763474
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
+    labels: *per_thread_labels
+
+  parent_inactive: *per_thread_cpu_ms
+  content_foreground: *per_thread_cpu_ms
+  content_background: *per_thread_cpu_ms
+  gpu_process: *per_thread_cpu_ms
+
+power.battery:
+  percentage_when_user_active:
+    type: custom_distribution
+    description: >
+      Records how many percent of battery was available for each period of
+      user activity.
+    range_min: 0
+    range_max: 100
+    bucket_count: 100
+    histogram_type: linear
+    unit: percent
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1769255
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1769255
+    data_sensitivity:
+      - interaction
+      - technical
+    notification_emails:
+      - florian@mozilla.com
+    expires: never
diff --git a/toolkit/components/processtools/moz.build b/toolkit/components/processtools/moz.build
new file mode 100644
index 0000000000..b7c164c1b0
--- /dev/null
+++ b/toolkit/components/processtools/moz.build
@@ -0,0 +1,51 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Toolkit", "Performance Monitoring")
+
+XPIDL_MODULE = "toolkit_processtools"
+
+XPCOM_MANIFESTS += [
+    "components.conf",
+]
+
+XPIDL_SOURCES += [
+    "nsIProcessToolsService.idl",
+]
+
+EXPORTS.mozilla += [
+    "ProcInfo.h",
+    "ProcInfo_linux.h",
+]
+
+EXPORTS += [
+    "ProcessToolsService.h",
+]
+
+UNIFIED_SOURCES += [
+    "ProcessToolsService.cpp",
+    "ProcInfo_common.cpp",
+]
+
+FINAL_LIBRARY = "xul"
+
+XPCSHELL_TESTS_MANIFESTS += ["tests/xpcshell/xpcshell.ini"]
+BROWSER_CHROME_MANIFESTS += ["tests/browser/browser.ini"]
+
+# Platform-specific implementations of `ProcInfo`.
+toolkit = CONFIG["MOZ_WIDGET_TOOLKIT"]
+if toolkit == "gtk" or toolkit == "android":
+    if CONFIG["OS_TARGET"] == "OpenBSD":
+        UNIFIED_SOURCES += ["ProcInfo_bsd.cpp"]
+    else:
+        UNIFIED_SOURCES += ["ProcInfo_linux.cpp"]
+elif toolkit == "windows":
+    UNIFIED_SOURCES += ["ProcInfo_win.cpp"]
+elif toolkit == "cocoa":
+    UNIFIED_SOURCES += ["ProcInfo.mm"]
+
+include("/ipc/chromium/chromium-config.mozbuild")
diff --git a/toolkit/components/processtools/nsIProcessToolsService.idl b/toolkit/components/processtools/nsIProcessToolsService.idl
new file mode 100644
index 0000000000..4298cdddf8
--- /dev/null
+++ b/toolkit/components/processtools/nsIProcessToolsService.idl
@@ -0,0 +1,48 @@
+/* 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/. */
+
+#include "nsISupports.idl"
+
+[scriptable, uuid(1341f571-ebed-4305-b264-4d8fc3b6b11c)]
+interface nsIProcessToolsService: nsISupports {
+    /**
+     * Kill a process running on this system.
+     *
+     * Does not cause a crash report to be generated and sent.
+     *
+     * # Note
+     *
+     * `pid` is the unique-to-the-system process identifier, as
+     * obtained with attribute `pid` of this service.
+     *
+     * Under Un*ix, that's what you obtain with `getpid()`, etc.
+     * Under Windows, that's what you obtain with `GetCurrentProcessId()`,
+     * NOT the same thing as the process `HANDLE`.
+     *
+     * # Failure
+     *
+     * Under Windows, if two processes race to `kill()` a third process,
+     * or two threads race to `kill()` a process there is a (small) window
+     * during which this can cause a crash in the losing process.
+     *
+     * # Caveats
+     *
+     * Under Windows, process killing is asynchronous. Therefore, this
+     * function can return before process `pid` is actually dead.
+     */
+    void kill(in unsigned long long pid);
+
+    /**
+     * Crash a process running on this system. Generates a SIGABRT on Linux and
+     * macOS, and a STATUS_ILLEGAL_INSTRUCTION on Windows.
+     *
+     * Does cause a crash report to be generated.
+     */
+    void crash(in unsigned long long pid);
+
+    /**
+     * The pid for the current process.
+     */
+    readonly attribute unsigned long long pid;
+};
diff --git a/toolkit/components/processtools/src/lib.rs b/toolkit/components/processtools/src/lib.rs
new file mode 100644
index 0000000000..a84aa9ef62
--- /dev/null
+++ b/toolkit/components/processtools/src/lib.rs
@@ -0,0 +1,177 @@
+/* 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/. */
+
+#[cfg(not(target_os = "windows"))]
+extern crate libc;
+#[cfg(target_os = "windows")]
+extern crate winapi;
+
+extern crate nserror;
+extern crate xpcom;
+
+use std::convert::TryInto;
+
+use nserror::{nsresult, NS_ERROR_FAILURE, NS_OK};
+use xpcom::{interfaces::nsIProcessToolsService, xpcom, xpcom_method, RefPtr};
+
+// Separate this `use` to avoid build-breaking warnings.
+#[cfg(target_os = "windows")]
+use nserror::NS_ERROR_NOT_AVAILABLE;
+
+#[no_mangle]
+pub unsafe extern "C" fn new_process_tools_service(result: *mut *const nsIProcessToolsService) {
+    let service: RefPtr<ProcessToolsService> = ProcessToolsService::new();
+    RefPtr::new(service.coerce::<nsIProcessToolsService>()).forget(&mut *result);
+}
+
+#[cfg(target_os = "windows")]
+use std::ffi::c_void;
+
+// We want to generate an exception that can be caught by the exception handler
+// when injecting in a remote process, STATUS_ACCESS_VIOLATION seems not to do,
+// it but the following code generates a STATUS_ILLEGAL_INSTRUCTION that seems
+// to do the trick
+#[cfg(target_os = "windows")]
+pub unsafe extern "system" fn crash_illegal_instruction(_arg: *mut c_void) -> u32 {
+    std::ptr::null_mut::<u32>().write(1);
+    0
+}
+
+// Implementation note:
+//
+// We're following the strategy employed by the `kvstore`.
+// See https://searchfox.org/mozilla-central/rev/a87a1c3b543475276e6d57a7a80cb02f3e42b6ed/toolkit/components/kvstore/src/lib.rs#78
+
+#[xpcom(implement(nsIProcessToolsService), atomic)]
+pub struct ProcessToolsService {}
+
+impl ProcessToolsService {
+    pub fn new() -> RefPtr<ProcessToolsService> {
+        ProcessToolsService::allocate(InitProcessToolsService {})
+    }
+
+    // Method `kill`.
+
+    xpcom_method!(
+        kill => Kill(id: u64)
+    );
+
+    #[cfg(target_os = "windows")]
+    pub fn kill(&self, pid: u64) -> Result<(), nsresult> {
+        let handle = unsafe {
+            winapi::um::processthreadsapi::OpenProcess(
+                /* dwDesiredAccess */
+                winapi::um::winnt::PROCESS_TERMINATE | winapi::um::winnt::SYNCHRONIZE,
+                /* bInheritHandle */ 0,
+                /* dwProcessId */ pid.try_into().unwrap(),
+            )
+        };
+        if handle.is_null() {
+            // Could not open process.
+            return Err(NS_ERROR_NOT_AVAILABLE);
+        }
+
+        let result = unsafe {
+            winapi::um::processthreadsapi::TerminateProcess(
+                /* hProcess */ handle, /* uExitCode */ 0,
+            )
+        };
+
+        // Close handle regardless of success.
+        let _ = unsafe { winapi::um::handleapi::CloseHandle(handle) };
+
+        if result == 0 {
+            return Err(NS_ERROR_FAILURE);
+        }
+        Ok(())
+    }
+
+    #[cfg(not(target_os = "windows"))]
+    pub fn kill(&self, pid: u64) -> Result<(), nsresult> {
+        let pid = pid.try_into().or(Err(NS_ERROR_FAILURE))?;
+        let result = unsafe { libc::kill(pid, libc::SIGKILL) };
+        if result == 0 {
+            Ok(())
+        } else {
+            Err(NS_ERROR_FAILURE)
+        }
+    }
+
+    // Method `crash`
+
+    xpcom_method!(
+        crash => Crash(id: u64)
+    );
+
+    #[cfg(target_os = "windows")]
+    pub fn crash(&self, pid: u64) -> Result<(), nsresult> {
+        let target_proc = unsafe {
+            winapi::um::processthreadsapi::OpenProcess(
+                /* dwDesiredAccess */
+                winapi::um::winnt::PROCESS_VM_OPERATION
+                    | winapi::um::winnt::PROCESS_CREATE_THREAD
+                    | winapi::um::winnt::PROCESS_QUERY_INFORMATION,
+                /* bInheritHandle */ 0,
+                /* dwProcessId */ pid.try_into().unwrap(),
+            )
+        };
+        if target_proc.is_null() {
+            // Could not open process.
+            return Err(NS_ERROR_NOT_AVAILABLE);
+        }
+
+        let new_thread = unsafe {
+            winapi::um::processthreadsapi::CreateRemoteThread(
+                /* hProcess */ target_proc,
+                /* lpThreadAttributes */ std::ptr::null_mut(),
+                /* dwStackSize */ 0,
+                /* lpStartAddress */ Some(crash_illegal_instruction),
+                /* lpParameter */ std::ptr::null_mut(),
+                /* dwCreationFlags */ 0,
+                /* lpThreadId */ std::ptr::null_mut(),
+            )
+        };
+
+        // Close handle regardless of success.
+        let _ = unsafe {
+            winapi::um::synchapi::WaitForSingleObject(new_thread, winapi::um::winbase::INFINITE);
+            winapi::um::handleapi::CloseHandle(new_thread);
+            winapi::um::handleapi::CloseHandle(target_proc);
+        };
+
+        if new_thread.is_null() {
+            return Err(NS_ERROR_FAILURE);
+        }
+        Ok(())
+    }
+
+    #[cfg(not(target_os = "windows"))]
+    pub fn crash(&self, pid: u64) -> Result<(), nsresult> {
+        let pid = pid.try_into().or(Err(NS_ERROR_FAILURE))?;
+        let result = unsafe { libc::kill(pid, libc::SIGABRT) };
+        if result == 0 {
+            Ok(())
+        } else {
+            Err(NS_ERROR_FAILURE)
+        }
+    }
+
+    // Attribute `pid`
+
+    xpcom_method!(
+        get_pid => GetPid() -> u64
+    );
+
+    #[cfg(not(target_os = "windows"))]
+    pub fn get_pid(&self) -> Result<u64, nsresult> {
+        let pid = unsafe { libc::getpid() } as u64;
+        Ok(pid)
+    }
+
+    #[cfg(target_os = "windows")]
+    pub fn get_pid(&self) -> Result<u64, nsresult> {
+        let pid = unsafe { winapi::um::processthreadsapi::GetCurrentProcessId() } as u64;
+        Ok(pid)
+    }
+}
diff --git a/toolkit/components/processtools/tests/browser/browser.ini b/toolkit/components/processtools/tests/browser/browser.ini
new file mode 100644
index 0000000000..3b32afefab
--- /dev/null
+++ b/toolkit/components/processtools/tests/browser/browser.ini
@@ -0,0 +1,12 @@
+[DEFAULT]
+prefs=
+  media.rdd-process.enabled=true
+
+support-files =
+  dummy.html
+
+[browser_test_powerMetrics.js]
+skip-if =
+  win11_2009 && !debug # bug 1819845
+[browser_test_procinfo.js]
+skip-if = (ccov && os == "linux") # https://bugzilla.mozilla.org/show_bug.cgi?id=1608080
diff --git a/toolkit/components/processtools/tests/browser/browser_test_powerMetrics.js b/toolkit/components/processtools/tests/browser/browser_test_powerMetrics.js
new file mode 100644
index 0000000000..14573fd8a2
--- /dev/null
+++ b/toolkit/components/processtools/tests/browser/browser_test_powerMetrics.js
@@ -0,0 +1,400 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Return a web-based URL for a given file based on the testing directory.
+ * @param {String} fileName
+ *        file that caller wants its web-based url
+ */
+function GetTestWebBasedURL(fileName) {
+  return (
+    getRootDirectory(gTestPath).replace(
+      "chrome://mochitests/content",
+      "http://example.org"
+    ) + fileName
+  );
+}
+
+const kNS_PER_MS = 1000000;
+
+function printProcInfo(procInfo) {
+  info(
+    `  pid: ${procInfo.pid}, type = parent, cpu time = ${
+      procInfo.cpuTime / kNS_PER_MS
+    }ms`
+  );
+  for (let child of procInfo.children) {
+    info(
+      `  pid: ${child.pid}, type = ${child.type}, cpu time = ${
+        child.cpuTime / kNS_PER_MS
+      }ms`
+    );
+  }
+}
+
+// It would be nice to have an API to list all the statically defined labels of
+// a labeled_counter. Hopefully bug 1672273 will help with this.
+const kGleanProcessTypeLabels = [
+  "parent.active",
+  "parent.active.playing-audio",
+  "parent.active.playing-video",
+  "parent.inactive",
+  "parent.inactive.playing-audio",
+  "parent.inactive.playing-video",
+  "prealloc",
+  "privilegedabout",
+  "rdd",
+  "socket",
+  "web.background",
+  "web.background-perceivable",
+  "web.foreground",
+  "extension",
+  "gpu",
+  "gmplugin",
+  "utility",
+  "__other__",
+];
+
+async function getChildCpuTime(pid) {
+  return (await ChromeUtils.requestProcInfo()).children.find(p => p.pid == pid)
+    .cpuTime;
+}
+
+add_task(async () => {
+  // Temporarily open a new foreground tab to make the current tab a background
+  // tab, and burn some CPU time in it while it's in the background.
+  const kBusyWaitForMs = 50;
+  let cpuTimeSpentOnBackgroundTab;
+  let firstBrowser = gBrowser.selectedTab.linkedBrowser;
+  let processPriorityChangedPromise = BrowserTestUtils.contentTopicObserved(
+    firstBrowser.browsingContext,
+    "ipc:process-priority-changed"
+  );
+  await BrowserTestUtils.withNewTab(
+    GetTestWebBasedURL("dummy.html"),
+    async () => {
+      await processPriorityChangedPromise;
+      // We can't be sure that a busy loop lasting for a specific duration
+      // will use the same amount of CPU time, as that would require a core
+      // to be fully available for our busy loop, which is unlikely on single
+      // core hardware.
+      // To be able to have a predictable amount of CPU time used, we need to
+      // check using ChromeUtils.requestProcInfo how much CPU time has actually
+      // been spent.
+      let pid = firstBrowser.frameLoader.remoteTab.osPid;
+      let initalCpuTime = await getChildCpuTime(pid);
+      let afterCpuTime;
+      do {
+        await SpecialPowers.spawn(
+          firstBrowser,
+          [kBusyWaitForMs],
+          async kBusyWaitForMs => {
+            let startTime = Date.now();
+            while (Date.now() - startTime < 10) {
+              // Burn CPU time...
+            }
+          }
+        );
+        afterCpuTime = await getChildCpuTime(pid);
+      } while (afterCpuTime - initalCpuTime < kBusyWaitForMs * kNS_PER_MS);
+      cpuTimeSpentOnBackgroundTab = Math.floor(
+        (afterCpuTime - initalCpuTime) / kNS_PER_MS
+      );
+    }
+  );
+
+  let beforeProcInfo = await ChromeUtils.requestProcInfo();
+  await Services.fog.testFlushAllChildren();
+
+  let cpuTimeByType = {},
+    gpuTimeByType = {};
+  for (let label of kGleanProcessTypeLabels) {
+    cpuTimeByType[label] =
+      Glean.power.cpuTimePerProcessTypeMs[label].testGetValue();
+    gpuTimeByType[label] =
+      Glean.power.gpuTimePerProcessTypeMs[label].testGetValue();
+  }
+  let totalCpuTime = Glean.power.totalCpuTimeMs.testGetValue();
+  let totalGpuTime = Glean.power.totalGpuTimeMs.testGetValue();
+
+  let afterProcInfo = await ChromeUtils.requestProcInfo();
+
+  info("CPU time from ProcInfo before calling testFlushAllChildren:");
+  printProcInfo(beforeProcInfo);
+
+  info("CPU time for each label:");
+  let totalCpuTimeByType = 0;
+  for (let label of kGleanProcessTypeLabels) {
+    totalCpuTimeByType += cpuTimeByType[label] ?? 0;
+    info(`  ${label} = ${cpuTimeByType[label]}`);
+  }
+
+  info("CPU time from ProcInfo after calling testFlushAllChildren:");
+  printProcInfo(afterProcInfo);
+
+  Assert.equal(
+    totalCpuTimeByType,
+    totalCpuTime,
+    "The sum of CPU time used by all process types should match totalCpuTimeMs"
+  );
+
+  // In infra the parent process time will be reported as parent.inactive,
+  // but when running the test locally the user might move the mouse a bit.
+  let parentTime =
+    (cpuTimeByType["parent.active"] || 0) +
+    (cpuTimeByType["parent.inactive"] || 0);
+  Assert.greaterOrEqual(
+    parentTime,
+    Math.floor(beforeProcInfo.cpuTime / kNS_PER_MS),
+    "reported parent cpu time should be at least what the first requestProcInfo returned"
+  );
+  Assert.lessOrEqual(
+    parentTime,
+    Math.ceil(afterProcInfo.cpuTime / kNS_PER_MS),
+    "reported parent cpu time should be at most what the second requestProcInfo returned"
+  );
+
+  kGleanProcessTypeLabels
+    .filter(label => label.startsWith("parent.") && label.includes(".playing-"))
+    .forEach(label => {
+      Assert.strictEqual(
+        cpuTimeByType[label],
+        undefined,
+        `no media was played so the CPU time for ${label} should be undefined`
+      );
+    });
+
+  if (beforeProcInfo.children.some(p => p.type == "preallocated")) {
+    Assert.greaterOrEqual(
+      cpuTimeByType.prealloc,
+      beforeProcInfo.children.reduce(
+        (time, p) =>
+          time +
+          (p.type == "preallocated" ? Math.floor(p.cpuTime / kNS_PER_MS) : 0),
+        0
+      ),
+      "reported cpu time for preallocated content processes should be at least the sum of what the first requestProcInfo returned."
+    );
+    // We can't compare with the values returned by the second requestProcInfo
+    // call because one preallocated content processes has been turned into
+    // a normal content process when we opened a tab.
+  } else {
+    info(
+      "no preallocated content process existed when we started our test, but some might have existed before"
+    );
+  }
+
+  if (beforeProcInfo.children.some(p => p.type == "privilegedabout")) {
+    Assert.greaterOrEqual(
+      cpuTimeByType.privilegedabout,
+      1,
+      "we used some CPU time in a foreground tab, but don't know how much as the process might have started as preallocated"
+    );
+  }
+
+  for (let label of [
+    "rdd",
+    "socket",
+    "extension",
+    "gpu",
+    "gmplugin",
+    "utility",
+  ]) {
+    if (!kGleanProcessTypeLabels.includes(label)) {
+      Assert.ok(
+        false,
+        `coding error in the test, ${label} isn't part of ${kGleanProcessTypeLabels.join(
+          ", "
+        )}`
+      );
+    }
+    if (beforeProcInfo.children.some(p => p.type == label)) {
+      Assert.greaterOrEqual(
+        cpuTimeByType[label],
+        Math.floor(
+          beforeProcInfo.children.find(p => p.type == label).cpuTime /
+            kNS_PER_MS
+        ),
+        "reported cpu time for " +
+          label +
+          " process should be at least what the first requestProcInfo returned."
+      );
+      Assert.lessOrEqual(
+        cpuTimeByType[label],
+        Math.ceil(
+          afterProcInfo.children.find(p => p.type == label).cpuTime / kNS_PER_MS
+        ),
+        "reported cpu time for " +
+          label +
+          " process should be at most what the second requestProcInfo returned."
+      );
+    } else {
+      info(
+        "no " +
+          label +
+          " process existed when we started our test, but some might have existed before"
+      );
+    }
+  }
+
+  Assert.greaterOrEqual(
+    cpuTimeByType["web.background"],
+    cpuTimeSpentOnBackgroundTab,
+    "web.background should be at least the time we spent."
+  );
+
+  Assert.greaterOrEqual(
+    cpuTimeByType["web.foreground"],
+    1,
+    "we used some CPU time in a foreground tab, but don't know how much"
+  );
+
+  // We only have web.background-perceivable CPU time if a muted video was
+  // played in a background tab.
+  Assert.strictEqual(
+    cpuTimeByType["web.background-perceivable"],
+    undefined,
+    "CPU time should only be recorded in the web.background-perceivable label"
+  );
+
+  // __other__ should be undefined, if it is not, we have a missing label in the metrics.yaml file.
+  Assert.strictEqual(
+    cpuTimeByType.__other__,
+    undefined,
+    "no CPU time should be recorded in the __other__ label"
+  );
+
+  info("GPU time for each label:");
+  let totalGpuTimeByType = undefined;
+  for (let label of kGleanProcessTypeLabels) {
+    if (gpuTimeByType[label] !== undefined) {
+      totalGpuTimeByType = (totalGpuTimeByType || 0) + gpuTimeByType[label];
+    }
+    info(`  ${label} = ${gpuTimeByType[label]}`);
+  }
+
+  Assert.equal(
+    totalGpuTimeByType,
+    totalGpuTime,
+    "The sum of GPU time used by all process types should match totalGpuTimeMs"
+  );
+
+  // __other__ should be undefined, if it is not, we have a missing label in the metrics.yaml file.
+  Assert.strictEqual(
+    gpuTimeByType.__other__,
+    undefined,
+    "no GPU time should be recorded in the __other__ label"
+  );
+
+  // Now test per-thread CPU time.
+  // We don't test parentActive as the user is not marked active on infra.
+  let processTypes = [
+    "parentInactive",
+    "contentBackground",
+    "contentForeground",
+  ];
+  if (beforeProcInfo.children.some(p => p.type == "gpu")) {
+    processTypes.push("gpuProcess");
+  }
+  // The list of accepted labels is not accessible to the JS code, so test only the main thread.
+  const kThreadName = "geckomain";
+  if (AppConstants.NIGHTLY_BUILD) {
+    for (let processType of processTypes) {
+      Assert.greater(
+        Glean.powerCpuMsPerThread[processType][kThreadName].testGetValue(),
+        0,
+        `some CPU time should have been recorded for the ${processType} main thread`
+      );
+      Assert.greater(
+        Glean.powerWakeupsPerThread[processType][kThreadName].testGetValue(),
+        0,
+        `some thread wake ups should have been recorded for the ${processType} main thread`
+      );
+    }
+  } else {
+    // We are not recording per thread CPU use outside of the Nightly channel.
+    for (let processType of processTypes) {
+      Assert.equal(
+        Glean.powerCpuMsPerThread[processType][kThreadName].testGetValue(),
+        undefined,
+        `no CPU time should have been recorded for the ${processType} main thread`
+      );
+      Assert.equal(
+        Glean.powerWakeupsPerThread[processType][kThreadName].testGetValue(),
+        undefined,
+        `no thread wake ups should have been recorded for the ${processType} main thread`
+      );
+    }
+  }
+});
+
+add_task(async function test_tracker_power() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["privacy.trackingprotection.enabled", false],
+      ["privacy.trackingprotection.annotate_channels", true],
+    ],
+  });
+  let initialValues = [];
+  for (let trackerType of [
+    "ad",
+    "analytics",
+    "cryptomining",
+    "fingerprinting",
+    "social",
+    "unknown",
+  ]) {
+    initialValues[trackerType] =
+      Glean.power.cpuTimePerTrackerTypeMs[trackerType].testGetValue() || 0;
+  }
+
+  await BrowserTestUtils.withNewTab(
+    GetTestWebBasedURL("dummy.html"),
+    async () => {
+      // Load a tracker in a subframe, as we only record CPU time used by third party trackers.
+      await SpecialPowers.spawn(
+        gBrowser.selectedTab.linkedBrowser,
+        [
+          GetTestWebBasedURL("dummy.html").replace(
+            "example.org",
+            "trackertest.org"
+          ),
+        ],
+        async frameUrl => {
+          let iframe = content.document.createElement("iframe");
+          iframe.setAttribute("src", frameUrl);
+          await new content.Promise(resolve => {
+            iframe.onload = resolve;
+            content.document.body.appendChild(iframe);
+          });
+        }
+      );
+    }
+  );
+
+  await Services.fog.testFlushAllChildren();
+
+  let unknownTrackerCPUTime =
+    Glean.power.cpuTimePerTrackerTypeMs.unknown.testGetValue() || 0;
+  Assert.greater(
+    unknownTrackerCPUTime,
+    initialValues.unknown,
+    "The CPU time of unknown trackers should have increased"
+  );
+
+  for (let trackerType of [
+    "ad",
+    "analytics",
+    "cryptomining",
+    "fingerprinting",
+    "social",
+  ]) {
+    Assert.equal(
+      Glean.power.cpuTimePerTrackerTypeMs[trackerType].testGetValue() || 0,
+      initialValues[trackerType],
+      `no new CPU time should have been recorded for ${trackerType} trackers`
+    );
+  }
+});
diff --git a/toolkit/components/processtools/tests/browser/browser_test_procinfo.js b/toolkit/components/processtools/tests/browser/browser_test_procinfo.js
new file mode 100644
index 0000000000..4201060bd0
--- /dev/null
+++ b/toolkit/components/processtools/tests/browser/browser_test_procinfo.js
@@ -0,0 +1,165 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const DUMMY_URL =
+  getRootDirectory(gTestPath).replace(
+    "chrome://mochitests/content",
+    "http://example.com"
+  ) + "/dummy.html";
+
+const HAS_THREAD_NAMES =
+  AppConstants.platform != "win" ||
+  AppConstants.isPlatformAndVersionAtLeast("win", 10);
+const isFissionEnabled = SpecialPowers.useRemoteSubframes;
+
+const SAMPLE_SIZE = 10;
+const NS_PER_MS = 1000000;
+
+function checkProcessCpuTime(proc) {
+  Assert.greater(proc.cpuTime, 0, "Got some cpu time");
+
+  let cpuThreads = 0;
+  for (let thread of proc.threads) {
+    cpuThreads += Math.floor(thread.cpuTime / NS_PER_MS);
+  }
+  Assert.greater(cpuThreads, 0, "Got some cpu time in the threads");
+  let processCpuTime = Math.ceil(proc.cpuTime / NS_PER_MS);
+  if (AppConstants.platform == "win" && processCpuTime < cpuThreads) {
+    // On Windows, our test jobs likely run in VMs without constant TSC,
+    // so we might have low precision CPU time measurements.
+    const MAX_DISCREPENCY = 100;
+    Assert.ok(
+      cpuThreads - processCpuTime < MAX_DISCREPENCY,
+      `on Windows, we accept a discrepency of up to ${MAX_DISCREPENCY}ms between the process CPU time and the sum of its threads' CPU time, process CPU time: ${processCpuTime}, sum of thread CPU time: ${cpuThreads}`
+    );
+  } else {
+    Assert.greaterOrEqual(
+      processCpuTime,
+      cpuThreads,
+      "The total CPU time of the process should be at least the sum of the CPU time spent by the still alive threads"
+    );
+  }
+}
+
+add_task(async function test_proc_info() {
+  // Open a few `about:home` tabs, they'll end up in `privilegedabout`.
+  let tabsAboutHome = [];
+  for (let i = 0; i < 5; ++i) {
+    let tab = BrowserTestUtils.addTab(gBrowser, "about:home");
+    tabsAboutHome.push(tab);
+    gBrowser.selectedTab = tab;
+    await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
+  }
+
+  await BrowserTestUtils.withNewTab(
+    { gBrowser, url: DUMMY_URL },
+    async function (browser) {
+      // We test `SAMPLE_SIZE` times to increase a tad the chance of encountering race conditions.
+      for (let z = 0; z < SAMPLE_SIZE; z++) {
+        let parentProc = await ChromeUtils.requestProcInfo();
+
+        Assert.equal(
+          parentProc.type,
+          "browser",
+          "Parent proc type should be browser"
+        );
+
+        checkProcessCpuTime(parentProc);
+
+        // Under Windows, thread names appeared with Windows 10.
+        if (HAS_THREAD_NAMES) {
+          Assert.ok(
+            parentProc.threads.some(thread => thread.name),
+            "At least one of the threads of the parent process is named"
+          );
+        }
+
+        Assert.ok(parentProc.memory > 0, "Memory was set");
+
+        // While it's very unlikely that the parent will disappear while we're running
+        // tests, some children can easily vanish. So we go twice through the list of
+        // children. Once to test stuff that all process data respects the invariants
+        // that don't care whether we have a race condition and once to test that at
+        // least one well-known process that should not be able to vanish during
+        // the test respects all the invariants.
+        for (let childProc of parentProc.children) {
+          Assert.notEqual(
+            childProc.type,
+            "browser",
+            "Child proc type should not be browser"
+          );
+
+          // We set the `childID` for child processes that have a `ContentParent`/`ContentChild`
+          // actor hierarchy.
+          if (childProc.type.startsWith("web")) {
+            Assert.notEqual(
+              childProc.childID,
+              0,
+              "Child proc should have been set"
+            );
+          }
+          Assert.notEqual(
+            childProc.type,
+            "unknown",
+            "Child proc type should be known"
+          );
+          if (childProc.type == "webIsolated") {
+            Assert.notEqual(
+              childProc.origin || "",
+              "",
+              "Child process should have an origin"
+            );
+          }
+
+          checkProcessCpuTime(childProc);
+        }
+
+        // We only check other properties on the `privilegedabout` subprocess, which
+        // as of this writing is always active and available.
+        var hasPrivilegedAbout = false;
+        var numberOfAboutTabs = 0;
+        for (let childProc of parentProc.children) {
+          if (childProc.type != "privilegedabout") {
+            continue;
+          }
+          hasPrivilegedAbout = true;
+          Assert.ok(childProc.memory > 0, "Memory was set");
+
+          for (var win of childProc.windows) {
+            if (win.documentURI.spec != "about:home") {
+              // We're only interested in about:home for this test.
+              continue;
+            }
+            numberOfAboutTabs++;
+            Assert.ok(
+              win.outerWindowId > 0,
+              `ContentParentID should be > 0 ${win.outerWindowId}`
+            );
+            if (win.documentTitle) {
+              // Unfortunately, we sometimes reach this point before the document is fully loaded, so
+              // `win.documentTitle` may still be empty.
+              Assert.equal(win.documentTitle, "New Tab");
+            }
+          }
+          Assert.ok(
+            numberOfAboutTabs >= tabsAboutHome.length,
+            "We have found at least as many about:home tabs as we opened"
+          );
+
+          // Once we have verified the privileged about process, bailout.
+          break;
+        }
+
+        Assert.ok(
+          hasPrivilegedAbout,
+          "We have found the privileged about process"
+        );
+      }
+
+      for (let tab of tabsAboutHome) {
+        BrowserTestUtils.removeTab(tab);
+      }
+    }
+  );
+});
diff --git a/toolkit/components/processtools/tests/browser/dummy.html b/toolkit/components/processtools/tests/browser/dummy.html
new file mode 100644
index 0000000000..e69dad24d4
--- /dev/null
+++ b/toolkit/components/processtools/tests/browser/dummy.html
@@ -0,0 +1,20 @@
+<!doctype html>
+<html>
+<head>
+<title>Dummy test page</title>
+<meta http-equiv="Content-Type" content="text/html;charset=utf-8"></meta>
+</head>
+<body>
+<p>Dummy test page</p>
+<div id="holder" class="">Holder</div>
+<script>
+  let text = "";
+  for (let i = 0; i < 1000; i++) {
+    text += "more";
+    // eslint-disable-next-line no-unsanitized/property
+    document.getElementById("holder").innerHTML = text;
+  }
+  document.getElementById("holder").classList.add("loaded");
+</script>
+</body>
+</html>
diff --git a/toolkit/components/processtools/tests/xpcshell/test_process_kill.js b/toolkit/components/processtools/tests/xpcshell/test_process_kill.js
new file mode 100644
index 0000000000..9781efaffc
--- /dev/null
+++ b/toolkit/components/processtools/tests/xpcshell/test_process_kill.js
@@ -0,0 +1,52 @@
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+"use strict";
+
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+
+const { Subprocess } = ChromeUtils.importESModule(
+  "resource://gre/modules/Subprocess.sys.mjs"
+);
+
+const ProcessTools = Cc["@mozilla.org/processtools-service;1"].getService(
+  Ci.nsIProcessToolsService
+);
+
+let PYTHON;
+
+// Find Python.
+add_task(async function setup() {
+  PYTHON = await Subprocess.pathSearch(Services.env.get("PYTHON"));
+});
+
+// Ensure that killing a process... kills the process.
+add_task(async function test_subprocess_kill() {
+  // We launch Python, as it's a long-running process and it exists
+  // on all desktop platforms on which we run tests.
+  let proc = await Subprocess.call({
+    command: PYTHON,
+    arguments: [],
+  });
+
+  let isTerminated = false;
+
+  proc.wait().then(() => {
+    isTerminated = true;
+  });
+
+  await new Promise(resolve => setTimeout(resolve, 100));
+  Assert.ok(
+    !isTerminated,
+    "We haven't killed the process yet, it should still be running."
+  );
+
+  // Time to kill the process.
+  ProcessTools.kill(proc.pid);
+
+  await new Promise(resolve => setTimeout(resolve, 100));
+  Assert.ok(
+    isTerminated,
+    "We have killed the process already, it shouldn't be running anymore."
+  );
+});
diff --git a/toolkit/components/processtools/tests/xpcshell/test_total_cpu_time.js b/toolkit/components/processtools/tests/xpcshell/test_total_cpu_time.js
new file mode 100644
index 0000000000..00f1ea2b6c
--- /dev/null
+++ b/toolkit/components/processtools/tests/xpcshell/test_total_cpu_time.js
@@ -0,0 +1,122 @@
+"use strict";
+
+var cpuThreadCount;
+
+add_task(async function setup() {
+  // FOG needs a profile directory to put its data in.
+  do_get_profile();
+
+  Services.fog.initializeFOG();
+
+  cpuThreadCount = (await Services.sysinfo.processInfo).count;
+});
+
+async function getCpuTimeFromProcInfo() {
+  const NS_PER_MS = 1000000;
+  let cpuTimeForProcess = p => p.cpuTime / NS_PER_MS;
+  let procInfo = await ChromeUtils.requestProcInfo();
+  return (
+    cpuTimeForProcess(procInfo) +
+    procInfo.children.map(cpuTimeForProcess).reduce((a, b) => a + b, 0)
+  );
+}
+
+add_task(async function test_totalCpuTime_in_parent() {
+  let startTime = Date.now();
+
+  let initialProcInfoCpuTime = Math.floor(await getCpuTimeFromProcInfo());
+  await Services.fog.testFlushAllChildren();
+
+  let initialCpuTime = Glean.power.totalCpuTimeMs.testGetValue();
+  Assert.greater(
+    initialCpuTime,
+    0,
+    "The CPU time used by starting the test harness should be more than 0"
+  );
+  let initialProcInfoCpuTime2 = Math.ceil(await getCpuTimeFromProcInfo());
+
+  Assert.greaterOrEqual(
+    initialCpuTime,
+    initialProcInfoCpuTime,
+    "The CPU time reported through Glean should be at least as much as the CPU time reported by ProcInfo before asking Glean for the data"
+  );
+  Assert.lessOrEqual(
+    initialCpuTime,
+    initialProcInfoCpuTime2,
+    "The CPU time reported through Glean should be no more than the CPU time reported by ProcInfo after asking Glean for the data"
+  );
+
+  // 50 is an arbitrary value, but the resolution is 16ms on Windows,
+  // so this needs to be significantly more than 16.
+  const kBusyWaitForMs = 50;
+  while (Date.now() - startTime < kBusyWaitForMs) {
+    // Burn CPU time...
+  }
+
+  let additionalProcInfoCpuTime =
+    Math.floor(await getCpuTimeFromProcInfo()) - initialProcInfoCpuTime2;
+  await Services.fog.testFlushAllChildren();
+
+  let additionalCpuTime =
+    Glean.power.totalCpuTimeMs.testGetValue() - initialCpuTime;
+  info(
+    `additional CPU time according to ProcInfo: ${additionalProcInfoCpuTime}ms and Glean ${additionalCpuTime}ms`
+  );
+
+  // On a machine where the CPU is very busy, our busy wait loop might burn less
+  // CPU than expected if other processes are being scheduled instead of us.
+  let expectedAdditionalCpuTime = Math.min(
+    additionalProcInfoCpuTime,
+    kBusyWaitForMs
+  );
+  Assert.greaterOrEqual(
+    additionalCpuTime,
+    expectedAdditionalCpuTime,
+    `The total CPU time should have increased by at least ${expectedAdditionalCpuTime}ms`
+  );
+  let wallClockTime = Date.now() - startTime;
+  Assert.lessOrEqual(
+    additionalCpuTime,
+    wallClockTime * cpuThreadCount,
+    `The total CPU time should have increased by at most the wall clock time (${wallClockTime}ms) * ${cpuThreadCount} CPU threads`
+  );
+});
+
+add_task(async function test_totalCpuTime_in_child() {
+  const MESSAGE_CHILD_TEST_DONE = "ChildTest:Done";
+
+  let startTime = Date.now();
+  await Services.fog.testFlushAllChildren();
+  let initialCpuTime = Glean.power.totalCpuTimeMs.testGetValue();
+
+  let initialProcInfoCpuTime = await getCpuTimeFromProcInfo();
+  run_test_in_child("test_total_cpu_time_child.js");
+  let burntCpuTime = await do_await_remote_message(MESSAGE_CHILD_TEST_DONE);
+  let additionalProcInfoCpuTime =
+    (await getCpuTimeFromProcInfo()) - initialProcInfoCpuTime;
+
+  await Services.fog.testFlushAllChildren();
+  let additionalCpuTime =
+    Glean.power.totalCpuTimeMs.testGetValue() - initialCpuTime;
+  info(
+    `additional CPU time according to ProcInfo: ${additionalProcInfoCpuTime}ms and Glean ${additionalCpuTime}ms`
+  );
+
+  // On a machine where the CPU is very busy, our busy wait loop might burn less
+  // CPU than expected if other processes are being scheduled instead of us.
+  let expectedAdditionalCpuTime = Math.min(
+    Math.floor(additionalProcInfoCpuTime),
+    burntCpuTime
+  );
+  Assert.greaterOrEqual(
+    additionalCpuTime,
+    expectedAdditionalCpuTime,
+    `The total CPU time should have increased by at least ${expectedAdditionalCpuTime}ms`
+  );
+  let wallClockTime = Date.now() - startTime;
+  Assert.lessOrEqual(
+    additionalCpuTime,
+    wallClockTime * cpuThreadCount,
+    `The total CPU time should have increased by at most the wall clock time (${wallClockTime}ms) * ${cpuThreadCount} CPU threads`
+  );
+});
diff --git a/toolkit/components/processtools/tests/xpcshell/test_total_cpu_time_child.js b/toolkit/components/processtools/tests/xpcshell/test_total_cpu_time_child.js
new file mode 100644
index 0000000000..88ac480a09
--- /dev/null
+++ b/toolkit/components/processtools/tests/xpcshell/test_total_cpu_time_child.js
@@ -0,0 +1,10 @@
+const MESSAGE_CHILD_TEST_DONE = "ChildTest:Done";
+
+function run_test() {
+  const kBusyWaitForMs = 50;
+  let startTime = Date.now();
+  while (Date.now() - startTime < kBusyWaitForMs) {
+    // Burn CPU time...
+  }
+  do_send_remote_message(MESSAGE_CHILD_TEST_DONE, kBusyWaitForMs);
+}
diff --git a/toolkit/components/processtools/tests/xpcshell/xpcshell.ini b/toolkit/components/processtools/tests/xpcshell/xpcshell.ini
new file mode 100644
index 0000000000..bd9bdaac93
--- /dev/null
+++ b/toolkit/components/processtools/tests/xpcshell/xpcshell.ini
@@ -0,0 +1,9 @@
+[DEFAULT]
+firefox-appdir = browser
+subprocess = true
+
+[test_process_kill.js]
+skip-if = os == 'android'
+[test_total_cpu_time.js]
+skip-if = socketprocess_networking
+support-files = test_total_cpu_time_child.js