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XPCSelfHostedShmem.cpp (3220B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      3 /* This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #include "XPCSelfHostedShmem.h"
      8 #include "xpcprivate.h"
      9 
     10 // static
     11 bool xpc::SelfHostedShmem::sSelfHostedUseSharedMemory = false;
     12 mozilla::StaticRefPtr<xpc::SelfHostedShmem>
     13    xpc::SelfHostedShmem::sSelfHostedXdr;
     14 
     15 NS_IMPL_ISUPPORTS(xpc::SelfHostedShmem, nsIMemoryReporter)
     16 
     17 // static
     18 xpc::SelfHostedShmem& xpc::SelfHostedShmem::GetSingleton() {
     19  MOZ_ASSERT_IF(!sSelfHostedXdr, NS_IsMainThread());
     20 
     21  if (!sSelfHostedXdr) {
     22    sSelfHostedXdr = new SelfHostedShmem;
     23  }
     24 
     25  return *sSelfHostedXdr;
     26 }
     27 
     28 void xpc::SelfHostedShmem::InitMemoryReporter() {
     29  mozilla::RegisterWeakMemoryReporter(this);
     30 }
     31 
     32 // static
     33 void xpc::SelfHostedShmem::Shutdown() {
     34  MOZ_ASSERT(NS_IsMainThread());
     35  // NOTE: We cannot call UnregisterWeakMemoryReporter(sSelfHostedXdr) as the
     36  // service is shutdown at the time this call is made. In any cases, this would
     37  // already be done when the memory reporter got destroyed.
     38  sSelfHostedXdr = nullptr;
     39 }
     40 
     41 void xpc::SelfHostedShmem::InitFromParent(ContentType aXdr) {
     42  MOZ_ASSERT(XRE_IsParentProcess());
     43  MOZ_ASSERT(NS_IsMainThread());
     44  MOZ_ASSERT(!mHandle && !mMem, "Shouldn't call this more than once");
     45 
     46  size_t len = aXdr.Length();
     47  auto handle = mozilla::ipc::shared_memory::CreateFreezable(len);
     48  if (NS_WARN_IF(!handle)) {
     49    return;
     50  }
     51 
     52  auto mapping = std::move(handle).Map();
     53  if (NS_WARN_IF(!mapping)) {
     54    return;
     55  }
     56 
     57  void* address = mapping.Address();
     58  memcpy(address, aXdr.Elements(), aXdr.LengthBytes());
     59 
     60  mHandle = std::move(mapping).Freeze();
     61  mMem = mHandle.Map();
     62 }
     63 
     64 bool xpc::SelfHostedShmem::InitFromChild(
     65    mozilla::ipc::ReadOnlySharedMemoryHandle aHandle) {
     66  MOZ_ASSERT(!XRE_IsParentProcess());
     67  MOZ_ASSERT(NS_IsMainThread());
     68  MOZ_ASSERT(!mMem, "Shouldn't call this more than once");
     69 
     70  mMem = aHandle.Map();
     71  return mMem.IsValid();
     72 }
     73 
     74 xpc::SelfHostedShmem::ContentType xpc::SelfHostedShmem::Content() const {
     75  if (!mMem) {
     76    return ContentType();
     77  }
     78  return mMem.DataAsSpan<uint8_t>();
     79 }
     80 
     81 const mozilla::ipc::ReadOnlySharedMemoryHandle& xpc::SelfHostedShmem::Handle()
     82    const {
     83  return mHandle;
     84 }
     85 
     86 NS_IMETHODIMP
     87 xpc::SelfHostedShmem::CollectReports(nsIHandleReportCallback* aHandleReport,
     88                                     nsISupports* aData, bool aAnonymize) {
     89  // If this is the parent process, then we have a handle and this instance owns
     90  // the data and shares it with other processes, otherwise this is shared data.
     91  if (XRE_IsParentProcess()) {
     92    // This does not exactly report the amount of data mapped by the system,
     93    // but the space requested when creating the handle.
     94    MOZ_COLLECT_REPORT("explicit/js-non-window/shared-memory/self-hosted-xdr",
     95                       KIND_NONHEAP, UNITS_BYTES, mMem.Size(),
     96                       "Memory used to initialize the JS engine with the "
     97                       "self-hosted code encoded by the parent process.");
     98  }
     99  return NS_OK;
    100 }