Add m-esr52 at 52.6.0

1 files changed, 497 insertions, 0 deletions

diff --git a/ipc/glue/Shmem.cpp b/ipc/glue/Shmem.cpp
new file mode 100644
index 000000000..f0cc3bf39
--- /dev/null
+++ b/ipc/glue/Shmem.cpp
@@ -0,0 +1,497 @@
+/* -*- 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 "Shmem.h"
+
+#include "ProtocolUtils.h"
+#include "SharedMemoryBasic.h"
+
+#include "mozilla/Unused.h"
+
+
+namespace mozilla {
+namespace ipc {
+
+class ShmemCreated : public IPC::Message
+{
+private:
+  typedef Shmem::id_t id_t;
+
+public:
+  ShmemCreated(int32_t routingId,
+               id_t aIPDLId,
+               size_t aSize,
+               SharedMemory::SharedMemoryType aType) :
+    IPC::Message(routingId, SHMEM_CREATED_MESSAGE_TYPE, NESTED_INSIDE_CPOW)
+  {
+    IPC::WriteParam(this, aIPDLId);
+    IPC::WriteParam(this, aSize);
+    IPC::WriteParam(this, int32_t(aType));
+  }
+
+  static bool
+  ReadInfo(const Message* msg, PickleIterator* iter,
+           id_t* aIPDLId,
+           size_t* aSize,
+           SharedMemory::SharedMemoryType* aType)
+  {
+    if (!IPC::ReadParam(msg, iter, aIPDLId) ||
+        !IPC::ReadParam(msg, iter, aSize) ||
+        !IPC::ReadParam(msg, iter, reinterpret_cast<int32_t*>(aType)))
+      return false;
+    return true;
+  }
+
+  void Log(const std::string& aPrefix,
+           FILE* aOutf) const
+  {
+    fputs("(special ShmemCreated msg)", aOutf);
+  }
+};
+
+class ShmemDestroyed : public IPC::Message
+{
+private:
+  typedef Shmem::id_t id_t;
+
+public:
+  ShmemDestroyed(int32_t routingId,
+                 id_t aIPDLId) :
+    IPC::Message(routingId, SHMEM_DESTROYED_MESSAGE_TYPE)
+  {
+    IPC::WriteParam(this, aIPDLId);
+  }
+};
+
+static SharedMemory*
+NewSegment(SharedMemory::SharedMemoryType aType)
+{
+  if (SharedMemory::TYPE_BASIC == aType) {
+    return new SharedMemoryBasic;
+  } else {
+    NS_ERROR("unknown Shmem type");
+    return nullptr;
+  }
+}
+
+static already_AddRefed<SharedMemory>
+CreateSegment(SharedMemory::SharedMemoryType aType, size_t aNBytes, size_t aExtraSize)
+{
+  RefPtr<SharedMemory> segment = NewSegment(aType);
+  if (!segment) {
+    return nullptr;
+  }
+  size_t size = SharedMemory::PageAlignedSize(aNBytes + aExtraSize);
+  if (!segment->Create(size) || !segment->Map(size)) {
+    return nullptr;
+  }
+  return segment.forget();
+}
+
+static already_AddRefed<SharedMemory>
+ReadSegment(const IPC::Message& aDescriptor, Shmem::id_t* aId, size_t* aNBytes, size_t aExtraSize)
+{
+  if (SHMEM_CREATED_MESSAGE_TYPE != aDescriptor.type()) {
+    NS_ERROR("expected 'shmem created' message");
+    return nullptr;
+  }
+  SharedMemory::SharedMemoryType type;
+  PickleIterator iter(aDescriptor);
+  if (!ShmemCreated::ReadInfo(&aDescriptor, &iter, aId, aNBytes, &type)) {
+    return nullptr;
+  }
+  RefPtr<SharedMemory> segment = NewSegment(type);
+  if (!segment) {
+    return nullptr;
+  }
+  if (!segment->ReadHandle(&aDescriptor, &iter)) {
+    NS_ERROR("trying to open invalid handle");
+    return nullptr;
+  }
+  aDescriptor.EndRead(iter);
+  size_t size = SharedMemory::PageAlignedSize(*aNBytes + aExtraSize);
+  if (!segment->Map(size)) {
+    return nullptr;
+  }
+  // close the handle to the segment after it is mapped
+  segment->CloseHandle();
+  return segment.forget();
+}
+
+static void
+DestroySegment(SharedMemory* aSegment)
+{
+  // the SharedMemory dtor closes and unmaps the actual OS shmem segment
+  if (aSegment) {
+    aSegment->Release();
+  }
+}
+
+
+#if defined(DEBUG)
+
+static const char sMagic[] =
+    "This little piggy went to market.\n"
+    "This little piggy stayed at home.\n"
+    "This little piggy has roast beef,\n"
+    "This little piggy had none.\n"
+    "And this little piggy cried \"Wee! Wee! Wee!\" all the way home";
+
+
+struct Header {
+  // Don't use size_t or bool here because their size depends on the
+  // architecture.
+  uint32_t mSize;
+  uint32_t mUnsafe;
+  char mMagic[sizeof(sMagic)];
+};
+
+static void
+GetSections(Shmem::SharedMemory* aSegment,
+            Header** aHeader,
+            char** aFrontSentinel,
+            char** aData,
+            char** aBackSentinel)
+{
+  MOZ_ASSERT(aSegment && aFrontSentinel && aData && aBackSentinel,
+             "null param(s)");
+
+  *aFrontSentinel = reinterpret_cast<char*>(aSegment->memory());
+  MOZ_ASSERT(*aFrontSentinel, "null memory()");
+
+  *aHeader = reinterpret_cast<Header*>(*aFrontSentinel);
+
+  size_t pageSize = Shmem::SharedMemory::SystemPageSize();
+  *aData = *aFrontSentinel + pageSize;
+
+  *aBackSentinel = *aFrontSentinel + aSegment->Size() - pageSize;
+}
+
+static Header*
+GetHeader(Shmem::SharedMemory* aSegment)
+{
+  Header* header;
+  char* dontcare;
+  GetSections(aSegment, &header, &dontcare, &dontcare, &dontcare);
+  return header;
+}
+
+static void
+Protect(SharedMemory* aSegment)
+{
+  MOZ_ASSERT(aSegment, "null segment");
+  aSegment->Protect(reinterpret_cast<char*>(aSegment->memory()),
+                    aSegment->Size(),
+                    RightsNone);
+}
+
+static void
+Unprotect(SharedMemory* aSegment)
+{
+  MOZ_ASSERT(aSegment, "null segment");
+  aSegment->Protect(reinterpret_cast<char*>(aSegment->memory()),
+                    aSegment->Size(),
+                    RightsRead | RightsWrite);
+}
+
+//
+// In debug builds, we specially allocate shmem segments.  The layout
+// is as follows
+//
+//   Page 0: "front sentinel"
+//     size of mapping
+//     magic bytes
+//   Page 1 through n-1:
+//     user data
+//   Page n: "back sentinel"
+//     [nothing]
+//
+// The mapping can be in one of the following states, wrt to the
+// current process.
+//
+//   State "unmapped": all pages are mapped with no access rights.
+//
+//   State "mapping": all pages are mapped with read/write access.
+//
+//   State "mapped": the front and back sentinels are mapped with no
+//     access rights, and all the other pages are mapped with
+//     read/write access.
+//
+// When a SharedMemory segment is first allocated, it starts out in
+// the "mapping" state for the process that allocates the segment, and
+// in the "unmapped" state for the other process.  The allocating
+// process will then create a Shmem, which takes the segment into the
+// "mapped" state, where it can be accessed by clients.
+//
+// When a Shmem is sent to another process in an IPDL message, the
+// segment transitions into the "unmapped" state for the sending
+// process, and into the "mapping" state for the receiving process.
+// The receiving process will then create a Shmem from the underlying
+// segment, and take the segment into the "mapped" state.
+//
+// In the "mapping" state, we use the front sentinel to verify the
+// integrity of the shmem segment.  If valid, it has a size_t
+// containing the number of bytes the user allocated followed by the
+// magic bytes above.
+//
+// In the "mapped" state, the front and back sentinels have no access
+// rights.  They act as guards against buffer overflows and underflows
+// in client code; if clients touch a sentinel, they die with SIGSEGV.
+//
+// The "unmapped" state is used to enforce single-owner semantics of
+// the shmem segment.  If a process other than the current owner tries
+// to touch the segment, it dies with SIGSEGV.
+//
+
+Shmem::Shmem(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+             SharedMemory* aSegment, id_t aId) :
+    mSegment(aSegment),
+    mData(nullptr),
+    mSize(0)
+{
+  MOZ_ASSERT(mSegment, "null segment");
+  MOZ_ASSERT(aId != 0, "invalid ID");
+
+  Unprotect(mSegment);
+
+  Header* header;
+  char* frontSentinel;
+  char* data;
+  char* backSentinel;
+  GetSections(aSegment, &header, &frontSentinel, &data, &backSentinel);
+
+  // do a quick validity check to avoid weird-looking crashes in libc
+  char check = *frontSentinel;
+  (void)check;
+
+  MOZ_ASSERT(!strncmp(header->mMagic, sMagic, sizeof(sMagic)),
+             "invalid segment");
+  mSize = static_cast<size_t>(header->mSize);
+
+  size_t pageSize = SharedMemory::SystemPageSize();
+  // transition into the "mapped" state by protecting the front and
+  // back sentinels (which guard against buffer under/overflows)
+  mSegment->Protect(frontSentinel, pageSize, RightsNone);
+  mSegment->Protect(backSentinel, pageSize, RightsNone);
+
+  // don't set these until we know they're valid
+  mData = data;
+  mId = aId;
+}
+
+void
+Shmem::AssertInvariants() const
+{
+  MOZ_ASSERT(mSegment, "null segment");
+  MOZ_ASSERT(mData, "null data pointer");
+  MOZ_ASSERT(mSize > 0, "invalid size");
+  // if the segment isn't owned by the current process, these will
+  // trigger SIGSEGV
+  char checkMappingFront = *reinterpret_cast<char*>(mData);
+  char checkMappingBack = *(reinterpret_cast<char*>(mData) + mSize - 1);
+
+  // avoid "unused" warnings for these variables:
+  Unused << checkMappingFront;
+  Unused << checkMappingBack;
+}
+
+void
+Shmem::RevokeRights(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead)
+{
+  AssertInvariants();
+
+  size_t pageSize = SharedMemory::SystemPageSize();
+  Header* header = GetHeader(mSegment);
+
+  // Open this up for reading temporarily
+  mSegment->Protect(reinterpret_cast<char*>(header), pageSize, RightsRead);
+
+  if (!header->mUnsafe) {
+    Protect(mSegment);
+  } else {
+    mSegment->Protect(reinterpret_cast<char*>(header), pageSize, RightsNone);
+  }
+}
+
+// static
+already_AddRefed<Shmem::SharedMemory>
+Shmem::Alloc(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+             size_t aNBytes,
+             SharedMemoryType aType,
+             bool aUnsafe,
+             bool aProtect)
+{
+  NS_ASSERTION(aNBytes <= UINT32_MAX, "Will truncate shmem segment size!");
+  MOZ_ASSERT(!aProtect || !aUnsafe, "protect => !unsafe");
+
+  size_t pageSize = SharedMemory::SystemPageSize();
+  // |2*pageSize| is for the front and back sentinel
+  RefPtr<SharedMemory> segment = CreateSegment(aType, aNBytes, 2*pageSize);
+  if (!segment) {
+    return nullptr;
+  }
+
+  Header* header;
+  char *frontSentinel;
+  char *data;
+  char *backSentinel;
+  GetSections(segment, &header, &frontSentinel, &data, &backSentinel);
+
+  // initialize the segment with Shmem-internal information
+
+  // NB: this can't be a static assert because technically pageSize
+  // isn't known at compile time, event though in practice it's always
+  // going to be 4KiB
+  MOZ_ASSERT(sizeof(Header) <= pageSize,
+             "Shmem::Header has gotten too big");
+  memcpy(header->mMagic, sMagic, sizeof(sMagic));
+  header->mSize = static_cast<uint32_t>(aNBytes);
+  header->mUnsafe = aUnsafe;
+
+  if (aProtect)
+    Protect(segment);
+
+  return segment.forget();
+}
+
+// static
+already_AddRefed<Shmem::SharedMemory>
+Shmem::OpenExisting(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+                    const IPC::Message& aDescriptor,
+                    id_t* aId,
+                    bool aProtect)
+{
+  size_t size;
+  size_t pageSize = SharedMemory::SystemPageSize();
+  // |2*pageSize| is for the front and back sentinels
+  RefPtr<SharedMemory> segment = ReadSegment(aDescriptor, aId, &size, 2*pageSize);
+  if (!segment) {
+    return nullptr;
+  }
+
+  Header* header = GetHeader(segment);
+
+  if (size != header->mSize) {
+    // Deallocation should zero out the header, so check for that.
+    if (header->mSize || header->mUnsafe || header->mMagic[0] ||
+        memcmp(header->mMagic, &header->mMagic[1], sizeof(header->mMagic)-1)) {
+      NS_ERROR("Wrong size for this Shmem!");
+    } else {
+      NS_WARNING("Shmem was deallocated");
+    }
+    return nullptr;
+  }
+
+  // The caller of this function may not know whether the segment is
+  // unsafe or not
+  if (!header->mUnsafe && aProtect)
+    Protect(segment);
+
+  return segment.forget();
+}
+
+// static
+void
+Shmem::Dealloc(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+               SharedMemory* aSegment)
+{
+  if (!aSegment)
+    return;
+
+  size_t pageSize = SharedMemory::SystemPageSize();
+  Header* header;
+  char *frontSentinel;
+  char *data;
+  char *backSentinel;
+  GetSections(aSegment, &header, &frontSentinel, &data, &backSentinel);
+
+  aSegment->Protect(frontSentinel, pageSize, RightsWrite | RightsRead);
+  memset(header->mMagic, 0, sizeof(sMagic));
+  header->mSize = 0;
+  header->mUnsafe = false;          // make it "safe" so as to catch errors
+
+  DestroySegment(aSegment);
+}
+
+
+#else  // !defined(DEBUG)
+
+// static
+already_AddRefed<Shmem::SharedMemory>
+Shmem::Alloc(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+             size_t aNBytes,
+             SharedMemoryType aType,
+             bool /*unused*/,
+             bool /*unused*/)
+{
+  RefPtr<SharedMemory> segment = CreateSegment(aType, aNBytes, sizeof(uint32_t));
+  if (!segment) {
+    return nullptr;
+  }
+
+  *PtrToSize(segment) = static_cast<uint32_t>(aNBytes);
+
+  return segment.forget();
+}
+
+// static
+already_AddRefed<Shmem::SharedMemory>
+Shmem::OpenExisting(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+                    const IPC::Message& aDescriptor,
+                    id_t* aId,
+                    bool /*unused*/)
+{
+  size_t size;
+  RefPtr<SharedMemory> segment = ReadSegment(aDescriptor, aId, &size, sizeof(uint32_t));
+  if (!segment) {
+    return nullptr;
+  }
+
+  // this is the only validity check done in non-DEBUG builds
+  if (size != static_cast<size_t>(*PtrToSize(segment))) {
+    return nullptr;
+  }
+
+  return segment.forget();
+}
+
+// static
+void
+Shmem::Dealloc(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+               SharedMemory* aSegment)
+{
+  DestroySegment(aSegment);
+}
+
+#endif  // if defined(DEBUG)
+
+IPC::Message*
+Shmem::ShareTo(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+               base::ProcessId aTargetPid,
+               int32_t routingId)
+{
+  AssertInvariants();
+
+  IPC::Message *msg = new ShmemCreated(routingId, mId, mSize, mSegment->Type());
+  if (!mSegment->ShareHandle(aTargetPid, msg)) {
+    return nullptr;
+  }
+  // close the handle to the segment after it is shared
+  mSegment->CloseHandle();
+  return msg;
+}
+
+IPC::Message*
+Shmem::UnshareFrom(IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead,
+                   base::ProcessId aTargetPid,
+                   int32_t routingId)
+{
+  AssertInvariants();
+  return new ShmemDestroyed(routingId, mId);
+}
+
+} // namespace ipc
+} // namespace mozilla