1 files changed, 139 insertions, 0 deletions
diff --git a/ipc/glue/SharedMemory.h b/ipc/glue/SharedMemory.h
new file mode 100644
index 0000000000..820a1d8954
--- /dev/null
+++ b/ipc/glue/SharedMemory.h
@@ -0,0 +1,139 @@
+/* -*- 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/. */
+
+#ifndef mozilla_ipc_SharedMemory_h
+#define mozilla_ipc_SharedMemory_h
+
+#include "nsDebug.h"
+#include "nsISupportsImpl.h"  // NS_INLINE_DECL_REFCOUNTING
+#include "mozilla/Attributes.h"
+
+#include "base/process.h"
+#include "chrome/common/ipc_message_utils.h"
+
+//
+// This is a low-level wrapper around platform shared memory.  Don't
+// use it directly; use Shmem allocated through IPDL interfaces.
+//
+namespace {
+enum Rights { RightsNone = 0, RightsRead = 1 << 0, RightsWrite = 1 << 1 };
+}  // namespace
+
+namespace mozilla {
+
+namespace ipc {
+class SharedMemory;
+}  // namespace ipc
+
+namespace ipc {
+
+class SharedMemory {
+ protected:
+  virtual ~SharedMemory() {
+    Unmapped();
+    Destroyed();
+  }
+
+ public:
+  enum OpenRights {
+    RightsReadOnly = RightsRead,
+    RightsReadWrite = RightsRead | RightsWrite,
+  };
+
+  size_t Size() const { return mMappedSize; }
+
+  virtual void* memory() const = 0;
+
+  virtual bool Create(size_t size) = 0;
+  virtual bool Map(size_t nBytes, void* fixed_address = nullptr) = 0;
+  virtual void Unmap() = 0;
+
+  virtual void CloseHandle() = 0;
+
+  virtual bool WriteHandle(IPC::MessageWriter* aWriter) = 0;
+  virtual bool ReadHandle(IPC::MessageReader* aReader) = 0;
+
+  void Protect(char* aAddr, size_t aSize, int aRights) {
+    char* memStart = reinterpret_cast<char*>(memory());
+    if (!memStart) MOZ_CRASH("SharedMemory region points at NULL!");
+    char* memEnd = memStart + Size();
+
+    char* protStart = aAddr;
+    if (!protStart) MOZ_CRASH("trying to Protect() a NULL region!");
+    char* protEnd = protStart + aSize;
+
+    if (!(memStart <= protStart && protEnd <= memEnd))
+      MOZ_CRASH("attempt to Protect() a region outside this SharedMemory");
+
+    // checks alignment etc.
+    SystemProtect(aAddr, aSize, aRights);
+  }
+
+  // bug 1168843, compositor thread may create shared memory instances that are
+  // destroyed by main thread on shutdown, so this must use thread-safe RC to
+  // avoid hitting assertion
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SharedMemory)
+
+  static void SystemProtect(char* aAddr, size_t aSize, int aRights);
+  [[nodiscard]] static bool SystemProtectFallible(char* aAddr, size_t aSize,
+                                                  int aRights);
+  static size_t SystemPageSize();
+  static size_t PageAlignedSize(size_t aSize);
+
+ protected:
+  SharedMemory();
+
+  // Implementations should call these methods on shmem usage changes,
+  // but *only if* the OS-specific calls are known to have succeeded.
+  // The methods are expected to be called in the pattern
+  //
+  //   Created (Mapped Unmapped)* Destroy
+  //
+  // but this isn't checked.
+  void Created(size_t aNBytes);
+  void Mapped(size_t aNBytes);
+  void Unmapped();
+  void Destroyed();
+
+  // The size of the shmem region requested in Create(), if
+  // successful.  SharedMemory instances that are opened from a
+  // foreign handle have an alloc size of 0, even though they have
+  // access to the alloc-size information.
+  size_t mAllocSize;
+  // The size of the region mapped in Map(), if successful.  All
+  // SharedMemorys that are mapped have a non-zero mapped size.
+  size_t mMappedSize;
+};
+
+template <typename HandleImpl>
+class SharedMemoryCommon : public SharedMemory {
+ public:
+  typedef HandleImpl Handle;
+
+  virtual Handle CloneHandle() = 0;
+  virtual bool IsHandleValid(const Handle& aHandle) const = 0;
+  virtual bool SetHandle(Handle aHandle, OpenRights aRights) = 0;
+
+  virtual bool WriteHandle(IPC::MessageWriter* aWriter) override {
+    Handle handle = CloneHandle();
+    if (!handle) {
+      return false;
+    }
+    IPC::WriteParam(aWriter, std::move(handle));
+    return true;
+  }
+
+  virtual bool ReadHandle(IPC::MessageReader* aReader) override {
+    Handle handle;
+    return IPC::ReadParam(aReader, &handle) && IsHandleValid(handle) &&
+           SetHandle(std::move(handle), RightsReadWrite);
+  }
+};
+
+}  // namespace ipc
+}  // namespace mozilla
+
+#endif  // ifndef mozilla_ipc_SharedMemory_h