PPAPI: Implement PPB_FileMapping on POSIX

BUG=83774
R=bbudge@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=247473

Review URL: https://codereview.chromium.org/69663002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247546 0039d316-1c4b-4281-b951-d872f2087c98

26 files changed, 1113 insertions, 13 deletions

diff --git a/chrome/browser/component_updater/ppapi_utils.cc b/chrome/browser/component_updater/ppapi_utils.cc
index bebb9a5..ddbf36d 100644
--- a/chrome/browser/component_updater/ppapi_utils.cc
+++ b/chrome/browser/component_updater/ppapi_utils.cc
@@ -41,6 +41,7 @@
 #include "ppapi/c/ppb_console.h"
 #include "ppapi/c/ppb_core.h"
 #include "ppapi/c/ppb_file_io.h"
+#include "ppapi/c/ppb_file_mapping.h"
 #include "ppapi/c/ppb_file_ref.h"
 #include "ppapi/c/ppb_file_system.h"
 #include "ppapi/c/ppb_fullscreen.h"
diff --git a/chrome/test/ppapi/ppapi_browsertest.cc b/chrome/test/ppapi/ppapi_browsertest.cc
index 6fc80e5..2e0c8b8 100644
--- a/chrome/test/ppapi/ppapi_browsertest.cc
+++ b/chrome/test/ppapi/ppapi_browsertest.cc
@@ -971,6 +971,16 @@ IN_PROC_BROWSER_TEST_F(PPAPIPrivateNaClPNaClTest, MAYBE_PNaCl_FileIO_Private) {
   );
 }
 
+// PPB_FileMapping is only implemented on POSIX currently.
+// http://crbug.com/83774
+#if defined(OS_WIN)
+#define MAYBE_FileMapping DISABLED_FileMapping
+#else
+#define MAYBE_FileMapping FileMapping
+#endif
+TEST_PPAPI_OUT_OF_PROCESS_VIA_HTTP(MAYBE_FileMapping)
+TEST_PPAPI_NACL(MAYBE_FileMapping)
+
 // Note, the FileRef tests are split into two, because all of them together
 // sometimes take too long on windows: crbug.com/336999
 IN_PROC_BROWSER_TEST_F(PPAPITest, FileRef1) {
diff --git a/content/renderer/pepper/pepper_plugin_instance_impl.cc b/content/renderer/pepper/pepper_plugin_instance_impl.cc
index 2069bc4..09b3a3d 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.cc
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.cc
@@ -2402,6 +2402,7 @@ ppapi::Resource* PepperPluginInstanceImpl::GetSingletonResource(
     case ppapi::BROKER_SINGLETON_ID:
     case ppapi::BROWSER_FONT_SINGLETON_ID:
     case ppapi::EXTENSIONS_COMMON_SINGLETON_ID:
+    case ppapi::FILE_MAPPING_SINGLETON_ID:
     case ppapi::FLASH_CLIPBOARD_SINGLETON_ID:
     case ppapi::FLASH_FILE_SINGLETON_ID:
     case ppapi::FLASH_FULLSCREEN_SINGLETON_ID:
diff --git a/content/renderer/pepper/plugin_module.cc b/content/renderer/pepper/plugin_module.cc
index 60de434..2ce03af 100644
--- a/content/renderer/pepper/plugin_module.cc
+++ b/content/renderer/pepper/plugin_module.cc
@@ -66,6 +66,7 @@
 #include "ppapi/c/ppb_console.h"
 #include "ppapi/c/ppb_core.h"
 #include "ppapi/c/ppb_file_io.h"
+#include "ppapi/c/ppb_file_mapping.h"
 #include "ppapi/c/ppb_file_ref.h"
 #include "ppapi/c/ppb_file_system.h"
 #include "ppapi/c/ppb_fullscreen.h"
diff --git a/ppapi/api/ppb_file_mapping.idl b/ppapi/api/ppb_file_mapping.idl
index 2a10946..7037955 100644
--- a/ppapi/api/ppb_file_mapping.idl
+++ b/ppapi/api/ppb_file_mapping.idl
@@ -9,6 +9,8 @@
  * memory.
  */
 
+[generate_thunk]
+
 label Chrome {
   [channel=dev] M34 = 0.1
 };
diff --git a/ppapi/c/ppb_file_mapping.h b/ppapi/c/ppb_file_mapping.h
index 6887bfd..3c1f87b 100644
--- a/ppapi/c/ppb_file_mapping.h
+++ b/ppapi/c/ppb_file_mapping.h
@@ -3,7 +3,7 @@
  * found in the LICENSE file.
  */
 
-/* From ppb_file_mapping.idl modified Wed Jan 22 12:25:44 2014. */
+/* From ppb_file_mapping.idl modified Mon Jan 27 11:00:43 2014. */
 
 #ifndef PPAPI_C_PPB_FILE_MAPPING_H_
 #define PPAPI_C_PPB_FILE_MAPPING_H_
diff --git a/ppapi/native_client/src/untrusted/pnacl_irt_shim/pnacl_shim.c b/ppapi/native_client/src/untrusted/pnacl_irt_shim/pnacl_shim.c
index 9e7a8b6..b1cbbd8 100644
--- a/ppapi/native_client/src/untrusted/pnacl_irt_shim/pnacl_shim.c
+++ b/ppapi/native_client/src/untrusted/pnacl_irt_shim/pnacl_shim.c
@@ -421,14 +421,14 @@ static int32_t Pnacl_M34_PPB_FileMapping_Map(PP_Instance instance, PP_Resource f
   return iface->Map(instance, file_io, length, map_protection, map_flags, offset, address, *callback);
 }
 
-static int32_t Pnacl_M34_PPB_FileMapping_Unmap(PP_Instance file_io, const void* address, int64_t length, struct PP_CompletionCallback* callback) {
+static int32_t Pnacl_M34_PPB_FileMapping_Unmap(PP_Instance instance, const void* address, int64_t length, struct PP_CompletionCallback* callback) {
   const struct PPB_FileMapping_0_1 *iface = Pnacl_WrapperInfo_PPB_FileMapping_0_1.real_iface;
-  return iface->Unmap(file_io, address, length, *callback);
+  return iface->Unmap(instance, address, length, *callback);
 }
 
-static int64_t Pnacl_M34_PPB_FileMapping_GetMapPageSize(PP_Instance file_io) {
+static int64_t Pnacl_M34_PPB_FileMapping_GetMapPageSize(PP_Instance instance) {
   const struct PPB_FileMapping_0_1 *iface = Pnacl_WrapperInfo_PPB_FileMapping_0_1.real_iface;
-  return iface->GetMapPageSize(file_io);
+  return iface->GetMapPageSize(instance);
 }
 
 /* End wrapper methods for PPB_FileMapping_0_1 */
@@ -4231,8 +4231,8 @@ static struct PPB_FileIO_1_1 Pnacl_Wrappers_PPB_FileIO_1_1 = {
 
 static struct PPB_FileMapping_0_1 Pnacl_Wrappers_PPB_FileMapping_0_1 = {
     .Map = (int32_t (*)(PP_Instance instance, PP_Resource file_io, int64_t length, uint32_t map_protection, uint32_t map_flags, int64_t offset, void** address, struct PP_CompletionCallback callback))&Pnacl_M34_PPB_FileMapping_Map,
-    .Unmap = (int32_t (*)(PP_Instance file_io, const void* address, int64_t length, struct PP_CompletionCallback callback))&Pnacl_M34_PPB_FileMapping_Unmap,
-    .GetMapPageSize = (int64_t (*)(PP_Instance file_io))&Pnacl_M34_PPB_FileMapping_GetMapPageSize
+    .Unmap = (int32_t (*)(PP_Instance instance, const void* address, int64_t length, struct PP_CompletionCallback callback))&Pnacl_M34_PPB_FileMapping_Unmap,
+    .GetMapPageSize = (int64_t (*)(PP_Instance instance))&Pnacl_M34_PPB_FileMapping_GetMapPageSize
 };
 
 static struct PPB_FileRef_1_0 Pnacl_Wrappers_PPB_FileRef_1_0 = {
diff --git a/ppapi/ppapi_proxy.gypi b/ppapi/ppapi_proxy.gypi
index 1edd49a..fe357d7 100644
--- a/ppapi/ppapi_proxy.gypi
+++ b/ppapi/ppapi_proxy.gypi
@@ -39,8 +39,16 @@
           'proxy/extensions_common_resource.h',
           'proxy/file_chooser_resource.cc',
           'proxy/file_chooser_resource.h',
+          'proxy/file_io_resource.cc',
+          'proxy/file_io_resource.h',
+          'proxy/file_mapping_resource.cc',
+          'proxy/file_mapping_resource.h',
+          'proxy/file_mapping_resource_posix.cc',
+          'proxy/file_mapping_resource_win.cc',
           'proxy/file_ref_resource.cc',
           'proxy/file_ref_resource.h',
+          'proxy/file_system_resource.cc',
+          'proxy/file_system_resource.h',
           'proxy/flash_clipboard_resource.cc',
           'proxy/flash_clipboard_resource.h',
           'proxy/flash_drm_resource.cc',
@@ -55,10 +63,6 @@
           'proxy/flash_menu_resource.h',
           'proxy/flash_resource.cc',
           'proxy/flash_resource.h',
-          'proxy/file_io_resource.cc',
-          'proxy/file_io_resource.h',
-          'proxy/file_system_resource.cc',
-          'proxy/file_system_resource.h',
           'proxy/gamepad_resource.cc',
           'proxy/gamepad_resource.h',
           'proxy/graphics_2d_resource.cc',
diff --git a/ppapi/ppapi_shared.gypi b/ppapi/ppapi_shared.gypi
index eda3de1..926dc02 100644
--- a/ppapi/ppapi_shared.gypi
+++ b/ppapi/ppapi_shared.gypi
@@ -163,6 +163,7 @@
           'thunk/ppb_file_io_api.h',
           'thunk/ppb_file_io_private_thunk.cc',
           'thunk/ppb_file_io_thunk.cc',
+          'thunk/ppb_file_mapping_thunk.cc',
           'thunk/ppb_file_ref_api.h',
           'thunk/ppb_file_ref_thunk.cc',
           'thunk/ppb_file_system_api.h',
diff --git a/ppapi/ppapi_sources.gypi b/ppapi/ppapi_sources.gypi
index c231418..6d78038 100644
--- a/ppapi/ppapi_sources.gypi
+++ b/ppapi/ppapi_sources.gypi
@@ -30,6 +30,7 @@
       'c/ppb_console.h',
       'c/ppb_core.h',
       'c/ppb_file_io.h',
+      'c/ppb_file_mapping.h',
       'c/ppb_file_ref.h',
       'c/ppb_file_system.h',
       'c/ppb_fullscreen.h',
@@ -433,6 +434,8 @@
       'tests/test_empty.h',
       'tests/test_file_io.cc',
       'tests/test_file_io.h',
+      'tests/test_file_mapping.cc',
+      'tests/test_file_mapping.h',
       'tests/test_file_ref.cc',
       'tests/test_file_ref.h',
       'tests/test_file_system.cc',
diff --git a/ppapi/proxy/file_io_resource.h b/ppapi/proxy/file_io_resource.h
index d6465fd..5d58035 100644
--- a/ppapi/proxy/file_io_resource.h
+++ b/ppapi/proxy/file_io_resource.h
@@ -69,7 +69,6 @@ class PPAPI_PROXY_EXPORT FileIOResource
       PP_FileHandle* handle,
       scoped_refptr<TrackedCallback> callback) OVERRIDE;
 
- private:
   // FileHandleHolder is used to guarantee that file operations will have a
   // valid FD to operate on, even if they're in a different thread.
   // If instead we just passed the raw FD, the FD could be closed before the
@@ -102,7 +101,11 @@ class PPAPI_PROXY_EXPORT FileIOResource
     ~FileHandleHolder();
     PP_FileHandle raw_handle_;
   };
+  scoped_refptr<FileHandleHolder> file_handle() {
+    return file_handle_;
+  }
 
+ private:
   // Class to perform file query operations across multiple threads.
   class QueryOp : public base::RefCountedThreadSafe<QueryOp> {
    public:
diff --git a/ppapi/proxy/file_mapping_resource.cc b/ppapi/proxy/file_mapping_resource.cc
new file mode 100644
index 0000000..5b18dbb
--- /dev/null
+++ b/ppapi/proxy/file_mapping_resource.cc
@@ -0,0 +1,160 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ppapi/proxy/file_mapping_resource.h"
+
+#include "base/bind.h"
+#include "base/numerics/safe_conversions.h"
+#include "base/task_runner_util.h"
+#include "ppapi/c/pp_errors.h"
+#include "ppapi/shared_impl/tracked_callback.h"
+#include "ppapi/shared_impl/var.h"
+#include "ppapi/thunk/enter.h"
+#include "ppapi/thunk/ppb_file_io_api.h"
+
+namespace ppapi {
+namespace proxy {
+
+FileMappingResource::FileMappingResource(Connection connection,
+                                         PP_Instance instance)
+    : PluginResource(connection, instance) {
+}
+
+FileMappingResource::~FileMappingResource() {
+}
+
+thunk::PPB_FileMapping_API* FileMappingResource::AsPPB_FileMapping_API() {
+  return this;
+}
+
+int32_t FileMappingResource::Map(PP_Instance /* instance */,
+                                 PP_Resource file_io,
+                                 int64_t length,
+                                 uint32_t protection,
+                                 uint32_t flags,
+                                 int64_t offset,
+                                 void** address,
+                                 scoped_refptr<TrackedCallback> callback) {
+  thunk::EnterResourceNoLock<thunk::PPB_FileIO_API> enter(file_io, true);
+  if (enter.failed())
+    return PP_ERROR_BADARGUMENT;
+  FileIOResource* file_io_resource =
+      static_cast<FileIOResource*>(enter.object());
+  scoped_refptr<FileIOResource::FileHandleHolder> file_handle =
+      file_io_resource->file_handle();
+  if (!FileIOResource::FileHandleHolder::IsValid(file_handle))
+    return PP_ERROR_FAILED;
+  if (length < 0 || offset < 0 ||
+      !base::IsValueInRangeForNumericType<off_t>(offset)) {
+    return PP_ERROR_BADARGUMENT;
+  }
+  if (!base::IsValueInRangeForNumericType<size_t>(length)) {
+    return PP_ERROR_NOMEMORY;
+  }
+
+  // Ensure any bits we don't recognize are zero.
+  if (protection &
+      ~(PP_FILEMAPPROTECTION_READ | PP_FILEMAPPROTECTION_WRITE)) {
+    return PP_ERROR_BADARGUMENT;
+  }
+  if (flags &
+      ~(PP_FILEMAPFLAG_SHARED | PP_FILEMAPFLAG_PRIVATE |
+        PP_FILEMAPFLAG_FIXED)) {
+    return PP_ERROR_BADARGUMENT;
+  }
+  // Ensure at least one of SHARED and PRIVATE is set.
+  if (!(flags & (PP_FILEMAPFLAG_SHARED | PP_FILEMAPFLAG_PRIVATE)))
+    return PP_ERROR_BADARGUMENT;
+  // Ensure at most one of SHARED and PRIVATE is set.
+  if ((flags & PP_FILEMAPFLAG_SHARED) &&
+      (flags & PP_FILEMAPFLAG_PRIVATE)) {
+    return PP_ERROR_BADARGUMENT;
+  }
+  if (!address)
+    return PP_ERROR_BADARGUMENT;
+
+  base::Callback<MapResult()> map_cb(
+      base::Bind(&FileMappingResource::DoMapBlocking, file_handle, *address,
+                 length, protection, flags, offset));
+  if (callback->is_blocking()) {
+    // The plugin could release its reference to this instance when we release
+    // the proxy lock below.
+    scoped_refptr<FileMappingResource> protect(this);
+    MapResult map_result;
+    {
+      // Release the proxy lock while making a potentially slow file call.
+      ProxyAutoUnlock unlock;
+      map_result = map_cb.Run();
+    }
+    OnMapCompleted(address, length, callback, map_result);
+    return map_result.result;
+  } else {
+    base::PostTaskAndReplyWithResult(
+      PpapiGlobals::Get()->GetFileTaskRunner(),
+      FROM_HERE,
+      map_cb,
+      RunWhileLocked(Bind(&FileMappingResource::OnMapCompleted,
+                          this,
+                          base::Unretained(address),
+                          length,
+                          callback)));
+    return PP_OK_COMPLETIONPENDING;
+  }
+}
+
+int32_t FileMappingResource::Unmap(PP_Instance /* instance */,
+                                   const void* address,
+                                   int64_t length,
+                                   scoped_refptr<TrackedCallback> callback) {
+  if (!address)
+    return PP_ERROR_BADARGUMENT;
+  if (!base::IsValueInRangeForNumericType<size_t>(length))
+    return PP_ERROR_BADARGUMENT;
+
+  base::Callback<int32_t()> unmap_cb(
+      base::Bind(&FileMappingResource::DoUnmapBlocking, address, length));
+  if (callback->is_blocking()) {
+    // Release the proxy lock while making a potentially slow file call.
+    ProxyAutoUnlock unlock;
+    return unmap_cb.Run();
+  } else {
+    base::PostTaskAndReplyWithResult(
+      PpapiGlobals::Get()->GetFileTaskRunner(),
+      FROM_HERE,
+      unmap_cb,
+      RunWhileLocked(Bind(&TrackedCallback::Run, callback)));
+    return PP_OK_COMPLETIONPENDING;
+  }
+}
+
+int64_t FileMappingResource::GetMapPageSize(PP_Instance /* instance */) {
+  return DoGetMapPageSize();
+}
+
+void FileMappingResource::OnMapCompleted(
+    void** mapped_address_out_param,
+    int64_t length,
+    scoped_refptr<TrackedCallback> callback,
+    const MapResult& map_result) {
+  if (callback->aborted()) {
+    if (map_result.result == PP_OK) {
+      // If the Map operation was successful, we need to Unmap to avoid leaks.
+      // The plugin won't get the address, so doesn't have a chance to do the
+      // Unmap.
+      PpapiGlobals::Get()->GetFileTaskRunner()->PostTask(
+          FROM_HERE,
+          base::Bind(base::IgnoreResult(&FileMappingResource::DoUnmapBlocking),
+                     map_result.address,
+                     length));
+    }
+    return;
+  }
+  if (map_result.result == PP_OK)
+    *mapped_address_out_param = map_result.address;
+  if (!callback->is_blocking())
+    callback->Run(map_result.result);
+}
+
+}  // namespace proxy
+}  // namespace ppapi
diff --git a/ppapi/proxy/file_mapping_resource.h b/ppapi/proxy/file_mapping_resource.h
new file mode 100644
index 0000000..240da21
--- /dev/null
+++ b/ppapi/proxy/file_mapping_resource.h
@@ -0,0 +1,77 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PPAPI_PROXY_FILE_MAPPING_RESOURCE_H_
+#define PPAPI_PROXY_FILE_MAPPING_RESOURCE_H_
+
+#include "ppapi/proxy/file_io_resource.h"
+#include "ppapi/proxy/plugin_resource.h"
+#include "ppapi/proxy/ppapi_proxy_export.h"
+#include "ppapi/thunk/ppb_file_mapping_api.h"
+
+namespace ppapi {
+namespace proxy {
+
+// The proxy-side resource for PPB_FileMapping.
+class PPAPI_PROXY_EXPORT FileMappingResource
+      : public PluginResource,
+        public thunk::PPB_FileMapping_API {
+ public:
+  FileMappingResource(Connection connection, PP_Instance instance);
+
+ private:
+  virtual ~FileMappingResource();
+
+  // Resource implementation.
+  virtual thunk::PPB_FileMapping_API* AsPPB_FileMapping_API() OVERRIDE;
+
+  // PPB_FileMapping_API implementation.
+  virtual int32_t Map(PP_Instance instance,
+                      PP_Resource file_io,
+                      int64_t length,
+                      uint32_t protection,
+                      uint32_t flags,
+                      int64_t offset,
+                      void** address,
+                      scoped_refptr<TrackedCallback> callback) OVERRIDE;
+  virtual int32_t Unmap(PP_Instance instance,
+                        const void* address,
+                        int64_t length,
+                        scoped_refptr<TrackedCallback> callback) OVERRIDE;
+  virtual int64_t GetMapPageSize(PP_Instance instance) OVERRIDE;
+
+  struct MapResult {
+    MapResult() : result(PP_ERROR_FAILED), address(NULL) {
+    }
+    int32_t result;
+    void* address;
+  };
+  void OnMapCompleted(void** mapped_address_out_param,
+                      int64_t length,
+                      scoped_refptr<TrackedCallback> callback,
+                      const MapResult& map_result);
+
+  // These functions perform potentially blocking operations so they should not
+  // be called on the main thread or while we hold the proxy lock. Their
+  // implementation is platform specific. See file_mapping_resource_posix.cc and
+  // file_mapping_resource_win.cc.
+  static MapResult DoMapBlocking(
+      scoped_refptr<FileIOResource::FileHandleHolder> handle,
+      void* address_hint,
+      int64_t length,
+      uint32_t protection,
+      uint32_t flags,
+      int64_t offset);
+  static int32_t DoUnmapBlocking(const void* address, int64_t length);
+  // DoGetMapPageSize is platform-specific, but fast enough that we can call it
+  // on the main thread with the lock.
+  static int64_t DoGetMapPageSize();
+
+  DISALLOW_COPY_AND_ASSIGN(FileMappingResource);
+};
+
+}  // namespace proxy
+}  // namespace ppapi
+
+#endif  // PPAPI_PROXY_FILE_MAPPING_RESOURCE_H_
diff --git a/ppapi/proxy/file_mapping_resource_posix.cc b/ppapi/proxy/file_mapping_resource_posix.cc
new file mode 100644
index 0000000..b1aff77
--- /dev/null
+++ b/ppapi/proxy/file_mapping_resource_posix.cc
@@ -0,0 +1,89 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ppapi/proxy/file_mapping_resource.h"
+
+#include <stdio.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "ppapi/c/pp_errors.h"
+
+namespace ppapi {
+namespace proxy {
+
+namespace {
+
+int32_t ErrnoToPPError(int error_code) {
+  switch (error_code) {
+    case EACCES:
+      return PP_ERROR_NOACCESS;
+    case EAGAIN:
+      return PP_ERROR_NOMEMORY;
+    case EINVAL:
+      return PP_ERROR_BADARGUMENT;
+    case ENFILE:
+    case ENOMEM:
+      return PP_ERROR_NOMEMORY;
+    default:
+      return PP_ERROR_FAILED;
+  }
+}
+
+}  // namespace
+
+// static
+FileMappingResource::MapResult FileMappingResource::DoMapBlocking(
+    scoped_refptr<FileIOResource::FileHandleHolder> handle,
+    void* address_hint,
+    int64_t length,
+    uint32_t map_protection,
+    uint32_t map_flags,
+    int64_t offset) {
+  int prot_for_mmap = 0;
+  if (map_protection & PP_FILEMAPPROTECTION_READ)
+    prot_for_mmap |= PROT_READ;
+  if (map_protection & PP_FILEMAPPROTECTION_WRITE)
+    prot_for_mmap |= PROT_WRITE;
+  if (prot_for_mmap == 0)
+    prot_for_mmap = PROT_NONE;
+
+  int flags_for_mmap = 0;
+  if (map_flags & PP_FILEMAPFLAG_SHARED)
+    flags_for_mmap |= MAP_SHARED;
+  if (map_flags & PP_FILEMAPFLAG_PRIVATE)
+    flags_for_mmap |= MAP_PRIVATE;
+  if (map_flags & PP_FILEMAPFLAG_FIXED)
+    flags_for_mmap |= MAP_FIXED;
+
+  MapResult map_result;
+  map_result.address =
+      mmap(address_hint,
+           static_cast<size_t>(length),
+           prot_for_mmap,
+           flags_for_mmap,
+           handle->raw_handle(),
+           static_cast<off_t>(offset));
+  if (map_result.address != MAP_FAILED)
+    map_result.result = PP_OK;
+  else
+    map_result.result = ErrnoToPPError(errno);
+  return map_result;
+}
+
+// static
+int32_t FileMappingResource::DoUnmapBlocking(const void* address,
+                                             int64_t length) {
+  if (munmap(const_cast<void*>(address), static_cast<size_t>(length)))
+    return ErrnoToPPError(errno);
+  return PP_OK;
+}
+
+// static
+int64_t FileMappingResource::DoGetMapPageSize() {
+  return getpagesize();
+}
+
+}  // namespace proxy
+}  // namespace ppapi
diff --git a/ppapi/proxy/file_mapping_resource_win.cc b/ppapi/proxy/file_mapping_resource_win.cc
new file mode 100644
index 0000000..70c3d20
--- /dev/null
+++ b/ppapi/proxy/file_mapping_resource_win.cc
@@ -0,0 +1,40 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ppapi/proxy/file_mapping_resource.h"
+
+#include "ppapi/c/pp_errors.h"
+
+namespace ppapi {
+namespace proxy {
+
+// static
+FileMappingResource::MapResult FileMappingResource::DoMapBlocking(
+    scoped_refptr<FileIOResource::FileHandleHolder> handle,
+    void* address_hint,
+    int64_t length,
+    uint32_t map_protection,
+    uint32_t map_flags,
+    int64_t offset) {
+  // TODO(dmichael): Implement for Windows (crbug.com/83774).
+  MapResult map_result;
+  map_result.result = PP_ERROR_NOTSUPPORTED;
+  return map_result;
+}
+
+// static
+int32_t FileMappingResource::DoUnmapBlocking(const void* address,
+                                             int64_t length) {
+  // TODO(dmichael): Implement for Windows (crbug.com/83774).
+  return PP_ERROR_NOTSUPPORTED;
+}
+
+// static
+int64_t FileMappingResource::DoGetMapPageSize() {
+  // TODO(dmichael): Implement for Windows (crbug.com/83774).
+  return 0;
+}
+
+}  // namespace proxy
+}  // namespace ppapi
diff --git a/ppapi/proxy/interface_list.cc b/ppapi/proxy/interface_list.cc
index 4044b27b..79789d7 100644
--- a/ppapi/proxy/interface_list.cc
+++ b/ppapi/proxy/interface_list.cc
@@ -35,6 +35,7 @@
 #include "ppapi/c/ppb_console.h"
 #include "ppapi/c/ppb_core.h"
 #include "ppapi/c/ppb_file_io.h"
+#include "ppapi/c/ppb_file_mapping.h"
 #include "ppapi/c/ppb_file_ref.h"
 #include "ppapi/c/ppb_file_system.h"
 #include "ppapi/c/ppb_fullscreen.h"
diff --git a/ppapi/proxy/ppb_instance_proxy.cc b/ppapi/proxy/ppb_instance_proxy.cc
index 6429f50..80715ad 100644
--- a/ppapi/proxy/ppb_instance_proxy.cc
+++ b/ppapi/proxy/ppb_instance_proxy.cc
@@ -19,6 +19,7 @@
 #include "ppapi/proxy/content_decryptor_private_serializer.h"
 #include "ppapi/proxy/enter_proxy.h"
 #include "ppapi/proxy/extensions_common_resource.h"
+#include "ppapi/proxy/file_mapping_resource.h"
 #include "ppapi/proxy/flash_clipboard_resource.h"
 #include "ppapi/proxy/flash_file_resource.h"
 #include "ppapi/proxy/flash_fullscreen_resource.h"
@@ -363,6 +364,9 @@ Resource* PPB_Instance_Proxy::GetSingletonResource(PP_Instance instance,
     case EXTENSIONS_COMMON_SINGLETON_ID:
       new_singleton = new ExtensionsCommonResource(connection, instance);
       break;
+    case FILE_MAPPING_SINGLETON_ID:
+      new_singleton = new FileMappingResource(connection, instance);
+      break;
     case GAMEPAD_SINGLETON_ID:
       new_singleton = new GamepadResource(connection, instance);
       break;
diff --git a/ppapi/shared_impl/resource.h b/ppapi/shared_impl/resource.h
index 8d15cd2..8446f92 100644
--- a/ppapi/shared_impl/resource.h
+++ b/ppapi/shared_impl/resource.h
@@ -34,6 +34,7 @@
   F(PPB_Ext_CrxFileSystem_Private_API) \
   F(PPB_FileChooser_API) \
   F(PPB_FileIO_API) \
+  F(PPB_FileMapping_API) \
   F(PPB_FileRef_API) \
   F(PPB_FileSystem_API) \
   F(PPB_Find_API) \
diff --git a/ppapi/shared_impl/singleton_resource_id.h b/ppapi/shared_impl/singleton_resource_id.h
index 1094c69..6441a2b 100644
--- a/ppapi/shared_impl/singleton_resource_id.h
+++ b/ppapi/shared_impl/singleton_resource_id.h
@@ -16,6 +16,7 @@ enum SingletonResourceID {
   BROKER_SINGLETON_ID,
   BROWSER_FONT_SINGLETON_ID,
   EXTENSIONS_COMMON_SINGLETON_ID,
+  FILE_MAPPING_SINGLETON_ID,
   FLASH_CLIPBOARD_SINGLETON_ID,
   FLASH_FILE_SINGLETON_ID,
   FLASH_FULLSCREEN_SINGLETON_ID,
diff --git a/ppapi/tests/all_c_includes.h b/ppapi/tests/all_c_includes.h
index 12da721..47a3d7d 100644
--- a/ppapi/tests/all_c_includes.h
+++ b/ppapi/tests/all_c_includes.h
@@ -69,6 +69,7 @@
 #include "ppapi/c/ppb_console.h"
 #include "ppapi/c/ppb_core.h"
 #include "ppapi/c/ppb_file_io.h"
+#include "ppapi/c/ppb_file_mapping.h"
 #include "ppapi/c/ppb_file_ref.h"
 #include "ppapi/c/ppb_file_system.h"
 #include "ppapi/c/ppb_fullscreen.h"
diff --git a/ppapi/tests/test_file_mapping.cc b/ppapi/tests/test_file_mapping.cc
new file mode 100644
index 0000000..8781a33
--- /dev/null
+++ b/ppapi/tests/test_file_mapping.cc
@@ -0,0 +1,540 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ppapi/tests/test_file_mapping.h"
+
+#include <string.h>
+
+#include <limits>
+#include <string>
+
+#include "ppapi/c/pp_errors.h"
+#include "ppapi/c/ppb_file_io.h"
+#include "ppapi/c/ppb_file_mapping.h"
+#include "ppapi/cpp/file_io.h"
+#include "ppapi/cpp/file_ref.h"
+#include "ppapi/cpp/file_system.h"
+#include "ppapi/cpp/instance.h"
+#include "ppapi/cpp/module.h"
+#include "ppapi/tests/test_utils.h"
+
+REGISTER_TEST_CASE(FileMapping);
+
+namespace {
+
+// TODO(dmichael): Move these to test_utils so we can share them?
+int32_t ReadEntireFile(PP_Instance instance,
+                       pp::FileIO* file_io,
+                       int32_t offset,
+                       std::string* data,
+                       CallbackType callback_type) {
+  TestCompletionCallback callback(instance, callback_type);
+  char buf[256];
+  int32_t read_offset = offset;
+
+  for (;;) {
+    callback.WaitForResult(
+        file_io->Read(read_offset, buf, sizeof(buf), callback.GetCallback()));
+    if (callback.result() < 0)
+      return callback.result();
+    if (callback.result() == 0)
+      break;
+    read_offset += callback.result();
+    data->append(buf, callback.result());
+  }
+
+  return PP_OK;
+}
+
+int32_t WriteEntireBuffer(PP_Instance instance,
+                          pp::FileIO* file_io,
+                          int32_t offset,
+                          const std::string& data,
+                          CallbackType callback_type) {
+  TestCompletionCallback callback(instance, callback_type);
+  int32_t write_offset = offset;
+  const char* buf = data.c_str();
+  int32_t size = data.size();
+
+  while (write_offset < offset + size) {
+    callback.WaitForResult(file_io->Write(write_offset,
+                                          &buf[write_offset - offset],
+                                          size - write_offset + offset,
+                                          callback.GetCallback()));
+    if (callback.result() < 0)
+      return callback.result();
+    if (callback.result() == 0)
+      return PP_ERROR_FAILED;
+    write_offset += callback.result();
+  }
+  callback.WaitForResult(file_io->Flush(callback.GetCallback()));
+  return callback.result();
+}
+
+}  // namespace
+
+std::string TestFileMapping::MapAndCheckResults(uint32_t prot,
+                                                uint32_t flags) {
+  TestCompletionCallback callback(instance_->pp_instance(), callback_type());
+
+  pp::FileSystem file_system(instance_, PP_FILESYSTEMTYPE_LOCALTEMPORARY);
+  pp::FileRef file_ref(file_system, "/mapped_file");
+
+  callback.WaitForResult(file_system.Open(1024, callback.GetCallback()));
+  ASSERT_EQ(PP_OK, callback.result());
+
+  const int64_t page_size =
+      file_mapping_if_->GetMapPageSize(instance_->pp_instance());
+  const int64_t kNumPages = 4;
+  // Make a string that's big enough that it spans all of the first |n-1| pages,
+  // plus a little bit of the |nth| page.
+  std::string file_contents((page_size * (kNumPages - 1)) + 128, 'a');
+
+  pp::FileIO file_io(instance_);
+  callback.WaitForResult(file_io.Open(file_ref,
+                                      PP_FILEOPENFLAG_CREATE |
+                                      PP_FILEOPENFLAG_TRUNCATE |
+                                      PP_FILEOPENFLAG_READ |
+                                      PP_FILEOPENFLAG_WRITE,
+                                      callback.GetCallback()));
+  ASSERT_EQ(PP_OK, callback.result());
+  ASSERT_EQ(PP_OK, WriteEntireBuffer(instance_->pp_instance(),
+                                     &file_io,
+                                     0,
+                                     file_contents,
+                                     callback_type()));
+
+  // TODO(dmichael): Use C++ interface.
+  void* address = NULL;
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io.pp_resource(),
+          kNumPages * page_size,
+          prot,
+          flags,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_OK, callback.result());
+  ASSERT_NE(NULL, address);
+
+  if (prot & PP_FILEMAPPROTECTION_READ) {
+    // Make sure we can read.
+    std::string mapped_data(static_cast<char*>(address), file_contents.size());
+    // The initial data should match.
+    ASSERT_EQ(file_contents, mapped_data);
+
+    // Now write some data and flush it.
+    const std::string file_contents2(file_contents.size(), 'x');
+    ASSERT_EQ(PP_OK, WriteEntireBuffer(instance_->pp_instance(),
+                                       &file_io,
+                                       0,
+                                       file_contents2,
+                                       callback_type()));
+    // If the region was mapped SHARED, it should get updated.
+    std::string mapped_data2(static_cast<char*>(address), file_contents.size());
+    if (flags & PP_FILEMAPFLAG_SHARED)
+      ASSERT_EQ(file_contents2, mapped_data2);
+    // In POSIX, it is unspecified in the PRIVATE case whether changes to the
+    // file are visible to the mapped region. So we can't really test anything
+    // here in that case.
+    // TODO(dmichael): Make sure our Pepper documentation reflects this.
+  }
+  if (prot & PP_FILEMAPPROTECTION_WRITE) {
+    std::string old_file_contents;
+    ASSERT_EQ(PP_OK, ReadEntireFile(instance_->pp_instance(),
+                                    &file_io,
+                                    0,
+                                    &old_file_contents,
+                                    callback_type()));
+    // Write something else to the mapped region, then unmap, and see if it
+    // gets written to the file. (Note we have to Unmap to make sure that the
+    // write is committed).
+    memset(address, 'y', file_contents.size());
+    // Note, we might not have read access to the mapped region here, so we
+    // make a string with the same contents without actually reading.
+    std::string mapped_data3(file_contents.size(), 'y');
+    callback.WaitForResult(
+        file_mapping_if_->Unmap(
+            instance_->pp_instance(), address, file_contents.size(),
+            callback.GetCallback().pp_completion_callback()));
+    CHECK_CALLBACK_BEHAVIOR(callback);
+    ASSERT_EQ(PP_OK, callback.result());
+    std::string new_file_contents;
+    ASSERT_EQ(PP_OK, ReadEntireFile(instance_->pp_instance(),
+                                    &file_io,
+                                    0,
+                                    &new_file_contents,
+                                    callback_type()));
+
+    // Sanity-check that the data we wrote isn't the same as what was already
+    // there, otherwise our test is invalid.
+    ASSERT_NE(mapped_data3, old_file_contents);
+    // If it's SHARED, the file should match what we wrote to the mapped region.
+    // Otherwise, it should not have changed.
+    if (flags & PP_FILEMAPFLAG_SHARED)
+      ASSERT_EQ(mapped_data3, new_file_contents);
+    else
+      ASSERT_EQ(old_file_contents, new_file_contents);
+  } else {
+    // We didn't do the "WRITE" test, but we still want to Unmap.
+    callback.WaitForResult(
+        file_mapping_if_->Unmap(
+            instance_->pp_instance(), address, file_contents.size(),
+            callback.GetCallback().pp_completion_callback()));
+    CHECK_CALLBACK_BEHAVIOR(callback);
+    ASSERT_EQ(PP_OK, callback.result());
+  }
+  PASS();
+}
+
+bool TestFileMapping::Init() {
+  // TODO(dmichael): Use unversioned string when this goes to stable?
+  file_mapping_if_ = static_cast<const PPB_FileMapping_0_1*>(
+      pp::Module::Get()->GetBrowserInterface(PPB_FILEMAPPING_INTERFACE_0_1));
+  return !!file_mapping_if_ && CheckTestingInterface() &&
+         EnsureRunningOverHTTP();
+}
+
+void TestFileMapping::RunTests(const std::string& filter) {
+  RUN_CALLBACK_TEST(TestFileMapping, BadParameters, filter);
+  RUN_CALLBACK_TEST(TestFileMapping, Map, filter);
+  RUN_CALLBACK_TEST(TestFileMapping, PartialRegions, filter);
+}
+
+std::string TestFileMapping::TestBadParameters() {
+  TestCompletionCallback callback(instance_->pp_instance(), callback_type());
+
+  pp::FileSystem file_system(instance_, PP_FILESYSTEMTYPE_LOCALTEMPORARY);
+  pp::FileRef file_ref(file_system, "/mapped_file");
+
+  callback.WaitForResult(file_system.Open(1024, callback.GetCallback()));
+  ASSERT_EQ(PP_OK, callback.result());
+
+  const int64_t page_size =
+      file_mapping_if_->GetMapPageSize(instance_->pp_instance());
+  // const int64_t kNumPages = 4;
+  // Make a string that's big enough that it spans 3 pages, plus a little extra.
+  //std::string file_contents((page_size * (kNumPages - 1)) + 128, 'a');
+  std::string file_contents(page_size, 'a');
+
+  pp::FileIO file_io(instance_);
+  callback.WaitForResult(file_io.Open(file_ref,
+                                      PP_FILEOPENFLAG_CREATE |
+                                      PP_FILEOPENFLAG_TRUNCATE |
+                                      PP_FILEOPENFLAG_READ |
+                                      PP_FILEOPENFLAG_WRITE,
+                                      callback.GetCallback()));
+  ASSERT_EQ(PP_OK, callback.result());
+  ASSERT_EQ(PP_OK, WriteEntireBuffer(instance_->pp_instance(),
+                                     &file_io,
+                                     0,
+                                     file_contents,
+                                     callback_type()));
+
+  // Bad instance.
+  void* address = NULL;
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          PP_Instance(0xbadbad),
+          file_io.pp_resource(),
+          page_size,
+          PP_FILEMAPPROTECTION_READ,
+          PP_FILEMAPFLAG_PRIVATE,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+  ASSERT_EQ(NULL, address);
+
+  // Bad resource.
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          PP_Resource(0xbadbad),
+          page_size,
+          PP_FILEMAPPROTECTION_READ,
+          PP_FILEMAPFLAG_PRIVATE,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+  ASSERT_EQ(NULL, address);
+
+  // Length too big.
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io.pp_resource(),
+          std::numeric_limits<int64_t>::max(),
+          PP_FILEMAPPROTECTION_READ,
+          PP_FILEMAPFLAG_PRIVATE,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_NOMEMORY, callback.result());
+  ASSERT_EQ(NULL, address);
+
+  // Length too small.
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io.pp_resource(),
+          -1,
+          PP_FILEMAPPROTECTION_READ,
+          PP_FILEMAPFLAG_PRIVATE,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+  ASSERT_EQ(NULL, address);
+  // TODO(dmichael): Check & test length that is not a multiple of page size???
+
+  // Bad protection.
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io.pp_resource(),
+          page_size,
+          ~PP_FILEMAPPROTECTION_READ,
+          PP_FILEMAPFLAG_PRIVATE,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+  ASSERT_EQ(NULL, address);
+
+  // No flags.
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io.pp_resource(),
+          page_size,
+          PP_FILEMAPPROTECTION_READ,
+          0,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+  ASSERT_EQ(NULL, address);
+
+  // Both flags.
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io.pp_resource(),
+          page_size,
+          PP_FILEMAPPROTECTION_READ,
+          PP_FILEMAPFLAG_SHARED | PP_FILEMAPFLAG_PRIVATE,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+  ASSERT_EQ(NULL, address);
+
+  // Bad flags.
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io.pp_resource(),
+          page_size,
+          PP_FILEMAPPROTECTION_READ,
+          ~PP_FILEMAPFLAG_SHARED,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+  ASSERT_EQ(NULL, address);
+
+  // Bad offset; not a multiple of page size.
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io.pp_resource(),
+          page_size,
+          PP_FILEMAPPROTECTION_READ,
+          ~PP_FILEMAPFLAG_SHARED,
+          1,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+  ASSERT_EQ(NULL, address);
+
+  // Unmap NULL.
+  callback.WaitForResult(
+      file_mapping_if_->Unmap(
+          instance_->pp_instance(),
+          NULL,
+          page_size,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+
+  // Unmap bad address.
+  callback.WaitForResult(
+      file_mapping_if_->Unmap(
+          instance_->pp_instance(),
+          reinterpret_cast<const void*>(0xdeadbeef),
+          page_size,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_ERROR_BADARGUMENT, callback.result());
+
+  PASS();
+}
+
+std::string TestFileMapping::TestMap() {
+  ASSERT_SUBTEST_SUCCESS(MapAndCheckResults(PP_FILEMAPPROTECTION_READ,
+                                            PP_FILEMAPFLAG_SHARED));
+  ASSERT_SUBTEST_SUCCESS(MapAndCheckResults(PP_FILEMAPPROTECTION_WRITE,
+                                            PP_FILEMAPFLAG_SHARED));
+  ASSERT_SUBTEST_SUCCESS(
+      MapAndCheckResults(PP_FILEMAPPROTECTION_WRITE | PP_FILEMAPPROTECTION_READ,
+                         PP_FILEMAPFLAG_SHARED));
+  ASSERT_SUBTEST_SUCCESS(MapAndCheckResults(PP_FILEMAPPROTECTION_READ,
+                                            PP_FILEMAPFLAG_PRIVATE));
+  ASSERT_SUBTEST_SUCCESS(MapAndCheckResults(PP_FILEMAPPROTECTION_WRITE,
+                                            PP_FILEMAPFLAG_PRIVATE));
+  ASSERT_SUBTEST_SUCCESS(
+      MapAndCheckResults(PP_FILEMAPPROTECTION_WRITE | PP_FILEMAPPROTECTION_READ,
+                         PP_FILEMAPFLAG_PRIVATE));
+  PASS();
+}
+
+std::string TestFileMapping::TestPartialRegions() {
+  TestCompletionCallback callback(instance_->pp_instance(), callback_type());
+
+  pp::FileSystem file_system(instance_, PP_FILESYSTEMTYPE_LOCALTEMPORARY);
+  pp::FileRef file_ref1(file_system, "/mapped_file1");
+  pp::FileRef file_ref2(file_system, "/mapped_file2");
+
+  callback.WaitForResult(file_system.Open(1024, callback.GetCallback()));
+  ASSERT_EQ(PP_OK, callback.result());
+
+  const int64_t page_size =
+      file_mapping_if_->GetMapPageSize(instance_->pp_instance());
+  const int64_t kNumPages = 3;
+  std::string file_contents1(kNumPages * page_size, 'a');
+
+  pp::FileIO file_io1(instance_);
+  callback.WaitForResult(file_io1.Open(file_ref1,
+                                       PP_FILEOPENFLAG_CREATE |
+                                       PP_FILEOPENFLAG_TRUNCATE |
+                                       PP_FILEOPENFLAG_READ |
+                                       PP_FILEOPENFLAG_WRITE,
+                                       callback.GetCallback()));
+  ASSERT_EQ(PP_OK, callback.result());
+  ASSERT_EQ(PP_OK, WriteEntireBuffer(instance_->pp_instance(),
+                                     &file_io1,
+                                     0,
+                                     file_contents1,
+                                     callback_type()));
+
+  // TODO(dmichael): Use C++ interface.
+  void* address = NULL;
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io1.pp_resource(),
+          kNumPages * page_size,
+          PP_FILEMAPPROTECTION_WRITE | PP_FILEMAPPROTECTION_READ,
+          PP_FILEMAPFLAG_SHARED,
+          0,
+          &address,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_OK, callback.result());
+  ASSERT_NE(NULL, address);
+
+  // Unmap only the middle page.
+  void* address_of_middle_page =
+      reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(address) + page_size);
+  callback.WaitForResult(
+      file_mapping_if_->Unmap(
+          instance_->pp_instance(),
+          address_of_middle_page,
+          page_size,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_OK, callback.result());
+
+  // Write another file, map it in to the middle hole that was left above.
+  pp::FileIO file_io2(instance_);
+  callback.WaitForResult(file_io2.Open(file_ref2,
+                                       PP_FILEOPENFLAG_CREATE |
+                                       PP_FILEOPENFLAG_TRUNCATE |
+                                       PP_FILEOPENFLAG_READ |
+                                       PP_FILEOPENFLAG_WRITE,
+                                       callback.GetCallback()));
+  ASSERT_EQ(PP_OK, callback.result());
+  // This second file will have 1 page worth of data.
+  std::string file_contents2(page_size, 'b');
+  ASSERT_EQ(PP_OK, WriteEntireBuffer(instance_->pp_instance(),
+                                     &file_io2,
+                                     0,
+                                     file_contents2,
+                                     callback_type()));
+  callback.WaitForResult(
+      file_mapping_if_->Map(
+          instance_->pp_instance(),
+          file_io2.pp_resource(),
+          page_size,
+          PP_FILEMAPPROTECTION_WRITE | PP_FILEMAPPROTECTION_READ,
+          PP_FILEMAPFLAG_SHARED | PP_FILEMAPFLAG_FIXED,
+          0,
+          &address_of_middle_page,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_OK, callback.result());
+  PASS();
+
+  // Write something else to the mapped region, then unmap, and see if it
+  // gets written to both files. (Note we have to Unmap to make sure that the
+  // write is committed).
+  memset(address, 'c', kNumPages * page_size);
+  callback.WaitForResult(
+      file_mapping_if_->Unmap(
+          instance_->pp_instance(), address, kNumPages * page_size,
+          callback.GetCallback().pp_completion_callback()));
+  CHECK_CALLBACK_BEHAVIOR(callback);
+  ASSERT_EQ(PP_OK, callback.result());
+  // The first and third page should have been written with 'c', but the
+  // second page should be untouched.
+  std::string expected_file_contents1 = std::string(page_size, 'c') +
+                                        std::string(page_size, 'a') +
+                                        std::string(page_size, 'c');
+  std::string new_file_contents1;
+  ASSERT_EQ(PP_OK, ReadEntireFile(instance_->pp_instance(),
+                                  &file_io1,
+                                  0,
+                                  &new_file_contents1,
+                                  callback_type()));
+  ASSERT_EQ(expected_file_contents1, new_file_contents1);
+
+  // The second file should have been entirely over-written.
+  std::string expected_file_contents2 = std::string(page_size, 'c');
+  std::string new_file_contents2;
+  ASSERT_EQ(PP_OK, ReadEntireFile(instance_->pp_instance(),
+                                  &file_io2,
+                                  0,
+                                  &new_file_contents2,
+                                  callback_type()));
+  ASSERT_EQ(expected_file_contents2, new_file_contents2);
+
+  // TODO(dmichael): Test non-zero offset
+
+  PASS();
+}
+
diff --git a/ppapi/tests/test_file_mapping.h b/ppapi/tests/test_file_mapping.h
new file mode 100644
index 0000000..bb83d26
--- /dev/null
+++ b/ppapi/tests/test_file_mapping.h
@@ -0,0 +1,37 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PAPPI_TESTS_TEST_FILE_MAPPING_H_
+#define PAPPI_TESTS_TEST_FILE_MAPPING_H_
+
+#include <string>
+
+#include "ppapi/tests/test_case.h"
+
+struct PPB_FileMapping_0_1;
+
+class TestFileMapping : public TestCase {
+ public:
+  explicit TestFileMapping(TestingInstance* instance)
+      : TestCase(instance),
+        file_mapping_if_(NULL) {
+  }
+  virtual ~TestFileMapping() {}
+
+ private:
+  // TestCase implementation.
+  virtual bool Init();
+  virtual void RunTests(const std::string& filter);
+
+  std::string MapAndCheckResults(uint32_t prot, uint32_t flags);
+
+  std::string TestBadParameters();
+  std::string TestMap();
+  std::string TestPartialRegions();
+
+  // TODO(dmichael): Use unversioned struct when it goes stable.
+  const PPB_FileMapping_0_1* file_mapping_if_;
+};
+
+#endif  // PAPPI_TESTS_TEST_FILE_MAPPING_H_
diff --git a/ppapi/thunk/enter.cc b/ppapi/thunk/enter.cc
index 2adc7f2..03937c9b 100644
--- a/ppapi/thunk/enter.cc
+++ b/ppapi/thunk/enter.cc
@@ -59,7 +59,6 @@ EnterBase::EnterBase(PP_Instance instance, SingletonResourceID resource_id,
                      const PP_CompletionCallback& callback)
     : resource_(GetSingletonResource(instance, resource_id)),
       retval_(PP_OK) {
-  DCHECK(resource_ || !instance);
   if (!resource_)
     retval_ = PP_ERROR_BADARGUMENT;
   callback_ = new TrackedCallback(resource_, callback);
diff --git a/ppapi/thunk/interfaces_ppb_public_dev_channel.h b/ppapi/thunk/interfaces_ppb_public_dev_channel.h
index 34e5de4..7269c4e 100644
--- a/ppapi/thunk/interfaces_ppb_public_dev_channel.h
+++ b/ppapi/thunk/interfaces_ppb_public_dev_channel.h
@@ -9,6 +9,7 @@
 
 // Interfaces go here.
 PROXIED_IFACE(PPB_AUDIOFRAME_INTERFACE_0_1, PPB_AudioFrame_0_1)
+PROXIED_IFACE(PPB_FILEMAPPING_INTERFACE_0_1, PPB_FileMapping_0_1)
 PROXIED_IFACE(PPB_FILEREF_INTERFACE_1_2, PPB_FileRef_1_2)
 PROXIED_IFACE(PPB_MEDIASTREAMAUDIOTRACK_INTERFACE_0_1,
               PPB_MediaStreamAudioTrack_0_1)
diff --git a/ppapi/thunk/ppb_file_mapping_api.h b/ppapi/thunk/ppb_file_mapping_api.h
new file mode 100644
index 0000000..530d04b
--- /dev/null
+++ b/ppapi/thunk/ppb_file_mapping_api.h
@@ -0,0 +1,46 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PPAPI_THUNK_PPB_FILE_MAPPING_API_H_
+#define PPAPI_THUNK_PPB_FILE_MAPPING_API_H_
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "ppapi/c/pp_instance.h"
+#include "ppapi/c/ppb_file_mapping.h"
+#include "ppapi/shared_impl/singleton_resource_id.h"
+#include "ppapi/thunk/ppapi_thunk_export.h"
+
+namespace ppapi {
+
+class TrackedCallback;
+
+namespace thunk {
+
+class PPAPI_THUNK_EXPORT PPB_FileMapping_API {
+ public:
+  virtual ~PPB_FileMapping_API() {}
+
+  virtual int32_t Map(PP_Instance instance,
+                      PP_Resource file_io,
+                      int64_t length,
+                      uint32_t map_protection,
+                      uint32_t map_flags,
+                      int64_t offset,
+                      void** address,
+                      scoped_refptr<TrackedCallback> callback) = 0;
+  virtual int32_t Unmap(PP_Instance instance,
+                        const void* address,
+                        int64_t length,
+                        scoped_refptr<TrackedCallback> callback) = 0;
+  virtual int64_t GetMapPageSize(PP_Instance instance) = 0;
+
+  static const SingletonResourceID kSingletonResourceID =
+      FILE_MAPPING_SINGLETON_ID;
+};
+
+}  // namespace thunk
+}  // namespace ppapi
+
+#endif  // PPAPI_THUNK_PPB_FILE_MAPPING_API_H_
diff --git a/ppapi/thunk/ppb_file_mapping_thunk.cc b/ppapi/thunk/ppb_file_mapping_thunk.cc
new file mode 100644
index 0000000..bdf29ca
--- /dev/null
+++ b/ppapi/thunk/ppb_file_mapping_thunk.cc
@@ -0,0 +1,77 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// From ppb_file_mapping.idl modified Mon Jan 27 11:00:43 2014.
+
+#include "ppapi/c/pp_completion_callback.h"
+#include "ppapi/c/pp_errors.h"
+#include "ppapi/c/ppb_file_mapping.h"
+#include "ppapi/shared_impl/tracked_callback.h"
+#include "ppapi/thunk/enter.h"
+#include "ppapi/thunk/ppapi_thunk_export.h"
+#include "ppapi/thunk/ppb_file_mapping_api.h"
+
+namespace ppapi {
+namespace thunk {
+
+namespace {
+
+int32_t Map(PP_Instance instance,
+            PP_Resource file_io,
+            int64_t length,
+            uint32_t map_protection,
+            uint32_t map_flags,
+            int64_t offset,
+            void** address,
+            struct PP_CompletionCallback callback) {
+  VLOG(4) << "PPB_FileMapping::Map()";
+  EnterInstanceAPI<PPB_FileMapping_API> enter(instance, callback);
+  if (enter.failed())
+    return enter.retval();
+  return enter.SetResult(enter.functions()->Map(instance,
+                                                file_io,
+                                                length,
+                                                map_protection,
+                                                map_flags,
+                                                offset,
+                                                address,
+                                                enter.callback()));
+}
+
+int32_t Unmap(PP_Instance instance,
+              const void* address,
+              int64_t length,
+              struct PP_CompletionCallback callback) {
+  VLOG(4) << "PPB_FileMapping::Unmap()";
+  EnterInstanceAPI<PPB_FileMapping_API> enter(instance, callback);
+  if (enter.failed())
+    return enter.retval();
+  return enter.SetResult(enter.functions()->Unmap(instance,
+                                                  address,
+                                                  length,
+                                                  enter.callback()));
+}
+
+int64_t GetMapPageSize(PP_Instance instance) {
+  VLOG(4) << "PPB_FileMapping::GetMapPageSize()";
+  EnterInstanceAPI<PPB_FileMapping_API> enter(instance);
+  if (enter.failed())
+    return 0;
+  return enter.functions()->GetMapPageSize(instance);
+}
+
+const PPB_FileMapping_0_1 g_ppb_filemapping_thunk_0_1 = {
+  &Map,
+  &Unmap,
+  &GetMapPageSize
+};
+
+}  // namespace
+
+PPAPI_THUNK_EXPORT const PPB_FileMapping_0_1* GetPPB_FileMapping_0_1_Thunk() {
+  return &g_ppb_filemapping_thunk_0_1;
+}
+
+}  // namespace thunk
+}  // namespace ppapi