Modified platform bitmap to support GDI being unavailable

skia/ext/bitmap_platform_device_win.cc

Index: skia/ext/bitmap_platform_device_win.cc
diff --git a/skia/ext/bitmap_platform_device_win.cc b/skia/ext/bitmap_platform_device_win.cc
index 63108209abc313b305256319246a06fa7d03424c..a692927eaa05ab02cd868c28571ea22c151d717c 100644
--- a/skia/ext/bitmap_platform_device_win.cc
+++ b/skia/ext/bitmap_platform_device_win.cc
@@ -6,6 +6,7 @@
 #include <psapi.h>
 
 #include "base/debug/gdi_debug_util_win.h"
+#include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "skia/ext/bitmap_platform_device_win.h"
 #include "skia/ext/platform_canvas.h"
@@ -16,6 +17,59 @@
 
 namespace {
 
+// This file contains an implementation of a Skia platform bitmap for drawing
+// and compositing graphics. The original implementation uses Windows GDI
+// to create the backing bitmap memory, however when using the sandbox security
+// policy win32k lockdown it's not possible to use GDI for security reasons.
+// Therefore this code also implements a fallback mechanism when a process is
+// under this security policy to directly map the shared section as memory
+// instead of using GDI. To catch new code which tries to explicitly rely on
+// this code using GDI some additional DCHECKs have been added to catch that
+// code during development.
+typedef decltype(GetProcessMitigationPolicy)* GetProcessMitigationPolicyType;
+
+// Get win32k lockdown policy using a lazy instance so it's only initialized
+// once and is thread-safe.
+class LazyIsWin32kLockdownEnabled {
+ public:
+  LazyIsWin32kLockdownEnabled()
+      : value_(IsWin32kLockdownEnabled()) {}
+
+  ~LazyIsWin32kLockdownEnabled() {}
+
+  bool value() { return value_; }
+
+ private:
+  static bool IsWin32kLockdownEnabled() {
+    GetProcessMitigationPolicyType get_process_mitigation_policy_func =
+            reinterpret_cast<GetProcessMitigationPolicyType>(
+                                              GetProcAddress(
+                                              GetModuleHandle(L"kernel32.dll"),
+                                              "GetProcessMitigationPolicy"));
+
+    if (!get_process_mitigation_policy_func)
+      return false;
+
+    PROCESS_MITIGATION_SYSTEM_CALL_DISABLE_POLICY policy = {0};
+    if (get_process_mitigation_policy_func(GetCurrentProcess(),
+                                           ProcessSystemCallDisablePolicy,
+                                           &policy,
+                                           sizeof(policy)))
+      return policy.DisallowWin32kSystemCalls != 0;
+
+    return false;
+  }
+ 
+  const bool value_;
+
+  DISALLOW_COPY_AND_ASSIGN(LazyIsWin32kLockdownEnabled);
+};
+
+bool IsWin32kLockdownEnabled() {
+  static base::LazyInstance<LazyIsWin32kLockdownEnabled> win32k_lockdown;

[Will Harris, 2015/09/10 17:34:45]

I think this needs a LAZY_INSTANCE_INITIALIZER

+  return win32k_lockdown.Get().value();
+}
+
 HBITMAP CreateHBitmap(int width, int height, bool is_opaque,
                              HANDLE shared_section, void** data) {
   // CreateDIBSection appears to get unhappy if we create an empty bitmap, so
@@ -57,6 +111,7 @@ namespace skia {
 
 void DrawToNativeContext(SkCanvas* canvas, HDC hdc, int x, int y,
                          const RECT* src_rect) {
+  DCHECK(!IsWin32kLockdownEnabled());
   PlatformDevice* platform_device = GetPlatformDevice(GetTopDevice(*canvas));
   if (platform_device)
     platform_device->DrawToHDC(hdc, x, y, src_rect);
@@ -65,6 +120,7 @@ void DrawToNativeContext(SkCanvas* canvas, HDC hdc, int x, int y,
 void PlatformDevice::DrawToHDC(HDC, int x, int y, const RECT* src_rect) {}
 
 HDC BitmapPlatformDevice::GetBitmapDC() {
+  DCHECK(!IsWin32kLockdownEnabled());
   if (!hdc_) {
     hdc_ = CreateCompatibleDC(NULL);
     InitializeDC(hdc_);
@@ -76,11 +132,13 @@ HDC BitmapPlatformDevice::GetBitmapDC() {
 }
 
 void BitmapPlatformDevice::ReleaseBitmapDC() {
-  SkASSERT(hdc_);
-  SelectObject(hdc_, old_hbitmap_);
-  DeleteDC(hdc_);
-  hdc_ = NULL;
-  old_hbitmap_ = NULL;
+  if (!IsWin32kLockdownEnabled()) {
+    SkASSERT(hdc_);
+    SelectObject(hdc_, old_hbitmap_);
+    DeleteDC(hdc_);
+    hdc_ = NULL;
+    old_hbitmap_ = NULL;
+  }
 }
 
 bool BitmapPlatformDevice::IsBitmapDCCreated()
@@ -108,7 +166,12 @@ void BitmapPlatformDevice::LoadConfig() {
 }
 
 static void DeleteHBitmapCallback(void* addr, void* context) {
-  DeleteObject(static_cast<HBITMAP>(context));
+  // If context is not NULL then it's a valid HBITMAP to delete.
+  // Otherwise we just unmap the pixel memory.
+  if (context)
+    DeleteObject(static_cast<HBITMAP>(context));
+  else
+    UnmapViewOfFile(addr);
 }
 
 static bool InstallHBitmapPixels(SkBitmap* bitmap, int width, int height,
@@ -133,10 +196,22 @@ BitmapPlatformDevice* BitmapPlatformDevice::Create(
     bool do_clear) {
 
   void* data;
-  HBITMAP hbitmap = CreateHBitmap(width, height, is_opaque, shared_section,
+
+  HBITMAP hbitmap = NULL;
+
+  if (IsWin32kLockdownEnabled()) {
+    CHECK(shared_section != NULL);
+    data = MapViewOfFile(shared_section, FILE_MAP_WRITE,
+        0, 0, width * height * 4);
+    DCHECK(data != NULL);
+    if (!data)
+      return NULL;
+  } else {
+    hbitmap = CreateHBitmap(width, height, is_opaque, shared_section,
                                   &data);
-  if (!hbitmap)
-    return NULL;
+    if (!hbitmap)
+      return NULL;
+  }
 
   SkBitmap bitmap;
   if (!InstallHBitmapPixels(&bitmap, width, height, is_opaque, data, hbitmap))
@@ -180,12 +255,14 @@ BitmapPlatformDevice::BitmapPlatformDevice(
   // The data object is already ref'ed for us by create().
   SkDEBUGCODE(begin_paint_count_ = 0);
   SetPlatformDevice(this, this);
-  // Initialize the clip region to the entire bitmap.
-  BITMAP bitmap_data;
-  if (GetObject(hbitmap_, sizeof(BITMAP), &bitmap_data)) {
-    SkIRect rect;
-    rect.set(0, 0, bitmap_data.bmWidth, bitmap_data.bmHeight);
-    clip_region_ = SkRegion(rect);
+  if (hbitmap) {
+    // Initialize the clip region to the entire bitmap.
+    BITMAP bitmap_data;
+    if (GetObject(hbitmap_, sizeof(BITMAP), &bitmap_data)) {
+      SkIRect rect;
+      rect.set(0, 0, bitmap_data.bmWidth, bitmap_data.bmHeight);
+      clip_region_ = SkRegion(rect);
+    }
   }
 }
 
@@ -213,6 +290,8 @@ void BitmapPlatformDevice::setMatrixClip(const SkMatrix& transform,
 
 void BitmapPlatformDevice::DrawToHDC(HDC dc, int x, int y,
                                      const RECT* src_rect) {
+  DCHECK(!IsWin32kLockdownEnabled());
+
   bool created_dc = !IsBitmapDCCreated();
   HDC source_dc = BeginPlatformPaint();
 
@@ -305,6 +384,7 @@ PlatformBitmap::~PlatformBitmap() {
 }
 
 bool PlatformBitmap::Allocate(int width, int height, bool is_opaque) {
+  DCHECK(!IsWin32kLockdownEnabled());
   void* data;
   HBITMAP hbitmap = CreateHBitmap(width, height, is_opaque, 0, &data);
   if (!hbitmap)