Mark the two Regions used GraphicsBitmaps as explicitly shared.

This fixes a goofy problem where forking a GUI process would cowify the
GraphicsBitmap for everyone making a hue confusing mess.

3 files changed, 11 insertions, 1 deletions

diff --git a/Kernel/MemoryManager.cpp b/Kernel/MemoryManager.cpp
index e719243e2f..60d1a9c127 100644
--- a/Kernel/MemoryManager.cpp
+++ b/Kernel/MemoryManager.cpp
@@ -563,11 +563,16 @@ RetainPtr<Region> Region::clone()
 {
     InterruptDisabler disabler;
 
-    if (is_readable && !is_writable) {
+    if (m_shared || (is_readable && !is_writable)) {
         // Create a new region backed by the same VMObject.
         return adopt(*new Region(linearAddress, size, m_vmo.copyRef(), m_offset_in_vmo, String(name), is_readable, is_writable));
     }
 
+    dbgprintf("%s<%u> Region::clone(): cowing %s (L%x)\n",
+              current->name().characters(),
+              current->pid(),
+              name.characters(),
+              linearAddress.get());
     // Set up a COW region. The parent (this) region becomes COW as well!
     for (size_t i = 0; i < page_count(); ++i)
         cow_map.set(i, true);
diff --git a/Kernel/MemoryManager.h b/Kernel/MemoryManager.h
index 17b99fcfe1..46cbe89edb 100644
--- a/Kernel/MemoryManager.h
+++ b/Kernel/MemoryManager.h
@@ -117,6 +117,8 @@ public:
     const VMObject& vmo() const { return *m_vmo; }
     VMObject& vmo() { return *m_vmo; }
 
+    void set_shared(bool shared) { m_shared = shared; }
+
     RetainPtr<Region> clone();
     bool contains(LinearAddress laddr) const
     {
@@ -156,6 +158,7 @@ public:
     String name;
     bool is_readable { true };
     bool is_writable { true };
+    bool m_shared { false };
     Bitmap cow_map;
 };
 
diff --git a/SharedGraphics/GraphicsBitmap.cpp b/SharedGraphics/GraphicsBitmap.cpp
index 00dcd3707a..3da6cce03c 100644
--- a/SharedGraphics/GraphicsBitmap.cpp
+++ b/SharedGraphics/GraphicsBitmap.cpp
@@ -21,12 +21,14 @@ GraphicsBitmap::GraphicsBitmap(Process& process, const Size& size)
     size_t size_in_bytes = size.width() * size.height() * sizeof(RGBA32);
     auto vmo = VMObject::create_anonymous(size_in_bytes);
     m_client_region = process.allocate_region_with_vmo(LinearAddress(), size_in_bytes, vmo.copyRef(), 0, "GraphicsBitmap (client)", true, true);
+    m_client_region->set_shared(true);
     m_client_region->commit(process);
 
     {
         auto& server = WSEventLoop::the().server_process();
         InterruptDisabler disabler;
         m_server_region = server.allocate_region_with_vmo(LinearAddress(), size_in_bytes, move(vmo), 0, "GraphicsBitmap (server)", true, true);
+        m_server_region->set_shared(true);
     }
     m_data = (RGBA32*)m_server_region->linearAddress.asPtr();
 }