Kernel: Make Kernel::VMObject allocation functions return KResultOr

This makes for nicer handling of errors compared to checking whether a
RefPtr is null. Additionally, this will give way to return different
types of errors in the future.

Kernel/Graphics/Bochs/GraphicsAdapter.cpp

@@ -88,7 +88,8 @@ UNMAP_AFTER_INIT void BochsGraphicsAdapter::initialize_framebuffer_devices()
 {
     // FIXME: Find a better way to determine default resolution...
     m_framebuffer_device = FramebufferDevice::create(*this, 0, PhysicalAddress(PCI::get_BAR0(pci_address()) & 0xfffffff0), 1024, 768, 1024 * sizeof(u32));
-    m_framebuffer_device->initialize();
+    // FIXME: Would be nice to be able to return a KResult here.
+    VERIFY(!m_framebuffer_device->initialize().is_error());
 }
 
 GraphicsDevice::Type BochsGraphicsAdapter::type() const

Kernel/Graphics/FramebufferDevice.cpp

@@ -36,18 +36,20 @@ KResultOr<Memory::Region*> FramebufferDevice::mmap(Process& process, FileDescrip
     if (range.size() != Memory::page_round_up(framebuffer_size_in_bytes()))
         return EOVERFLOW;
 
-    auto vmobject = Memory::AnonymousVMObject::try_create_for_physical_range(m_framebuffer_address, Memory::page_round_up(framebuffer_size_in_bytes()));
-    if (!vmobject)
-        return ENOMEM;
-    m_userspace_real_framebuffer_vmobject = vmobject;
+    auto maybe_vmobject = Memory::AnonymousVMObject::try_create_for_physical_range(m_framebuffer_address, Memory::page_round_up(framebuffer_size_in_bytes()));
+    if (maybe_vmobject.is_error())
+        return maybe_vmobject.error();
+    m_userspace_real_framebuffer_vmobject = maybe_vmobject.release_value();
 
-    m_real_framebuffer_vmobject = Memory::AnonymousVMObject::try_create_for_physical_range(m_framebuffer_address, Memory::page_round_up(framebuffer_size_in_bytes()));
-    if (!m_real_framebuffer_vmobject)
-        return ENOMEM;
+    auto maybe_real_framebuffer_vmobject = Memory::AnonymousVMObject::try_create_for_physical_range(m_framebuffer_address, Memory::page_round_up(framebuffer_size_in_bytes()));
+    if (maybe_real_framebuffer_vmobject.is_error())
+        return maybe_real_framebuffer_vmobject.error();
+    m_real_framebuffer_vmobject = maybe_real_framebuffer_vmobject.release_value();
 
-    m_swapped_framebuffer_vmobject = Memory::AnonymousVMObject::try_create_with_size(Memory::page_round_up(framebuffer_size_in_bytes()), AllocationStrategy::AllocateNow);
-    if (!m_swapped_framebuffer_vmobject)
-        return ENOMEM;
+    auto maybe_swapped_framebuffer_vmobject = Memory::AnonymousVMObject::try_create_with_size(Memory::page_round_up(framebuffer_size_in_bytes()), AllocationStrategy::AllocateNow);
+    if (maybe_swapped_framebuffer_vmobject.is_error())
+        return maybe_swapped_framebuffer_vmobject.error();
+    m_swapped_framebuffer_vmobject = maybe_swapped_framebuffer_vmobject.release_value();
 
     m_real_framebuffer_region = MM.allocate_kernel_region_with_vmobject(*m_real_framebuffer_vmobject, Memory::page_round_up(framebuffer_size_in_bytes()), "Framebuffer", Memory::Region::Access::ReadWrite);
     if (!m_real_framebuffer_region)
@@ -107,16 +109,29 @@ String FramebufferDevice::device_name() const
     return String::formatted("fb{}", minor());
 }
 
-UNMAP_AFTER_INIT void FramebufferDevice::initialize()
+UNMAP_AFTER_INIT KResult FramebufferDevice::initialize()
 {
-    m_real_framebuffer_vmobject = Memory::AnonymousVMObject::try_create_for_physical_range(m_framebuffer_address, Memory::page_round_up(framebuffer_size_in_bytes()));
-    VERIFY(m_real_framebuffer_vmobject);
+    // FIXME: Would be nice to be able to unify this with mmap above, but this
+    //        function is UNMAP_AFTER_INIT for the time being.
+    auto maybe_real_framebuffer_vmobject = Memory::AnonymousVMObject::try_create_for_physical_range(m_framebuffer_address, Memory::page_round_up(framebuffer_size_in_bytes()));
+    if (maybe_real_framebuffer_vmobject.is_error())
+        return maybe_real_framebuffer_vmobject.error();
+    m_real_framebuffer_vmobject = maybe_real_framebuffer_vmobject.release_value();
+
+    auto maybe_swapped_framebuffer_vmobject = Memory::AnonymousVMObject::try_create_with_size(Memory::page_round_up(framebuffer_size_in_bytes()), AllocationStrategy::AllocateNow);
+    if (maybe_swapped_framebuffer_vmobject.is_error())
+        return maybe_swapped_framebuffer_vmobject.error();
+    m_swapped_framebuffer_vmobject = maybe_swapped_framebuffer_vmobject.release_value();
+
     m_real_framebuffer_region = MM.allocate_kernel_region_with_vmobject(*m_real_framebuffer_vmobject, Memory::page_round_up(framebuffer_size_in_bytes()), "Framebuffer", Memory::Region::Access::ReadWrite);
-    VERIFY(m_real_framebuffer_region);
-    m_swapped_framebuffer_vmobject = Memory::AnonymousVMObject::try_create_with_size(Memory::page_round_up(framebuffer_size_in_bytes()), AllocationStrategy::AllocateNow);
-    VERIFY(m_swapped_framebuffer_vmobject);
+    if (!m_real_framebuffer_region)
+        return ENOMEM;
+
     m_swapped_framebuffer_region = MM.allocate_kernel_region_with_vmobject(*m_swapped_framebuffer_vmobject, Memory::page_round_up(framebuffer_size_in_bytes()), "Framebuffer Swap (Blank)", Memory::Region::Access::ReadWrite);
-    VERIFY(m_swapped_framebuffer_region);
+    if (!m_swapped_framebuffer_region)
+        return ENOMEM;
+
+    return KSuccess;
 }
 
 UNMAP_AFTER_INIT FramebufferDevice::FramebufferDevice(const GraphicsDevice& adapter, size_t output_port_index, PhysicalAddress addr, size_t width, size_t height, size_t pitch)

Kernel/Graphics/FramebufferDevice.h

@@ -34,7 +34,7 @@ public:
     size_t framebuffer_size_in_bytes() const;
 
     virtual ~FramebufferDevice() {};
-    void initialize();
+    KResult initialize();
 
 private:
     // ^File

Kernel/Graphics/Intel/NativeGraphicsAdapter.cpp

@@ -639,6 +639,7 @@ void IntelNativeGraphicsAdapter::initialize_framebuffer_devices()
     VERIFY(m_framebuffer_height != 0);
     VERIFY(m_framebuffer_width != 0);
     m_framebuffer_device = FramebufferDevice::create(*this, 0, address, m_framebuffer_width, m_framebuffer_height, m_framebuffer_pitch);
-    m_framebuffer_device->initialize();
+    // FIXME: Would be nice to be able to return a KResult here.
+    VERIFY(!m_framebuffer_device->initialize().is_error());
 }
 }

Kernel/Graphics/VGACompatibleAdapter.cpp

@@ -33,7 +33,8 @@ UNMAP_AFTER_INIT void VGACompatibleAdapter::initialize_framebuffer_devices()
     VERIFY(m_framebuffer_height != 0);
     VERIFY(m_framebuffer_pitch != 0);
     m_framebuffer_device = FramebufferDevice::create(*this, 0, m_framebuffer_address, m_framebuffer_width, m_framebuffer_height, m_framebuffer_pitch);
-    m_framebuffer_device->initialize();
+    // FIXME: Would be nice to be able to return KResult here.
+    VERIFY(!m_framebuffer_device->initialize().is_error());
 }
 
 UNMAP_AFTER_INIT VGACompatibleAdapter::VGACompatibleAdapter(PCI::Address address)

Kernel/Graphics/VirtIOGPU/FrameBufferDevice.cpp

@@ -15,15 +15,18 @@ FrameBufferDevice::FrameBufferDevice(GPU& virtio_gpu, ScanoutID scanout)
     , m_gpu(virtio_gpu)
     , m_scanout(scanout)
 {
-    if (display_info().enabled)
-        create_framebuffer();
+    if (display_info().enabled) {
+        // FIXME: This should be in a place where we can handle allocation failures.
+        auto result = create_framebuffer();
+        VERIFY(!result.is_error());
+    }
 }
 
 FrameBufferDevice::~FrameBufferDevice()
 {
 }
 
-void FrameBufferDevice::create_framebuffer()
+KResult FrameBufferDevice::create_framebuffer()
 {
     // First delete any existing framebuffers to free the memory first
     m_framebuffer = nullptr;
@@ -40,12 +43,17 @@ void FrameBufferDevice::create_framebuffer()
     for (auto i = 0u; i < num_needed_pages; ++i) {
         pages.append(write_sink_page);
     }
-    m_framebuffer_sink_vmobject = Memory::AnonymousVMObject::try_create_with_physical_pages(pages.span());
+    auto maybe_framebuffer_sink_vmobject = Memory::AnonymousVMObject::try_create_with_physical_pages(pages.span());
+    if (maybe_framebuffer_sink_vmobject.is_error())
+        return maybe_framebuffer_sink_vmobject.error();
+    m_framebuffer_sink_vmobject = maybe_framebuffer_sink_vmobject.release_value();
 
     MutexLocker locker(m_gpu.operation_lock());
     m_current_buffer = &buffer_from_index(m_last_set_buffer_index.load());
     create_buffer(m_main_buffer, 0, m_buffer_size);
     create_buffer(m_back_buffer, m_buffer_size, m_buffer_size);
+
+    return KSuccess;
 }
 
 void FrameBufferDevice::create_buffer(Buffer& buffer, size_t framebuffer_offset, size_t framebuffer_size)
@@ -124,7 +132,10 @@ bool FrameBufferDevice::try_to_set_resolution(size_t width, size_t height)
         .width = (u32)width,
         .height = (u32)height,
     };
-    create_framebuffer();
+
+    // FIXME: Would be nice to be able to return KResultOr here.
+    if (auto result = create_framebuffer(); result.is_error())
+        return false;
     return true;
 }
 
@@ -255,9 +266,18 @@ KResultOr<Memory::Region*> FrameBufferDevice::mmap(Process& process, FileDescrip
     if (m_userspace_mmap_region)
         return ENOMEM;
 
-    auto vmobject = m_are_writes_active ? m_framebuffer->vmobject().try_clone() : m_framebuffer_sink_vmobject;
-    if (vmobject.is_null())
-        return ENOMEM;
+    RefPtr<Memory::VMObject> vmobject;
+    if (m_are_writes_active) {
+        auto maybe_vmobject = m_framebuffer->vmobject().try_clone();
+        if (maybe_vmobject.is_error())
+            return maybe_vmobject.error();
+
+        vmobject = maybe_vmobject.release_value();
+    } else {
+        vmobject = m_framebuffer_sink_vmobject;
+        if (vmobject.is_null())
+            return ENOMEM;
+    }
 
     auto result = process.address_space().allocate_region_with_vmobject(
         range,
@@ -277,9 +297,10 @@ void FrameBufferDevice::deactivate_writes()
     m_are_writes_active = false;
     if (m_userspace_mmap_region) {
         auto* region = m_userspace_mmap_region.unsafe_ptr();
-        auto vm_object = m_framebuffer_sink_vmobject->try_clone();
-        VERIFY(vm_object);
-        region->set_vmobject(vm_object.release_nonnull());
+        auto maybe_vm_object = m_framebuffer_sink_vmobject->try_clone();
+        // FIXME: Would be nice to be able to return a KResult here.
+        VERIFY(!maybe_vm_object.is_error());
+        region->set_vmobject(maybe_vm_object.release_value());
         region->remap();
     }
     set_buffer(0);

Kernel/Graphics/VirtIOGPU/FrameBufferDevice.h

@@ -56,7 +56,7 @@ private:
     Protocol::DisplayInfoResponse::Display const& display_info() const;
     Protocol::DisplayInfoResponse::Display& display_info();
 
-    void create_framebuffer();
+    KResult create_framebuffer();
     void create_buffer(Buffer&, size_t, size_t);
     void set_buffer(int);