Kernel: Make kernel region allocators return KResultOr<NOP<Region>>

This expands the reach of error propagation greatly throughout the
kernel. Sadly, it also exposes the fact that we're allocating (and
doing other fallible things) in constructors all over the place.

This patch doesn't attempt to address that of course. That's work for
our future selves.

Kernel/Graphics/Console/ContiguousFramebufferConsole.cpp

@@ -28,8 +28,9 @@ void ContiguousFramebufferConsole::set_resolution(size_t width, size_t height, s
     m_pitch = pitch;
 
     dbgln("Framebuffer Console: taking {} bytes", Memory::page_round_up(pitch * height));
-    m_framebuffer_region = MM.allocate_kernel_region(m_framebuffer_address, Memory::page_round_up(pitch * height), "Framebuffer Console", Memory::Region::Access::ReadWrite, Memory::Region::Cacheable::Yes);
-    VERIFY(m_framebuffer_region);
+    auto region_or_error = MM.allocate_kernel_region(m_framebuffer_address, Memory::page_round_up(pitch * height), "Framebuffer Console", Memory::Region::Access::ReadWrite, Memory::Region::Cacheable::Yes);
+    VERIFY(!region_or_error.is_error());
+    m_framebuffer_region = region_or_error.release_value();
 
     // Just to start cleanly, we clean the entire framebuffer
     memset(m_framebuffer_region->vaddr().as_ptr(), 0, pitch * height);

Kernel/Graphics/Console/VGAConsole.cpp

@@ -11,7 +11,7 @@ namespace Kernel::Graphics {
 
 UNMAP_AFTER_INIT VGAConsole::VGAConsole(const VGACompatibleAdapter& adapter, Mode mode, size_t width, size_t height)
     : Console(width, height)
-    , m_vga_region(MM.allocate_kernel_region(PhysicalAddress(0xa0000), Memory::page_round_up(0xc0000 - 0xa0000), "VGA Display", Memory::Region::Access::ReadWrite).release_nonnull())
+    , m_vga_region(MM.allocate_kernel_region(PhysicalAddress(0xa0000), Memory::page_round_up(0xc0000 - 0xa0000), "VGA Display", Memory::Region::Access::ReadWrite).release_value())
     , m_adapter(adapter)
     , m_mode(mode)
 {

Kernel/Graphics/FramebufferDevice.cpp

@@ -51,13 +51,8 @@ KResultOr<Memory::Region*> FramebufferDevice::mmap(Process& process, FileDescrip
         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)
-        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);
-    if (!m_swapped_framebuffer_region)
-        return ENOMEM;
+    m_real_framebuffer_region = TRY(MM.allocate_kernel_region_with_vmobject(*m_real_framebuffer_vmobject, Memory::page_round_up(framebuffer_size_in_bytes()), "Framebuffer", Memory::Region::Access::ReadWrite));
+    m_swapped_framebuffer_region = TRY(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));
 
     RefPtr<Memory::VMObject> chosen_vmobject;
     if (m_graphical_writes_enabled) {
@@ -123,13 +118,8 @@ UNMAP_AFTER_INIT KResult FramebufferDevice::initialize()
         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)
-        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);
-    if (!m_swapped_framebuffer_region)
-        return ENOMEM;
+    m_real_framebuffer_region = TRY(MM.allocate_kernel_region_with_vmobject(*m_real_framebuffer_vmobject, Memory::page_round_up(framebuffer_size_in_bytes()), "Framebuffer", Memory::Region::Access::ReadWrite));
+    m_swapped_framebuffer_region = TRY(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));
 
     return KSuccess;
 }

Kernel/Graphics/Intel/NativeGraphicsAdapter.cpp

@@ -189,7 +189,11 @@ IntelNativeGraphicsAdapter::IntelNativeGraphicsAdapter(PCI::Address address)
     VERIFY(bar0_space_size == 0x80000);
     dmesgln("Intel Native Graphics Adapter @ {}, MMIO @ {}, space size is {:x} bytes", address, PhysicalAddress(PCI::get_BAR0(address)), bar0_space_size);
     dmesgln("Intel Native Graphics Adapter @ {}, framebuffer @ {}", address, PhysicalAddress(PCI::get_BAR2(address)));
-    m_registers_region = MM.allocate_kernel_region(PhysicalAddress(PCI::get_BAR0(address)).page_base(), bar0_space_size, "Intel Native Graphics Registers", Memory::Region::Access::ReadWrite);
+    auto region_or_error = MM.allocate_kernel_region(PhysicalAddress(PCI::get_BAR0(address)).page_base(), bar0_space_size, "Intel Native Graphics Registers", Memory::Region::Access::ReadWrite);
+    if (region_or_error.is_error()) {
+        TODO();
+    }
+    m_registers_region = region_or_error.release_value();
     PCI::enable_bus_mastering(address);
     {
         SpinlockLocker control_lock(m_control_lock);

Kernel/Graphics/VirtIOGPU/FrameBufferDevice.cpp

@@ -35,7 +35,7 @@ KResult FrameBufferDevice::create_framebuffer()
     // Allocate frame buffer for both front and back
     auto& info = display_info();
     m_buffer_size = calculate_framebuffer_size(info.rect.width, info.rect.height);
-    m_framebuffer = MM.allocate_kernel_region(m_buffer_size * 2, String::formatted("VirtGPU FrameBuffer #{}", m_scanout.value()), Memory::Region::Access::ReadWrite, AllocationStrategy::AllocateNow);
+    m_framebuffer = TRY(MM.allocate_kernel_region(m_buffer_size * 2, String::formatted("VirtGPU FrameBuffer #{}", m_scanout.value()), Memory::Region::Access::ReadWrite, AllocationStrategy::AllocateNow));
     auto write_sink_page = MM.allocate_user_physical_page(Memory::MemoryManager::ShouldZeroFill::No).release_nonnull();
     auto num_needed_pages = m_framebuffer->vmobject().page_count();
 
@@ -43,10 +43,7 @@ KResult FrameBufferDevice::create_framebuffer()
     for (auto i = 0u; i < num_needed_pages; ++i) {
         pages.append(write_sink_page);
     }
-    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();
+    m_framebuffer_sink_vmobject = TRY(Memory::AnonymousVMObject::try_create_with_physical_pages(pages.span()));
 
     MutexLocker locker(m_gpu.operation_lock());
     m_current_buffer = &buffer_from_index(m_last_set_buffer_index.load());

Kernel/Graphics/VirtIOGPU/GPU.cpp

@@ -48,8 +48,11 @@ void GPU::initialize()
 
 GPU::GPU(PCI::Address address)
     : VirtIO::Device(address)
-    , m_scratch_space(MM.allocate_contiguous_kernel_region(32 * PAGE_SIZE, "VirtGPU Scratch Space", Memory::Region::Access::ReadWrite))
 {
+    auto region_or_error = MM.allocate_contiguous_kernel_region(32 * PAGE_SIZE, "VirtGPU Scratch Space", Memory::Region::Access::ReadWrite);
+    if (region_or_error.is_error())
+        TODO();
+    m_scratch_space = region_or_error.release_value();
 }
 
 GPU::~GPU()