Kernel: Replace KResult and KResultOr<T> with Error and ErrorOr<T>

We now use AK::Error and AK::ErrorOr<T> in both kernel and userspace!
This was a slightly tedious refactoring that took a long time, so it's
not unlikely that some bugs crept in.

Nevertheless, it does pass basic functionality testing, and it's just
real nice to finally see the same pattern in all contexts. :^)

AK/OwnPtr.h

@@ -6,13 +6,9 @@
 
 #pragma once
 
+#include <AK/Error.h>
 #include <AK/NonnullOwnPtr.h>
 #include <AK/RefCounted.h>
-#ifdef KERNEL
-# include <Kernel/API/KResult.h>
-#else
-# include <AK/Error.h>
-#endif
 
 #define OWNPTR_SCRUB_BYTE 0xf0
 
@@ -209,16 +205,6 @@ inline OwnPtr<T> adopt_own_if_nonnull(T* object)
  return {};
 }
 
-#ifdef KERNEL
-template<typename T>
-inline Kernel::KResultOr<NonnullOwnPtr<T>> adopt_nonnull_own_or_enomem(T* object)
-{
- auto result = adopt_own_if_nonnull(object);
- if (!result)
- return ENOMEM;
- return result.release_nonnull();
-}
-#else
 template<typename T>
 inline ErrorOr<NonnullOwnPtr<T>> adopt_nonnull_own_or_enomem(T* object)
 {
@@ -227,7 +213,6 @@ inline ErrorOr<NonnullOwnPtr<T>> adopt_nonnull_own_or_enomem(T* object)
  return ENOMEM;
  return result.release_nonnull();
 }
-#endif
 
 template<typename T, class... Args>
 requires(IsConstructible<T, Args...>) inline OwnPtr<T> try_make(Args&&... args)

AK/Try.h

@@ -7,7 +7,7 @@
 #pragma once
 
 // NOTE: This macro works with any result type that has the expected APIs.
-// It's designed with AK::Result and Kernel::KResult in mind.
+// It's designed with AK::Result and AK::Error in mind.
 
 #define TRY(expression) \
  ({ \

Kernel/Arch/aarch64/dummy.cpp

@@ -44,7 +44,7 @@ namespace Kernel {
 void dump_backtrace(PrintToScreen) { }
 
 // KString.cpp
-KResultOr<NonnullOwnPtr<KString>> KString::try_create_uninitialized(size_t, char*&) { return ENOMEM; }
+ErrorOr<NonnullOwnPtr<KString>> KString::try_create_uninitialized(size_t, char*&) { return ENOMEM; }
 void KString::operator delete(void*) { }
 
 // SafeMem.h

Kernel/Bus/PCI/Access.cpp

@@ -5,8 +5,8 @@
  */
 
 #include <AK/ByteReader.h>
+#include <AK/Error.h>
 #include <AK/HashTable.h>
-#include <Kernel/API/KResult.h>
 #include <Kernel/Arch/x86/IO.h>
 #include <Kernel/Bus/PCI/Access.h>
 #include <Kernel/Debug.h>

Kernel/Bus/PCI/SysFSPCI.cpp

@@ -59,19 +59,19 @@ PCIDeviceAttributeSysFSComponent::PCIDeviceAttributeSysFSComponent(String name,
 {
 }
 
-KResultOr<size_t> PCIDeviceAttributeSysFSComponent::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, OpenFileDescription*) const
+ErrorOr<size_t> PCIDeviceAttributeSysFSComponent::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, OpenFileDescription*) const
 {
  auto blob = TRY(try_to_generate_buffer());
 
  if ((size_t)offset >= blob->size())
- return KSuccess;
+ return 0;
 
  ssize_t nread = min(static_cast<off_t>(blob->size() - offset), static_cast<off_t>(count));
  TRY(buffer.write(blob->data() + offset, nread));
  return nread;
 }
 
-KResultOr<NonnullOwnPtr<KBuffer>> PCIDeviceAttributeSysFSComponent::try_to_generate_buffer() const
+ErrorOr<NonnullOwnPtr<KBuffer>> PCIDeviceAttributeSysFSComponent::try_to_generate_buffer() const
 {
  String value;
  switch (m_field_bytes_width) {

Kernel/Bus/PCI/SysFSPCI.h

@@ -37,11 +37,11 @@ class PCIDeviceAttributeSysFSComponent : public SysFSComponent {
 public:
  static NonnullRefPtr<PCIDeviceAttributeSysFSComponent> create(String name, const PCIDeviceSysFSDirectory& device, PCI::RegisterOffset offset, size_t field_bytes_width);
 
- virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer&, OpenFileDescription*) const override;
+ virtual ErrorOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer&, OpenFileDescription*) const override;
  virtual ~PCIDeviceAttributeSysFSComponent() {};
 
 protected:
- KResultOr<NonnullOwnPtr<KBuffer>> try_to_generate_buffer() const;
+ ErrorOr<NonnullOwnPtr<KBuffer>> try_to_generate_buffer() const;
  PCIDeviceAttributeSysFSComponent(String name, const PCIDeviceSysFSDirectory& device, PCI::RegisterOffset offset, size_t field_bytes_width);
  NonnullRefPtr<PCIDeviceSysFSDirectory> m_device;
  PCI::RegisterOffset m_offset;

Kernel/Bus/USB/SysFSUSB.cpp

@@ -23,7 +23,7 @@ SysFSUSBDeviceInformation::~SysFSUSBDeviceInformation()
 {
 }
 
-KResult SysFSUSBDeviceInformation::try_generate(KBufferBuilder& builder)
+ErrorOr<void> SysFSUSBDeviceInformation::try_generate(KBufferBuilder& builder)
 {
  VERIFY(m_lock.is_locked());
  JsonArraySerializer array { builder };
@@ -44,10 +44,10 @@ KResult SysFSUSBDeviceInformation::try_generate(KBufferBuilder& builder)
  obj.add("num_configurations", m_device->device_descriptor().num_configurations);
  obj.finish();
  array.finish();
- return KSuccess;
+ return {};
 }
 
-KResult SysFSUSBDeviceInformation::refresh_data(OpenFileDescription& description) const
+ErrorOr<void> SysFSUSBDeviceInformation::refresh_data(OpenFileDescription& description) const
 {
  MutexLocker lock(m_lock);
  auto& cached_data = description.data();
@@ -60,24 +60,24 @@ KResult SysFSUSBDeviceInformation::refresh_data(OpenFileDescription& description
  typed_cached_data.buffer = builder.build();
  if (!typed_cached_data.buffer)
  return ENOMEM;
- return KSuccess;
+ return {};
 }
 
-KResultOr<size_t> SysFSUSBDeviceInformation::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, OpenFileDescription* description) const
+ErrorOr<size_t> SysFSUSBDeviceInformation::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, OpenFileDescription* description) const
 {
  dbgln_if(PROCFS_DEBUG, "SysFSUSBDeviceInformation @ {}: read_bytes offset: {} count: {}", name(), offset, count);
 
  VERIFY(offset >= 0);
  VERIFY(buffer.user_or_kernel_ptr());
 
  if (!description)
- return KResult(EIO);
+ return Error::from_errno(EIO);
 
  MutexLocker locker(m_lock);
 
  if (!description->data()) {
  dbgln("SysFSUSBDeviceInformation: Do not have cached data!");
- return KResult(EIO);
+ return Error::from_errno(EIO);
  }
 
  auto& typed_cached_data = static_cast<SysFSInodeData&>(*description->data());
@@ -91,7 +91,7 @@ KResultOr<size_t> SysFSUSBDeviceInformation::read_bytes(off_t offset, size_t cou
  return nread;
 }
 
-KResult SysFSUSBBusDirectory::traverse_as_directory(unsigned fsid, Function<bool(FileSystem::DirectoryEntryView const&)> callback) const
+ErrorOr<void> SysFSUSBBusDirectory::traverse_as_directory(unsigned fsid, Function<bool(FileSystem::DirectoryEntryView const&)> callback) const
 {
  SpinlockLocker lock(m_lock);
  // Note: if the parent directory is null, it means something bad happened as this should not happen for the USB directory.
@@ -103,7 +103,7 @@ KResult SysFSUSBBusDirectory::traverse_as_directory(unsigned fsid, Function<bool
  InodeIdentifier identifier = { fsid, device_node.component_index() };
  callback({ device_node.name(), identifier, 0 });
  }
- return KSuccess;
+ return {};
 }
 
 RefPtr<SysFSComponent> SysFSUSBBusDirectory::lookup(StringView name)