Kernel: Factor address space management out of the Process class

This patch adds Space, a class representing a process's address space.

- Each Process has a Space.
- The Space owns the PageDirectory and all Regions in the Process.

This allows us to reorganize sys$execve() so that it constructs and
populates a new Space fully before committing to it.

Previously, we would construct the new address space while still
running in the old one, and encountering an error meant we had to do
tedious and error-prone rollback.

Those problems are now gone, replaced by what's hopefully a set of much
smaller problems and missing cleanups. :^)

Kernel/CMakeLists.txt

@@ -212,6 +212,7 @@ set(KERNEL_SOURCES
  VM/RangeAllocator.cpp
  VM/Region.cpp
  VM/SharedInodeVMObject.cpp
+ VM/Space.cpp
  VM/VMObject.cpp
  WaitQueue.cpp
  init.cpp

Kernel/CoreDump.cpp

@@ -59,7 +59,7 @@ OwnPtr<CoreDump> CoreDump::create(NonnullRefPtr<Process> process, const String&
 CoreDump::CoreDump(NonnullRefPtr<Process> process, NonnullRefPtr<FileDescription>&& fd)
  : m_process(move(process))
  , m_fd(move(fd))
- , m_num_program_headers(m_process->m_regions.size() + 1) // +1 for NOTE segment
+ , m_num_program_headers(m_process->space().region_count() + 1) // +1 for NOTE segment
 {
 }
 
@@ -137,7 +137,7 @@ KResult CoreDump::write_elf_header()
 KResult CoreDump::write_program_headers(size_t notes_size)
 {
  size_t offset = sizeof(Elf32_Ehdr) + m_num_program_headers * sizeof(Elf32_Phdr);
- for (auto& region : m_process->m_regions) {
+ for (auto& region : m_process->space().regions()) {
  Elf32_Phdr phdr {};
 
  phdr.p_type = PT_LOAD;
@@ -178,7 +178,7 @@ KResult CoreDump::write_program_headers(size_t notes_size)
 
 KResult CoreDump::write_regions()
 {
- for (auto& region : m_process->m_regions) {
+ for (auto& region : m_process->space().regions()) {
  if (region.is_kernel())
  continue;
 
@@ -258,13 +258,13 @@ ByteBuffer CoreDump::create_notes_threads_data() const
 ByteBuffer CoreDump::create_notes_regions_data() const
 {
  ByteBuffer regions_data;
- for (size_t region_index = 0; region_index < m_process->m_regions.size(); ++region_index) {
+ for (size_t region_index = 0; region_index < m_process->space().region_count(); ++region_index) {
 
  ByteBuffer memory_region_info_buffer;
  ELF::Core::MemoryRegionInfo info {};
  info.header.type = ELF::Core::NotesEntryHeader::Type::MemoryRegionInfo;
 
- auto& region = m_process->m_regions[region_index];
+ auto& region = m_process->space().regions()[region_index];
  info.region_start = reinterpret_cast<uint32_t>(region.vaddr().as_ptr());
  info.region_end = reinterpret_cast<uint32_t>(region.vaddr().as_ptr() + region.size());
  info.program_header_index = region_index;
@@ -316,7 +316,7 @@ ByteBuffer CoreDump::create_notes_segment_data() const
 
 KResult CoreDump::write()
 {
- ScopedSpinLock lock(m_process->get_lock());
+ ScopedSpinLock lock(m_process->space().get_lock());
  ProcessPagingScope scope(m_process);
 
  ByteBuffer notes_segment = create_notes_segment_data();

Kernel/Devices/BXVGADevice.cpp

@@ -185,7 +185,7 @@ KResultOr<Region*> BXVGADevice::mmap(Process& process, FileDescription&, const R
  auto vmobject = AnonymousVMObject::create_for_physical_range(m_framebuffer_address, framebuffer_size_in_bytes());
  if (!vmobject)
  return ENOMEM;
- return process.allocate_region_with_vmobject(
+ return process.space().allocate_region_with_vmobject(
  range,
  vmobject.release_nonnull(),
  0,

Kernel/Devices/MBVGADevice.cpp

@@ -64,7 +64,7 @@ KResultOr<Region*> MBVGADevice::mmap(Process& process, FileDescription&, const R
  auto vmobject = AnonymousVMObject::create_for_physical_range(m_framebuffer_address, framebuffer_size_in_bytes());
  if (!vmobject)
  return ENOMEM;
- return process.allocate_region_with_vmobject(
+ return process.space().allocate_region_with_vmobject(
  range,
  vmobject.release_nonnull(),
  0,

Kernel/Devices/MemoryDevice.cpp

@@ -66,7 +66,7 @@ KResultOr<Region*> MemoryDevice::mmap(Process& process, FileDescription&, const
  if (!vmobject)
  return ENOMEM;
  dbgln("MemoryDevice: Mapped physical memory at {} for range of {} bytes", viewed_address, range.size());
- return process.allocate_region_with_vmobject(
+ return process.space().allocate_region_with_vmobject(
  range,
  vmobject.release_nonnull(),
  0,

Kernel/FileSystem/AnonymousFile.cpp

@@ -47,7 +47,7 @@ KResultOr<Region*> AnonymousFile::mmap(Process& process, FileDescription&, const
  if (range.size() != m_vmobject->size())
  return EINVAL;
 
- return process.allocate_region_with_vmobject(range, m_vmobject, offset, {}, prot, shared);
+ return process.space().allocate_region_with_vmobject(range, m_vmobject, offset, {}, prot, shared);
 }
 
 }

Kernel/FileSystem/InodeFile.cpp

@@ -117,7 +117,7 @@ KResultOr<Region*> InodeFile::mmap(Process& process, FileDescription& descriptio
  vmobject = PrivateInodeVMObject::create_with_inode(inode());
  if (!vmobject)
  return ENOMEM;
- return process.allocate_region_with_vmobject(range, vmobject.release_nonnull(), offset, description.absolute_path(), prot, shared);
+ return process.space().allocate_region_with_vmobject(range, vmobject.release_nonnull(), offset, description.absolute_path(), prot, shared);
 }
 
 String InodeFile::absolute_path(const FileDescription& description) const

Kernel/FileSystem/ProcFS.cpp

@@ -317,8 +317,8 @@ static bool procfs$pid_vm(InodeIdentifier identifier, KBufferBuilder& builder)
  return false;
  JsonArraySerializer array { builder };
  {
- ScopedSpinLock lock(process->get_lock());
- for (auto& region : process->regions()) {
+ ScopedSpinLock lock(process->space().get_lock());
+ for (auto& region : process->space().regions()) {
  if (!region.is_user_accessible() && !Process::current()->is_superuser())
  continue;
  auto region_object = array.add_object();

Kernel/Forward.h

@@ -62,6 +62,7 @@ class Region;
 class Scheduler;
 class SchedulerPerProcessorData;
 class Socket;
+class Space;
 template<typename BaseType>
 class SpinLock;
 class RecursiveSpinLock;

Kernel/PerformanceEventBuffer.cpp

@@ -121,15 +121,15 @@ bool PerformanceEventBuffer::to_json(KBufferBuilder& builder, ProcessID pid, con
 {
  auto process = Process::from_pid(pid);
  ASSERT(process);
- ScopedSpinLock locker(process->get_lock());
+ ScopedSpinLock locker(process->space().get_lock());
 
  JsonObjectSerializer object(builder);
  object.add("pid", pid.value());
  object.add("executable", executable_path);
 
  {
  auto region_array = object.add_array("regions");
- for (const auto& region : process->regions()) {
+ for (const auto& region : process->space().regions()) {
  auto region_object = region_array.add_object();
  region_object.add("base", region.vaddr().get());
  region_object.add("size", region.size());