Kernel: Let PageDirectory own the associated RangeAllocator.

Since we transition to a new PageDirectory on exec(), we need a matching
RangeAllocator to go with the new directory. Instead of juggling this in
Process and MemoryManager, simply attach the RangeAllocator to the
PageDirectory instead.

Fixes #61.

Kernel/Process.cpp

@@ -75,8 +75,8 @@ Range Process::allocate_range(LinearAddress laddr, size_t size)
     laddr.mask(PAGE_MASK);
     size = PAGE_ROUND_UP(size);
     if (laddr.is_null())
-        return m_range_allocator.allocate_anywhere(size);
-    return m_range_allocator.allocate_specific(laddr, size);
+        return page_directory().range_allocator().allocate_anywhere(size);
+    return page_directory().range_allocator().allocate_specific(laddr, size);
 }
 
 Region* Process::allocate_region(LinearAddress laddr, size_t size, String&& name, bool is_readable, bool is_writable, bool commit)
@@ -117,7 +117,7 @@ bool Process::deallocate_region(Region& region)
     InterruptDisabler disabler;
     for (int i = 0; i < m_regions.size(); ++i) {
         if (m_regions[i] == &region) {
-            m_range_allocator.deallocate({ region.laddr(), region.size() });
+            page_directory().range_allocator().deallocate({ region.laddr(), region.size() });
             MM.unmap_region(region);
             m_regions.remove(i);
             return true;
@@ -313,7 +313,7 @@ int Process::do_exec(String path, Vector<String> arguments, Vector<String> envir
     dword entry_eip = 0;
     // FIXME: Is there a race here?
     auto old_page_directory = move(m_page_directory);
-    m_page_directory = PageDirectory::create();
+    m_page_directory = PageDirectory::create_for_userspace();
 #ifdef MM_DEBUG
     dbgprintf("Process %u exec: PD=%x created\n", pid(), m_page_directory.ptr());
 #endif
@@ -542,9 +542,6 @@ Process* Process::create_kernel_process(String&& name, void (*e)())
     return process;
 }
 
-static const dword userspace_range_base = 0x01000000;
-static const dword kernelspace_range_base = 0xc0000000;
-
 Process::Process(String&& name, uid_t uid, gid_t gid, pid_t ppid, RingLevel ring, RetainPtr<Inode>&& cwd, RetainPtr<Inode>&& executable, TTY* tty, Process* fork_parent)
     : m_name(move(name))
     , m_pid(next_pid++) // FIXME: RACE: This variable looks racy!
@@ -557,11 +554,10 @@ Process::Process(String&& name, uid_t uid, gid_t gid, pid_t ppid, RingLevel ring
     , m_executable(move(executable))
     , m_tty(tty)
     , m_ppid(ppid)
-    , m_range_allocator(LinearAddress(userspace_range_base), kernelspace_range_base - userspace_range_base)
 {
     dbgprintf("Process: New process PID=%u with name=%s\n", m_pid, m_name.characters());
 
-    m_page_directory = PageDirectory::create();
+    m_page_directory = PageDirectory::create_for_userspace();
 #ifdef MM_DEBUG
     dbgprintf("Process %u ctor: PD=%x created\n", pid(), m_page_directory.ptr());
 #endif

Kernel/Process.h

@@ -331,7 +331,6 @@ private:
 
     RetainPtr<ProcessTracer> m_tracer;
     OwnPtr<ELFLoader> m_elf_loader;
-    RangeAllocator m_range_allocator;
 
     Lock m_big_lock { "Process" };
 };

Kernel/VM/MemoryManager.cpp

@@ -20,7 +20,6 @@ MemoryManager& MM
 }
 
 MemoryManager::MemoryManager()
-    : m_range_allocator(LinearAddress(0xc0000000), 0x3f000000)
 {
     // FIXME: This is not the best way to do memory map detection.
     //        Rewrite to use BIOS int 15,e820 once we have VM86 support.
@@ -402,7 +401,7 @@ RetainPtr<Region> MemoryManager::allocate_kernel_region(size_t size, String&& na
     InterruptDisabler disabler;
 
     ASSERT(!(size % PAGE_SIZE));
-    auto range = m_range_allocator.allocate_anywhere(size);
+    auto range = kernel_page_directory().range_allocator().allocate_anywhere(size);
     ASSERT(range.is_valid());
     auto region = adopt(*new Region(range, move(name), true, true, false));
     MM.map_region_at_address(*m_kernel_page_directory, *region, range.base(), false);

Kernel/VM/MemoryManager.h

@@ -13,7 +13,6 @@
 #include <AK/Weakable.h>
 #include <Kernel/LinearAddress.h>
 #include <Kernel/VM/PhysicalPage.h>
-#include <Kernel/VM/RangeAllocator.h>
 #include <Kernel/VM/Region.h>
 #include <Kernel/VM/VMObject.h>
 #include <Kernel/FileSystem/InodeIdentifier.h>
@@ -217,8 +216,6 @@ private:
     HashTable<Region*> m_user_regions;
     HashTable<Region*> m_kernel_regions;
 
-    RangeAllocator m_range_allocator;
-
     size_t m_ram_size { 0 };
     bool m_quickmap_in_use { false };
 };

Kernel/VM/PageDirectory.cpp

@@ -3,12 +3,17 @@
 #include <Kernel/Process.h>
 #include <Kernel/Thread.h>
 
+static const dword userspace_range_base = 0x01000000;
+static const dword kernelspace_range_base = 0xc0000000;
+
 PageDirectory::PageDirectory(PhysicalAddress paddr)
+    : m_range_allocator(LinearAddress(0xc0000000), 0x3f000000)
 {
     m_directory_page = PhysicalPage::create_eternal(paddr, true);
 }
 
 PageDirectory::PageDirectory()
+    : m_range_allocator(LinearAddress(userspace_range_base), kernelspace_range_base - userspace_range_base)
 {
     MM.populate_page_directory(*this);
 }

Kernel/VM/PageDirectory.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <Kernel/VM/PhysicalPage.h>
+#include <Kernel/VM/RangeAllocator.h>
 #include <AK/HashMap.h>
 #include <AK/Retainable.h>
 #include <AK/RetainPtr.h>
@@ -8,7 +9,7 @@
 class PageDirectory : public Retainable<PageDirectory> {
     friend class MemoryManager;
 public:
-    static Retained<PageDirectory> create() { return adopt(*new PageDirectory); }
+    static Retained<PageDirectory> create_for_userspace() { return adopt(*new PageDirectory); }
     static Retained<PageDirectory> create_at_fixed_address(PhysicalAddress paddr) { return adopt(*new PageDirectory(paddr)); }
     ~PageDirectory();
 
@@ -17,10 +18,13 @@ public:
 
     void flush(LinearAddress);
 
+    RangeAllocator& range_allocator() { return m_range_allocator; }
+
 private:
     PageDirectory();
     explicit PageDirectory(PhysicalAddress);
 
+    RangeAllocator m_range_allocator;
     RetainPtr<PhysicalPage> m_directory_page;
     HashMap<unsigned, RetainPtr<PhysicalPage>> m_physical_pages;
 };