kernel/page_allocator.cpp

   1 /*
   2 lightOS kernel
   3 Copyright (C) 2006-2009 Jörg Pfähler
   4
   5 This program is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU General Public License
   7 as published by the Free Software Foundation; either version 2
   8 of the License, or (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program; if not, write to the Free Software
  17 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  18 */
  19 #include <kernel/context.hpp>
  20 #include <kernel/page_allocator.hpp>
  21 #include <kernel/virtual_memory.hpp>
  22 using kernel::page_allocator;
  23 using kernel::virtual_memory;
  24
  25 // TODO: Remove
  26 #include <kernel/log.hpp>
  27
  28 SINGLETON_INSTANCE(kernel::page_allocator);
  29
  30 page_allocator::page_allocator()
  31   : m_size(0), m_stack_size(0), m_page_count(0), m_stack(virtual_memory::page_stack_begin<void*>()),
  32     m_stack_top(virtual_memory::page_stack_begin<void*>())
  33 {
  34 }
  35
  36 page_allocator::~page_allocator()
  37 {
  38 }
  39
  40 void *page_allocator::allocate()
  41 {
  42   SCOPED_LOCK(m_lock, scope);
  43
  44   if (UNLIKELY(m_stack_size == 0))
  45   {
  46     // TODO: We might want to unmap the pages that are used as the stack itself, we might want to do that at
  47     //       once
  48     // TODO: Remove when other parts of the kernel honor this error
  49     FATAL("page_allocator: No free pages");
  50     return 0;
  51   }
  52
  53   --m_size;
  54   --m_stack_size;
  55   return *m_stack++;
  56 }
  57
  58 void page_allocator::free(void *page)
  59 {
  60   SCOPED_LOCK(m_lock, scope);
  61
  62   if (UNLIKELY(m_stack == m_stack_top))
  63   {
  64     kernel_context &Context = kernel_context::instance();
  65     if (Context.create_page_tables(page,
  66                                    adjust_pointer(m_stack, - virtual_memory::page_size),
  67                                    lightOS::context::write | lightOS::context::global) == true)
  68     {
  69       ++m_size;
  70       return;
  71     }
  72     m_stack_top -= page_size_in<void*>::value;
  73   }
  74
  75   ++m_size;
  76   ++m_stack_size;
  77   *--m_stack = page;
  78 }