trunk/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 <cstdint>
  20 #include <kernel/debug.hpp>
  21 #include <kernel/context.hpp>
  22 #include <kernel/processor.hpp>
  23 #include <kernel/page_allocator.hpp>
  24 #include <lightOS/c++utils.hpp>
  25 using namespace std;
  26 using namespace kernel;
  27
  28 size_t page_allocator::mPageSize = PAGE_SIZE;
  29 page_allocator page_allocator::m_instance = page_allocator();
  30
  31 page_allocator::page_allocator()
  32         : mCapacity(0), mSize(0), mStack(reinterpret_cast<uintptr_t*>(KERNEL_MEMORY_PAGE_ALLOCATOR_START))
  33 {
  34 }
  35
  36 page_allocator::~page_allocator()
  37 {
  38 }
  39
  40 void *page_allocator::allocate()
  41 {
  42         if (mSize == 0)
  43         {
  44                 FATAL("page_allocator: No free pages" << endl);
  45                 processor::halt();
  46         }
  47
  48         LOCK(mLock);
  49
  50                 --mSize;
  51                 void *Page = reinterpret_cast<void*>(*mStack++);
  52
  53         UNLOCK(mLock);
  54
  55         return Page;
  56 }
  57
  58 void page_allocator::free(void *page)
  59 {
  60         LOCK(mLock);
  61
  62                 if (mSize == mCapacity &&
  63                         (reinterpret_cast<uintptr_t>(mStack) & (mPageSize - 1)) == 0)
  64                 {
  65                         kernelContext &Context = kernelContext::instance();
  66                         if (Context.create_page_tables( page,
  67                                                                                         adjust_pointer(mStack, - mPageSize),
  68                                                                                         lightOS::context::write | lightOS::context::global) == true)
  69                         {
  70                                 UNLOCK(mLock);
  71                                 return;
  72                         }
  73                 }
  74
  75                 ++mSize;
  76                 if (mSize > mCapacity)++mCapacity;
  77                 *--mStack = reinterpret_cast<uintptr_t>(page);
  78
  79         UNLOCK(mLock);
  80 }