kernel/core/mm/swmem.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2008  Tomas 'ZeXx86' Jedrzejek (zexx86@gmail.com)
   4  *
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (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, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19
  20 #include <system.h>
  21 #include <arch/io.h>
  22 #include <string.h>
  23 #include <build.h>
  24 #include <proc.h>
  25
  26 #define SWMEM_PAGE      0x2000
  27
  28 #define SWMEM_LOW       0x500000
  29 #define SWMEM_HIGH      0x800000
  30
  31 #define SWMEM_ARRAY     (SWMEM_HIGH - SWMEM_LOW) / SWMEM_PAGE
  32
  33 #define SWMEM_PAGE_FREE 0x0
  34 #define SWMEM_PAGE_USED 0x1
  35
  36 unsigned char swmempage[SWMEM_ARRAY];
  37
  38 void *swmalloc (unsigned size)
  39 {
  40         unsigned i, y, r;
  41
  42         for (i = 0; i < SWMEM_ARRAY; i ++) {
  43                 if (swmempage[i] == SWMEM_PAGE_FREE) {  /* FREE */
  44                         r = 0;
  45                         if (size > SWMEM_PAGE) {
  46                                 for (y = 0; y < (size/SWMEM_PAGE)+1; y ++) {
  47                                         if (swmempage[i+y] == SWMEM_PAGE_FREE)
  48                                                 swmempage[i+y] = SWMEM_PAGE_USED;
  49                                         else {
  50                                                 r = 1;
  51                                                 break;
  52                                         }
  53
  54                                         if (r)
  55                                                 break;
  56                                 }
  57                         } else
  58                                 swmempage[i] = SWMEM_PAGE_USED;
  59
  60                         if (r) {
  61                                 i += y;
  62                                 continue;
  63                         }
  64
  65                         return (void *) ((i * SWMEM_PAGE) + SWMEM_LOW);
  66                 }
  67         }
  68
  69         return (void *) 0;
  70 }
  71
  72 unsigned swfree (void *ptr, unsigned size)
  73 {
  74         unsigned i = ((unsigned) ptr - SWMEM_LOW) / SWMEM_PAGE;
  75         unsigned y;
  76
  77         if (swmempage[i] != SWMEM_PAGE_USED)
  78                 return 0;
  79
  80         if (size > SWMEM_PAGE) {
  81                 for (y = 0; y < (size/SWMEM_PAGE)+1; y ++) {
  82                         if (swmempage[i+y] == SWMEM_PAGE_USED)
  83                                 swmempage[i+y] = SWMEM_PAGE_FREE;
  84                         else
  85                                 return 0;
  86                 }
  87         } else
  88                 swmempage[i] = SWMEM_PAGE_FREE;
  89
  90         return 1;
  91 }
  92
  93 unsigned int swmem_init ()
  94 {
  95         memset (swmempage, 0, SWMEM_ARRAY);
  96
  97         return 1;
  98 }