kernel/mem/physical.c

0001 /*                    The Quest Operating System
0002  *  Copyright (C) 2005-2010  Richard West, Boston University
0003  *
0004  *  This program is free software: you can redistribute it and/or modify
0005  *  it under the terms of the GNU General Public License as published by
0006  *  the Free Software Foundation, either version 3 of the License, or
0007  *  (at your option) any later version.
0008  *
0009  *  This program is distributed in the hope that it will be useful,
0010  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
0011  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0012  *  GNU General Public License for more details.
0013  *
0014  *  You should have received a copy of the GNU General Public License
0015  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
0016  */
0017
0018 #include "mem/physical.h"
0019 #include "kernel.h"
0020
0021 /* Declare space for bitmap (physical) memory usage table.
0022  * PHYS_INDEX_MAX entries of 32-bit integers each for a 4K page => 4GB
0023  * memory limit when PHYS_INDEX_MAX=32768
0024  */
0025 uint32 mm_table[PHYS_INDEX_MAX] __attribute__ ((aligned (4096)));
0026 uint32 mm_limit;                /* Actual physical page limit */
0027
0028 /* Find free page in mm_table
0029  *
0030  * Returns physical address rather than virtual, since we we don't
0031  * want user-level pages mapped into kernel page tables in all cases
0032  */
0033 uint32
0034 alloc_phys_frame (void)
0035 {
0036
0037   int i;
0038
0039   for (i = 0; i < mm_limit; i++)
0040     if (BITMAP_TST (mm_table, i)) {     /* Free page */
0041       BITMAP_CLR (mm_table, i);
0042       return (i << 12);         /* physical byte address of free page/frame */
0043     }
0044
0045   return -1;                    /* Error -- no free page? */
0046 }
0047
0048 uint32
0049 alloc_phys_frames (uint32 count)
0050 {
0051
0052   int i, j;
0053
0054   for (i = 0; i < mm_limit - count + 1; i++) {
0055     for (j = 0; j < count; j++) {
0056       if (!BITMAP_TST (mm_table, i + j)) {      /* Is not free page? */
0057         i = i + j;
0058         goto keep_searching;
0059       }
0060     }
0061     /* found window: */
0062     for (j = 0; j < count; j++) {
0063       BITMAP_CLR (mm_table, i + j);
0064     }
0065     return (i << 12);           /* physical byte address of free frames */
0066   keep_searching:
0067     ;
0068   }
0069   return -1;                    /* Error -- no free page? */
0070 }
0071
0072 void
0073 free_phys_frame (uint32 frame)
0074 {
0075   BITMAP_SET (mm_table, frame >> 12);
0076 }
0077
0078 void
0079 free_phys_frames (uint32 frame, uint32 count)
0080 {
0081   int i;
0082   frame >>= 12;
0083   for (i = 0; i < count; i++)
0084     BITMAP_SET (mm_table, frame + i);
0085 }
0086
0087 /*
0088  * Local Variables:
0089  * indent-tabs-mode: nil
0090  * mode: C
0091  * c-file-style: "gnu"
0092  * c-basic-offset: 2
0093  * End:
0094  */
0095
0096 /* vi: set et sw=2 sts=2: */