syslinux/memdisk/e820func.c
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   1/* ----------------------------------------------------------------------- *
   2 *
   3 *   Copyright 2001-2008 H. Peter Anvin - All Rights Reserved
   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, Inc., 53 Temple Place Ste 330,
   8 *   Boston MA 02111-1307, USA; either version 2 of the License, or
   9 *   (at your option) any later version; incorporated herein by reference.
  10 *
  11 * ----------------------------------------------------------------------- */
  12
  13/*
  14 * e820func.c
  15 *
  16 * E820 range database manager
  17 */
  18
  19#include <stdint.h>
  20#ifdef TEST
  21#include <string.h>
  22#else
  23#include "memdisk.h"            /* For memset() */
  24#endif
  25#include "e820.h"
  26
  27#define MAXRANGES       1024
  28/* All of memory starts out as one range of "indeterminate" type */
  29struct e820range ranges[MAXRANGES];
  30int nranges;
  31
  32void e820map_init(void)
  33{
  34    memset(ranges, 0, sizeof(ranges));
  35    nranges = 1;
  36    ranges[1].type = -1U;
  37}
  38
  39static void insertrange_at(int where, uint64_t start, uint32_t type)
  40{
  41    int i;
  42
  43    for (i = nranges; i > where; i--)
  44        ranges[i] = ranges[i - 1];
  45
  46    ranges[where].start = start;
  47    ranges[where].type = type;
  48
  49    nranges++;
  50    ranges[nranges].start = 0ULL;
  51    ranges[nranges].type = -1U;
  52}
  53
  54void insertrange(uint64_t start, uint64_t len, uint32_t type)
  55{
  56    uint64_t last;
  57    uint32_t oldtype;
  58    int i, j;
  59
  60    /* Remove this to make len == 0 mean all of memory */
  61    if (len == 0)
  62        return;                 /* Nothing to insert */
  63
  64    last = start + len - 1;     /* May roll over */
  65
  66    i = 0;
  67    oldtype = -2U;
  68    while (start > ranges[i].start && ranges[i].type != -1U) {
  69        oldtype = ranges[i].type;
  70        i++;
  71    }
  72
  73    /* Consider the replacement policy.  This current one is "overwrite." */
  74
  75    if (start < ranges[i].start || ranges[i].type == -1U)
  76        insertrange_at(i++, start, type);
  77
  78    while (i == 0 || last > ranges[i].start - 1) {
  79        oldtype = ranges[i].type;
  80        ranges[i].type = type;
  81        i++;
  82    }
  83
  84    if (last < ranges[i].start - 1)
  85        insertrange_at(i, last + 1, oldtype);
  86
  87    /* Now the map is correct, but quite possibly not optimal.  Scan the
  88       map for ranges which are redundant and remove them. */
  89    i = j = 1;
  90    oldtype = ranges[0].type;
  91    while (i < nranges) {
  92        if (ranges[i].type == oldtype) {
  93            i++;
  94        } else {
  95            oldtype = ranges[i].type;
  96            if (i != j)
  97                ranges[j] = ranges[i];
  98            i++;
  99            j++;
 100        }
 101    }
 102
 103    if (i != j) {
 104        ranges[j] = ranges[i];  /* Termination sentinel copy */
 105        nranges -= (i - j);
 106    }
 107}
 108
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