Ingo Molnar wrote:
no, to be fully generic it would have to be able to 'split' e820 entries
up and punch holes into them - but we dont want to go that far i think.
The most common problem is mismatch at the end of a range.
For what it's worth, I have a set of code to do this, written in order
to canonicalize and modify e820 data structures for memdisk.
The key to it is the observation that the e820-delivered (address, len,
type) tuples isn't actually the data structure you want -- what you want
is an ordered list of (address, type) tuples, where type may includes
undefined (the e820 default type - i.e. unused, available address space).
In addition to the attached code, to do this right, we probably want a
function to do filtering (only clobber entries of a specfic type, in
this case type 1) as opposed to blind clobber; with an ordered array
this is quite trivial.
-hpa
/* ----------------------------------------------------------------------- *
*
* Copyright 2001-2008 H. Peter Anvin - All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, Inc., 53 Temple Place Ste 330,
* Boston MA 02111-1307, USA; either version 2 of the License, or
* (at your option) any later version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* e820.h
*
* Common routines for e820 memory map management
*/
#include <stdint.h>
struct e820range {
uint64_t start;
uint32_t type;
} __attribute__((packed));
extern struct e820range ranges[];
extern int nranges;
extern uint32_t dos_mem, low_mem, high_mem;
extern void e820map_init(void);
extern void insertrange(uint64_t, uint64_t, uint32_t);
extern void get_mem(void);
extern void parse_mem(void);
/* ----------------------------------------------------------------------- *
*
* Copyright 2001-2008 H. Peter Anvin - All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, Inc., 53 Temple Place Ste 330,
* Boston MA 02111-1307, USA; either version 2 of the License, or
* (at your option) any later version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* e820func.c
*
* E820 range database manager
*/
#include <stdint.h>
#include "memdisk.h" /* For memset() */
#include "e820.h"
#define MAXRANGES 64
/* All of memory starts out as one range of "indeterminate" type */
struct e820range ranges[MAXRANGES];
int nranges;
void e820map_init(void)
{
memset(ranges, 0, sizeof(ranges));
nranges = 1;
ranges[1].type = -1;
}
static void insertrange_at(int where, uint64_t start, uint32_t type)
{
int i;
for ( i = nranges ; i > where ; i-- )
ranges[i] = ranges[i-1];
ranges[where].start = start;
ranges[where].type = type;
nranges++;
ranges[nranges].start = 0ULL;
ranges[nranges].type = (uint32_t)-1;
}
void insertrange(uint64_t start, uint64_t len, uint32_t type)
{
uint64_t last;
uint32_t oldtype;
int i, j;
/* Remove this to make len == 0 mean all of memory */
if ( len == 0 )
return; /* Nothing to insert */
last = start+len-1; /* May roll over */
i = 0;
oldtype = -2;
while ( start > ranges[i].start && ranges[i].type != -1 ) {
oldtype = ranges[i].type;
i++;
}
/* Consider the replacement policy. This current one is "overwrite." */
if ( start < ranges[i].start || ranges[i].type == -1 )
insertrange_at(i++, start, type);
while ( i == 0 || last > ranges[i].start-1 ) {
oldtype = ranges[i].type;
ranges[i].type = type;
i++;
}
if ( last < ranges[i].start-1 )
insertrange_at(i, last+1, oldtype);
/* Now the map is correct, but quite possibly not optimal. Scan the
map for ranges which are redundant and remove them. */
i = j = 1;
oldtype = ranges[0].type;
while ( i < nranges ) {
if ( ranges[i].type == oldtype ) {
i++;
} else {
oldtype = ranges[i].type;
if ( i != j )
ranges[j] = ranges[i];
i++; j++;
}
}
if ( i != j ) {
ranges[j] = ranges[i]; /* Termination sentinel copy */
nranges -= (i-j);
}
}
