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basememsize() updates the BIOS FBMS counter at 40:13.

This commit is contained in:
Michael Brown 2005-04-09 14:16:25 +00:00
parent a800e9657d
commit fd95189c4d
1 changed files with 16 additions and 7 deletions
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23
src/arch/i386/firmware/pcbios/memsizes.c
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@ -2,14 +2,11 @@
#include "stddef.h"
#include "realmode.h"
#include "init.h"
#include "etherboot.h"
#include "memsizes.h"
#define CF ( 1 << 0 )
#ifndef MEMSIZES_DEBUG
#define MEMSIZES_DEBUG 0
#endif
/* by Eric Biederman */
struct meminfo meminfo;
@ -19,10 +16,18 @@ BASEMEMSIZE - Get size of the conventional (base) memory
**************************************************************************/
static unsigned short basememsize ( void ) {
uint16_t int12_basememsize, fbms_basememsize;
uint16_t basememsize;
/* There are two methods for retrieving the base memory size:
* INT 12 and the BIOS FBMS counter at 40:13. We read both
* and use the smaller value, to be paranoid.
*
* We then store the smaller value in the BIOS FBMS counter so
* that other code (e.g. basemem.c) can rely on it and not
* have to use INT 12. This is especially important because
* basemem.c functions can be called in a context in which
* there is no real-mode stack (e.g. when trying to allocate
* memory for a real-mode stack...)
*/
REAL_EXEC ( rm_basememsize,
@ -34,8 +39,12 @@ static unsigned short basememsize ( void ) {
get_real ( fbms_basememsize, 0x40, 0x13 );
return ( int12_basememsize < fbms_basememsize ?
int12_basememsize : fbms_basememsize );
basememsize = ( int12_basememsize < fbms_basememsize ?
int12_basememsize : fbms_basememsize );
put_real ( basememsize, 0x40, 0x13 );
return basememsize;
}
/**************************************************************************
@ -204,7 +213,7 @@ void get_memsizes ( void ) {
}
}
#if MEMSIZES_DEBUG
#ifdef DEBUG_MEMSIZES
printf ( "basememsize %d\n", meminfo.basememsize );
printf ( "memsize %d\n", meminfo.memsize );
printf ( "Memory regions(%d):\n", meminfo.map_count );