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/* ----------------------------------------------------------------------- *
*
* Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
* Copyright 2009 H. Peter Anvin - All Rights Reserved
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom
* the Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall
* be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* ----------------------------------------------------------------------- */
/*
* memscan.c
*
* Query the system for free memory
*/
#include <assert.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <com32.h>
#include <syslinux/memscan.h>
struct e820_entry {
uint64_t start;
uint64_t len;
uint32_t type;
};
int syslinux_scan_memory(scan_memory_callback_t callback, void *data)
{
static com32sys_t ireg;
com32sys_t oreg;
struct e820_entry *e820buf;
uint64_t start, len, maxlen;
int memfound = 0;
int rv;
addr_t dosmem;
const addr_t bios_data = 0x510; /* Amount to reserve for BIOS data */
/* Use INT 12h to get DOS memory */
__intcall(0x12, &__com32_zero_regs, &oreg);
dosmem = oreg.eax.w[0] << 10;
if (dosmem < 32 * 1024 || dosmem > 640 * 1024) {
/* INT 12h reports nonsense... now what? */
uint16_t ebda_seg = *(uint16_t *) 0x40e;
if (ebda_seg >= 0x8000 && ebda_seg < 0xa000)
dosmem = ebda_seg << 4;
else
dosmem = 640 * 1024; /* Hope for the best... */
}
rv = callback(data, bios_data, dosmem - bios_data, true);
if (rv)
return rv;
/* First try INT 15h AX=E820h */
e820buf = lzalloc(sizeof *e820buf);
if (!e820buf)
return -1;
ireg.eax.l = 0xe820;
ireg.edx.l = 0x534d4150;
ireg.ebx.l = 0;
ireg.ecx.l = sizeof(*e820buf);
ireg.es = SEG(e820buf);
ireg.edi.w[0] = OFFS(e820buf);
do {
__intcall(0x15, &ireg, &oreg);
if ((oreg.eflags.l & EFLAGS_CF) ||
(oreg.eax.l != 0x534d4150) || (oreg.ecx.l < 20))
break;
start = e820buf->start;
len = e820buf->len;
if (start < 0x100000000ULL) {
/* Don't rely on E820 being valid for low memory. Doing so
could mean stuff like overwriting the PXE stack even when
using "keeppxe", etc. */
if (start < 0x100000ULL) {
if (len > 0x100000ULL - start)
len -= 0x100000ULL - start;
else
len = 0;
start = 0x100000ULL;
}
maxlen = 0x100000000ULL - start;
if (len > maxlen)
len = maxlen;
if (len) {
rv = callback(data, (addr_t) start, (addr_t) len,
e820buf->type == 1);
if (rv)
return rv;
memfound = 1;
}
}
ireg.ebx.l = oreg.ebx.l;
} while (oreg.ebx.l);
lfree(e820buf);
if (memfound)
return 0;
/* Next try INT 15h AX=E801h */
ireg.eax.w[0] = 0xe801;
__intcall(0x15, &ireg, &oreg);
if (!(oreg.eflags.l & EFLAGS_CF) && oreg.ecx.w[0]) {
rv = callback(data, (addr_t) 1 << 20, oreg.ecx.w[0] << 10, true);
if (rv)
return rv;
if (oreg.edx.w[0]) {
rv = callback(data, (addr_t) 16 << 20, oreg.edx.w[0] << 16, true);
if (rv)
return rv;
}
return 0;
}
/* Finally try INT 15h AH=88h */
ireg.eax.w[0] = 0x8800;
if (!(oreg.eflags.l & EFLAGS_CF) && oreg.eax.w[0]) {
rv = callback(data, (addr_t) 1 << 20, oreg.ecx.w[0] << 10, true);
if (rv)
return rv;
}
return 0;
}
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