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Memory probing support for the new x86 setup code

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Probe memory (INT 15h: E820, E801, 88).

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
H. Peter Anvin 2007-07-11 12:18:50 -07:00 committed by Linus Torvalds
parent 3b53d3045b
commit 449f2ab946
1 changed files with 99 additions and 0 deletions
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arch/i386/boot/memory.c Normal file
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/* -*- linux-c -*- ------------------------------------------------------- *
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright 2007 rPath, Inc. - All Rights Reserved
*
* This file is part of the Linux kernel, and is made available under
* the terms of the GNU General Public License version 2.
*
* ----------------------------------------------------------------------- */
/*
* arch/i386/boot/memory.c
*
* Memory detection code
*/
#include "boot.h"
#define SMAP 0x534d4150 /* ASCII "SMAP" */
static int detect_memory_e820(void)
{
u32 next = 0;
u32 size, id;
u8 err;
struct e820entry *desc = boot_params.e820_map;
do {
size = sizeof(struct e820entry);
id = SMAP;
asm("int $0x15; setc %0"
: "=am" (err), "+b" (next), "+d" (id), "+c" (size),
"=m" (*desc)
: "D" (desc), "a" (0xe820));
if (err || id != SMAP)
break;
boot_params.e820_entries++;
desc++;
} while (next && boot_params.e820_entries < E820MAX);
return boot_params.e820_entries;
}
static int detect_memory_e801(void)
{
u16 ax, bx, cx, dx;
u8 err;
bx = cx = dx = 0;
ax = 0xe801;
asm("stc; int $0x15; setc %0"
: "=m" (err), "+a" (ax), "+b" (bx), "+c" (cx), "+d" (dx));
if (err)
return -1;
/* Do we really need to do this? */
if (cx || dx) {
ax = cx;
bx = dx;
}
if (ax > 15*1024)
return -1; /* Bogus! */
/* This ignores memory above 16MB if we have a memory hole
there. If someone actually finds a machine with a memory
hole at 16MB and no support for 0E820h they should probably
generate a fake e820 map. */
boot_params.alt_mem_k = (ax == 15*1024) ? (dx << 6)+ax : ax;
return 0;
}
static int detect_memory_88(void)
{
u16 ax;
u8 err;
ax = 0x8800;
asm("stc; int $0x15; setc %0" : "=bcdm" (err), "+a" (ax));
boot_params.screen_info.ext_mem_k = ax;
return -err;
}
int detect_memory(void)
{
if (detect_memory_e820() > 0)
return 0;
if (!detect_memory_e801())
return 0;
return detect_memory_88();
}