x86, setup: "glove box" BIOS interrupts in the MCA code

 *

 *   Copyright (C) 1991, 1992 Linus Torvalds

 *   Copyright 2007 rPath, Inc. - All Rights Reserved

 *   Copyright 2009 Intel Corporation; author H. Peter Anvin

 *

 *   This file is part of the Linux kernel, and is made available under

 *   the terms of the GNU General Public License version 2.

int query_mca(void)

{

	u8 err;

	u16 es, bx, len;

	asm("pushw %%es ; "

	    "int $0x15 ; "

	    "setc %0 ; "

	    "movw %%es, %1 ; "

	    "popw %%es"

	    : "=acd" (err), "=acdSD" (es), "=b" (bx)

	    : "a" (0xc000));

	if (err)

	struct biosregs ireg, oreg;

	u16 len;

	initregs(&ireg);

	ireg.ah = 0xc0;

	intcall(0x15, &ireg, &oreg);

	if (oreg.eflags & X86_EFLAGS_CF)

		return -1;	/* No MCA present */

	set_fs(es);

	len = rdfs16(bx);

	set_fs(oreg.es);

	len = rdfs16(oreg.bx);

	if (len > sizeof(boot_params.sys_desc_table))

		len = sizeof(boot_params.sys_desc_table);

	copy_from_fs(&boot_params.sys_desc_table, bx, len);

	copy_from_fs(&boot_params.sys_desc_table, oreg.bx, len);

	return 0;

}