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

Impact: BIOS proofing

"Glove box" off BIOS interrupts in the MCA code.

LKML-Reference: <49DE7F79.4030106@zytor.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>

arch/x86/boot/mca.c

@@ -2,6 +2,7 @@
  *
  *   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.
@@ -16,26 +17,22 @@
 
 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;
 }