Commit 3435d347 authored by H. Peter Anvin's avatar H. Peter Anvin Committed by H. Peter Anvin
Browse files

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



Impact: BIOS proofing

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

LKML-Reference: <49DE7F79.4030106@zytor.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent d54ea252

arch/x86/boot/edd.c

+31 −40
Original line number Diff line number Diff line
@@ -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.
@@ -22,17 +23,17 @@ 
 */

static int read_mbr(u8 devno, void *buf)

{

	u16 ax, bx, cx, dx;

	struct biosregs ireg, oreg;



	ax = 0x0201;		/* Legacy Read, one sector */

	cx = 0x0001;		/* Sector 0-0-1 */

	dx = devno;

	bx = (size_t)buf;

	asm volatile("pushfl; stc; int $0x13; setc %%al; popfl"

		     : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx)

		     : : "esi", "edi", "memory");

	initregs(&ireg);

	ireg.ax = 0x0201;		/* Legacy Read, one sector */

	ireg.cx = 0x0001;		/* Sector 0-0-1 */

	ireg.dl = devno;

	ireg.bx = (size_t)buf;



	return -(u8)ax;		/* 0 or -1 */

	intcall(0x13, &ireg, &oreg);



	return -(oreg.eflags & X86_EFLAGS_CF); /* 0 or -1 */

}



static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig)
@@ -72,56 +73,46 @@ static u32 read_mbr_sig(u8 devno, struct edd_info *ei, u32 *mbrsig) 


static int get_edd_info(u8 devno, struct edd_info *ei)

{

	u16 ax, bx, cx, dx, di;

	struct biosregs ireg, oreg;



	memset(ei, 0, sizeof *ei);



	/* Check Extensions Present */



	ax = 0x4100;

	bx = EDDMAGIC1;

	dx = devno;

	asm("pushfl; stc; int $0x13; setc %%al; popfl"

	    : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx)

	    : : "esi", "edi");

	initregs(&ireg);

	ireg.ah = 0x41;

	ireg.bx = EDDMAGIC1;

	ireg.dl = devno;

	intcall(0x13, &ireg, &oreg);



	if ((u8)ax)

	if (oreg.eflags & X86_EFLAGS_CF)

		return -1;	/* No extended information */



	if (bx != EDDMAGIC2)

	if (oreg.bx != EDDMAGIC2)

		return -1;



	ei->device  = devno;

	ei->version = ax >> 8;	/* EDD version number */

	ei->interface_support = cx; /* EDD functionality subsets */

	ei->version = oreg.ah;		 /* EDD version number */

	ei->interface_support = oreg.cx; /* EDD functionality subsets */



	/* Extended Get Device Parameters */



	ei->params.length = sizeof(ei->params);

	ax = 0x4800;

	dx = devno;

	asm("pushfl; int $0x13; popfl"

	    : "+a" (ax), "+d" (dx), "=m" (ei->params)

	    : "S" (&ei->params)

	    : "ebx", "ecx", "edi");

	ireg.ah = 0x48;

	ireg.si = (size_t)&ei->params;

	intcall(0x13, &ireg, &oreg);



	/* Get legacy CHS parameters */



	/* Ralf Brown recommends setting ES:DI to 0:0 */

	ax = 0x0800;

	dx = devno;

	di = 0;

	asm("pushw %%es; "

	    "movw %%di,%%es; "

	    "pushfl; stc; int $0x13; setc %%al; popfl; "

	    "popw %%es"

	    : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di)

	    : : "esi");



	if ((u8)ax == 0) {

		ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2);

		ei->legacy_max_head = dx >> 8;

		ei->legacy_sectors_per_track = cx & 0x3f;

	ireg.ah = 0x08;

	ireg.es = 0;

	intcall(0x13, &ireg, &oreg);



	if (!(oreg.eflags & X86_EFLAGS_CF)) {

		ei->legacy_max_cylinder = oreg.ch + ((oreg.cl & 0xc0) << 2);

		ei->legacy_max_head = oreg.dh;

		ei->legacy_sectors_per_track = oreg.cl & 0x3f;

	}



	return 0;