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Commit d54ea252 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 APM code 



Impact: BIOS proofing

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

LKML-Reference: <49DE7F79.4030106@zytor.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
parent df7699c5

arch/x86/boot/apm.c

+29 −47
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

 *

 *   Original APM BIOS checking by Stephen Rothwell, May 1994

 *   (sfr@canb.auug.org.au)
@@ -19,75 +20,56 @@ 


int query_apm_bios(void)

{

	u16 ax, bx, cx, dx, di;

	u32 ebx, esi;

	u8 err;

	struct biosregs ireg, oreg;



	/* APM BIOS installation check */

	ax = 0x5300;

	bx = cx = 0;

	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"

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

		     : : "esi", "edi");

	initregs(&ireg);

	ireg.ah = 0x53;

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



	if (err)

	if (oreg.flags & X86_EFLAGS_CF)

		return -1;		/* No APM BIOS */



	if (bx != 0x504d)	/* "PM" signature */

	if (oreg.bx != 0x504d)		/* "PM" signature */

		return -1;



	if (!(cx & 0x02))		/* 32 bits supported? */

	if (!(oreg.cx & 0x02))		/* 32 bits supported? */

		return -1;



	/* Disconnect first, just in case */

	ax = 0x5304;

	bx = 0;

	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"

		     : "+a" (ax), "+b" (bx)

		     : : "ecx", "edx", "esi", "edi");



	/* Paranoia */

	ebx = esi = 0;

	cx = dx = di = 0;

	ireg.al = 0x04;

	intcall(0x15, &ireg, NULL);



	/* 32-bit connect */

	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %6"

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

		       "+S" (esi), "+D" (di), "=m" (err)

		     : "a" (0x5303));



	boot_params.apm_bios_info.cseg = ax;

	boot_params.apm_bios_info.offset = ebx;

	boot_params.apm_bios_info.cseg_16 = cx;

	boot_params.apm_bios_info.dseg = dx;

	boot_params.apm_bios_info.cseg_len = (u16)esi;

	boot_params.apm_bios_info.cseg_16_len = esi >> 16;

	boot_params.apm_bios_info.dseg_len = di;



	if (err)

	ireg.al = 0x03;

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



	boot_params.apm_bios_info.cseg        = oreg.ax;

	boot_params.apm_bios_info.offset      = oreg.ebx;

	boot_params.apm_bios_info.cseg_16     = oreg.cx;

	boot_params.apm_bios_info.dseg        = oreg.dx;

	boot_params.apm_bios_info.cseg_len    = oreg.si;

	boot_params.apm_bios_info.cseg_16_len = oreg.hsi;

	boot_params.apm_bios_info.dseg_len    = oreg.di;



	if (oreg.flags & X86_EFLAGS_CF)

		return -1;



	/* Redo the installation check as the 32-bit connect;

	   some BIOSes return different flags this way... */



	ax = 0x5300;

	bx = cx = 0;

	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"

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

		     : : "esi", "edi");

	ireg.al = 0x00;

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



	if (err || bx != 0x504d) {

	if ((oreg.eflags & X86_EFLAGS_CF) || oreg.bx != 0x504d) {

		/* Failure with 32-bit connect, try to disconect and ignore */

		ax = 0x5304;

		bx = 0;

		asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"

			     : "+a" (ax), "+b" (bx)

			     : : "ecx", "edx", "esi", "edi");

		ireg.al = 0x04;

		intcall(0x15, &ireg, NULL);

		return -1;

	}



	boot_params.apm_bios_info.version = ax;

	boot_params.apm_bios_info.flags = cx;

	boot_params.apm_bios_info.version = oreg.ax;

	boot_params.apm_bios_info.flags   = oreg.cx;

	return 0;

}