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Subject[tip:x86/setup] x86, setup: "glove box" BIOS interrupts in the APM code
Commit-ID:  d54ea252e4c92357226992cf65d94616a96e6fce
Gitweb: http://git.kernel.org/tip/d54ea252e4c92357226992cf65d94616a96e6fce
Author: H. Peter Anvin <hpa@linux.intel.com>
AuthorDate: Wed, 1 Apr 2009 18:14:26 -0700
Committer: H. Peter Anvin <hpa@zytor.com>
CommitDate: Thu, 9 Apr 2009 16:08:11 -0700

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: H. Peter Anvin <hpa@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>


---
arch/x86/boot/apm.c | 76 +++++++++++++++++++-------------------------------
1 files changed, 29 insertions(+), 47 deletions(-)

diff --git a/arch/x86/boot/apm.c b/arch/x86/boot/apm.c
index 7aa6033..ee27483 100644
--- a/arch/x86/boot/apm.c
+++ b/arch/x86/boot/apm.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
*
* 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;
}


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