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>

1 files changed, 29 insertions, 47 deletions

diff --git a/arch/x86/boot/apm.c b/arch/x86/boot/apm.c
index 7aa6033001f9..ee274834ea8b 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;
 }