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x86, setup: ACPI 3, BIOS workaround for E820-probing code

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Impact: ACPI 3 spec compliance, BIOS bug workaround

The ACPI 3 spec added another field to the E820 buffer -- which is
backwards incompatible, since it contains a validity bit.
Furthermore, there has been at least one report of a BIOS which
assumes that the buffer it is pointed at is the same buffer as for the
previous E820 call.  Therefore, read the data into a temporary buffer
and copy the standard part of it if and only if the valid bit is set.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin 2009-03-28 13:53:26 -07:00
parent 32ec7fd08b
commit c549e71d07
1 changed files with 17 additions and 4 deletions
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21
arch/x86/boot/memory.c
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@ -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.
@ -16,6 +17,11 @@
#define SMAP 0x534d4150 /* ASCII "SMAP" */
struct e820_ext_entry {
struct e820entry std;
u32 ext_flags;
} __attribute__((packed));
static int detect_memory_e820(void)
{
int count = 0;
@ -23,9 +29,10 @@ static int detect_memory_e820(void)
u32 size, id, edi;
u8 err;
struct e820entry *desc = boot_params.e820_map;
static struct e820_ext_entry buf; /* static so it is zeroed */
do {
size = sizeof(struct e820entry);
size = sizeof buf;
/* Important: %edx and %esi are clobbered by some BIOSes,
so they must be either used for the error output
@ -33,8 +40,8 @@ static int detect_memory_e820(void)
is something out there clobbering %ebp and %edi, too. */
asm("pushl %%ebp; int $0x15; popl %%ebp; setc %0"
: "=d" (err), "+b" (next), "=a" (id), "+c" (size),
"=D" (edi), "=m" (*desc)
: "D" (desc), "d" (SMAP), "a" (0xe820)
"=D" (edi), "+m" (buf)
: "D" (&buf), "d" (SMAP), "a" (0xe820)
: "esi");
/* BIOSes which terminate the chain with CF = 1 as opposed
@ -53,8 +60,14 @@ static int detect_memory_e820(void)
break;
}
/* ACPI 3.0 added the extended flags support. If bit 0
in the extended flags is zero, we're supposed to simply
ignore the entry -- a backwards incompatible change! */
if (size > 20 && !(buf.ext_flags & 1))
continue;
*desc++ = buf.std;
count++;
desc++;
} while (next && count < ARRAY_SIZE(boot_params.e820_map));
return boot_params.e820_entries = count;