Commit-ID: c549e71d073a6e9a4847497344db28a784061455
Gitweb: http://git.kernel.org/tip/c549e71d073a6e9a4847497344db28a784061455
Author: H. Peter Anvin <hpa@xxxxxxxxx>
AuthorDate: Sat, 28 Mar 2009 13:53:26 -0700
Committer: H. Peter Anvin <hpa@xxxxxxxxx>
CommitDate: Sat, 28 Mar 2009 18:20:07 -0700
x86, setup: ACPI 3, BIOS workaround for E820-probing code
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@xxxxxxxxx>
---
arch/x86/boot/memory.c | 21 +++++++++++++++++----
1 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index fcdb10a..d5d2360 100644
--- a/arch/x86/boot/memory.c
+++ b/arch/x86/boot/memory.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
*
* 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;
--
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