[GIT PULL] x86 setup BIOS workarounds

From: H. Peter Anvin
Date: Wed Apr 01 2009 - 12:41:27 EST


Hi Linus,

These three patches work around one identified and two hypothetical
BIOS problems with the E820 memory probe.

The identified problem is one specific box which clobbers %esi; the
other two patches protect %edi and %ebp, and implements handling for
the backwards-incompatible(!) E820 handling in ACPI 3.


The following changes since commit 15f7176eb1cccec0a332541285ee752b935c1c85:
Linus Torvalds (1):
Merge git://git.kernel.org/.../davem/net-2.6

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git x86/setup

H. Peter Anvin (2):
x86, setup: preemptively save/restore edi and ebp around INT 15 E820
x86, setup: ACPI 3, BIOS workaround for E820-probing code

Michael K. Johnson (1):
x86, setup: mark %esi as clobbered in E820 BIOS call

arch/x86/boot/memory.c | 33 ++++++++++++++++++++++++---------
1 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index 8c3c25f..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.
@@ -16,24 +17,32 @@

#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;
u32 next = 0;
- u32 size, id;
+ 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 is clobbered by some BIOSes,
- so it must be either used for the error output
- or explicitly marked clobbered. */
- asm("int $0x15; setc %0"
+ /* Important: %edx and %esi are clobbered by some BIOSes,
+ so they must be either used for the error output
+ or explicitly marked clobbered. Given that, assume there
+ 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),
- "=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
to %ebx = 0 don't always report the SMAP signature on
@@ -51,8 +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;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/