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-rw-r--r--arch/x86/boot/memory.c39
1 files changed, 30 insertions, 9 deletions
diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index 8c3c25f3557..5054c2ddd1a 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 +17,38 @@
#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 */
+
+ /*
+ * Set this here so that if the BIOS doesn't change this field
+ * but still doesn't change %ecx, we're still okay...
+ */
+ buf.ext_flags = 1;
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 +66,14 @@ 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;