From cd670599b7b00d9263f6f11a05c0edeb9cbedaf3 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Wed, 1 Apr 2009 11:35:00 -0700
Subject: [PATCH] x86, setup: guard against pre-ACPI 3 e820 code not updating
%ecx
Impact: BIOS bug safety
For pre-ACPI 3 BIOSes, pre-initialize the end of the e820 buffer just
in case the BIOS returns an unchanged %ecx but without actually
touching the ACPI 3 extended flags field.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
arch/x86/boot/memory.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index d5d2360763dc..5054c2ddd1a0 100644
--- a/arch/x86/boot/memory.c
+++ b/arch/x86/boot/memory.c
@@ -31,6 +31,12 @@ static int detect_memory_e820(void)
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 buf;