From 60ac98213914cc615c67e84bfb964aa95a080d13 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Tue, 17 Mar 2009 11:38:23 -0700 Subject: [PATCH] x86-32: tighten the bound on additional memory to map Impact: Tighten bound to avoid masking errors The definition of MAPPING_BEYOND_END was excessive; this has a nasty tendency to mask bugs. We have learned over time that this kind of bug hiding can cause some very strange errors. Therefore, tighten the bound to only need to map the actual kernel area. Signed-off-by: H. Peter Anvin Cc: Jeremy Fitzhardinge Cc: Yinghai Lu --- arch/x86/kernel/head_32.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index fc884b90b6d2..30683883e0cd 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -60,7 +60,8 @@ #endif /* Enough space to fit pagetables for the low memory linear map */ -MAPPING_BEYOND_END = (PAGE_TABLE_SIZE(1 << (32 - PAGE_SHIFT)) * PAGE_SIZE) +MAPPING_BEYOND_END = \ + PAGE_TABLE_SIZE(((1<<32) - __PAGE_OFFSET) >> PAGE_SHIFT) << PAGE_SHIFT /* * Worst-case size of the kernel mapping we need to make: