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x86-32: tighten the bound on additional memory to map

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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 <hpa@linux.intel.com>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Yinghai Lu <yinghai@kernel.org>
This commit is contained in:
H. Peter Anvin 2009-03-17 11:38:23 -07:00
parent b8a22a6273
commit 60ac982139
1 changed files with 2 additions and 1 deletions
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3
arch/x86/kernel/head_32.S
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@ -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: