wby mapping beyond end by "MAPPING_BEYOND_END" ?

From: Wang Baisheng
Date: Fri Dec 21 2012 - 01:58:50 EST

Hi All,

For x86, in arch/x86/kernel/head_32.S, for Initializing page tables,
why mapping beyond end by "MAPPING_BEYOND_END":

* End condition: we must map up to the end + MAPPING_BEYOND_END.
movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
cmpl %ebp,%eax
jb 10b

According vmlinux.lds.S, the paging table is between __brk_base and
_end. So why map MAPPING_BEYOND_END after _end ?

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