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xtensa: fix fast_store_prohibited _PAGE_WRITABLE_BIT test 

Before _PAGE_WRITABLE_BIT test fast_store_prohibited must make sure that
PTE is present. Otherwise 'writable' bit is undefined and may be reused
in the 'file offset' or 'swap type' PTE fields.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>
This commit is contained in:
Max Filippov 2013-05-18 23:34:30 +04:00 committed by Chris Zankel
parent 7711ece9b3
commit 51fc41a906
1 changed files with 6 additions and 1 deletions
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7
arch/xtensa/kernel/entry.S
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@ -1792,10 +1792,15 @@ ENTRY(fast_store_prohibited)
l32i a0, a0, 0
beqz a0, 2f
/* Note that we assume _PAGE_WRITABLE_BIT is only set if pte is valid.*/
/*
* Note that we test _PAGE_WRITABLE_BIT only if PTE is present
* and is not PAGE_NONE. See pgtable.h for possible PTE layouts.
*/
_PTE_OFFSET(a0, a1, a4)
l32i a4, a0, 0 # read pteval
movi a1, _PAGE_CA_INVALID
ball a4, a1, 2f
bbci.l a4, _PAGE_WRITABLE_BIT, 2f
movi a1, _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_HW_WRITE