There's a worrying function translation_exists in parisc cacheflush.h,
unaffected by split ptlock since flush_dcache_page is using it on some
other mm, without any relevant lock. Oh well, make it a slightly more
robust by factoring the pfn check within it. And it looked liable to
confuse a camouflaged swap or file entry with a good pte: fix that too.
Signed-off-by: Hugh Dickins <[email protected]>
---
arch/parisc/kernel/cache.c | 24 +++++++++---------------
include/asm-parisc/cacheflush.h | 35 +++++++++++++++++++----------------
2 files changed, 28 insertions(+), 31 deletions(-)
--- mm2/arch/parisc/kernel/cache.c 2005-03-02 07:38:56.000000000 +0000
+++ mm3/arch/parisc/kernel/cache.c 2005-10-22 14:06:30.000000000 +0100
@@ -266,7 +266,6 @@ void flush_dcache_page(struct page *page
unsigned long offset;
unsigned long addr;
pgoff_t pgoff;
- pte_t *pte;
unsigned long pfn = page_to_pfn(page);
@@ -297,21 +296,16 @@ void flush_dcache_page(struct page *page
* taking a page fault if the pte doesn't exist.
* This is just for speed. If the page translation
* isn't there, there's no point exciting the
- * nadtlb handler into a nullification frenzy */
-
-
- if(!(pte = translation_exists(mpnt, addr)))
- continue;
-
- /* make sure we really have this page: the private
+ * nadtlb handler into a nullification frenzy.
+ *
+ * Make sure we really have this page: the private
* mappings may cover this area but have COW'd this
- * particular page */
- if(pte_pfn(*pte) != pfn)
- continue;
-
- __flush_cache_page(mpnt, addr);
-
- break;
+ * particular page.
+ */
+ if (translation_exists(mpnt, addr, pfn)) {
+ __flush_cache_page(mpnt, addr);
+ break;
+ }
}
flush_dcache_mmap_unlock(mapping);
}
--- mm2/include/asm-parisc/cacheflush.h 2005-10-11 12:07:49.000000000 +0100
+++ mm3/include/asm-parisc/cacheflush.h 2005-10-22 14:06:30.000000000 +0100
@@ -100,30 +100,34 @@ static inline void flush_cache_range(str
/* Simple function to work out if we have an existing address translation
* for a user space vma. */
-static inline pte_t *__translation_exists(struct mm_struct *mm,
- unsigned long addr)
+static inline int translation_exists(struct vm_area_struct *vma,
+ unsigned long addr, unsigned long pfn)
{
- pgd_t *pgd = pgd_offset(mm, addr);
+ pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
pmd_t *pmd;
- pte_t *pte;
+ pte_t pte;
if(pgd_none(*pgd))
- return NULL;
+ return 0;
pmd = pmd_offset(pgd, addr);
if(pmd_none(*pmd) || pmd_bad(*pmd))
- return NULL;
+ return 0;
- pte = pte_offset_map(pmd, addr);
+ /* We cannot take the pte lock here: flush_cache_page is usually
+ * called with pte lock already held. Whereas flush_dcache_page
+ * takes flush_dcache_mmap_lock, which is lower in the hierarchy:
+ * the vma itself is secure, but the pte might come or go racily.
+ */
+ pte = *pte_offset_map(pmd, addr);
+ /* But pte_unmap() does nothing on this architecture */
+
+ /* Filter out coincidental file entries and swap entries */
+ if (!(pte_val(pte) & (_PAGE_FLUSH|_PAGE_PRESENT)))
+ return 0;
- /* The PA flush mappings show up as pte_none, but they're
- * valid none the less */
- if(pte_none(*pte) && ((pte_val(*pte) & _PAGE_FLUSH) == 0))
- return NULL;
- return pte;
+ return pte_pfn(pte) == pfn;
}
-#define translation_exists(vma, addr) __translation_exists((vma)->vm_mm, addr)
-
/* Private function to flush a page from the cache of a non-current
* process. cr25 contains the Page Directory of the current user
@@ -175,9 +179,8 @@ flush_cache_page(struct vm_area_struct *
{
BUG_ON(!vma->vm_mm->context);
- if(likely(translation_exists(vma, vmaddr)))
+ if (likely(translation_exists(vma, vmaddr, pfn)))
__flush_cache_page(vma, vmaddr);
}
#endif
-
-
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