powerpc: Add 64 bit version of huge_ptep_set_wrprotect
The implementation of huge_ptep_set_wrprotect() directly calls
ptep_set_wrprotect() to mark a hugepte write protected. However this
call is not appropriate on ppc64 kernels as this is a small page only
implementation. This can lead to the hash not being flushed correctly
when a mapping is being converted to COW, allowing processes to continue
using the original copy.
Currently huge_ptep_set_wrprotect() unconditionally calls
ptep_set_wrprotect(). This is fine on ppc32 kernels as this call is
generic. On 64 bit this is implemented as:
pte_update(mm, addr, ptep, _PAGE_RW, 0);
On ppc64 this last parameter is the page size and is passed directly on
to hpte_need_flush():
hpte_need_flush(mm, addr, ptep, old, huge);
And this directly affects the page size we pass to flush_hash_page():
flush_hash_page(vaddr, rpte, psize, ssize, 0);
As this changes the way the hash is calculated we will flush the wrong
pages, potentially leaving live hashes to the original page.
Move the definition of huge_ptep_set_wrprotect() to the 32/64 bit specific
headers.
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-powerpc/pgtable-ppc64.h b/include/asm-powerpc/pgtable-ppc64.h
index 2e48be8..b2754d4 100644
--- a/include/asm-powerpc/pgtable-ppc64.h
+++ b/include/asm-powerpc/pgtable-ppc64.h
@@ -312,6 +312,15 @@
return;
old = pte_update(mm, addr, ptep, _PAGE_RW, 0);
}
+static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
+ unsigned long addr, pte_t *ptep)
+{
+ unsigned long old;
+
+ if ((pte_val(*ptep) & _PAGE_RW) == 0)
+ return;
+ old = pte_update(mm, addr, ptep, _PAGE_RW, 1);
+}
/*
* We currently remove entries from the hashtable regardless of whether