[PATCH] ppc32: Fix pte_update for 64-bit PTEs

While the existing pte_update code handled atomically modifying a 64-bit PTE,
it did not return all 64-bits of the PTE before it was modified.  This causes
problems in some places that expect the full PTE to be returned, like
ptep_get_and_clear().

Created a new pte_update function that is conditional on CONFIG_PTE_64BIT.  It
atomically reads the low PTE word which all PTE flags are required to be in
and returns a premodified full 64-bit PTE.

Since we now have an explicit 64-bit PTE version of pte_update we can also
remove the hack that existed to get the low PTE word regardless of size.

Signed-off-by: Kumar Gala <kumar.gala@freescale.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 25 insertions, 4 deletions

diff --git a/include/asm-ppc/pgtable.h b/include/asm-ppc/pgtable.h
index 19dfb7abaa21..2e88cd9feffe 100644
--- a/include/asm-ppc/pgtable.h
+++ b/include/asm-ppc/pgtable.h
@@ -526,10 +526,10 @@ extern void add_hash_page(unsigned context, unsigned long va,
  * Atomic PTE updates.
  *
  * pte_update clears and sets bit atomically, and returns
- * the old pte value.
- * The ((unsigned long)(p+1) - 4) hack is to get to the least-significant
- * 32 bits of the PTE regardless of whether PTEs are 32 or 64 bits.
+ * the old pte value.  In the 64-bit PTE case we lock around the
+ * low PTE word since we expect ALL flag bits to be there
  */
+#ifndef CONFIG_PTE_64BIT
 static inline unsigned long pte_update(pte_t *p, unsigned long clr,
                                        unsigned long set)
 {
@@ -543,10 +543,31 @@ static inline unsigned long pte_update(pte_t *p, unsigned long clr,
 "       stwcx.  %1,0,%3\n\
         bne-    1b"
         : "=&r" (old), "=&r" (tmp), "=m" (*p)
-        : "r" ((unsigned long)(p+1) - 4), "r" (clr), "r" (set), "m" (*p)
+        : "r" (p), "r" (clr), "r" (set), "m" (*p)
         : "cc" );
         return old;
 }
+#else
+static inline unsigned long long pte_update(pte_t *p, unsigned long clr,
+                                       unsigned long set)
+{
+        unsigned long long old;
+        unsigned long tmp;
+
+        __asm__ __volatile__("\
+1:      lwarx   %L0,0,%4\n\
+        lwzx    %0,0,%3\n\
+        andc    %1,%L0,%5\n\
+        or      %1,%1,%6\n"
+        PPC405_ERR77(0,%3)
+"       stwcx.  %1,0,%4\n\
+        bne-    1b"
+        : "=&r" (old), "=&r" (tmp), "=m" (*p)
+        : "r" (p), "r" ((unsigned long)(p) + 4), "r" (clr), "r" (set), "m" (*p)
+        : "cc" );
+        return old;
+}
+#endif
 
 /*
  * set_pte stores a linux PTE into the linux page table.