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-rw-r--r--include/asm-generic/pgtable.h57
-rw-r--r--mm/mprotect.c10
2 files changed, 61 insertions, 6 deletions
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 44ef329531c..4fce3db2cec 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -197,6 +197,63 @@ static inline int pmd_none_or_clear_bad(pmd_t *pmd)
}
#endif /* CONFIG_MMU */
+static inline pte_t __ptep_modify_prot_start(struct mm_struct *mm,
+ unsigned long addr,
+ pte_t *ptep)
+{
+ /*
+ * Get the current pte state, but zero it out to make it
+ * non-present, preventing the hardware from asynchronously
+ * updating it.
+ */
+ return ptep_get_and_clear(mm, addr, ptep);
+}
+
+static inline void __ptep_modify_prot_commit(struct mm_struct *mm,
+ unsigned long addr,
+ pte_t *ptep, pte_t pte)
+{
+ /*
+ * The pte is non-present, so there's no hardware state to
+ * preserve.
+ */
+ set_pte_at(mm, addr, ptep, pte);
+}
+
+#ifndef __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
+/*
+ * Start a pte protection read-modify-write transaction, which
+ * protects against asynchronous hardware modifications to the pte.
+ * The intention is not to prevent the hardware from making pte
+ * updates, but to prevent any updates it may make from being lost.
+ *
+ * This does not protect against other software modifications of the
+ * pte; the appropriate pte lock must be held over the transation.
+ *
+ * Note that this interface is intended to be batchable, meaning that
+ * ptep_modify_prot_commit may not actually update the pte, but merely
+ * queue the update to be done at some later time. The update must be
+ * actually committed before the pte lock is released, however.
+ */
+static inline pte_t ptep_modify_prot_start(struct mm_struct *mm,
+ unsigned long addr,
+ pte_t *ptep)
+{
+ return __ptep_modify_prot_start(mm, addr, ptep);
+}
+
+/*
+ * Commit an update to a pte, leaving any hardware-controlled bits in
+ * the PTE unmodified.
+ */
+static inline void ptep_modify_prot_commit(struct mm_struct *mm,
+ unsigned long addr,
+ pte_t *ptep, pte_t pte)
+{
+ __ptep_modify_prot_commit(mm, addr, ptep, pte);
+}
+#endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
+
/*
* A facility to provide lazy MMU batching. This allows PTE updates and
* page invalidations to be delayed until a call to leave lazy MMU mode
diff --git a/mm/mprotect.c b/mm/mprotect.c
index a5bf31c2737..acfe7c8d72f 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -47,19 +47,17 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
if (pte_present(oldpte)) {
pte_t ptent;
- /* Avoid an SMP race with hardware updated dirty/clean
- * bits by wiping the pte and then setting the new pte
- * into place.
- */
- ptent = ptep_get_and_clear(mm, addr, pte);
+ ptent = ptep_modify_prot_start(mm, addr, pte);
ptent = pte_modify(ptent, newprot);
+
/*
* Avoid taking write faults for pages we know to be
* dirty.
*/
if (dirty_accountable && pte_dirty(ptent))
ptent = pte_mkwrite(ptent);
- set_pte_at(mm, addr, pte, ptent);
+
+ ptep_modify_prot_commit(mm, addr, pte, ptent);
#ifdef CONFIG_MIGRATION
} else if (!pte_file(oldpte)) {
swp_entry_t entry = pte_to_swp_entry(oldpte);