diff options
| -rw-r--r-- | include/asm-generic/pgtable.h | 57 | ||||
| -rw-r--r-- | mm/mprotect.c | 10 |
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); |