diff options
Diffstat (limited to 'kernel/mm/mmu_notifier.c')
| -rw-r--r-- | kernel/mm/mmu_notifier.c | 396 |
1 files changed, 396 insertions, 0 deletions
diff --git a/kernel/mm/mmu_notifier.c b/kernel/mm/mmu_notifier.c new file mode 100644 index 000000000..3b9b3d074 --- /dev/null +++ b/kernel/mm/mmu_notifier.c @@ -0,0 +1,396 @@ +/* + * linux/mm/mmu_notifier.c + * + * Copyright (C) 2008 Qumranet, Inc. + * Copyright (C) 2008 SGI + * Christoph Lameter <clameter@sgi.com> + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + */ + +#include <linux/rculist.h> +#include <linux/mmu_notifier.h> +#include <linux/export.h> +#include <linux/mm.h> +#include <linux/err.h> +#include <linux/srcu.h> +#include <linux/rcupdate.h> +#include <linux/sched.h> +#include <linux/slab.h> + +/* global SRCU for all MMs */ +static struct srcu_struct srcu; + +/* + * This function allows mmu_notifier::release callback to delay a call to + * a function that will free appropriate resources. The function must be + * quick and must not block. + */ +void mmu_notifier_call_srcu(struct rcu_head *rcu, + void (*func)(struct rcu_head *rcu)) +{ + call_srcu(&srcu, rcu, func); +} +EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu); + +void mmu_notifier_synchronize(void) +{ + /* Wait for any running method to finish. */ + srcu_barrier(&srcu); +} +EXPORT_SYMBOL_GPL(mmu_notifier_synchronize); + +/* + * This function can't run concurrently against mmu_notifier_register + * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap + * runs with mm_users == 0. Other tasks may still invoke mmu notifiers + * in parallel despite there being no task using this mm any more, + * through the vmas outside of the exit_mmap context, such as with + * vmtruncate. This serializes against mmu_notifier_unregister with + * the mmu_notifier_mm->lock in addition to SRCU and it serializes + * against the other mmu notifiers with SRCU. struct mmu_notifier_mm + * can't go away from under us as exit_mmap holds an mm_count pin + * itself. + */ +void __mmu_notifier_release(struct mm_struct *mm) +{ + struct mmu_notifier *mn; + int id; + + /* + * SRCU here will block mmu_notifier_unregister until + * ->release returns. + */ + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) + /* + * If ->release runs before mmu_notifier_unregister it must be + * handled, as it's the only way for the driver to flush all + * existing sptes and stop the driver from establishing any more + * sptes before all the pages in the mm are freed. + */ + if (mn->ops->release) + mn->ops->release(mn, mm); + + spin_lock(&mm->mmu_notifier_mm->lock); + while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) { + mn = hlist_entry(mm->mmu_notifier_mm->list.first, + struct mmu_notifier, + hlist); + /* + * We arrived before mmu_notifier_unregister so + * mmu_notifier_unregister will do nothing other than to wait + * for ->release to finish and for mmu_notifier_unregister to + * return. + */ + hlist_del_init_rcu(&mn->hlist); + } + spin_unlock(&mm->mmu_notifier_mm->lock); + srcu_read_unlock(&srcu, id); + + /* + * synchronize_srcu here prevents mmu_notifier_release from returning to + * exit_mmap (which would proceed with freeing all pages in the mm) + * until the ->release method returns, if it was invoked by + * mmu_notifier_unregister. + * + * The mmu_notifier_mm can't go away from under us because one mm_count + * is held by exit_mmap. + */ + synchronize_srcu(&srcu); +} + +/* + * If no young bitflag is supported by the hardware, ->clear_flush_young can + * unmap the address and return 1 or 0 depending if the mapping previously + * existed or not. + */ +int __mmu_notifier_clear_flush_young(struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + struct mmu_notifier *mn; + int young = 0, id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { + if (mn->ops->clear_flush_young) + young |= mn->ops->clear_flush_young(mn, mm, start, end); + } + srcu_read_unlock(&srcu, id); + + return young; +} + +int __mmu_notifier_test_young(struct mm_struct *mm, + unsigned long address) +{ + struct mmu_notifier *mn; + int young = 0, id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { + if (mn->ops->test_young) { + young = mn->ops->test_young(mn, mm, address); + if (young) + break; + } + } + srcu_read_unlock(&srcu, id); + + return young; +} + +void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, + pte_t pte) +{ + struct mmu_notifier *mn; + int id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { + if (mn->ops->change_pte) + mn->ops->change_pte(mn, mm, address, pte); + } + srcu_read_unlock(&srcu, id); +} + +void __mmu_notifier_invalidate_page(struct mm_struct *mm, + unsigned long address) +{ + struct mmu_notifier *mn; + int id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { + if (mn->ops->invalidate_page) + mn->ops->invalidate_page(mn, mm, address); + } + srcu_read_unlock(&srcu, id); +} + +void __mmu_notifier_invalidate_range_start(struct mm_struct *mm, + unsigned long start, unsigned long end) +{ + struct mmu_notifier *mn; + int id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { + if (mn->ops->invalidate_range_start) + mn->ops->invalidate_range_start(mn, mm, start, end); + } + srcu_read_unlock(&srcu, id); +} +EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start); + +void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, + unsigned long start, unsigned long end) +{ + struct mmu_notifier *mn; + int id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { + /* + * Call invalidate_range here too to avoid the need for the + * subsystem of having to register an invalidate_range_end + * call-back when there is invalidate_range already. Usually a + * subsystem registers either invalidate_range_start()/end() or + * invalidate_range(), so this will be no additional overhead + * (besides the pointer check). + */ + if (mn->ops->invalidate_range) + mn->ops->invalidate_range(mn, mm, start, end); + if (mn->ops->invalidate_range_end) + mn->ops->invalidate_range_end(mn, mm, start, end); + } + srcu_read_unlock(&srcu, id); +} +EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end); + +void __mmu_notifier_invalidate_range(struct mm_struct *mm, + unsigned long start, unsigned long end) +{ + struct mmu_notifier *mn; + int id; + + id = srcu_read_lock(&srcu); + hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { + if (mn->ops->invalidate_range) + mn->ops->invalidate_range(mn, mm, start, end); + } + srcu_read_unlock(&srcu, id); +} +EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range); + +static int do_mmu_notifier_register(struct mmu_notifier *mn, + struct mm_struct *mm, + int take_mmap_sem) +{ + struct mmu_notifier_mm *mmu_notifier_mm; + int ret; + + BUG_ON(atomic_read(&mm->mm_users) <= 0); + + /* + * Verify that mmu_notifier_init() already run and the global srcu is + * initialized. + */ + BUG_ON(!srcu.per_cpu_ref); + + ret = -ENOMEM; + mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL); + if (unlikely(!mmu_notifier_mm)) + goto out; + + if (take_mmap_sem) + down_write(&mm->mmap_sem); + ret = mm_take_all_locks(mm); + if (unlikely(ret)) + goto out_clean; + + if (!mm_has_notifiers(mm)) { + INIT_HLIST_HEAD(&mmu_notifier_mm->list); + spin_lock_init(&mmu_notifier_mm->lock); + + mm->mmu_notifier_mm = mmu_notifier_mm; + mmu_notifier_mm = NULL; + } + atomic_inc(&mm->mm_count); + + /* + * Serialize the update against mmu_notifier_unregister. A + * side note: mmu_notifier_release can't run concurrently with + * us because we hold the mm_users pin (either implicitly as + * current->mm or explicitly with get_task_mm() or similar). + * We can't race against any other mmu notifier method either + * thanks to mm_take_all_locks(). + */ + spin_lock(&mm->mmu_notifier_mm->lock); + hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list); + spin_unlock(&mm->mmu_notifier_mm->lock); + + mm_drop_all_locks(mm); +out_clean: + if (take_mmap_sem) + up_write(&mm->mmap_sem); + kfree(mmu_notifier_mm); +out: + BUG_ON(atomic_read(&mm->mm_users) <= 0); + return ret; +} + +/* + * Must not hold mmap_sem nor any other VM related lock when calling + * this registration function. Must also ensure mm_users can't go down + * to zero while this runs to avoid races with mmu_notifier_release, + * so mm has to be current->mm or the mm should be pinned safely such + * as with get_task_mm(). If the mm is not current->mm, the mm_users + * pin should be released by calling mmput after mmu_notifier_register + * returns. mmu_notifier_unregister must be always called to + * unregister the notifier. mm_count is automatically pinned to allow + * mmu_notifier_unregister to safely run at any time later, before or + * after exit_mmap. ->release will always be called before exit_mmap + * frees the pages. + */ +int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm) +{ + return do_mmu_notifier_register(mn, mm, 1); +} +EXPORT_SYMBOL_GPL(mmu_notifier_register); + +/* + * Same as mmu_notifier_register but here the caller must hold the + * mmap_sem in write mode. + */ +int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm) +{ + return do_mmu_notifier_register(mn, mm, 0); +} +EXPORT_SYMBOL_GPL(__mmu_notifier_register); + +/* this is called after the last mmu_notifier_unregister() returned */ +void __mmu_notifier_mm_destroy(struct mm_struct *mm) +{ + BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list)); + kfree(mm->mmu_notifier_mm); + mm->mmu_notifier_mm = LIST_POISON1; /* debug */ +} + +/* + * This releases the mm_count pin automatically and frees the mm + * structure if it was the last user of it. It serializes against + * running mmu notifiers with SRCU and against mmu_notifier_unregister + * with the unregister lock + SRCU. All sptes must be dropped before + * calling mmu_notifier_unregister. ->release or any other notifier + * method may be invoked concurrently with mmu_notifier_unregister, + * and only after mmu_notifier_unregister returned we're guaranteed + * that ->release or any other method can't run anymore. + */ +void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm) +{ + BUG_ON(atomic_read(&mm->mm_count) <= 0); + + if (!hlist_unhashed(&mn->hlist)) { + /* + * SRCU here will force exit_mmap to wait for ->release to + * finish before freeing the pages. + */ + int id; + + id = srcu_read_lock(&srcu); + /* + * exit_mmap will block in mmu_notifier_release to guarantee + * that ->release is called before freeing the pages. + */ + if (mn->ops->release) + mn->ops->release(mn, mm); + srcu_read_unlock(&srcu, id); + + spin_lock(&mm->mmu_notifier_mm->lock); + /* + * Can not use list_del_rcu() since __mmu_notifier_release + * can delete it before we hold the lock. + */ + hlist_del_init_rcu(&mn->hlist); + spin_unlock(&mm->mmu_notifier_mm->lock); + } + + /* + * Wait for any running method to finish, of course including + * ->release if it was run by mmu_notifier_release instead of us. + */ + synchronize_srcu(&srcu); + + BUG_ON(atomic_read(&mm->mm_count) <= 0); + + mmdrop(mm); +} +EXPORT_SYMBOL_GPL(mmu_notifier_unregister); + +/* + * Same as mmu_notifier_unregister but no callback and no srcu synchronization. + */ +void mmu_notifier_unregister_no_release(struct mmu_notifier *mn, + struct mm_struct *mm) +{ + spin_lock(&mm->mmu_notifier_mm->lock); + /* + * Can not use list_del_rcu() since __mmu_notifier_release + * can delete it before we hold the lock. + */ + hlist_del_init_rcu(&mn->hlist); + spin_unlock(&mm->mmu_notifier_mm->lock); + + BUG_ON(atomic_read(&mm->mm_count) <= 0); + mmdrop(mm); +} +EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release); + +static int __init mmu_notifier_init(void) +{ + return init_srcu_struct(&srcu); +} +subsys_initcall(mmu_notifier_init); |