| /* |
| * 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 */ |
| struct srcu_struct srcu; |
| |
| /* |
| * 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; |
| struct hlist_node *n; |
| int id; |
| |
| /* |
| * RCU here will block mmu_notifier_unregister until |
| * ->release returns. |
| */ |
| id = srcu_read_lock(&srcu); |
| hlist_for_each_entry_rcu(mn, n, &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); |
| srcu_read_unlock(&srcu, id); |
| |
| 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 ->release to finish and |
| * mmu_notifier_unregister to return. |
| */ |
| hlist_del_init_rcu(&mn->hlist); |
| } |
| spin_unlock(&mm->mmu_notifier_mm->lock); |
| |
| /* |
| * synchronize_srcu here prevents mmu_notifier_release to |
| * return to exit_mmap (which would proceed 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 hold 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 address) |
| { |
| struct mmu_notifier *mn; |
| struct hlist_node *n; |
| int young = 0, id; |
| |
| id = srcu_read_lock(&srcu); |
| hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { |
| if (mn->ops->clear_flush_young) |
| young |= mn->ops->clear_flush_young(mn, mm, address); |
| } |
| srcu_read_unlock(&srcu, id); |
| |
| return young; |
| } |
| |
| int __mmu_notifier_test_young(struct mm_struct *mm, |
| unsigned long address) |
| { |
| struct mmu_notifier *mn; |
| struct hlist_node *n; |
| int young = 0, id; |
| |
| id = srcu_read_lock(&srcu); |
| hlist_for_each_entry_rcu(mn, n, &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; |
| struct hlist_node *n; |
| int id; |
| |
| id = srcu_read_lock(&srcu); |
| hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { |
| if (mn->ops->change_pte) |
| mn->ops->change_pte(mn, mm, address, pte); |
| /* |
| * Some drivers don't have change_pte, |
| * so we must call invalidate_page in that case. |
| */ |
| else if (mn->ops->invalidate_page) |
| mn->ops->invalidate_page(mn, mm, address); |
| } |
| srcu_read_unlock(&srcu, id); |
| } |
| |
| void __mmu_notifier_invalidate_page(struct mm_struct *mm, |
| unsigned long address) |
| { |
| struct mmu_notifier *mn; |
| struct hlist_node *n; |
| int id; |
| |
| id = srcu_read_lock(&srcu); |
| hlist_for_each_entry_rcu(mn, n, &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; |
| struct hlist_node *n; |
| int id; |
| |
| id = srcu_read_lock(&srcu); |
| hlist_for_each_entry_rcu(mn, n, &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); |
| } |
| |
| void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, |
| unsigned long start, unsigned long end) |
| { |
| struct mmu_notifier *mn; |
| struct hlist_node *n; |
| int id; |
| |
| id = srcu_read_lock(&srcu); |
| hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) { |
| if (mn->ops->invalidate_range_end) |
| mn->ops->invalidate_range_end(mn, mm, start, end); |
| } |
| srcu_read_unlock(&srcu, id); |
| } |
| |
| 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); |
| |
| if (take_mmap_sem) |
| down_write(&mm->mmap_sem); |
| ret = mm_take_all_locks(mm); |
| if (unlikely(ret)) |
| goto out; |
| |
| if (!mm_has_notifiers(mm)) { |
| mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), |
| GFP_KERNEL); |
| if (unlikely(!mmu_notifier_mm)) { |
| ret = -ENOMEM; |
| goto out_of_mem; |
| } |
| INIT_HLIST_HEAD(&mmu_notifier_mm->list); |
| spin_lock_init(&mmu_notifier_mm->lock); |
| |
| mm->mmu_notifier_mm = mmu_notifier_mm; |
| } |
| 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); |
| |
| out_of_mem: |
| mm_drop_all_locks(mm); |
| out: |
| if (take_mmap_sem) |
| up_write(&mm->mmap_sem); |
| |
| 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)) { |
| /* |
| * RCU here will force exit_mmap to wait ->release to finish |
| * before freeing the pages. |
| */ |
| int id; |
| |
| id = srcu_read_lock(&srcu); |
| /* |
| * exit_mmap will block in mmu_notifier_release to |
| * guarantee ->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); |
| hlist_del_rcu(&mn->hlist); |
| spin_unlock(&mm->mmu_notifier_mm->lock); |
| } |
| |
| /* |
| * Wait any running method to finish, of course including |
| * ->release if it was run by mmu_notifier_relase instead of us. |
| */ |
| synchronize_srcu(&srcu); |
| |
| BUG_ON(atomic_read(&mm->mm_count) <= 0); |
| |
| mmdrop(mm); |
| } |
| EXPORT_SYMBOL_GPL(mmu_notifier_unregister); |
| |
| static int __init mmu_notifier_init(void) |
| { |
| return init_srcu_struct(&srcu); |
| } |
| |
| module_init(mmu_notifier_init); |