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1132 lines
35 KiB
1132 lines
35 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* linux/mm/mmu_notifier.c |
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* |
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* Copyright (C) 2008 Qumranet, Inc. |
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* Copyright (C) 2008 SGI |
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* Christoph Lameter <[email protected]> |
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*/ |
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|
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#include <linux/rculist.h> |
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#include <linux/mmu_notifier.h> |
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#include <linux/export.h> |
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#include <linux/mm.h> |
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#include <linux/err.h> |
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#include <linux/interval_tree.h> |
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#include <linux/srcu.h> |
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#include <linux/rcupdate.h> |
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#include <linux/sched.h> |
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#include <linux/sched/mm.h> |
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#include <linux/slab.h> |
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|
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/* global SRCU for all MMs */ |
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DEFINE_STATIC_SRCU(srcu); |
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|
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#ifdef CONFIG_LOCKDEP |
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struct lockdep_map __mmu_notifier_invalidate_range_start_map = { |
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.name = "mmu_notifier_invalidate_range_start" |
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}; |
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#endif |
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|
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/* |
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* The mmu_notifier_subscriptions structure is allocated and installed in |
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* mm->notifier_subscriptions inside the mm_take_all_locks() protected |
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* critical section and it's released only when mm_count reaches zero |
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* in mmdrop(). |
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*/ |
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struct mmu_notifier_subscriptions { |
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/* all mmu notifiers registered in this mm are queued in this list */ |
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struct hlist_head list; |
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bool has_itree; |
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/* to serialize the list modifications and hlist_unhashed */ |
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spinlock_t lock; |
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unsigned long invalidate_seq; |
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unsigned long active_invalidate_ranges; |
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struct rb_root_cached itree; |
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wait_queue_head_t wq; |
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struct hlist_head deferred_list; |
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}; |
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|
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/* |
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* This is a collision-retry read-side/write-side 'lock', a lot like a |
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* seqcount, however this allows multiple write-sides to hold it at |
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* once. Conceptually the write side is protecting the values of the PTEs in |
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* this mm, such that PTES cannot be read into SPTEs (shadow PTEs) while any |
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* writer exists. |
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* |
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* Note that the core mm creates nested invalidate_range_start()/end() regions |
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* within the same thread, and runs invalidate_range_start()/end() in parallel |
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* on multiple CPUs. This is designed to not reduce concurrency or block |
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* progress on the mm side. |
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* |
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* As a secondary function, holding the full write side also serves to prevent |
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* writers for the itree, this is an optimization to avoid extra locking |
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* during invalidate_range_start/end notifiers. |
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* |
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* The write side has two states, fully excluded: |
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* - mm->active_invalidate_ranges != 0 |
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* - subscriptions->invalidate_seq & 1 == True (odd) |
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* - some range on the mm_struct is being invalidated |
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* - the itree is not allowed to change |
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* |
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* And partially excluded: |
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* - mm->active_invalidate_ranges != 0 |
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* - subscriptions->invalidate_seq & 1 == False (even) |
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* - some range on the mm_struct is being invalidated |
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* - the itree is allowed to change |
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* |
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* Operations on notifier_subscriptions->invalidate_seq (under spinlock): |
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* seq |= 1 # Begin writing |
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* seq++ # Release the writing state |
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* seq & 1 # True if a writer exists |
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* |
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* The later state avoids some expensive work on inv_end in the common case of |
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* no mmu_interval_notifier monitoring the VA. |
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*/ |
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static bool |
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mn_itree_is_invalidating(struct mmu_notifier_subscriptions *subscriptions) |
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{ |
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lockdep_assert_held(&subscriptions->lock); |
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return subscriptions->invalidate_seq & 1; |
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} |
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|
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static struct mmu_interval_notifier * |
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mn_itree_inv_start_range(struct mmu_notifier_subscriptions *subscriptions, |
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const struct mmu_notifier_range *range, |
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unsigned long *seq) |
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{ |
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struct interval_tree_node *node; |
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struct mmu_interval_notifier *res = NULL; |
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|
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spin_lock(&subscriptions->lock); |
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subscriptions->active_invalidate_ranges++; |
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node = interval_tree_iter_first(&subscriptions->itree, range->start, |
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range->end - 1); |
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if (node) { |
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subscriptions->invalidate_seq |= 1; |
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res = container_of(node, struct mmu_interval_notifier, |
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interval_tree); |
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} |
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|
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*seq = subscriptions->invalidate_seq; |
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spin_unlock(&subscriptions->lock); |
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return res; |
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} |
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|
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static struct mmu_interval_notifier * |
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mn_itree_inv_next(struct mmu_interval_notifier *interval_sub, |
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const struct mmu_notifier_range *range) |
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{ |
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struct interval_tree_node *node; |
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|
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node = interval_tree_iter_next(&interval_sub->interval_tree, |
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range->start, range->end - 1); |
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if (!node) |
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return NULL; |
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return container_of(node, struct mmu_interval_notifier, interval_tree); |
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} |
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|
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static void mn_itree_inv_end(struct mmu_notifier_subscriptions *subscriptions) |
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{ |
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struct mmu_interval_notifier *interval_sub; |
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struct hlist_node *next; |
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|
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spin_lock(&subscriptions->lock); |
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if (--subscriptions->active_invalidate_ranges || |
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!mn_itree_is_invalidating(subscriptions)) { |
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spin_unlock(&subscriptions->lock); |
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return; |
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} |
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|
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/* Make invalidate_seq even */ |
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subscriptions->invalidate_seq++; |
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|
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/* |
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* The inv_end incorporates a deferred mechanism like rtnl_unlock(). |
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* Adds and removes are queued until the final inv_end happens then |
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* they are progressed. This arrangement for tree updates is used to |
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* avoid using a blocking lock during invalidate_range_start. |
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*/ |
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hlist_for_each_entry_safe(interval_sub, next, |
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&subscriptions->deferred_list, |
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deferred_item) { |
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if (RB_EMPTY_NODE(&interval_sub->interval_tree.rb)) |
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interval_tree_insert(&interval_sub->interval_tree, |
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&subscriptions->itree); |
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else |
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interval_tree_remove(&interval_sub->interval_tree, |
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&subscriptions->itree); |
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hlist_del(&interval_sub->deferred_item); |
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} |
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spin_unlock(&subscriptions->lock); |
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|
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wake_up_all(&subscriptions->wq); |
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} |
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|
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/** |
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* mmu_interval_read_begin - Begin a read side critical section against a VA |
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* range |
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* @interval_sub: The interval subscription |
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* |
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* mmu_iterval_read_begin()/mmu_iterval_read_retry() implement a |
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* collision-retry scheme similar to seqcount for the VA range under |
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* subscription. If the mm invokes invalidation during the critical section |
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* then mmu_interval_read_retry() will return true. |
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* |
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* This is useful to obtain shadow PTEs where teardown or setup of the SPTEs |
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* require a blocking context. The critical region formed by this can sleep, |
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* and the required 'user_lock' can also be a sleeping lock. |
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* |
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* The caller is required to provide a 'user_lock' to serialize both teardown |
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* and setup. |
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* |
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* The return value should be passed to mmu_interval_read_retry(). |
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*/ |
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unsigned long |
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mmu_interval_read_begin(struct mmu_interval_notifier *interval_sub) |
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{ |
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struct mmu_notifier_subscriptions *subscriptions = |
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interval_sub->mm->notifier_subscriptions; |
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unsigned long seq; |
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bool is_invalidating; |
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|
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/* |
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* If the subscription has a different seq value under the user_lock |
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* than we started with then it has collided. |
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* |
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* If the subscription currently has the same seq value as the |
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* subscriptions seq, then it is currently between |
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* invalidate_start/end and is colliding. |
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* |
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* The locking looks broadly like this: |
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* mn_tree_invalidate_start(): mmu_interval_read_begin(): |
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* spin_lock |
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* seq = READ_ONCE(interval_sub->invalidate_seq); |
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* seq == subs->invalidate_seq |
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* spin_unlock |
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* spin_lock |
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* seq = ++subscriptions->invalidate_seq |
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* spin_unlock |
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* op->invalidate_range(): |
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* user_lock |
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* mmu_interval_set_seq() |
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* interval_sub->invalidate_seq = seq |
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* user_unlock |
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* |
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* [Required: mmu_interval_read_retry() == true] |
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* |
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* mn_itree_inv_end(): |
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* spin_lock |
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* seq = ++subscriptions->invalidate_seq |
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* spin_unlock |
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* |
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* user_lock |
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* mmu_interval_read_retry(): |
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* interval_sub->invalidate_seq != seq |
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* user_unlock |
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* |
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* Barriers are not needed here as any races here are closed by an |
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* eventual mmu_interval_read_retry(), which provides a barrier via the |
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* user_lock. |
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*/ |
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spin_lock(&subscriptions->lock); |
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/* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */ |
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seq = READ_ONCE(interval_sub->invalidate_seq); |
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is_invalidating = seq == subscriptions->invalidate_seq; |
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spin_unlock(&subscriptions->lock); |
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|
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/* |
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* interval_sub->invalidate_seq must always be set to an odd value via |
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* mmu_interval_set_seq() using the provided cur_seq from |
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* mn_itree_inv_start_range(). This ensures that if seq does wrap we |
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* will always clear the below sleep in some reasonable time as |
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* subscriptions->invalidate_seq is even in the idle state. |
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*/ |
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lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); |
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lock_map_release(&__mmu_notifier_invalidate_range_start_map); |
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if (is_invalidating) |
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wait_event(subscriptions->wq, |
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READ_ONCE(subscriptions->invalidate_seq) != seq); |
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|
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/* |
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* Notice that mmu_interval_read_retry() can already be true at this |
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* point, avoiding loops here allows the caller to provide a global |
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* time bound. |
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*/ |
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|
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return seq; |
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} |
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EXPORT_SYMBOL_GPL(mmu_interval_read_begin); |
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|
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static void mn_itree_release(struct mmu_notifier_subscriptions *subscriptions, |
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struct mm_struct *mm) |
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{ |
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struct mmu_notifier_range range = { |
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.flags = MMU_NOTIFIER_RANGE_BLOCKABLE, |
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.event = MMU_NOTIFY_RELEASE, |
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.mm = mm, |
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.start = 0, |
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.end = ULONG_MAX, |
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}; |
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struct mmu_interval_notifier *interval_sub; |
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unsigned long cur_seq; |
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bool ret; |
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|
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for (interval_sub = |
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mn_itree_inv_start_range(subscriptions, &range, &cur_seq); |
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interval_sub; |
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interval_sub = mn_itree_inv_next(interval_sub, &range)) { |
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ret = interval_sub->ops->invalidate(interval_sub, &range, |
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cur_seq); |
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WARN_ON(!ret); |
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} |
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mn_itree_inv_end(subscriptions); |
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} |
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|
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/* |
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* This function can't run concurrently against mmu_notifier_register |
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* because mm->mm_users > 0 during mmu_notifier_register and exit_mmap |
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* runs with mm_users == 0. Other tasks may still invoke mmu notifiers |
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* in parallel despite there being no task using this mm any more, |
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* through the vmas outside of the exit_mmap context, such as with |
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* vmtruncate. This serializes against mmu_notifier_unregister with |
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* the notifier_subscriptions->lock in addition to SRCU and it serializes |
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* against the other mmu notifiers with SRCU. struct mmu_notifier_subscriptions |
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* can't go away from under us as exit_mmap holds an mm_count pin |
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* itself. |
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*/ |
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static void mn_hlist_release(struct mmu_notifier_subscriptions *subscriptions, |
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struct mm_struct *mm) |
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{ |
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struct mmu_notifier *subscription; |
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int id; |
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|
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/* |
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* SRCU here will block mmu_notifier_unregister until |
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* ->release returns. |
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*/ |
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id = srcu_read_lock(&srcu); |
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hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, |
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srcu_read_lock_held(&srcu)) |
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/* |
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* If ->release runs before mmu_notifier_unregister it must be |
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* handled, as it's the only way for the driver to flush all |
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* existing sptes and stop the driver from establishing any more |
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* sptes before all the pages in the mm are freed. |
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*/ |
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if (subscription->ops->release) |
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subscription->ops->release(subscription, mm); |
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|
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spin_lock(&subscriptions->lock); |
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while (unlikely(!hlist_empty(&subscriptions->list))) { |
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subscription = hlist_entry(subscriptions->list.first, |
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struct mmu_notifier, hlist); |
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/* |
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* We arrived before mmu_notifier_unregister so |
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* mmu_notifier_unregister will do nothing other than to wait |
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* for ->release to finish and for mmu_notifier_unregister to |
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* return. |
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*/ |
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hlist_del_init_rcu(&subscription->hlist); |
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} |
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spin_unlock(&subscriptions->lock); |
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srcu_read_unlock(&srcu, id); |
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|
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/* |
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* synchronize_srcu here prevents mmu_notifier_release from returning to |
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* exit_mmap (which would proceed with freeing all pages in the mm) |
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* until the ->release method returns, if it was invoked by |
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* mmu_notifier_unregister. |
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* |
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* The notifier_subscriptions can't go away from under us because |
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* one mm_count is held by exit_mmap. |
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*/ |
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synchronize_srcu(&srcu); |
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} |
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|
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void __mmu_notifier_release(struct mm_struct *mm) |
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{ |
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struct mmu_notifier_subscriptions *subscriptions = |
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mm->notifier_subscriptions; |
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|
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if (subscriptions->has_itree) |
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mn_itree_release(subscriptions, mm); |
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|
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if (!hlist_empty(&subscriptions->list)) |
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mn_hlist_release(subscriptions, mm); |
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} |
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|
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/* |
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* If no young bitflag is supported by the hardware, ->clear_flush_young can |
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* unmap the address and return 1 or 0 depending if the mapping previously |
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* existed or not. |
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*/ |
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int __mmu_notifier_clear_flush_young(struct mm_struct *mm, |
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unsigned long start, |
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unsigned long end) |
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{ |
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struct mmu_notifier *subscription; |
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int young = 0, id; |
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|
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id = srcu_read_lock(&srcu); |
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hlist_for_each_entry_rcu(subscription, |
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&mm->notifier_subscriptions->list, hlist, |
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srcu_read_lock_held(&srcu)) { |
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if (subscription->ops->clear_flush_young) |
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young |= subscription->ops->clear_flush_young( |
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subscription, mm, start, end); |
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} |
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srcu_read_unlock(&srcu, id); |
|
|
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return young; |
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} |
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|
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int __mmu_notifier_clear_young(struct mm_struct *mm, |
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unsigned long start, |
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unsigned long end) |
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{ |
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struct mmu_notifier *subscription; |
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int young = 0, id; |
|
|
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id = srcu_read_lock(&srcu); |
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hlist_for_each_entry_rcu(subscription, |
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&mm->notifier_subscriptions->list, hlist, |
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srcu_read_lock_held(&srcu)) { |
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if (subscription->ops->clear_young) |
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young |= subscription->ops->clear_young(subscription, |
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mm, start, end); |
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} |
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srcu_read_unlock(&srcu, id); |
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|
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return young; |
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} |
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|
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int __mmu_notifier_test_young(struct mm_struct *mm, |
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unsigned long address) |
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{ |
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struct mmu_notifier *subscription; |
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int young = 0, id; |
|
|
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id = srcu_read_lock(&srcu); |
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hlist_for_each_entry_rcu(subscription, |
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&mm->notifier_subscriptions->list, hlist, |
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srcu_read_lock_held(&srcu)) { |
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if (subscription->ops->test_young) { |
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young = subscription->ops->test_young(subscription, mm, |
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address); |
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if (young) |
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break; |
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} |
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} |
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srcu_read_unlock(&srcu, id); |
|
|
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return young; |
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} |
|
|
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void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, |
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pte_t pte) |
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{ |
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struct mmu_notifier *subscription; |
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int id; |
|
|
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id = srcu_read_lock(&srcu); |
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hlist_for_each_entry_rcu(subscription, |
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&mm->notifier_subscriptions->list, hlist, |
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srcu_read_lock_held(&srcu)) { |
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if (subscription->ops->change_pte) |
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subscription->ops->change_pte(subscription, mm, address, |
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pte); |
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} |
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srcu_read_unlock(&srcu, id); |
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} |
|
|
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static int mn_itree_invalidate(struct mmu_notifier_subscriptions *subscriptions, |
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const struct mmu_notifier_range *range) |
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{ |
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struct mmu_interval_notifier *interval_sub; |
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unsigned long cur_seq; |
|
|
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for (interval_sub = |
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mn_itree_inv_start_range(subscriptions, range, &cur_seq); |
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interval_sub; |
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interval_sub = mn_itree_inv_next(interval_sub, range)) { |
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bool ret; |
|
|
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ret = interval_sub->ops->invalidate(interval_sub, range, |
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cur_seq); |
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if (!ret) { |
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if (WARN_ON(mmu_notifier_range_blockable(range))) |
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continue; |
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goto out_would_block; |
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} |
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} |
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return 0; |
|
|
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out_would_block: |
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/* |
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* On -EAGAIN the non-blocking caller is not allowed to call |
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* invalidate_range_end() |
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*/ |
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mn_itree_inv_end(subscriptions); |
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return -EAGAIN; |
|
} |
|
|
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static int mn_hlist_invalidate_range_start( |
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struct mmu_notifier_subscriptions *subscriptions, |
|
struct mmu_notifier_range *range) |
|
{ |
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struct mmu_notifier *subscription; |
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int ret = 0; |
|
int id; |
|
|
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id = srcu_read_lock(&srcu); |
|
hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, |
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srcu_read_lock_held(&srcu)) { |
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const struct mmu_notifier_ops *ops = subscription->ops; |
|
|
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if (ops->invalidate_range_start) { |
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int _ret; |
|
|
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if (!mmu_notifier_range_blockable(range)) |
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non_block_start(); |
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_ret = ops->invalidate_range_start(subscription, range); |
|
if (!mmu_notifier_range_blockable(range)) |
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non_block_end(); |
|
if (_ret) { |
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pr_info("%pS callback failed with %d in %sblockable context.\n", |
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ops->invalidate_range_start, _ret, |
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!mmu_notifier_range_blockable(range) ? |
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"non-" : |
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""); |
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WARN_ON(mmu_notifier_range_blockable(range) || |
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_ret != -EAGAIN); |
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/* |
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* We call all the notifiers on any EAGAIN, |
|
* there is no way for a notifier to know if |
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* its start method failed, thus a start that |
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* does EAGAIN can't also do end. |
|
*/ |
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WARN_ON(ops->invalidate_range_end); |
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ret = _ret; |
|
} |
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} |
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} |
|
|
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if (ret) { |
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/* |
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* Must be non-blocking to get here. If there are multiple |
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* notifiers and one or more failed start, any that succeeded |
|
* start are expecting their end to be called. Do so now. |
|
*/ |
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hlist_for_each_entry_rcu(subscription, &subscriptions->list, |
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hlist, srcu_read_lock_held(&srcu)) { |
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if (!subscription->ops->invalidate_range_end) |
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continue; |
|
|
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subscription->ops->invalidate_range_end(subscription, |
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range); |
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} |
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} |
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srcu_read_unlock(&srcu, id); |
|
|
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return ret; |
|
} |
|
|
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int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range) |
|
{ |
|
struct mmu_notifier_subscriptions *subscriptions = |
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range->mm->notifier_subscriptions; |
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int ret; |
|
|
|
if (subscriptions->has_itree) { |
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ret = mn_itree_invalidate(subscriptions, range); |
|
if (ret) |
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return ret; |
|
} |
|
if (!hlist_empty(&subscriptions->list)) |
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return mn_hlist_invalidate_range_start(subscriptions, range); |
|
return 0; |
|
} |
|
|
|
static void |
|
mn_hlist_invalidate_end(struct mmu_notifier_subscriptions *subscriptions, |
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struct mmu_notifier_range *range, bool only_end) |
|
{ |
|
struct mmu_notifier *subscription; |
|
int id; |
|
|
|
id = srcu_read_lock(&srcu); |
|
hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, |
|
srcu_read_lock_held(&srcu)) { |
|
/* |
|
* 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). |
|
* |
|
* We skip call to invalidate_range() if we know it is safe ie |
|
* call site use mmu_notifier_invalidate_range_only_end() which |
|
* is safe to do when we know that a call to invalidate_range() |
|
* already happen under page table lock. |
|
*/ |
|
if (!only_end && subscription->ops->invalidate_range) |
|
subscription->ops->invalidate_range(subscription, |
|
range->mm, |
|
range->start, |
|
range->end); |
|
if (subscription->ops->invalidate_range_end) { |
|
if (!mmu_notifier_range_blockable(range)) |
|
non_block_start(); |
|
subscription->ops->invalidate_range_end(subscription, |
|
range); |
|
if (!mmu_notifier_range_blockable(range)) |
|
non_block_end(); |
|
} |
|
} |
|
srcu_read_unlock(&srcu, id); |
|
} |
|
|
|
void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range, |
|
bool only_end) |
|
{ |
|
struct mmu_notifier_subscriptions *subscriptions = |
|
range->mm->notifier_subscriptions; |
|
|
|
lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); |
|
if (subscriptions->has_itree) |
|
mn_itree_inv_end(subscriptions); |
|
|
|
if (!hlist_empty(&subscriptions->list)) |
|
mn_hlist_invalidate_end(subscriptions, range, only_end); |
|
lock_map_release(&__mmu_notifier_invalidate_range_start_map); |
|
} |
|
|
|
void __mmu_notifier_invalidate_range(struct mm_struct *mm, |
|
unsigned long start, unsigned long end) |
|
{ |
|
struct mmu_notifier *subscription; |
|
int id; |
|
|
|
id = srcu_read_lock(&srcu); |
|
hlist_for_each_entry_rcu(subscription, |
|
&mm->notifier_subscriptions->list, hlist, |
|
srcu_read_lock_held(&srcu)) { |
|
if (subscription->ops->invalidate_range) |
|
subscription->ops->invalidate_range(subscription, mm, |
|
start, end); |
|
} |
|
srcu_read_unlock(&srcu, id); |
|
} |
|
|
|
/* |
|
* Same as mmu_notifier_register but here the caller must hold the mmap_lock in |
|
* write mode. A NULL mn signals the notifier is being registered for itree |
|
* mode. |
|
*/ |
|
int __mmu_notifier_register(struct mmu_notifier *subscription, |
|
struct mm_struct *mm) |
|
{ |
|
struct mmu_notifier_subscriptions *subscriptions = NULL; |
|
int ret; |
|
|
|
mmap_assert_write_locked(mm); |
|
BUG_ON(atomic_read(&mm->mm_users) <= 0); |
|
|
|
if (!mm->notifier_subscriptions) { |
|
/* |
|
* kmalloc cannot be called under mm_take_all_locks(), but we |
|
* know that mm->notifier_subscriptions can't change while we |
|
* hold the write side of the mmap_lock. |
|
*/ |
|
subscriptions = kzalloc( |
|
sizeof(struct mmu_notifier_subscriptions), GFP_KERNEL); |
|
if (!subscriptions) |
|
return -ENOMEM; |
|
|
|
INIT_HLIST_HEAD(&subscriptions->list); |
|
spin_lock_init(&subscriptions->lock); |
|
subscriptions->invalidate_seq = 2; |
|
subscriptions->itree = RB_ROOT_CACHED; |
|
init_waitqueue_head(&subscriptions->wq); |
|
INIT_HLIST_HEAD(&subscriptions->deferred_list); |
|
} |
|
|
|
ret = mm_take_all_locks(mm); |
|
if (unlikely(ret)) |
|
goto out_clean; |
|
|
|
/* |
|
* 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(). |
|
* |
|
* release semantics on the initialization of the |
|
* mmu_notifier_subscriptions's contents are provided for unlocked |
|
* readers. acquire can only be used while holding the mmgrab or |
|
* mmget, and is safe because once created the |
|
* mmu_notifier_subscriptions is not freed until the mm is destroyed. |
|
* As above, users holding the mmap_lock or one of the |
|
* mm_take_all_locks() do not need to use acquire semantics. |
|
*/ |
|
if (subscriptions) |
|
smp_store_release(&mm->notifier_subscriptions, subscriptions); |
|
|
|
if (subscription) { |
|
/* Pairs with the mmdrop in mmu_notifier_unregister_* */ |
|
mmgrab(mm); |
|
subscription->mm = mm; |
|
subscription->users = 1; |
|
|
|
spin_lock(&mm->notifier_subscriptions->lock); |
|
hlist_add_head_rcu(&subscription->hlist, |
|
&mm->notifier_subscriptions->list); |
|
spin_unlock(&mm->notifier_subscriptions->lock); |
|
} else |
|
mm->notifier_subscriptions->has_itree = true; |
|
|
|
mm_drop_all_locks(mm); |
|
BUG_ON(atomic_read(&mm->mm_users) <= 0); |
|
return 0; |
|
|
|
out_clean: |
|
kfree(subscriptions); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(__mmu_notifier_register); |
|
|
|
/** |
|
* mmu_notifier_register - Register a notifier on a mm |
|
* @subscription: The notifier to attach |
|
* @mm: The mm to attach the notifier to |
|
* |
|
* Must not hold mmap_lock 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() or mmu_notifier_put() must be always called to |
|
* unregister the notifier. |
|
* |
|
* While the caller has a mmu_notifier get the subscription->mm pointer will remain |
|
* valid, and can be converted to an active mm pointer via mmget_not_zero(). |
|
*/ |
|
int mmu_notifier_register(struct mmu_notifier *subscription, |
|
struct mm_struct *mm) |
|
{ |
|
int ret; |
|
|
|
mmap_write_lock(mm); |
|
ret = __mmu_notifier_register(subscription, mm); |
|
mmap_write_unlock(mm); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(mmu_notifier_register); |
|
|
|
static struct mmu_notifier * |
|
find_get_mmu_notifier(struct mm_struct *mm, const struct mmu_notifier_ops *ops) |
|
{ |
|
struct mmu_notifier *subscription; |
|
|
|
spin_lock(&mm->notifier_subscriptions->lock); |
|
hlist_for_each_entry_rcu(subscription, |
|
&mm->notifier_subscriptions->list, hlist, |
|
lockdep_is_held(&mm->notifier_subscriptions->lock)) { |
|
if (subscription->ops != ops) |
|
continue; |
|
|
|
if (likely(subscription->users != UINT_MAX)) |
|
subscription->users++; |
|
else |
|
subscription = ERR_PTR(-EOVERFLOW); |
|
spin_unlock(&mm->notifier_subscriptions->lock); |
|
return subscription; |
|
} |
|
spin_unlock(&mm->notifier_subscriptions->lock); |
|
return NULL; |
|
} |
|
|
|
/** |
|
* mmu_notifier_get_locked - Return the single struct mmu_notifier for |
|
* the mm & ops |
|
* @ops: The operations struct being subscribe with |
|
* @mm : The mm to attach notifiers too |
|
* |
|
* This function either allocates a new mmu_notifier via |
|
* ops->alloc_notifier(), or returns an already existing notifier on the |
|
* list. The value of the ops pointer is used to determine when two notifiers |
|
* are the same. |
|
* |
|
* Each call to mmu_notifier_get() must be paired with a call to |
|
* mmu_notifier_put(). The caller must hold the write side of mm->mmap_lock. |
|
* |
|
* While the caller has a mmu_notifier get the mm pointer will remain valid, |
|
* and can be converted to an active mm pointer via mmget_not_zero(). |
|
*/ |
|
struct mmu_notifier *mmu_notifier_get_locked(const struct mmu_notifier_ops *ops, |
|
struct mm_struct *mm) |
|
{ |
|
struct mmu_notifier *subscription; |
|
int ret; |
|
|
|
mmap_assert_write_locked(mm); |
|
|
|
if (mm->notifier_subscriptions) { |
|
subscription = find_get_mmu_notifier(mm, ops); |
|
if (subscription) |
|
return subscription; |
|
} |
|
|
|
subscription = ops->alloc_notifier(mm); |
|
if (IS_ERR(subscription)) |
|
return subscription; |
|
subscription->ops = ops; |
|
ret = __mmu_notifier_register(subscription, mm); |
|
if (ret) |
|
goto out_free; |
|
return subscription; |
|
out_free: |
|
subscription->ops->free_notifier(subscription); |
|
return ERR_PTR(ret); |
|
} |
|
EXPORT_SYMBOL_GPL(mmu_notifier_get_locked); |
|
|
|
/* this is called after the last mmu_notifier_unregister() returned */ |
|
void __mmu_notifier_subscriptions_destroy(struct mm_struct *mm) |
|
{ |
|
BUG_ON(!hlist_empty(&mm->notifier_subscriptions->list)); |
|
kfree(mm->notifier_subscriptions); |
|
mm->notifier_subscriptions = 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 *subscription, |
|
struct mm_struct *mm) |
|
{ |
|
BUG_ON(atomic_read(&mm->mm_count) <= 0); |
|
|
|
if (!hlist_unhashed(&subscription->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 (subscription->ops->release) |
|
subscription->ops->release(subscription, mm); |
|
srcu_read_unlock(&srcu, id); |
|
|
|
spin_lock(&mm->notifier_subscriptions->lock); |
|
/* |
|
* Can not use list_del_rcu() since __mmu_notifier_release |
|
* can delete it before we hold the lock. |
|
*/ |
|
hlist_del_init_rcu(&subscription->hlist); |
|
spin_unlock(&mm->notifier_subscriptions->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); |
|
|
|
static void mmu_notifier_free_rcu(struct rcu_head *rcu) |
|
{ |
|
struct mmu_notifier *subscription = |
|
container_of(rcu, struct mmu_notifier, rcu); |
|
struct mm_struct *mm = subscription->mm; |
|
|
|
subscription->ops->free_notifier(subscription); |
|
/* Pairs with the get in __mmu_notifier_register() */ |
|
mmdrop(mm); |
|
} |
|
|
|
/** |
|
* mmu_notifier_put - Release the reference on the notifier |
|
* @subscription: The notifier to act on |
|
* |
|
* This function must be paired with each mmu_notifier_get(), it releases the |
|
* reference obtained by the get. If this is the last reference then process |
|
* to free the notifier will be run asynchronously. |
|
* |
|
* Unlike mmu_notifier_unregister() the get/put flow only calls ops->release |
|
* when the mm_struct is destroyed. Instead free_notifier is always called to |
|
* release any resources held by the user. |
|
* |
|
* As ops->release is not guaranteed to be called, the user must ensure that |
|
* all sptes are dropped, and no new sptes can be established before |
|
* mmu_notifier_put() is called. |
|
* |
|
* This function can be called from the ops->release callback, however the |
|
* caller must still ensure it is called pairwise with mmu_notifier_get(). |
|
* |
|
* Modules calling this function must call mmu_notifier_synchronize() in |
|
* their __exit functions to ensure the async work is completed. |
|
*/ |
|
void mmu_notifier_put(struct mmu_notifier *subscription) |
|
{ |
|
struct mm_struct *mm = subscription->mm; |
|
|
|
spin_lock(&mm->notifier_subscriptions->lock); |
|
if (WARN_ON(!subscription->users) || --subscription->users) |
|
goto out_unlock; |
|
hlist_del_init_rcu(&subscription->hlist); |
|
spin_unlock(&mm->notifier_subscriptions->lock); |
|
|
|
call_srcu(&srcu, &subscription->rcu, mmu_notifier_free_rcu); |
|
return; |
|
|
|
out_unlock: |
|
spin_unlock(&mm->notifier_subscriptions->lock); |
|
} |
|
EXPORT_SYMBOL_GPL(mmu_notifier_put); |
|
|
|
static int __mmu_interval_notifier_insert( |
|
struct mmu_interval_notifier *interval_sub, struct mm_struct *mm, |
|
struct mmu_notifier_subscriptions *subscriptions, unsigned long start, |
|
unsigned long length, const struct mmu_interval_notifier_ops *ops) |
|
{ |
|
interval_sub->mm = mm; |
|
interval_sub->ops = ops; |
|
RB_CLEAR_NODE(&interval_sub->interval_tree.rb); |
|
interval_sub->interval_tree.start = start; |
|
/* |
|
* Note that the representation of the intervals in the interval tree |
|
* considers the ending point as contained in the interval. |
|
*/ |
|
if (length == 0 || |
|
check_add_overflow(start, length - 1, |
|
&interval_sub->interval_tree.last)) |
|
return -EOVERFLOW; |
|
|
|
/* Must call with a mmget() held */ |
|
if (WARN_ON(atomic_read(&mm->mm_users) <= 0)) |
|
return -EINVAL; |
|
|
|
/* pairs with mmdrop in mmu_interval_notifier_remove() */ |
|
mmgrab(mm); |
|
|
|
/* |
|
* If some invalidate_range_start/end region is going on in parallel |
|
* we don't know what VA ranges are affected, so we must assume this |
|
* new range is included. |
|
* |
|
* If the itree is invalidating then we are not allowed to change |
|
* it. Retrying until invalidation is done is tricky due to the |
|
* possibility for live lock, instead defer the add to |
|
* mn_itree_inv_end() so this algorithm is deterministic. |
|
* |
|
* In all cases the value for the interval_sub->invalidate_seq should be |
|
* odd, see mmu_interval_read_begin() |
|
*/ |
|
spin_lock(&subscriptions->lock); |
|
if (subscriptions->active_invalidate_ranges) { |
|
if (mn_itree_is_invalidating(subscriptions)) |
|
hlist_add_head(&interval_sub->deferred_item, |
|
&subscriptions->deferred_list); |
|
else { |
|
subscriptions->invalidate_seq |= 1; |
|
interval_tree_insert(&interval_sub->interval_tree, |
|
&subscriptions->itree); |
|
} |
|
interval_sub->invalidate_seq = subscriptions->invalidate_seq; |
|
} else { |
|
WARN_ON(mn_itree_is_invalidating(subscriptions)); |
|
/* |
|
* The starting seq for a subscription not under invalidation |
|
* should be odd, not equal to the current invalidate_seq and |
|
* invalidate_seq should not 'wrap' to the new seq any time |
|
* soon. |
|
*/ |
|
interval_sub->invalidate_seq = |
|
subscriptions->invalidate_seq - 1; |
|
interval_tree_insert(&interval_sub->interval_tree, |
|
&subscriptions->itree); |
|
} |
|
spin_unlock(&subscriptions->lock); |
|
return 0; |
|
} |
|
|
|
/** |
|
* mmu_interval_notifier_insert - Insert an interval notifier |
|
* @interval_sub: Interval subscription to register |
|
* @start: Starting virtual address to monitor |
|
* @length: Length of the range to monitor |
|
* @mm: mm_struct to attach to |
|
* @ops: Interval notifier operations to be called on matching events |
|
* |
|
* This function subscribes the interval notifier for notifications from the |
|
* mm. Upon return the ops related to mmu_interval_notifier will be called |
|
* whenever an event that intersects with the given range occurs. |
|
* |
|
* Upon return the range_notifier may not be present in the interval tree yet. |
|
* The caller must use the normal interval notifier read flow via |
|
* mmu_interval_read_begin() to establish SPTEs for this range. |
|
*/ |
|
int mmu_interval_notifier_insert(struct mmu_interval_notifier *interval_sub, |
|
struct mm_struct *mm, unsigned long start, |
|
unsigned long length, |
|
const struct mmu_interval_notifier_ops *ops) |
|
{ |
|
struct mmu_notifier_subscriptions *subscriptions; |
|
int ret; |
|
|
|
might_lock(&mm->mmap_lock); |
|
|
|
subscriptions = smp_load_acquire(&mm->notifier_subscriptions); |
|
if (!subscriptions || !subscriptions->has_itree) { |
|
ret = mmu_notifier_register(NULL, mm); |
|
if (ret) |
|
return ret; |
|
subscriptions = mm->notifier_subscriptions; |
|
} |
|
return __mmu_interval_notifier_insert(interval_sub, mm, subscriptions, |
|
start, length, ops); |
|
} |
|
EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert); |
|
|
|
int mmu_interval_notifier_insert_locked( |
|
struct mmu_interval_notifier *interval_sub, struct mm_struct *mm, |
|
unsigned long start, unsigned long length, |
|
const struct mmu_interval_notifier_ops *ops) |
|
{ |
|
struct mmu_notifier_subscriptions *subscriptions = |
|
mm->notifier_subscriptions; |
|
int ret; |
|
|
|
mmap_assert_write_locked(mm); |
|
|
|
if (!subscriptions || !subscriptions->has_itree) { |
|
ret = __mmu_notifier_register(NULL, mm); |
|
if (ret) |
|
return ret; |
|
subscriptions = mm->notifier_subscriptions; |
|
} |
|
return __mmu_interval_notifier_insert(interval_sub, mm, subscriptions, |
|
start, length, ops); |
|
} |
|
EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert_locked); |
|
|
|
static bool |
|
mmu_interval_seq_released(struct mmu_notifier_subscriptions *subscriptions, |
|
unsigned long seq) |
|
{ |
|
bool ret; |
|
|
|
spin_lock(&subscriptions->lock); |
|
ret = subscriptions->invalidate_seq != seq; |
|
spin_unlock(&subscriptions->lock); |
|
return ret; |
|
} |
|
|
|
/** |
|
* mmu_interval_notifier_remove - Remove a interval notifier |
|
* @interval_sub: Interval subscription to unregister |
|
* |
|
* This function must be paired with mmu_interval_notifier_insert(). It cannot |
|
* be called from any ops callback. |
|
* |
|
* Once this returns ops callbacks are no longer running on other CPUs and |
|
* will not be called in future. |
|
*/ |
|
void mmu_interval_notifier_remove(struct mmu_interval_notifier *interval_sub) |
|
{ |
|
struct mm_struct *mm = interval_sub->mm; |
|
struct mmu_notifier_subscriptions *subscriptions = |
|
mm->notifier_subscriptions; |
|
unsigned long seq = 0; |
|
|
|
might_sleep(); |
|
|
|
spin_lock(&subscriptions->lock); |
|
if (mn_itree_is_invalidating(subscriptions)) { |
|
/* |
|
* remove is being called after insert put this on the |
|
* deferred list, but before the deferred list was processed. |
|
*/ |
|
if (RB_EMPTY_NODE(&interval_sub->interval_tree.rb)) { |
|
hlist_del(&interval_sub->deferred_item); |
|
} else { |
|
hlist_add_head(&interval_sub->deferred_item, |
|
&subscriptions->deferred_list); |
|
seq = subscriptions->invalidate_seq; |
|
} |
|
} else { |
|
WARN_ON(RB_EMPTY_NODE(&interval_sub->interval_tree.rb)); |
|
interval_tree_remove(&interval_sub->interval_tree, |
|
&subscriptions->itree); |
|
} |
|
spin_unlock(&subscriptions->lock); |
|
|
|
/* |
|
* The possible sleep on progress in the invalidation requires the |
|
* caller not hold any locks held by invalidation callbacks. |
|
*/ |
|
lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); |
|
lock_map_release(&__mmu_notifier_invalidate_range_start_map); |
|
if (seq) |
|
wait_event(subscriptions->wq, |
|
mmu_interval_seq_released(subscriptions, seq)); |
|
|
|
/* pairs with mmgrab in mmu_interval_notifier_insert() */ |
|
mmdrop(mm); |
|
} |
|
EXPORT_SYMBOL_GPL(mmu_interval_notifier_remove); |
|
|
|
/** |
|
* mmu_notifier_synchronize - Ensure all mmu_notifiers are freed |
|
* |
|
* This function ensures that all outstanding async SRU work from |
|
* mmu_notifier_put() is completed. After it returns any mmu_notifier_ops |
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* associated with an unused mmu_notifier will no longer be called. |
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* |
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* Before using the caller must ensure that all of its mmu_notifiers have been |
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* fully released via mmu_notifier_put(). |
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* |
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* Modules using the mmu_notifier_put() API should call this in their __exit |
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* function to avoid module unloading races. |
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*/ |
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void mmu_notifier_synchronize(void) |
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{ |
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synchronize_srcu(&srcu); |
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} |
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EXPORT_SYMBOL_GPL(mmu_notifier_synchronize); |
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|
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bool |
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mmu_notifier_range_update_to_read_only(const struct mmu_notifier_range *range) |
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{ |
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if (!range->vma || range->event != MMU_NOTIFY_PROTECTION_VMA) |
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return false; |
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/* Return true if the vma still have the read flag set. */ |
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return range->vma->vm_flags & VM_READ; |
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} |
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EXPORT_SYMBOL_GPL(mmu_notifier_range_update_to_read_only);
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|