Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 437 insertions, 0 deletions

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
new file mode 100644
index 000000000..06dedb175
--- /dev/null
+++ b/mm/mmu_notifier.c
@@ -0,0 +1,437 @@
+/*
+ *  linux/mm/mmu_notifier.c
+ *
+ *  Copyright (C) 2008  Qumranet, Inc.
+ *  Copyright (C) 2008  SGI
+ *             Christoph Lameter <cl@linux.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/sched/mm.h>
+#include <linux/slab.h>
+
+/* global SRCU for all MMs */
+DEFINE_STATIC_SRCU(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_clear_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_young)
+			young |= mn->ops->clear_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);
+}
+
+int __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
+				  unsigned long start, unsigned long end,
+				  bool blockable)
+{
+	struct mmu_notifier *mn;
+	int ret = 0;
+	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) {
+			int _ret = mn->ops->invalidate_range_start(mn, mm, start, end, blockable);
+			if (_ret) {
+				pr_info("%pS callback failed with %d in %sblockable context.\n",
+						mn->ops->invalidate_range_start, _ret,
+						!blockable ? "non-" : "");
+				ret = _ret;
+			}
+		}
+	}
+	srcu_read_unlock(&srcu, id);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start);
+
+void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
+					 unsigned long start,
+					 unsigned long end,
+					 bool only_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).
+		 *
+		 * 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 && 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);
+
+/*
+ * Must be called while holding mm->mmap_sem for either read or write.
+ * The result is guaranteed to be valid until mm->mmap_sem is dropped.
+ */
+bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
+{
+	struct mmu_notifier *mn;
+	int id;
+	bool ret = false;
+
+	WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
+
+	if (!mm_has_notifiers(mm))
+		return ret;
+
+	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_start &&
+		    !mn->ops->invalidate_range_end)
+				continue;
+
+		if (!(mn->ops->flags & MMU_INVALIDATE_DOES_NOT_BLOCK)) {
+			ret = true;
+			break;
+		}
+	}
+	srcu_read_unlock(&srcu, id);
+	return ret;
+}
+
+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);
+
+	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;
+	}
+	mmgrab(mm);
+
+	/*
+	 * 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_rcu(&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);