1 files changed, 435 insertions, 0 deletions
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
new file mode 100644
index 000000000000..d53f72dba7fe
--- /dev/null
+++ b/include/linux/mmap_lock.h
@@ -0,0 +1,435 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MMAP_LOCK_H
+#define _LINUX_MMAP_LOCK_H
+
+/* Avoid a dependency loop by declaring here. */
+extern int rcuwait_wake_up(struct rcuwait *w);
+
+#include <linux/lockdep.h>
+#include <linux/mm_types.h>
+#include <linux/mmdebug.h>
+#include <linux/rwsem.h>
+#include <linux/tracepoint-defs.h>
+#include <linux/types.h>
+#include <linux/cleanup.h>
+#include <linux/sched/mm.h>
+
+#define MMAP_LOCK_INITIALIZER(name) \
+	.mmap_lock = __RWSEM_INITIALIZER((name).mmap_lock),
+
+DECLARE_TRACEPOINT(mmap_lock_start_locking);
+DECLARE_TRACEPOINT(mmap_lock_acquire_returned);
+DECLARE_TRACEPOINT(mmap_lock_released);
+
+#ifdef CONFIG_TRACING
+
+void __mmap_lock_do_trace_start_locking(struct mm_struct *mm, bool write);
+void __mmap_lock_do_trace_acquire_returned(struct mm_struct *mm, bool write,
+					   bool success);
+void __mmap_lock_do_trace_released(struct mm_struct *mm, bool write);
+
+static inline void __mmap_lock_trace_start_locking(struct mm_struct *mm,
+						   bool write)
+{
+	if (tracepoint_enabled(mmap_lock_start_locking))
+		__mmap_lock_do_trace_start_locking(mm, write);
+}
+
+static inline void __mmap_lock_trace_acquire_returned(struct mm_struct *mm,
+						      bool write, bool success)
+{
+	if (tracepoint_enabled(mmap_lock_acquire_returned))
+		__mmap_lock_do_trace_acquire_returned(mm, write, success);
+}
+
+static inline void __mmap_lock_trace_released(struct mm_struct *mm, bool write)
+{
+	if (tracepoint_enabled(mmap_lock_released))
+		__mmap_lock_do_trace_released(mm, write);
+}
+
+#else /* !CONFIG_TRACING */
+
+static inline void __mmap_lock_trace_start_locking(struct mm_struct *mm,
+						   bool write)
+{
+}
+
+static inline void __mmap_lock_trace_acquire_returned(struct mm_struct *mm,
+						      bool write, bool success)
+{
+}
+
+static inline void __mmap_lock_trace_released(struct mm_struct *mm, bool write)
+{
+}
+
+#endif /* CONFIG_TRACING */
+
+static inline void mmap_assert_locked(const struct mm_struct *mm)
+{
+	rwsem_assert_held(&mm->mmap_lock);
+}
+
+static inline void mmap_assert_write_locked(const struct mm_struct *mm)
+{
+	rwsem_assert_held_write(&mm->mmap_lock);
+}
+
+#ifdef CONFIG_PER_VMA_LOCK
+
+static inline void mm_lock_seqcount_init(struct mm_struct *mm)
+{
+	seqcount_init(&mm->mm_lock_seq);
+}
+
+static inline void mm_lock_seqcount_begin(struct mm_struct *mm)
+{
+	do_raw_write_seqcount_begin(&mm->mm_lock_seq);
+}
+
+static inline void mm_lock_seqcount_end(struct mm_struct *mm)
+{
+	ASSERT_EXCLUSIVE_WRITER(mm->mm_lock_seq);
+	do_raw_write_seqcount_end(&mm->mm_lock_seq);
+}
+
+static inline bool mmap_lock_speculate_try_begin(struct mm_struct *mm, unsigned int *seq)
+{
+	/*
+	 * Since mmap_lock is a sleeping lock, and waiting for it to become
+	 * unlocked is more or less equivalent with taking it ourselves, don't
+	 * bother with the speculative path if mmap_lock is already write-locked
+	 * and take the slow path, which takes the lock.
+	 */
+	return raw_seqcount_try_begin(&mm->mm_lock_seq, *seq);
+}
+
+static inline bool mmap_lock_speculate_retry(struct mm_struct *mm, unsigned int seq)
+{
+	return read_seqcount_retry(&mm->mm_lock_seq, seq);
+}
+
+static inline void vma_lock_init(struct vm_area_struct *vma, bool reset_refcnt)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	static struct lock_class_key lockdep_key;
+
+	lockdep_init_map(&vma->vmlock_dep_map, "vm_lock", &lockdep_key, 0);
+#endif
+	if (reset_refcnt)
+		refcount_set(&vma->vm_refcnt, 0);
+	vma->vm_lock_seq = UINT_MAX;
+}
+
+static inline bool is_vma_writer_only(int refcnt)
+{
+	/*
+	 * With a writer and no readers, refcnt is VMA_LOCK_OFFSET if the vma
+	 * is detached and (VMA_LOCK_OFFSET + 1) if it is attached. Waiting on
+	 * a detached vma happens only in vma_mark_detached() and is a rare
+	 * case, therefore most of the time there will be no unnecessary wakeup.
+	 */
+	return (refcnt & VMA_LOCK_OFFSET) && refcnt <= VMA_LOCK_OFFSET + 1;
+}
+
+static inline void vma_refcount_put(struct vm_area_struct *vma)
+{
+	/* Use a copy of vm_mm in case vma is freed after we drop vm_refcnt */
+	struct mm_struct *mm = vma->vm_mm;
+	int oldcnt;
+
+	rwsem_release(&vma->vmlock_dep_map, _RET_IP_);
+	if (!__refcount_dec_and_test(&vma->vm_refcnt, &oldcnt)) {
+
+		if (is_vma_writer_only(oldcnt - 1))
+			rcuwait_wake_up(&mm->vma_writer_wait);
+	}
+}
+
+/*
+ * Use only while holding mmap read lock which guarantees that locking will not
+ * fail (nobody can concurrently write-lock the vma). vma_start_read() should
+ * not be used in such cases because it might fail due to mm_lock_seq overflow.
+ * This functionality is used to obtain vma read lock and drop the mmap read lock.
+ */
+static inline bool vma_start_read_locked_nested(struct vm_area_struct *vma, int subclass)
+{
+	int oldcnt;
+
+	mmap_assert_locked(vma->vm_mm);
+	if (unlikely(!__refcount_inc_not_zero_limited_acquire(&vma->vm_refcnt, &oldcnt,
+							      VMA_REF_LIMIT)))
+		return false;
+
+	rwsem_acquire_read(&vma->vmlock_dep_map, 0, 1, _RET_IP_);
+	return true;
+}
+
+/*
+ * Use only while holding mmap read lock which guarantees that locking will not
+ * fail (nobody can concurrently write-lock the vma). vma_start_read() should
+ * not be used in such cases because it might fail due to mm_lock_seq overflow.
+ * This functionality is used to obtain vma read lock and drop the mmap read lock.
+ */
+static inline bool vma_start_read_locked(struct vm_area_struct *vma)
+{
+	return vma_start_read_locked_nested(vma, 0);
+}
+
+static inline void vma_end_read(struct vm_area_struct *vma)
+{
+	vma_refcount_put(vma);
+}
+
+/* WARNING! Can only be used if mmap_lock is expected to be write-locked */
+static inline bool __is_vma_write_locked(struct vm_area_struct *vma, unsigned int *mm_lock_seq)
+{
+	mmap_assert_write_locked(vma->vm_mm);
+
+	/*
+	 * current task is holding mmap_write_lock, both vma->vm_lock_seq and
+	 * mm->mm_lock_seq can't be concurrently modified.
+	 */
+	*mm_lock_seq = vma->vm_mm->mm_lock_seq.sequence;
+	return (vma->vm_lock_seq == *mm_lock_seq);
+}
+
+int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq,
+		int state);
+
+/*
+ * Begin writing to a VMA.
+ * Exclude concurrent readers under the per-VMA lock until the currently
+ * write-locked mmap_lock is dropped or downgraded.
+ */
+static inline void vma_start_write(struct vm_area_struct *vma)
+{
+	unsigned int mm_lock_seq;
+
+	if (__is_vma_write_locked(vma, &mm_lock_seq))
+		return;
+
+	__vma_start_write(vma, mm_lock_seq, TASK_UNINTERRUPTIBLE);
+}
+
+/**
+ * vma_start_write_killable - Begin writing to a VMA.
+ * @vma: The VMA we are going to modify.
+ *
+ * Exclude concurrent readers under the per-VMA lock until the currently
+ * write-locked mmap_lock is dropped or downgraded.
+ *
+ * Context: May sleep while waiting for readers to drop the vma read lock.
+ * Caller must already hold the mmap_lock for write.
+ *
+ * Return: 0 for a successful acquisition.  -EINTR if a fatal signal was
+ * received.
+ */
+static inline __must_check
+int vma_start_write_killable(struct vm_area_struct *vma)
+{
+	unsigned int mm_lock_seq;
+
+	if (__is_vma_write_locked(vma, &mm_lock_seq))
+		return 0;
+	return __vma_start_write(vma, mm_lock_seq, TASK_KILLABLE);
+}
+
+static inline void vma_assert_write_locked(struct vm_area_struct *vma)
+{
+	unsigned int mm_lock_seq;
+
+	VM_BUG_ON_VMA(!__is_vma_write_locked(vma, &mm_lock_seq), vma);
+}
+
+static inline void vma_assert_locked(struct vm_area_struct *vma)
+{
+	unsigned int mm_lock_seq;
+
+	VM_BUG_ON_VMA(refcount_read(&vma->vm_refcnt) <= 1 &&
+		      !__is_vma_write_locked(vma, &mm_lock_seq), vma);
+}
+
+/*
+ * WARNING: to avoid racing with vma_mark_attached()/vma_mark_detached(), these
+ * assertions should be made either under mmap_write_lock or when the object
+ * has been isolated under mmap_write_lock, ensuring no competing writers.
+ */
+static inline void vma_assert_attached(struct vm_area_struct *vma)
+{
+	WARN_ON_ONCE(!refcount_read(&vma->vm_refcnt));
+}
+
+static inline void vma_assert_detached(struct vm_area_struct *vma)
+{
+	WARN_ON_ONCE(refcount_read(&vma->vm_refcnt));
+}
+
+static inline void vma_mark_attached(struct vm_area_struct *vma)
+{
+	vma_assert_write_locked(vma);
+	vma_assert_detached(vma);
+	refcount_set_release(&vma->vm_refcnt, 1);
+}
+
+void vma_mark_detached(struct vm_area_struct *vma);
+
+struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
+					  unsigned long address);
+
+/*
+ * Locks next vma pointed by the iterator. Confirms the locked vma has not
+ * been modified and will retry under mmap_lock protection if modification
+ * was detected. Should be called from read RCU section.
+ * Returns either a valid locked VMA, NULL if no more VMAs or -EINTR if the
+ * process was interrupted.
+ */
+struct vm_area_struct *lock_next_vma(struct mm_struct *mm,
+				     struct vma_iterator *iter,
+				     unsigned long address);
+
+#else /* CONFIG_PER_VMA_LOCK */
+
+static inline void mm_lock_seqcount_init(struct mm_struct *mm) {}
+static inline void mm_lock_seqcount_begin(struct mm_struct *mm) {}
+static inline void mm_lock_seqcount_end(struct mm_struct *mm) {}
+
+static inline bool mmap_lock_speculate_try_begin(struct mm_struct *mm, unsigned int *seq)
+{
+	return false;
+}
+
+static inline bool mmap_lock_speculate_retry(struct mm_struct *mm, unsigned int seq)
+{
+	return true;
+}
+static inline void vma_lock_init(struct vm_area_struct *vma, bool reset_refcnt) {}
+static inline void vma_end_read(struct vm_area_struct *vma) {}
+static inline void vma_start_write(struct vm_area_struct *vma) {}
+static inline __must_check
+int vma_start_write_killable(struct vm_area_struct *vma) { return 0; }
+static inline void vma_assert_write_locked(struct vm_area_struct *vma)
+		{ mmap_assert_write_locked(vma->vm_mm); }
+static inline void vma_assert_attached(struct vm_area_struct *vma) {}
+static inline void vma_assert_detached(struct vm_area_struct *vma) {}
+static inline void vma_mark_attached(struct vm_area_struct *vma) {}
+static inline void vma_mark_detached(struct vm_area_struct *vma) {}
+
+static inline struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
+		unsigned long address)
+{
+	return NULL;
+}
+
+static inline void vma_assert_locked(struct vm_area_struct *vma)
+{
+	mmap_assert_locked(vma->vm_mm);
+}
+
+#endif /* CONFIG_PER_VMA_LOCK */
+
+static inline void mmap_write_lock(struct mm_struct *mm)
+{
+	__mmap_lock_trace_start_locking(mm, true);
+	down_write(&mm->mmap_lock);
+	mm_lock_seqcount_begin(mm);
+	__mmap_lock_trace_acquire_returned(mm, true, true);
+}
+
+static inline void mmap_write_lock_nested(struct mm_struct *mm, int subclass)
+{
+	__mmap_lock_trace_start_locking(mm, true);
+	down_write_nested(&mm->mmap_lock, subclass);
+	mm_lock_seqcount_begin(mm);
+	__mmap_lock_trace_acquire_returned(mm, true, true);
+}
+
+static inline int mmap_write_lock_killable(struct mm_struct *mm)
+{
+	int ret;
+
+	__mmap_lock_trace_start_locking(mm, true);
+	ret = down_write_killable(&mm->mmap_lock);
+	if (!ret)
+		mm_lock_seqcount_begin(mm);
+	__mmap_lock_trace_acquire_returned(mm, true, ret == 0);
+	return ret;
+}
+
+/*
+ * Drop all currently-held per-VMA locks.
+ * This is called from the mmap_lock implementation directly before releasing
+ * a write-locked mmap_lock (or downgrading it to read-locked).
+ * This should normally NOT be called manually from other places.
+ * If you want to call this manually anyway, keep in mind that this will release
+ * *all* VMA write locks, including ones from further up the stack.
+ */
+static inline void vma_end_write_all(struct mm_struct *mm)
+{
+	mmap_assert_write_locked(mm);
+	mm_lock_seqcount_end(mm);
+}
+
+static inline void mmap_write_unlock(struct mm_struct *mm)
+{
+	__mmap_lock_trace_released(mm, true);
+	vma_end_write_all(mm);
+	up_write(&mm->mmap_lock);
+}
+
+static inline void mmap_write_downgrade(struct mm_struct *mm)
+{
+	__mmap_lock_trace_acquire_returned(mm, false, true);
+	vma_end_write_all(mm);
+	downgrade_write(&mm->mmap_lock);
+}
+
+static inline void mmap_read_lock(struct mm_struct *mm)
+{
+	__mmap_lock_trace_start_locking(mm, false);
+	down_read(&mm->mmap_lock);
+	__mmap_lock_trace_acquire_returned(mm, false, true);
+}
+
+static inline int mmap_read_lock_killable(struct mm_struct *mm)
+{
+	int ret;
+
+	__mmap_lock_trace_start_locking(mm, false);
+	ret = down_read_killable(&mm->mmap_lock);
+	__mmap_lock_trace_acquire_returned(mm, false, ret == 0);
+	return ret;
+}
+
+static inline bool mmap_read_trylock(struct mm_struct *mm)
+{
+	bool ret;
+
+	__mmap_lock_trace_start_locking(mm, false);
+	ret = down_read_trylock(&mm->mmap_lock) != 0;
+	__mmap_lock_trace_acquire_returned(mm, false, ret);
+	return ret;
+}
+
+static inline void mmap_read_unlock(struct mm_struct *mm)
+{
+	__mmap_lock_trace_released(mm, false);
+	up_read(&mm->mmap_lock);
+}
+
+DEFINE_GUARD(mmap_read_lock, struct mm_struct *,
+	     mmap_read_lock(_T), mmap_read_unlock(_T))
+
+static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
+{
+	__mmap_lock_trace_released(mm, false);
+	up_read_non_owner(&mm->mmap_lock);
+}
+
+static inline int mmap_lock_is_contended(struct mm_struct *mm)
+{
+	return rwsem_is_contended(&mm->mmap_lock);
+}
+
+#endif /* _LINUX_MMAP_LOCK_H */