/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MMU_NOTIFIER_H
#define _LINUX_MMU_NOTIFIER_H

#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/mm_types.h>
#include <linux/mmap_lock.h>
#include <linux/srcu.h>
#include <linux/interval_tree.h>

struct mmu_notifier_subscriptions;
struct mmu_notifier;
struct mmu_notifier_range;
struct mmu_interval_notifier;

/**
 * enum mmu_notifier_event - reason for the mmu notifier callback
 * @MMU_NOTIFY_UNMAP: either munmap() that unmap the range or a mremap() that
 * move the range
 *
 * @MMU_NOTIFY_CLEAR: clear page table entry (many reasons for this like
 * madvise() or replacing a page by another one, ...).
 *
 * @MMU_NOTIFY_PROTECTION_VMA: update is due to protection change for the range
 * ie using the vma access permission (vm_page_prot) to update the whole range
 * is enough no need to inspect changes to the CPU page table (mprotect()
 * syscall)
 *
 * @MMU_NOTIFY_PROTECTION_PAGE: update is due to change in read/write flag for
 * pages in the range so to mirror those changes the user must inspect the CPU
 * page table (from the end callback).
 *
 * @MMU_NOTIFY_SOFT_DIRTY: soft dirty accounting (still same page and same
 * access flags). User should soft dirty the page in the end callback to make
 * sure that anyone relying on soft dirtiness catch pages that might be written
 * through non CPU mappings.
 *
 * @MMU_NOTIFY_RELEASE: used during mmu_interval_notifier invalidate to signal
 * that the mm refcount is zero and the range is no longer accessible.
 *
 * @MMU_NOTIFY_MIGRATE: used during migrate_vma_collect() invalidate to signal
 * a device driver to possibly ignore the invalidation if the
 * owner field matches the driver's device private pgmap owner.
 *
 * @MMU_NOTIFY_EXCLUSIVE: conversion of a page table entry to device-exclusive.
 * The owner is initialized to the value provided by the caller of
 * make_device_exclusive(), such that this caller can filter out these
 * events.
 */
enum mmu_notifier_event {
        MMU_NOTIFY_UNMAP = 0,
        MMU_NOTIFY_CLEAR,
        MMU_NOTIFY_PROTECTION_VMA,
        MMU_NOTIFY_PROTECTION_PAGE,
        MMU_NOTIFY_SOFT_DIRTY,
        MMU_NOTIFY_RELEASE,
        MMU_NOTIFY_MIGRATE,
        MMU_NOTIFY_EXCLUSIVE,
};

#define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)

struct mmu_notifier_ops {
        /*
         * Called either by mmu_notifier_unregister or when the mm is
         * being destroyed by exit_mmap, always before all pages are
         * freed. This can run concurrently with other mmu notifier
         * methods (the ones invoked outside the mm context) and it
         * should tear down all secondary mmu mappings and freeze the
         * secondary mmu. If this method isn't implemented you've to
         * be sure that nothing could possibly write to the pages
         * through the secondary mmu by the time the last thread with
         * tsk->mm == mm exits.
         *
         * As side note: the pages freed after ->release returns could
         * be immediately reallocated by the gart at an alias physical
         * address with a different cache model, so if ->release isn't
         * implemented because all _software_ driven memory accesses
         * through the secondary mmu are terminated by the time the
         * last thread of this mm quits, you've also to be sure that
         * speculative _hardware_ operations can't allocate dirty
         * cachelines in the cpu that could not be snooped and made
         * coherent with the other read and write operations happening
         * through the gart alias address, so leading to memory
         * corruption.
         */
        void (*release)(struct mmu_notifier *subscription,
                        struct mm_struct *mm);

        /*
         * clear_flush_young is called after the VM is
         * test-and-clearing the young/accessed bitflag in the
         * pte. This way the VM will provide proper aging to the
         * accesses to the page through the secondary MMUs and not
         * only to the ones through the Linux pte.
         * Start-end is necessary in case the secondary MMU is mapping the page
         * at a smaller granularity than the primary MMU.
         */
        int (*clear_flush_young)(struct mmu_notifier *subscription,
                                 struct mm_struct *mm,
                                 unsigned long start,
                                 unsigned long end);

        /*
         * clear_young is a lightweight version of clear_flush_young. Like the
         * latter, it is supposed to test-and-clear the young/accessed bitflag
         * in the secondary pte, but it may omit flushing the secondary tlb.
         */
        int (*clear_young)(struct mmu_notifier *subscription,
                           struct mm_struct *mm,
                           unsigned long start,
                           unsigned long end);

        /*
         * test_young is called to check the young/accessed bitflag in
         * the secondary pte. This is used to know if the page is
         * frequently used without actually clearing the flag or tearing
         * down the secondary mapping on the page.
         */
        int (*test_young)(struct mmu_notifier *subscription,
                          struct mm_struct *mm,
                          unsigned long address);

        /*
         * invalidate_range_start() and invalidate_range_end() must be
         * paired and are called only when the mmap_lock and/or the
         * locks protecting the reverse maps are held. If the subsystem
         * can't guarantee that no additional references are taken to
         * the pages in the range, it has to implement the
         * invalidate_range() notifier to remove any references taken
         * after invalidate_range_start().
         *
         * Invalidation of multiple concurrent ranges may be
         * optionally permitted by the driver. Either way the
         * establishment of sptes is forbidden in the range passed to
         * invalidate_range_begin/end for the whole duration of the
         * invalidate_range_begin/end critical section.
         *
         * invalidate_range_start() is called when all pages in the
         * range are still mapped and have at least a refcount of one.
         *
         * invalidate_range_end() is called when all pages in the
         * range have been unmapped and the pages have been freed by
         * the VM.
         *
         * The VM will remove the page table entries and potentially
         * the page between invalidate_range_start() and
         * invalidate_range_end(). If the page must not be freed
         * because of pending I/O or other circumstances then the
         * invalidate_range_start() callback (or the initial mapping
         * by the driver) must make sure that the refcount is kept
         * elevated.
         *
         * If the driver increases the refcount when the pages are
         * initially mapped into an address space then either
         * invalidate_range_start() or invalidate_range_end() may
         * decrease the refcount. If the refcount is decreased on
         * invalidate_range_start() then the VM can free pages as page
         * table entries are removed.  If the refcount is only
         * dropped on invalidate_range_end() then the driver itself
         * will drop the last refcount but it must take care to flush
         * any secondary tlb before doing the final free on the
         * page. Pages will no longer be referenced by the linux
         * address space but may still be referenced by sptes until
         * the last refcount is dropped.
         *
         * If blockable argument is set to false then the callback cannot
         * sleep and has to return with -EAGAIN if sleeping would be required.
         * 0 should be returned otherwise. Please note that notifiers that can
         * fail invalidate_range_start are not allowed to implement
         * invalidate_range_end, as there is no mechanism for informing the
         * notifier that its start failed.
         */
        int (*invalidate_range_start)(struct mmu_notifier *subscription,
                                      const struct mmu_notifier_range *range);
        void (*invalidate_range_end)(struct mmu_notifier *subscription,
                                     const struct mmu_notifier_range *range);

        /*
         * arch_invalidate_secondary_tlbs() is used to manage a non-CPU TLB
         * which shares page-tables with the CPU. The
         * invalidate_range_start()/end() callbacks should not be implemented as
         * invalidate_secondary_tlbs() already catches the points in time when
         * an external TLB needs to be flushed.
         *
         * This requires arch_invalidate_secondary_tlbs() to be called while
         * holding the ptl spin-lock and therefore this callback is not allowed
         * to sleep.
         *
         * This is called by architecture code whenever invalidating a TLB
         * entry. It is assumed that any secondary TLB has the same rules for
         * when invalidations are required. If this is not the case architecture
         * code will need to call this explicitly when required for secondary
         * TLB invalidation.
         */
        void (*arch_invalidate_secondary_tlbs)(
                                        struct mmu_notifier *subscription,
                                        struct mm_struct *mm,
                                        unsigned long start,
                                        unsigned long end);

        /*
         * These callbacks are used with the get/put interface to manage the
         * lifetime of the mmu_notifier memory. alloc_notifier() returns a new
         * notifier for use with the mm.
         *
         * free_notifier() is only called after the mmu_notifier has been
         * fully put, calls to any ops callback are prevented and no ops
         * callbacks are currently running. It is called from a SRCU callback
         * and cannot sleep.
         */
        struct mmu_notifier *(*alloc_notifier)(struct mm_struct *mm);
        void (*free_notifier)(struct mmu_notifier *subscription);
};

/*
 * The notifier chains are protected by mmap_lock and/or the reverse map
 * semaphores. Notifier chains are only changed when all reverse maps and
 * the mmap_lock locks are taken.
 *
 * Therefore notifier chains can only be traversed when either
 *
 * 1. mmap_lock is held.
 * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem).
 * 3. No other concurrent thread can access the list (release)
 */
struct mmu_notifier {
        struct hlist_node hlist;
        const struct mmu_notifier_ops *ops;
        struct mm_struct *mm;
        struct rcu_head rcu;
        unsigned int users;
};

/**
 * struct mmu_interval_notifier_ops - callback for range notification
 * @invalidate: Upon return the caller must stop using any SPTEs within this
 *              range. This function can sleep. Return false only if sleeping
 *              was required but mmu_notifier_range_blockable(range) is false.
 */
struct mmu_interval_notifier_ops {
        bool (*invalidate)(struct mmu_interval_notifier *interval_sub,
                           const struct mmu_notifier_range *range,
                           unsigned long cur_seq);
};

struct mmu_interval_notifier {
        struct interval_tree_node interval_tree;
        const struct mmu_interval_notifier_ops *ops;
        struct mm_struct *mm;
        struct hlist_node deferred_item;
        unsigned long invalidate_seq;
};

#ifdef CONFIG_MMU_NOTIFIER

#ifdef CONFIG_LOCKDEP
extern struct lockdep_map __mmu_notifier_invalidate_range_start_map;
#endif

struct mmu_notifier_range {
        struct mm_struct *mm;
        unsigned long start;
        unsigned long end;
        unsigned flags;
        enum mmu_notifier_event event;
        void *owner;
};

static inline int mm_has_notifiers(struct mm_struct *mm)
{
        return unlikely(mm->notifier_subscriptions);
}

struct mmu_notifier *mmu_notifier_get_locked(const struct mmu_notifier_ops *ops,
                                             struct mm_struct *mm);
static inline struct mmu_notifier *
mmu_notifier_get(const struct mmu_notifier_ops *ops, struct mm_struct *mm)
{
        struct mmu_notifier *ret;

        mmap_write_lock(mm);
        ret = mmu_notifier_get_locked(ops, mm);
        mmap_write_unlock(mm);
        return ret;
}
void mmu_notifier_put(struct mmu_notifier *subscription);
void mmu_notifier_synchronize(void);

extern int mmu_notifier_register(struct mmu_notifier *subscription,
                                 struct mm_struct *mm);
extern int __mmu_notifier_register(struct mmu_notifier *subscription,
                                   struct mm_struct *mm);
extern void mmu_notifier_unregister(struct mmu_notifier *subscription,
                                    struct mm_struct *mm);

unsigned long
mmu_interval_read_begin(struct mmu_interval_notifier *interval_sub);
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);
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);
void mmu_interval_notifier_remove(struct mmu_interval_notifier *interval_sub);

/**
 * mmu_interval_set_seq - Save the invalidation sequence
 * @interval_sub: The subscription passed to invalidate
 * @cur_seq: The cur_seq passed to the invalidate() callback
 *
 * This must be called unconditionally from the invalidate callback of a
 * struct mmu_interval_notifier_ops under the same lock that is used to call
 * mmu_interval_read_retry(). It updates the sequence number for later use by
 * mmu_interval_read_retry(). The provided cur_seq will always be odd.
 *
 * If the caller does not call mmu_interval_read_begin() or
 * mmu_interval_read_retry() then this call is not required.
 */
static inline void
mmu_interval_set_seq(struct mmu_interval_notifier *interval_sub,
                     unsigned long cur_seq)
{
        WRITE_ONCE(interval_sub->invalidate_seq, cur_seq);
}

/**
 * mmu_interval_read_retry - End a read side critical section against a VA range
 * @interval_sub: The subscription
 * @seq: The return of the paired mmu_interval_read_begin()
 *
 * This MUST be called under a user provided lock that is also held
 * unconditionally by op->invalidate() when it calls mmu_interval_set_seq().
 *
 * Each call should be paired with a single mmu_interval_read_begin() and
 * should be used to conclude the read side.
 *
 * Returns: true if an invalidation collided with this critical section, and
 * the caller should retry.
 */
static inline bool
mmu_interval_read_retry(struct mmu_interval_notifier *interval_sub,
                        unsigned long seq)
{
        return interval_sub->invalidate_seq != seq;
}

/**
 * mmu_interval_check_retry - Test if a collision has occurred
 * @interval_sub: The subscription
 * @seq: The return of the matching mmu_interval_read_begin()
 *
 * This can be used in the critical section between mmu_interval_read_begin()
 * and mmu_interval_read_retry().
 *
 * This call can be used as part of loops and other expensive operations to
 * expedite a retry.
 * It can be called many times and does not have to hold the user
 * provided lock.
 *
 * Returns: true indicates an invalidation has collided with this critical
 * region and a future mmu_interval_read_retry() will return true.
 * False is not reliable and only suggests a collision may not have
 * occurred.
 */
static inline bool
mmu_interval_check_retry(struct mmu_interval_notifier *interval_sub,
                         unsigned long seq)
{
        /* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */
        return READ_ONCE(interval_sub->invalidate_seq) != seq;
}

extern void __mmu_notifier_subscriptions_destroy(struct mm_struct *mm);
extern void __mmu_notifier_release(struct mm_struct *mm);
extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
                                          unsigned long start,
                                          unsigned long end);
extern int __mmu_notifier_clear_young(struct mm_struct *mm,
                                      unsigned long start,
                                      unsigned long end);
extern int __mmu_notifier_test_young(struct mm_struct *mm,
                                     unsigned long address);
extern int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *r);
extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r);
extern void __mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm,
                                        unsigned long start, unsigned long end);
extern bool
mmu_notifier_range_update_to_read_only(const struct mmu_notifier_range *range);

static inline bool
mmu_notifier_range_blockable(const struct mmu_notifier_range *range)
{
        return (range->flags & MMU_NOTIFIER_RANGE_BLOCKABLE);
}

static inline void mmu_notifier_release(struct mm_struct *mm)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_release(mm);
}

static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
                                          unsigned long start,
                                          unsigned long end)
{
        if (mm_has_notifiers(mm))
                return __mmu_notifier_clear_flush_young(mm, start, end);
        return 0;
}

static inline int mmu_notifier_clear_young(struct mm_struct *mm,
                                           unsigned long start,
                                           unsigned long end)
{
        if (mm_has_notifiers(mm))
                return __mmu_notifier_clear_young(mm, start, end);
        return 0;
}

static inline int mmu_notifier_test_young(struct mm_struct *mm,
                                          unsigned long address)
{
        if (mm_has_notifiers(mm))
                return __mmu_notifier_test_young(mm, address);
        return 0;
}

static inline void
mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
{
        might_sleep();

        lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
        if (mm_has_notifiers(range->mm)) {
                range->flags |= MMU_NOTIFIER_RANGE_BLOCKABLE;
                __mmu_notifier_invalidate_range_start(range);
        }
        lock_map_release(&__mmu_notifier_invalidate_range_start_map);
}

/*
 * This version of mmu_notifier_invalidate_range_start() avoids blocking, but it
 * can return an error if a notifier can't proceed without blocking, in which
 * case you're not allowed to modify PTEs in the specified range.
 *
 * This is mainly intended for OOM handling.
 */
static inline int __must_check
mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
{
        int ret = 0;

        lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
        if (mm_has_notifiers(range->mm)) {
                range->flags &= ~MMU_NOTIFIER_RANGE_BLOCKABLE;
                ret = __mmu_notifier_invalidate_range_start(range);
        }
        lock_map_release(&__mmu_notifier_invalidate_range_start_map);
        return ret;
}

static inline void
mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
{
        if (mmu_notifier_range_blockable(range))
                might_sleep();

        if (mm_has_notifiers(range->mm))
                __mmu_notifier_invalidate_range_end(range);
}

static inline void mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm,
                                        unsigned long start, unsigned long end)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);
}

static inline void mmu_notifier_subscriptions_init(struct mm_struct *mm)
{
        mm->notifier_subscriptions = NULL;
}

static inline void mmu_notifier_subscriptions_destroy(struct mm_struct *mm)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_subscriptions_destroy(mm);
}


static inline void mmu_notifier_range_init(struct mmu_notifier_range *range,
                                           enum mmu_notifier_event event,
                                           unsigned flags,
                                           struct mm_struct *mm,
                                           unsigned long start,
                                           unsigned long end)
{
        range->event = event;
        range->mm = mm;
        range->start = start;
        range->end = end;
        range->flags = flags;
}

static inline void mmu_notifier_range_init_owner(
                        struct mmu_notifier_range *range,
                        enum mmu_notifier_event event, unsigned int flags,
                        struct mm_struct *mm, unsigned long start,
                        unsigned long end, void *owner)
{
        mmu_notifier_range_init(range, event, flags, mm, start, end);
        range->owner = owner;
}

#define clear_flush_young_ptes_notify(__vma, __address, __ptep, __nr)   \
({                                                                      \
        int __young;                                                    \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        unsigned int ___nr = __nr;                                      \
        __young = clear_flush_young_ptes(___vma, ___address, __ptep, ___nr);    \
        __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
                                                  ___address,           \
                                                  ___address +          \
                                                  ___nr * PAGE_SIZE);   \
        __young;                                                        \
})

#define pmdp_clear_flush_young_notify(__vma, __address, __pmdp)         \
({                                                                      \
        int __young;                                                    \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        __young = pmdp_clear_flush_young(___vma, ___address, __pmdp);   \
        __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
                                                  ___address,           \
                                                  ___address +          \
                                                        PMD_SIZE);      \
        __young;                                                        \
})

#define ptep_clear_young_notify(__vma, __address, __ptep)               \
({                                                                      \
        int __young;                                                    \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        __young = ptep_test_and_clear_young(___vma, ___address, __ptep);\
        __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address,  \
                                            ___address + PAGE_SIZE);    \
        __young;                                                        \
})

#define pmdp_clear_young_notify(__vma, __address, __pmdp)               \
({                                                                      \
        int __young;                                                    \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        __young = pmdp_test_and_clear_young(___vma, ___address, __pmdp);\
        __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address,  \
                                            ___address + PMD_SIZE);     \
        __young;                                                        \
})

#else /* CONFIG_MMU_NOTIFIER */

struct mmu_notifier_range {
        unsigned long start;
        unsigned long end;
};

static inline void _mmu_notifier_range_init(struct mmu_notifier_range *range,
                                            unsigned long start,
                                            unsigned long end)
{
        range->start = start;
        range->end = end;
}

#define mmu_notifier_range_init(range,event,flags,mm,start,end)  \
        _mmu_notifier_range_init(range, start, end)
#define mmu_notifier_range_init_owner(range, event, flags, mm, start, \
                                        end, owner) \
        _mmu_notifier_range_init(range, start, end)

static inline bool
mmu_notifier_range_blockable(const struct mmu_notifier_range *range)
{
        return true;
}

static inline int mm_has_notifiers(struct mm_struct *mm)
{
        return 0;
}

static inline void mmu_notifier_release(struct mm_struct *mm)
{
}

static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
                                          unsigned long start,
                                          unsigned long end)
{
        return 0;
}

static inline int mmu_notifier_clear_young(struct mm_struct *mm,
                                           unsigned long start,
                                           unsigned long end)
{
        return 0;
}

static inline int mmu_notifier_test_young(struct mm_struct *mm,
                                          unsigned long address)
{
        return 0;
}

static inline void
mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
{
}

static inline int
mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
{
        return 0;
}

static inline
void mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
{
}

static inline void mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm,
                                  unsigned long start, unsigned long end)
{
}

static inline void mmu_notifier_subscriptions_init(struct mm_struct *mm)
{
}

static inline void mmu_notifier_subscriptions_destroy(struct mm_struct *mm)
{
}

#define mmu_notifier_range_update_to_read_only(r) false

#define clear_flush_young_ptes_notify clear_flush_young_ptes
#define pmdp_clear_flush_young_notify pmdp_clear_flush_young
#define ptep_clear_young_notify ptep_test_and_clear_young
#define pmdp_clear_young_notify pmdp_test_and_clear_young

static inline void mmu_notifier_synchronize(void)
{
}

#endif /* CONFIG_MMU_NOTIFIER */

#endif /* _LINUX_MMU_NOTIFIER_H */