/* 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/srcu.h>

struct mmu_notifier;
struct mmu_notifier_ops;

/**
 * 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 dirtyness catch pages that might be written
 * through non CPU mappings.
 */
enum mmu_notifier_event {
        MMU_NOTIFY_UNMAP = 0,
        MMU_NOTIFY_CLEAR,
        MMU_NOTIFY_PROTECTION_VMA,
        MMU_NOTIFY_PROTECTION_PAGE,
        MMU_NOTIFY_SOFT_DIRTY,
};

#ifdef CONFIG_MMU_NOTIFIER

/*
 * The mmu notifier_mm structure is allocated and installed in
 * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
 * critical section and it's released only when mm_count reaches zero
 * in mmdrop().
 */
struct mmu_notifier_mm {
        /* all mmu notifiers registerd in this mm are queued in this list */
        struct hlist_head list;
        /* to serialize the list modifications and hlist_unhashed */
        spinlock_t lock;
};

#define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)

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

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 *mn,
                        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 *mn,
                                 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 *mn,
                           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 *mn,
                          struct mm_struct *mm,
                          unsigned long address);

        /*
         * change_pte is called in cases that pte mapping to page is changed:
         * for example, when ksm remaps pte to point to a new shared page.
         */
        void (*change_pte)(struct mmu_notifier *mn,
                           struct mm_struct *mm,
                           unsigned long address,
                           pte_t pte);

        /*
         * invalidate_range_start() and invalidate_range_end() must be
         * paired and are called only when the mmap_sem 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
         * droppped 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. 0 should be returned
         * otherwise. Please note that if invalidate_range_start approves
         * a non-blocking behavior then the same applies to
         * invalidate_range_end.
         *
         */
        int (*invalidate_range_start)(struct mmu_notifier *mn,
                                      const struct mmu_notifier_range *range);
        void (*invalidate_range_end)(struct mmu_notifier *mn,
                                     const struct mmu_notifier_range *range);

        /*
         * invalidate_range() is either called between
         * invalidate_range_start() and invalidate_range_end() when the
         * VM has to free pages that where unmapped, but before the
         * pages are actually freed, or outside of _start()/_end() when
         * a (remote) TLB is necessary.
         *
         * If invalidate_range() is used to manage a non-CPU TLB with
         * shared page-tables, it not necessary to implement the
         * invalidate_range_start()/end() notifiers, as
         * invalidate_range() alread catches the points in time when an
         * external TLB range needs to be flushed. For more in depth
         * discussion on this see Documentation/vm/mmu_notifier.rst
         *
         * Note that this function might be called with just a sub-range
         * of what was passed to invalidate_range_start()/end(), if
         * called between those functions.
         */
        void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm,
                                 unsigned long start, unsigned long end);
};

/*
 * The notifier chains are protected by mmap_sem and/or the reverse map
 * semaphores. Notifier chains are only changed when all reverse maps and
 * the mmap_sem locks are taken.
 *
 * Therefore notifier chains can only be traversed when either
 *
 * 1. mmap_sem 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;
};

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

extern int mmu_notifier_register(struct mmu_notifier *mn,
                                 struct mm_struct *mm);
extern int __mmu_notifier_register(struct mmu_notifier *mn,
                                   struct mm_struct *mm);
extern void mmu_notifier_unregister(struct mmu_notifier *mn,
                                    struct mm_struct *mm);
extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
                                               struct mm_struct *mm);
extern void __mmu_notifier_mm_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 void __mmu_notifier_change_pte(struct mm_struct *mm,
                                      unsigned long address, pte_t pte);
extern int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *r);
extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r,
                                  bool only_end);
extern void __mmu_notifier_invalidate_range(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_change_pte(struct mm_struct *mm,
                                           unsigned long address, pte_t pte)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_change_pte(mm, address, pte);
}

static inline void
mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
{
        if (mm_has_notifiers(range->mm)) {
                range->flags |= MMU_NOTIFIER_RANGE_BLOCKABLE;
                __mmu_notifier_invalidate_range_start(range);
        }
}

static inline int
mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
{
        if (mm_has_notifiers(range->mm)) {
                range->flags &= ~MMU_NOTIFIER_RANGE_BLOCKABLE;
                return __mmu_notifier_invalidate_range_start(range);
        }
        return 0;
}

static inline void
mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
{
        if (mm_has_notifiers(range->mm))
                __mmu_notifier_invalidate_range_end(range, false);
}

static inline void
mmu_notifier_invalidate_range_only_end(struct mmu_notifier_range *range)
{
        if (mm_has_notifiers(range->mm))
                __mmu_notifier_invalidate_range_end(range, true);
}

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

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

static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_mm_destroy(mm);
}


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

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

#define ptep_clear_flush_notify(__vma, __address, __ptep)               \
({                                                                      \
        unsigned long ___addr = __address & PAGE_MASK;                  \
        struct mm_struct *___mm = (__vma)->vm_mm;                       \
        pte_t ___pte;                                                   \
                                                                        \
        ___pte = ptep_clear_flush(__vma, __address, __ptep);            \
        mmu_notifier_invalidate_range(___mm, ___addr,                   \
                                        ___addr + PAGE_SIZE);           \
                                                                        \
        ___pte;                                                         \
})

#define pmdp_huge_clear_flush_notify(__vma, __haddr, __pmd)             \
({                                                                      \
        unsigned long ___haddr = __haddr & HPAGE_PMD_MASK;              \
        struct mm_struct *___mm = (__vma)->vm_mm;                       \
        pmd_t ___pmd;                                                   \
                                                                        \
        ___pmd = pmdp_huge_clear_flush(__vma, __haddr, __pmd);          \
        mmu_notifier_invalidate_range(___mm, ___haddr,                  \
                                      ___haddr + HPAGE_PMD_SIZE);       \
                                                                        \
        ___pmd;                                                         \
})

#define pudp_huge_clear_flush_notify(__vma, __haddr, __pud)             \
({                                                                      \
        unsigned long ___haddr = __haddr & HPAGE_PUD_MASK;              \
        struct mm_struct *___mm = (__vma)->vm_mm;                       \
        pud_t ___pud;                                                   \
                                                                        \
        ___pud = pudp_huge_clear_flush(__vma, __haddr, __pud);          \
        mmu_notifier_invalidate_range(___mm, ___haddr,                  \
                                      ___haddr + HPAGE_PUD_SIZE);       \
                                                                        \
        ___pud;                                                         \
})

/*
 * set_pte_at_notify() sets the pte _after_ running the notifier.
 * This is safe to start by updating the secondary MMUs, because the primary MMU
 * pte invalidate must have already happened with a ptep_clear_flush() before
 * set_pte_at_notify() has been invoked.  Updating the secondary MMUs first is
 * required when we change both the protection of the mapping from read-only to
 * read-write and the pfn (like during copy on write page faults). Otherwise the
 * old page would remain mapped readonly in the secondary MMUs after the new
 * page is already writable by some CPU through the primary MMU.
 */
#define set_pte_at_notify(__mm, __address, __ptep, __pte)               \
({                                                                      \
        struct mm_struct *___mm = __mm;                                 \
        unsigned long ___address = __address;                           \
        pte_t ___pte = __pte;                                           \
                                                                        \
        mmu_notifier_change_pte(___mm, ___address, ___pte);             \
        set_pte_at(___mm, ___address, __ptep, ___pte);                  \
})

extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
                                   void (*func)(struct rcu_head *rcu));

#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,vma,mm,start,end)  \
        _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_test_young(struct mm_struct *mm,
                                          unsigned long address)
{
        return 0;
}

static inline void mmu_notifier_change_pte(struct mm_struct *mm,
                                           unsigned long address, pte_t pte)
{
}

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_invalidate_range_only_end(struct mmu_notifier_range *range)
{
}

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

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

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

#define mmu_notifier_range_update_to_read_only(r) false

#define ptep_clear_flush_young_notify ptep_clear_flush_young
#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
#define ptep_clear_flush_notify ptep_clear_flush
#define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush
#define pudp_huge_clear_flush_notify pudp_huge_clear_flush
#define set_pte_at_notify set_pte_at

#endif /* CONFIG_MMU_NOTIFIER */

#endif /* _LINUX_MMU_NOTIFIER_H */