v4.19.13 snapshot.
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
new file mode 100644
index 0000000..133ba78
--- /dev/null
+++ b/include/linux/mmu_notifier.h
@@ -0,0 +1,520 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MMU_NOTIFIER_H
+#define _LINUX_MMU_NOTIFIER_H
+
+#include <linux/types.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;
+
+/* mmu_notifier_ops flags */
+#define MMU_INVALIDATE_DOES_NOT_BLOCK (0x01)
+
+#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;
+};
+
+struct mmu_notifier_ops {
+ /*
+ * Flags to specify behavior of callbacks for this MMU notifier.
+ * Used to determine which context an operation may be called.
+ *
+ * MMU_INVALIDATE_DOES_NOT_BLOCK: invalidate_range_* callbacks do not
+ * block
+ */
+ int flags;
+
+ /*
+ * 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.
+ *
+ */
+ int (*invalidate_range_start)(struct mmu_notifier *mn,
+ struct mm_struct *mm,
+ unsigned long start, unsigned long end,
+ bool blockable);
+ void (*invalidate_range_end)(struct mmu_notifier *mn,
+ struct mm_struct *mm,
+ unsigned long start, unsigned long end);
+
+ /*
+ * 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.
+ *
+ * If this callback cannot block, and invalidate_range_{start,end}
+ * cannot block, mmu_notifier_ops.flags should have
+ * MMU_INVALIDATE_DOES_NOT_BLOCK set.
+ */
+ 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 mm_struct *mm,
+ unsigned long start, unsigned long end,
+ bool blockable);
+extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
+ unsigned long start, unsigned long end,
+ bool only_end);
+extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
+ unsigned long start, unsigned long end);
+extern bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm);
+
+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 mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ if (mm_has_notifiers(mm))
+ __mmu_notifier_invalidate_range_start(mm, start, end, true);
+}
+
+static inline int mmu_notifier_invalidate_range_start_nonblock(struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ if (mm_has_notifiers(mm))
+ return __mmu_notifier_invalidate_range_start(mm, start, end, false);
+ return 0;
+}
+
+static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ if (mm_has_notifiers(mm))
+ __mmu_notifier_invalidate_range_end(mm, start, end, false);
+}
+
+static inline void mmu_notifier_invalidate_range_only_end(struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ if (mm_has_notifiers(mm))
+ __mmu_notifier_invalidate_range_end(mm, start, end, 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);
+}
+
+#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));
+extern void mmu_notifier_synchronize(void);
+
+#else /* CONFIG_MMU_NOTIFIER */
+
+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 mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+}
+
+static inline int mmu_notifier_invalidate_range_start_nonblock(struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ return 0;
+}
+
+static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+}
+
+static inline void mmu_notifier_invalidate_range_only_end(struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+}
+
+static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+}
+
+static inline bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
+{
+ return false;
+}
+
+static inline void mmu_notifier_mm_init(struct mm_struct *mm)
+{
+}
+
+static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
+{
+}
+
+#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 */