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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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d1751118c8
Before this patch, when there's any pgtable allocation issues happened
during change_protection(), the error will be ignored from the syscall.
For shmem, there will be an error dumped into the host dmesg. Two issues
with that:
(1) Doing a trace dump when allocation fails is not anything close to
grace.
(2) The user should be notified with any kind of such error, so the user
can trap it and decide what to do next, either by retrying, or stop
the process properly, or anything else.
For userfault users, this will change the API of UFFDIO_WRITEPROTECT when
pgtable allocation failure happened. It should not normally break anyone,
though. If it breaks, then in good ways.
One man-page update will be on the way to introduce the new -ENOMEM for
UFFDIO_WRITEPROTECT. Not marking stable so we keep the old behavior on
the 5.19-till-now kernels.
[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20230104225207.1066932-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: James Houghton <jthoughton@google.com>
Acked-by: James Houghton <jthoughton@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
324 lines
8.6 KiB
C
324 lines
8.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* include/linux/userfaultfd_k.h
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*
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* Copyright (C) 2015 Red Hat, Inc.
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*
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*/
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#ifndef _LINUX_USERFAULTFD_K_H
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#define _LINUX_USERFAULTFD_K_H
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#ifdef CONFIG_USERFAULTFD
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#include <linux/userfaultfd.h> /* linux/include/uapi/linux/userfaultfd.h */
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#include <linux/fcntl.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <asm-generic/pgtable_uffd.h>
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#include <linux/hugetlb_inline.h>
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/* The set of all possible UFFD-related VM flags. */
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#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR)
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/*
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* CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
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* new flags, since they might collide with O_* ones. We want
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* to re-use O_* flags that couldn't possibly have a meaning
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* from userfaultfd, in order to leave a free define-space for
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* shared O_* flags.
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*/
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#define UFFD_CLOEXEC O_CLOEXEC
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#define UFFD_NONBLOCK O_NONBLOCK
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#define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
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#define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS)
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extern int sysctl_unprivileged_userfaultfd;
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extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
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/*
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* The mode of operation for __mcopy_atomic and its helpers.
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*
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* This is almost an implementation detail (mcopy_atomic below doesn't take this
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* as a parameter), but it's exposed here because memory-kind-specific
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* implementations (e.g. hugetlbfs) need to know the mode of operation.
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*/
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enum mcopy_atomic_mode {
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/* A normal copy_from_user into the destination range. */
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MCOPY_ATOMIC_NORMAL,
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/* Don't copy; map the destination range to the zero page. */
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MCOPY_ATOMIC_ZEROPAGE,
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/* Just install pte(s) with the existing page(s) in the page cache. */
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MCOPY_ATOMIC_CONTINUE,
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};
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extern int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
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struct vm_area_struct *dst_vma,
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unsigned long dst_addr, struct page *page,
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bool newly_allocated, bool wp_copy);
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extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
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unsigned long src_start, unsigned long len,
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atomic_t *mmap_changing, __u64 mode);
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extern ssize_t mfill_zeropage(struct mm_struct *dst_mm,
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unsigned long dst_start,
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unsigned long len,
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atomic_t *mmap_changing);
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extern ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long dst_start,
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unsigned long len, atomic_t *mmap_changing);
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extern int mwriteprotect_range(struct mm_struct *dst_mm,
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unsigned long start, unsigned long len,
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bool enable_wp, atomic_t *mmap_changing);
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extern long uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *vma,
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unsigned long start, unsigned long len, bool enable_wp);
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/* mm helpers */
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static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
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struct vm_userfaultfd_ctx vm_ctx)
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{
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return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx;
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}
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/*
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* Never enable huge pmd sharing on some uffd registered vmas:
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*
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* - VM_UFFD_WP VMAs, because write protect information is per pgtable entry.
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*
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* - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for
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* VMAs which share huge pmds. (If you have two mappings to the same
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* underlying pages, and fault in the non-UFFD-registered one with a write,
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* with huge pmd sharing this would *also* setup the second UFFD-registered
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* mapping, and we'd not get minor faults.)
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*/
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static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma)
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{
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return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
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}
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/*
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* Don't do fault around for either WP or MINOR registered uffd range. For
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* MINOR registered range, fault around will be a total disaster and ptes can
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* be installed without notifications; for WP it should mostly be fine as long
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* as the fault around checks for pte_none() before the installation, however
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* to be super safe we just forbid it.
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*/
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static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
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{
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return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
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}
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static inline bool userfaultfd_missing(struct vm_area_struct *vma)
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{
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return vma->vm_flags & VM_UFFD_MISSING;
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}
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static inline bool userfaultfd_wp(struct vm_area_struct *vma)
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{
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return vma->vm_flags & VM_UFFD_WP;
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}
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static inline bool userfaultfd_minor(struct vm_area_struct *vma)
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{
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return vma->vm_flags & VM_UFFD_MINOR;
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}
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static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
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pte_t pte)
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{
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return userfaultfd_wp(vma) && pte_uffd_wp(pte);
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}
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static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
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pmd_t pmd)
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{
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return userfaultfd_wp(vma) && pmd_uffd_wp(pmd);
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}
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static inline bool userfaultfd_armed(struct vm_area_struct *vma)
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{
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return vma->vm_flags & __VM_UFFD_FLAGS;
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}
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static inline bool vma_can_userfault(struct vm_area_struct *vma,
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unsigned long vm_flags)
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{
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if ((vm_flags & VM_UFFD_MINOR) &&
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(!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
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return false;
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#ifndef CONFIG_PTE_MARKER_UFFD_WP
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/*
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* If user requested uffd-wp but not enabled pte markers for
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* uffd-wp, then shmem & hugetlbfs are not supported but only
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* anonymous.
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*/
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if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
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return false;
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#endif
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return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
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vma_is_shmem(vma);
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}
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extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
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extern void dup_userfaultfd_complete(struct list_head *);
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extern void mremap_userfaultfd_prep(struct vm_area_struct *,
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struct vm_userfaultfd_ctx *);
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extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *,
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unsigned long from, unsigned long to,
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unsigned long len);
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extern bool userfaultfd_remove(struct vm_area_struct *vma,
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unsigned long start,
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unsigned long end);
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extern int userfaultfd_unmap_prep(struct mm_struct *mm, unsigned long start,
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unsigned long end, struct list_head *uf);
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extern void userfaultfd_unmap_complete(struct mm_struct *mm,
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struct list_head *uf);
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#else /* CONFIG_USERFAULTFD */
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/* mm helpers */
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static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
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unsigned long reason)
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{
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return VM_FAULT_SIGBUS;
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}
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static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
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struct vm_userfaultfd_ctx vm_ctx)
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{
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return true;
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}
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static inline bool userfaultfd_missing(struct vm_area_struct *vma)
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{
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return false;
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}
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static inline bool userfaultfd_wp(struct vm_area_struct *vma)
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{
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return false;
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}
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static inline bool userfaultfd_minor(struct vm_area_struct *vma)
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{
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return false;
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}
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static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
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pte_t pte)
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{
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return false;
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}
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static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
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pmd_t pmd)
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{
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return false;
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}
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static inline bool userfaultfd_armed(struct vm_area_struct *vma)
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{
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return false;
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}
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static inline int dup_userfaultfd(struct vm_area_struct *vma,
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struct list_head *l)
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{
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return 0;
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}
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static inline void dup_userfaultfd_complete(struct list_head *l)
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{
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}
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static inline void mremap_userfaultfd_prep(struct vm_area_struct *vma,
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struct vm_userfaultfd_ctx *ctx)
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{
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}
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static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx,
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unsigned long from,
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unsigned long to,
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unsigned long len)
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{
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}
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static inline bool userfaultfd_remove(struct vm_area_struct *vma,
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unsigned long start,
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unsigned long end)
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{
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return true;
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}
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static inline int userfaultfd_unmap_prep(struct mm_struct *mm,
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unsigned long start, unsigned long end,
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struct list_head *uf)
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{
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return 0;
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}
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static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
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struct list_head *uf)
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{
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}
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static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
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{
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return false;
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}
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#endif /* CONFIG_USERFAULTFD */
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static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
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{
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#ifdef CONFIG_PTE_MARKER_UFFD_WP
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return is_pte_marker_entry(entry) &&
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(pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
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#else
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return false;
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#endif
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}
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static inline bool pte_marker_uffd_wp(pte_t pte)
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{
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#ifdef CONFIG_PTE_MARKER_UFFD_WP
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swp_entry_t entry;
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if (!is_swap_pte(pte))
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return false;
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entry = pte_to_swp_entry(pte);
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return pte_marker_entry_uffd_wp(entry);
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#else
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return false;
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#endif
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}
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/*
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* Returns true if this is a swap pte and was uffd-wp wr-protected in either
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* forms (pte marker or a normal swap pte), false otherwise.
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*/
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static inline bool pte_swp_uffd_wp_any(pte_t pte)
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{
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#ifdef CONFIG_PTE_MARKER_UFFD_WP
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if (!is_swap_pte(pte))
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return false;
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if (pte_swp_uffd_wp(pte))
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return true;
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if (pte_marker_uffd_wp(pte))
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return true;
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#endif
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return false;
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}
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#endif /* _LINUX_USERFAULTFD_K_H */
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