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726 lines
18 KiB
726 lines
18 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* mm/userfaultfd.c |
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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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#include <linux/mm.h> |
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#include <linux/sched/signal.h> |
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#include <linux/pagemap.h> |
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#include <linux/rmap.h> |
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#include <linux/swap.h> |
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#include <linux/swapops.h> |
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#include <linux/userfaultfd_k.h> |
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#include <linux/mmu_notifier.h> |
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#include <linux/hugetlb.h> |
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#include <linux/shmem_fs.h> |
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#include <asm/tlbflush.h> |
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#include "internal.h" |
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static __always_inline |
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struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, |
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unsigned long dst_start, |
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unsigned long len) |
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{ |
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/* |
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* Make sure that the dst range is both valid and fully within a |
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* single existing vma. |
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*/ |
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struct vm_area_struct *dst_vma; |
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|
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dst_vma = find_vma(dst_mm, dst_start); |
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if (!dst_vma) |
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return NULL; |
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if (dst_start < dst_vma->vm_start || |
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dst_start + len > dst_vma->vm_end) |
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return NULL; |
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/* |
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* Check the vma is registered in uffd, this is required to |
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* enforce the VM_MAYWRITE check done at uffd registration |
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* time. |
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*/ |
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if (!dst_vma->vm_userfaultfd_ctx.ctx) |
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return NULL; |
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return dst_vma; |
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} |
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|
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/* |
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* Install PTEs, to map dst_addr (within dst_vma) to page. |
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* |
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* This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem |
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* and anon, and for both shared and private VMAs. |
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*/ |
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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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{ |
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int ret; |
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pte_t _dst_pte, *dst_pte; |
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bool writable = dst_vma->vm_flags & VM_WRITE; |
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bool vm_shared = dst_vma->vm_flags & VM_SHARED; |
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bool page_in_cache = page->mapping; |
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spinlock_t *ptl; |
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struct inode *inode; |
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pgoff_t offset, max_off; |
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_dst_pte = mk_pte(page, dst_vma->vm_page_prot); |
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if (page_in_cache && !vm_shared) |
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writable = false; |
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if (writable || !page_in_cache) |
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_dst_pte = pte_mkdirty(_dst_pte); |
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if (writable) { |
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if (wp_copy) |
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_dst_pte = pte_mkuffd_wp(_dst_pte); |
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else |
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_dst_pte = pte_mkwrite(_dst_pte); |
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} |
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dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); |
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if (vma_is_shmem(dst_vma)) { |
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/* serialize against truncate with the page table lock */ |
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inode = dst_vma->vm_file->f_inode; |
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offset = linear_page_index(dst_vma, dst_addr); |
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max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
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ret = -EFAULT; |
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if (unlikely(offset >= max_off)) |
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goto out_unlock; |
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} |
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ret = -EEXIST; |
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if (!pte_none(*dst_pte)) |
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goto out_unlock; |
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if (page_in_cache) |
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page_add_file_rmap(page, false); |
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else |
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page_add_new_anon_rmap(page, dst_vma, dst_addr, false); |
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|
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/* |
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* Must happen after rmap, as mm_counter() checks mapping (via |
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* PageAnon()), which is set by __page_set_anon_rmap(). |
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*/ |
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inc_mm_counter(dst_mm, mm_counter(page)); |
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if (newly_allocated) |
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lru_cache_add_inactive_or_unevictable(page, dst_vma); |
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set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
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|
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/* No need to invalidate - it was non-present before */ |
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update_mmu_cache(dst_vma, dst_addr, dst_pte); |
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ret = 0; |
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out_unlock: |
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pte_unmap_unlock(dst_pte, ptl); |
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return ret; |
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} |
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static int mcopy_atomic_pte(struct mm_struct *dst_mm, |
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pmd_t *dst_pmd, |
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struct vm_area_struct *dst_vma, |
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unsigned long dst_addr, |
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unsigned long src_addr, |
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struct page **pagep, |
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bool wp_copy) |
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{ |
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void *page_kaddr; |
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int ret; |
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struct page *page; |
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if (!*pagep) { |
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ret = -ENOMEM; |
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page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr); |
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if (!page) |
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goto out; |
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page_kaddr = kmap_atomic(page); |
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ret = copy_from_user(page_kaddr, |
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(const void __user *) src_addr, |
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PAGE_SIZE); |
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kunmap_atomic(page_kaddr); |
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|
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/* fallback to copy_from_user outside mmap_lock */ |
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if (unlikely(ret)) { |
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ret = -ENOENT; |
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*pagep = page; |
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/* don't free the page */ |
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goto out; |
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} |
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} else { |
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page = *pagep; |
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*pagep = NULL; |
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} |
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/* |
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* The memory barrier inside __SetPageUptodate makes sure that |
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* preceding stores to the page contents become visible before |
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* the set_pte_at() write. |
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*/ |
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__SetPageUptodate(page); |
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ret = -ENOMEM; |
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if (mem_cgroup_charge(page, dst_mm, GFP_KERNEL)) |
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goto out_release; |
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ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
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page, true, wp_copy); |
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if (ret) |
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goto out_release; |
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out: |
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return ret; |
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out_release: |
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put_page(page); |
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goto out; |
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} |
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static int mfill_zeropage_pte(struct mm_struct *dst_mm, |
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pmd_t *dst_pmd, |
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struct vm_area_struct *dst_vma, |
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unsigned long dst_addr) |
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{ |
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pte_t _dst_pte, *dst_pte; |
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spinlock_t *ptl; |
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int ret; |
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pgoff_t offset, max_off; |
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struct inode *inode; |
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_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), |
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dst_vma->vm_page_prot)); |
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dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); |
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if (dst_vma->vm_file) { |
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/* the shmem MAP_PRIVATE case requires checking the i_size */ |
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inode = dst_vma->vm_file->f_inode; |
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offset = linear_page_index(dst_vma, dst_addr); |
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max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
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ret = -EFAULT; |
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if (unlikely(offset >= max_off)) |
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goto out_unlock; |
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} |
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ret = -EEXIST; |
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if (!pte_none(*dst_pte)) |
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goto out_unlock; |
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set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
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/* No need to invalidate - it was non-present before */ |
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update_mmu_cache(dst_vma, dst_addr, dst_pte); |
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ret = 0; |
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out_unlock: |
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pte_unmap_unlock(dst_pte, ptl); |
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return ret; |
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} |
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|
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/* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */ |
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static int mcontinue_atomic_pte(struct mm_struct *dst_mm, |
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pmd_t *dst_pmd, |
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struct vm_area_struct *dst_vma, |
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unsigned long dst_addr, |
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bool wp_copy) |
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{ |
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struct inode *inode = file_inode(dst_vma->vm_file); |
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pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); |
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struct page *page; |
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int ret; |
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ret = shmem_getpage(inode, pgoff, &page, SGP_READ); |
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if (ret) |
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goto out; |
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if (!page) { |
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ret = -EFAULT; |
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goto out; |
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} |
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ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
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page, false, wp_copy); |
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if (ret) |
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goto out_release; |
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unlock_page(page); |
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ret = 0; |
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out: |
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return ret; |
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out_release: |
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unlock_page(page); |
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put_page(page); |
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goto out; |
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} |
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static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) |
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{ |
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pgd_t *pgd; |
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p4d_t *p4d; |
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pud_t *pud; |
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pgd = pgd_offset(mm, address); |
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p4d = p4d_alloc(mm, pgd, address); |
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if (!p4d) |
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return NULL; |
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pud = pud_alloc(mm, p4d, address); |
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if (!pud) |
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return NULL; |
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/* |
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* Note that we didn't run this because the pmd was |
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* missing, the *pmd may be already established and in |
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* turn it may also be a trans_huge_pmd. |
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*/ |
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return pmd_alloc(mm, pud, address); |
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} |
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#ifdef CONFIG_HUGETLB_PAGE |
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/* |
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* __mcopy_atomic processing for HUGETLB vmas. Note that this routine is |
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* called with mmap_lock held, it will release mmap_lock before returning. |
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*/ |
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static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, |
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struct vm_area_struct *dst_vma, |
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unsigned long dst_start, |
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unsigned long src_start, |
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unsigned long len, |
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enum mcopy_atomic_mode mode) |
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{ |
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int vm_shared = dst_vma->vm_flags & VM_SHARED; |
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ssize_t err; |
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pte_t *dst_pte; |
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unsigned long src_addr, dst_addr; |
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long copied; |
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struct page *page; |
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unsigned long vma_hpagesize; |
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pgoff_t idx; |
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u32 hash; |
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struct address_space *mapping; |
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/* |
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* There is no default zero huge page for all huge page sizes as |
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* supported by hugetlb. A PMD_SIZE huge pages may exist as used |
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* by THP. Since we can not reliably insert a zero page, this |
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* feature is not supported. |
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*/ |
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if (mode == MCOPY_ATOMIC_ZEROPAGE) { |
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mmap_read_unlock(dst_mm); |
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return -EINVAL; |
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} |
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src_addr = src_start; |
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dst_addr = dst_start; |
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copied = 0; |
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page = NULL; |
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vma_hpagesize = vma_kernel_pagesize(dst_vma); |
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/* |
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* Validate alignment based on huge page size |
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*/ |
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err = -EINVAL; |
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if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1)) |
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goto out_unlock; |
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retry: |
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/* |
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* On routine entry dst_vma is set. If we had to drop mmap_lock and |
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* retry, dst_vma will be set to NULL and we must lookup again. |
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*/ |
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if (!dst_vma) { |
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err = -ENOENT; |
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dst_vma = find_dst_vma(dst_mm, dst_start, len); |
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if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) |
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goto out_unlock; |
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err = -EINVAL; |
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if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) |
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goto out_unlock; |
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vm_shared = dst_vma->vm_flags & VM_SHARED; |
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} |
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/* |
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* If not shared, ensure the dst_vma has a anon_vma. |
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*/ |
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err = -ENOMEM; |
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if (!vm_shared) { |
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if (unlikely(anon_vma_prepare(dst_vma))) |
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goto out_unlock; |
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} |
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while (src_addr < src_start + len) { |
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BUG_ON(dst_addr >= dst_start + len); |
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/* |
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* Serialize via i_mmap_rwsem and hugetlb_fault_mutex. |
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* i_mmap_rwsem ensures the dst_pte remains valid even |
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* in the case of shared pmds. fault mutex prevents |
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* races with other faulting threads. |
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*/ |
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mapping = dst_vma->vm_file->f_mapping; |
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i_mmap_lock_read(mapping); |
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idx = linear_page_index(dst_vma, dst_addr); |
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hash = hugetlb_fault_mutex_hash(mapping, idx); |
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mutex_lock(&hugetlb_fault_mutex_table[hash]); |
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err = -ENOMEM; |
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dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize); |
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if (!dst_pte) { |
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mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
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i_mmap_unlock_read(mapping); |
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goto out_unlock; |
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} |
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if (mode != MCOPY_ATOMIC_CONTINUE && |
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!huge_pte_none(huge_ptep_get(dst_pte))) { |
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err = -EEXIST; |
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mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
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i_mmap_unlock_read(mapping); |
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goto out_unlock; |
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} |
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err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, |
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dst_addr, src_addr, mode, &page); |
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|
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mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
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i_mmap_unlock_read(mapping); |
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cond_resched(); |
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if (unlikely(err == -ENOENT)) { |
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mmap_read_unlock(dst_mm); |
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BUG_ON(!page); |
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err = copy_huge_page_from_user(page, |
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(const void __user *)src_addr, |
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vma_hpagesize / PAGE_SIZE, |
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true); |
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if (unlikely(err)) { |
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err = -EFAULT; |
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goto out; |
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} |
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mmap_read_lock(dst_mm); |
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dst_vma = NULL; |
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goto retry; |
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} else |
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BUG_ON(page); |
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if (!err) { |
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dst_addr += vma_hpagesize; |
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src_addr += vma_hpagesize; |
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copied += vma_hpagesize; |
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|
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if (fatal_signal_pending(current)) |
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err = -EINTR; |
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} |
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if (err) |
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break; |
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} |
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out_unlock: |
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mmap_read_unlock(dst_mm); |
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out: |
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if (page) |
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put_page(page); |
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BUG_ON(copied < 0); |
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BUG_ON(err > 0); |
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BUG_ON(!copied && !err); |
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return copied ? copied : err; |
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} |
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#else /* !CONFIG_HUGETLB_PAGE */ |
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/* fail at build time if gcc attempts to use this */ |
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extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, |
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struct vm_area_struct *dst_vma, |
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unsigned long dst_start, |
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unsigned long src_start, |
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unsigned long len, |
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enum mcopy_atomic_mode mode); |
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#endif /* CONFIG_HUGETLB_PAGE */ |
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|
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static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, |
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pmd_t *dst_pmd, |
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struct vm_area_struct *dst_vma, |
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unsigned long dst_addr, |
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unsigned long src_addr, |
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struct page **page, |
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enum mcopy_atomic_mode mode, |
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bool wp_copy) |
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{ |
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ssize_t err; |
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|
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if (mode == MCOPY_ATOMIC_CONTINUE) { |
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return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
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wp_copy); |
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} |
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|
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/* |
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* The normal page fault path for a shmem will invoke the |
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* fault, fill the hole in the file and COW it right away. The |
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* result generates plain anonymous memory. So when we are |
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* asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll |
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* generate anonymous memory directly without actually filling |
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* the hole. For the MAP_PRIVATE case the robustness check |
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* only happens in the pagetable (to verify it's still none) |
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* and not in the radix tree. |
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*/ |
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if (!(dst_vma->vm_flags & VM_SHARED)) { |
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if (mode == MCOPY_ATOMIC_NORMAL) |
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err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, |
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dst_addr, src_addr, page, |
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wp_copy); |
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else |
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err = mfill_zeropage_pte(dst_mm, dst_pmd, |
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dst_vma, dst_addr); |
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} else { |
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VM_WARN_ON_ONCE(wp_copy); |
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err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, |
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dst_addr, src_addr, |
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mode != MCOPY_ATOMIC_NORMAL, |
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page); |
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} |
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|
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return err; |
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} |
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|
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static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, |
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unsigned long dst_start, |
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unsigned long src_start, |
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unsigned long len, |
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enum mcopy_atomic_mode mcopy_mode, |
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atomic_t *mmap_changing, |
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__u64 mode) |
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{ |
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struct vm_area_struct *dst_vma; |
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ssize_t err; |
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pmd_t *dst_pmd; |
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unsigned long src_addr, dst_addr; |
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long copied; |
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struct page *page; |
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bool wp_copy; |
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|
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/* |
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* Sanitize the command parameters: |
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*/ |
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BUG_ON(dst_start & ~PAGE_MASK); |
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BUG_ON(len & ~PAGE_MASK); |
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|
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/* Does the address range wrap, or is the span zero-sized? */ |
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BUG_ON(src_start + len <= src_start); |
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BUG_ON(dst_start + len <= dst_start); |
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|
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src_addr = src_start; |
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dst_addr = dst_start; |
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copied = 0; |
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page = NULL; |
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retry: |
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mmap_read_lock(dst_mm); |
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|
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/* |
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* If memory mappings are changing because of non-cooperative |
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* operation (e.g. mremap) running in parallel, bail out and |
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* request the user to retry later |
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*/ |
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err = -EAGAIN; |
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if (mmap_changing && atomic_read(mmap_changing)) |
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goto out_unlock; |
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|
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/* |
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* Make sure the vma is not shared, that the dst range is |
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* both valid and fully within a single existing vma. |
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*/ |
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err = -ENOENT; |
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dst_vma = find_dst_vma(dst_mm, dst_start, len); |
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if (!dst_vma) |
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goto out_unlock; |
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|
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err = -EINVAL; |
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/* |
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* shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but |
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* it will overwrite vm_ops, so vma_is_anonymous must return false. |
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*/ |
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if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) && |
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dst_vma->vm_flags & VM_SHARED)) |
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goto out_unlock; |
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|
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/* |
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* validate 'mode' now that we know the dst_vma: don't allow |
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* a wrprotect copy if the userfaultfd didn't register as WP. |
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*/ |
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wp_copy = mode & UFFDIO_COPY_MODE_WP; |
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if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP)) |
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goto out_unlock; |
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|
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/* |
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* If this is a HUGETLB vma, pass off to appropriate routine |
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*/ |
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if (is_vm_hugetlb_page(dst_vma)) |
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return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start, |
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src_start, len, mcopy_mode); |
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|
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if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) |
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goto out_unlock; |
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if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE) |
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goto out_unlock; |
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|
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/* |
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* Ensure the dst_vma has a anon_vma or this page |
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* would get a NULL anon_vma when moved in the |
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* dst_vma. |
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*/ |
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err = -ENOMEM; |
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if (!(dst_vma->vm_flags & VM_SHARED) && |
|
unlikely(anon_vma_prepare(dst_vma))) |
|
goto out_unlock; |
|
|
|
while (src_addr < src_start + len) { |
|
pmd_t dst_pmdval; |
|
|
|
BUG_ON(dst_addr >= dst_start + len); |
|
|
|
dst_pmd = mm_alloc_pmd(dst_mm, dst_addr); |
|
if (unlikely(!dst_pmd)) { |
|
err = -ENOMEM; |
|
break; |
|
} |
|
|
|
dst_pmdval = pmd_read_atomic(dst_pmd); |
|
/* |
|
* If the dst_pmd is mapped as THP don't |
|
* override it and just be strict. |
|
*/ |
|
if (unlikely(pmd_trans_huge(dst_pmdval))) { |
|
err = -EEXIST; |
|
break; |
|
} |
|
if (unlikely(pmd_none(dst_pmdval)) && |
|
unlikely(__pte_alloc(dst_mm, dst_pmd))) { |
|
err = -ENOMEM; |
|
break; |
|
} |
|
/* If an huge pmd materialized from under us fail */ |
|
if (unlikely(pmd_trans_huge(*dst_pmd))) { |
|
err = -EFAULT; |
|
break; |
|
} |
|
|
|
BUG_ON(pmd_none(*dst_pmd)); |
|
BUG_ON(pmd_trans_huge(*dst_pmd)); |
|
|
|
err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
|
src_addr, &page, mcopy_mode, wp_copy); |
|
cond_resched(); |
|
|
|
if (unlikely(err == -ENOENT)) { |
|
void *page_kaddr; |
|
|
|
mmap_read_unlock(dst_mm); |
|
BUG_ON(!page); |
|
|
|
page_kaddr = kmap(page); |
|
err = copy_from_user(page_kaddr, |
|
(const void __user *) src_addr, |
|
PAGE_SIZE); |
|
kunmap(page); |
|
if (unlikely(err)) { |
|
err = -EFAULT; |
|
goto out; |
|
} |
|
goto retry; |
|
} else |
|
BUG_ON(page); |
|
|
|
if (!err) { |
|
dst_addr += PAGE_SIZE; |
|
src_addr += PAGE_SIZE; |
|
copied += PAGE_SIZE; |
|
|
|
if (fatal_signal_pending(current)) |
|
err = -EINTR; |
|
} |
|
if (err) |
|
break; |
|
} |
|
|
|
out_unlock: |
|
mmap_read_unlock(dst_mm); |
|
out: |
|
if (page) |
|
put_page(page); |
|
BUG_ON(copied < 0); |
|
BUG_ON(err > 0); |
|
BUG_ON(!copied && !err); |
|
return copied ? copied : err; |
|
} |
|
|
|
ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, |
|
unsigned long src_start, unsigned long len, |
|
atomic_t *mmap_changing, __u64 mode) |
|
{ |
|
return __mcopy_atomic(dst_mm, dst_start, src_start, len, |
|
MCOPY_ATOMIC_NORMAL, mmap_changing, mode); |
|
} |
|
|
|
ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, |
|
unsigned long len, atomic_t *mmap_changing) |
|
{ |
|
return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE, |
|
mmap_changing, 0); |
|
} |
|
|
|
ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start, |
|
unsigned long len, atomic_t *mmap_changing) |
|
{ |
|
return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE, |
|
mmap_changing, 0); |
|
} |
|
|
|
int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, |
|
unsigned long len, bool enable_wp, |
|
atomic_t *mmap_changing) |
|
{ |
|
struct vm_area_struct *dst_vma; |
|
pgprot_t newprot; |
|
int err; |
|
|
|
/* |
|
* Sanitize the command parameters: |
|
*/ |
|
BUG_ON(start & ~PAGE_MASK); |
|
BUG_ON(len & ~PAGE_MASK); |
|
|
|
/* Does the address range wrap, or is the span zero-sized? */ |
|
BUG_ON(start + len <= start); |
|
|
|
mmap_read_lock(dst_mm); |
|
|
|
/* |
|
* If memory mappings are changing because of non-cooperative |
|
* operation (e.g. mremap) running in parallel, bail out and |
|
* request the user to retry later |
|
*/ |
|
err = -EAGAIN; |
|
if (mmap_changing && atomic_read(mmap_changing)) |
|
goto out_unlock; |
|
|
|
err = -ENOENT; |
|
dst_vma = find_dst_vma(dst_mm, start, len); |
|
/* |
|
* Make sure the vma is not shared, that the dst range is |
|
* both valid and fully within a single existing vma. |
|
*/ |
|
if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) |
|
goto out_unlock; |
|
if (!userfaultfd_wp(dst_vma)) |
|
goto out_unlock; |
|
if (!vma_is_anonymous(dst_vma)) |
|
goto out_unlock; |
|
|
|
if (enable_wp) |
|
newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE)); |
|
else |
|
newprot = vm_get_page_prot(dst_vma->vm_flags); |
|
|
|
change_protection(dst_vma, start, start + len, newprot, |
|
enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE); |
|
|
|
err = 0; |
|
out_unlock: |
|
mmap_read_unlock(dst_mm); |
|
return err; |
|
}
|
|
|