4 * Copyright (C) 2015 Red Hat, Inc.
6 * This work is licensed under the terms of the GNU GPL, version 2. See
7 * the COPYING file in the top-level directory.
11 #include <linux/pagemap.h>
12 #include <linux/rmap.h>
13 #include <linux/swap.h>
14 #include <linux/swapops.h>
15 #include <linux/userfaultfd_k.h>
16 #include <linux/mmu_notifier.h>
17 #include <asm/tlbflush.h>
20 static int mcopy_atomic_pte(struct mm_struct *dst_mm,
22 struct vm_area_struct *dst_vma,
23 unsigned long dst_addr,
24 unsigned long src_addr)
26 struct mem_cgroup *memcg;
27 pte_t _dst_pte, *dst_pte;
34 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
38 page_kaddr = kmap(page);
40 if (copy_from_user(page_kaddr, (const void __user *) src_addr,
42 goto out_kunmap_release;
46 * The memory barrier inside __SetPageUptodate makes sure that
47 * preceeding stores to the page contents become visible before
48 * the set_pte_at() write.
50 __SetPageUptodate(page);
53 if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg))
56 _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
57 if (dst_vma->vm_flags & VM_WRITE)
58 _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
61 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
62 if (!pte_none(*dst_pte))
63 goto out_release_uncharge_unlock;
65 inc_mm_counter(dst_mm, MM_ANONPAGES);
66 page_add_new_anon_rmap(page, dst_vma, dst_addr);
67 mem_cgroup_commit_charge(page, memcg, false);
68 lru_cache_add_active_or_unevictable(page, dst_vma);
70 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
72 /* No need to invalidate - it was non-present before */
73 update_mmu_cache(dst_vma, dst_addr, dst_pte);
75 pte_unmap_unlock(dst_pte, ptl);
79 out_release_uncharge_unlock:
80 pte_unmap_unlock(dst_pte, ptl);
81 mem_cgroup_cancel_charge(page, memcg);
83 page_cache_release(page);
90 static int mfill_zeropage_pte(struct mm_struct *dst_mm,
92 struct vm_area_struct *dst_vma,
93 unsigned long dst_addr)
95 pte_t _dst_pte, *dst_pte;
99 _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
100 dst_vma->vm_page_prot));
102 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
103 if (!pte_none(*dst_pte))
105 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
106 /* No need to invalidate - it was non-present before */
107 update_mmu_cache(dst_vma, dst_addr, dst_pte);
110 pte_unmap_unlock(dst_pte, ptl);
114 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
120 pgd = pgd_offset(mm, address);
121 pud = pud_alloc(mm, pgd, address);
124 * Note that we didn't run this because the pmd was
125 * missing, the *pmd may be already established and in
126 * turn it may also be a trans_huge_pmd.
128 pmd = pmd_alloc(mm, pud, address);
132 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
133 unsigned long dst_start,
134 unsigned long src_start,
138 struct vm_area_struct *dst_vma;
141 unsigned long src_addr, dst_addr;
145 * Sanitize the command parameters:
147 BUG_ON(dst_start & ~PAGE_MASK);
148 BUG_ON(len & ~PAGE_MASK);
150 /* Does the address range wrap, or is the span zero-sized? */
151 BUG_ON(src_start + len <= src_start);
152 BUG_ON(dst_start + len <= dst_start);
154 down_read(&dst_mm->mmap_sem);
157 * Make sure the vma is not shared, that the dst range is
158 * both valid and fully within a single existing vma.
161 dst_vma = find_vma(dst_mm, dst_start);
162 if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
164 if (dst_start < dst_vma->vm_start ||
165 dst_start + len > dst_vma->vm_end)
169 * Be strict and only allow __mcopy_atomic on userfaultfd
170 * registered ranges to prevent userland errors going
171 * unnoticed. As far as the VM consistency is concerned, it
172 * would be perfectly safe to remove this check, but there's
173 * no useful usage for __mcopy_atomic ouside of userfaultfd
174 * registered ranges. This is after all why these are ioctls
175 * belonging to the userfaultfd and not syscalls.
177 if (!dst_vma->vm_userfaultfd_ctx.ctx)
181 * FIXME: only allow copying on anonymous vmas, tmpfs should
188 * Ensure the dst_vma has a anon_vma or this page
189 * would get a NULL anon_vma when moved in the
193 if (unlikely(anon_vma_prepare(dst_vma)))
196 for (src_addr = src_start, dst_addr = dst_start;
197 src_addr < src_start + len; ) {
199 BUG_ON(dst_addr >= dst_start + len);
200 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
201 if (unlikely(!dst_pmd)) {
206 dst_pmdval = pmd_read_atomic(dst_pmd);
208 * If the dst_pmd is mapped as THP don't
209 * override it and just be strict.
211 if (unlikely(pmd_trans_huge(dst_pmdval))) {
215 if (unlikely(pmd_none(dst_pmdval)) &&
216 unlikely(__pte_alloc(dst_mm, dst_vma, dst_pmd,
221 /* If an huge pmd materialized from under us fail */
222 if (unlikely(pmd_trans_huge(*dst_pmd))) {
227 BUG_ON(pmd_none(*dst_pmd));
228 BUG_ON(pmd_trans_huge(*dst_pmd));
231 err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
234 err = mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma,
240 dst_addr += PAGE_SIZE;
241 src_addr += PAGE_SIZE;
244 if (fatal_signal_pending(current))
252 up_read(&dst_mm->mmap_sem);
255 BUG_ON(!copied && !err);
256 return copied ? copied : err;
259 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
260 unsigned long src_start, unsigned long len)
262 return __mcopy_atomic(dst_mm, dst_start, src_start, len, false);
265 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
268 return __mcopy_atomic(dst_mm, start, 0, len, true);