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,
27 struct mem_cgroup *memcg;
28 pte_t _dst_pte, *dst_pte;
36 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
40 page_kaddr = kmap_atomic(page);
41 ret = copy_from_user(page_kaddr,
42 (const void __user *) src_addr,
44 kunmap_atomic(page_kaddr);
46 /* fallback to copy_from_user outside mmap_sem */
50 /* don't free the page */
59 * The memory barrier inside __SetPageUptodate makes sure that
60 * preceeding stores to the page contents become visible before
61 * the set_pte_at() write.
63 __SetPageUptodate(page);
66 if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false))
69 _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
70 if (dst_vma->vm_flags & VM_WRITE)
71 _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
74 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
75 if (!pte_none(*dst_pte))
76 goto out_release_uncharge_unlock;
78 inc_mm_counter(dst_mm, MM_ANONPAGES);
79 page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
80 mem_cgroup_commit_charge(page, memcg, false, false);
81 lru_cache_add_active_or_unevictable(page, dst_vma);
83 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
85 /* No need to invalidate - it was non-present before */
86 update_mmu_cache(dst_vma, dst_addr, dst_pte);
88 pte_unmap_unlock(dst_pte, ptl);
92 out_release_uncharge_unlock:
93 pte_unmap_unlock(dst_pte, ptl);
94 mem_cgroup_cancel_charge(page, memcg, false);
96 page_cache_release(page);
100 static int mfill_zeropage_pte(struct mm_struct *dst_mm,
102 struct vm_area_struct *dst_vma,
103 unsigned long dst_addr)
105 pte_t _dst_pte, *dst_pte;
109 _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
110 dst_vma->vm_page_prot));
112 dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
113 if (!pte_none(*dst_pte))
115 set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
116 /* No need to invalidate - it was non-present before */
117 update_mmu_cache(dst_vma, dst_addr, dst_pte);
120 pte_unmap_unlock(dst_pte, ptl);
124 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
130 pgd = pgd_offset(mm, address);
131 pud = pud_alloc(mm, pgd, address);
134 * Note that we didn't run this because the pmd was
135 * missing, the *pmd may be already established and in
136 * turn it may also be a trans_huge_pmd.
138 pmd = pmd_alloc(mm, pud, address);
142 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
143 unsigned long dst_start,
144 unsigned long src_start,
148 struct vm_area_struct *dst_vma;
151 unsigned long src_addr, dst_addr;
156 * Sanitize the command parameters:
158 BUG_ON(dst_start & ~PAGE_MASK);
159 BUG_ON(len & ~PAGE_MASK);
161 /* Does the address range wrap, or is the span zero-sized? */
162 BUG_ON(src_start + len <= src_start);
163 BUG_ON(dst_start + len <= dst_start);
165 src_addr = src_start;
166 dst_addr = dst_start;
170 down_read(&dst_mm->mmap_sem);
173 * Make sure the vma is not shared, that the dst range is
174 * both valid and fully within a single existing vma.
177 dst_vma = find_vma(dst_mm, dst_start);
178 if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
180 if (dst_start < dst_vma->vm_start ||
181 dst_start + len > dst_vma->vm_end)
185 * Be strict and only allow __mcopy_atomic on userfaultfd
186 * registered ranges to prevent userland errors going
187 * unnoticed. As far as the VM consistency is concerned, it
188 * would be perfectly safe to remove this check, but there's
189 * no useful usage for __mcopy_atomic ouside of userfaultfd
190 * registered ranges. This is after all why these are ioctls
191 * belonging to the userfaultfd and not syscalls.
193 if (!dst_vma->vm_userfaultfd_ctx.ctx)
197 * FIXME: only allow copying on anonymous vmas, tmpfs should
204 * Ensure the dst_vma has a anon_vma or this page
205 * would get a NULL anon_vma when moved in the
209 if (unlikely(anon_vma_prepare(dst_vma)))
212 while (src_addr < src_start + len) {
215 BUG_ON(dst_addr >= dst_start + len);
217 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
218 if (unlikely(!dst_pmd)) {
223 dst_pmdval = pmd_read_atomic(dst_pmd);
225 * If the dst_pmd is mapped as THP don't
226 * override it and just be strict.
228 if (unlikely(pmd_trans_huge(dst_pmdval))) {
232 if (unlikely(pmd_none(dst_pmdval)) &&
233 unlikely(__pte_alloc(dst_mm, dst_vma, dst_pmd,
238 /* If an huge pmd materialized from under us fail */
239 if (unlikely(pmd_trans_huge(*dst_pmd))) {
244 BUG_ON(pmd_none(*dst_pmd));
245 BUG_ON(pmd_trans_huge(*dst_pmd));
248 err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
249 dst_addr, src_addr, &page);
251 err = mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma,
256 if (unlikely(err == -EFAULT)) {
259 up_read(&dst_mm->mmap_sem);
262 page_kaddr = kmap(page);
263 err = copy_from_user(page_kaddr,
264 (const void __user *) src_addr,
276 dst_addr += PAGE_SIZE;
277 src_addr += PAGE_SIZE;
280 if (fatal_signal_pending(current))
288 up_read(&dst_mm->mmap_sem);
291 page_cache_release(page);
294 BUG_ON(!copied && !err);
295 return copied ? copied : err;
298 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
299 unsigned long src_start, unsigned long len)
301 return __mcopy_atomic(dst_mm, dst_start, src_start, len, false);
304 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
307 return __mcopy_atomic(dst_mm, start, 0, len, true);