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mm/userfaultfd.c
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// SPDX-License-Identifier: GPL-2.0-only |
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/* * mm/userfaultfd.c * * Copyright (C) 2015 Red Hat, Inc. |
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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> #include <linux/rmap.h> #include <linux/swap.h> #include <linux/swapops.h> #include <linux/userfaultfd_k.h> #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> #include "internal.h" static int mcopy_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, struct vm_area_struct *dst_vma, unsigned long dst_addr, |
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unsigned long src_addr, struct page **pagep) |
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{ struct mem_cgroup *memcg; pte_t _dst_pte, *dst_pte; spinlock_t *ptl; |
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void *page_kaddr; int ret; |
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struct page *page; |
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pgoff_t offset, max_off; struct inode *inode; |
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|
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if (!*pagep) { ret = -ENOMEM; page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr); if (!page) goto out; page_kaddr = kmap_atomic(page); ret = copy_from_user(page_kaddr, (const void __user *) src_addr, PAGE_SIZE); kunmap_atomic(page_kaddr); /* fallback to copy_from_user outside mmap_sem */ if (unlikely(ret)) { |
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ret = -ENOENT; |
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*pagep = page; /* don't free the page */ goto out; } } else { page = *pagep; *pagep = NULL; } |
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/* * The memory barrier inside __SetPageUptodate makes sure that * preceeding stores to the page contents become visible before * the set_pte_at() write. */ __SetPageUptodate(page); ret = -ENOMEM; |
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if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false)) |
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goto out_release; _dst_pte = mk_pte(page, dst_vma->vm_page_prot); if (dst_vma->vm_flags & VM_WRITE) _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte)); |
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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) { /* the shmem MAP_PRIVATE case requires checking the i_size */ inode = dst_vma->vm_file->f_inode; offset = linear_page_index(dst_vma, dst_addr); max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); ret = -EFAULT; if (unlikely(offset >= max_off)) goto out_release_uncharge_unlock; } ret = -EEXIST; |
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if (!pte_none(*dst_pte)) goto out_release_uncharge_unlock; inc_mm_counter(dst_mm, MM_ANONPAGES); |
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page_add_new_anon_rmap(page, dst_vma, dst_addr, false); |
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mem_cgroup_commit_charge(page, memcg, false, false); |
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lru_cache_add_active_or_unevictable(page, dst_vma); set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); /* No need to invalidate - it was non-present before */ update_mmu_cache(dst_vma, dst_addr, dst_pte); pte_unmap_unlock(dst_pte, ptl); ret = 0; out: return ret; out_release_uncharge_unlock: pte_unmap_unlock(dst_pte, ptl); |
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mem_cgroup_cancel_charge(page, memcg, false); |
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out_release: |
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put_page(page); |
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goto out; |
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} static int mfill_zeropage_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, struct vm_area_struct *dst_vma, unsigned long dst_addr) { pte_t _dst_pte, *dst_pte; spinlock_t *ptl; int ret; |
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pgoff_t offset, max_off; struct inode *inode; |
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_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), 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) { /* the shmem MAP_PRIVATE case requires checking the i_size */ inode = dst_vma->vm_file->f_inode; offset = linear_page_index(dst_vma, dst_addr); max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); ret = -EFAULT; if (unlikely(offset >= max_off)) goto out_unlock; } ret = -EEXIST; |
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if (!pte_none(*dst_pte)) goto out_unlock; set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); /* No need to invalidate - it was non-present before */ update_mmu_cache(dst_vma, dst_addr, dst_pte); ret = 0; out_unlock: pte_unmap_unlock(dst_pte, ptl); return ret; } static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) { 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); if (!p4d) return NULL; pud = pud_alloc(mm, p4d, address); if (!pud) return NULL; /* * Note that we didn't run this because the pmd was * missing, the *pmd may be already established and in * turn it may also be a trans_huge_pmd. */ return pmd_alloc(mm, pud, address); |
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} |
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#ifdef CONFIG_HUGETLB_PAGE /* * __mcopy_atomic processing for HUGETLB vmas. Note that this routine is * called with mmap_sem held, it will release mmap_sem before returning. */ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma, unsigned long dst_start, unsigned long src_start, unsigned long len, bool zeropage) { |
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int vm_alloc_shared = dst_vma->vm_flags & VM_SHARED; int vm_shared = dst_vma->vm_flags & VM_SHARED; |
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ssize_t err; pte_t *dst_pte; unsigned long src_addr, dst_addr; long copied; struct page *page; struct hstate *h; unsigned long vma_hpagesize; pgoff_t idx; u32 hash; struct address_space *mapping; /* * There is no default zero huge page for all huge page sizes as * supported by hugetlb. A PMD_SIZE huge pages may exist as used * by THP. Since we can not reliably insert a zero page, this * feature is not supported. */ if (zeropage) { up_read(&dst_mm->mmap_sem); return -EINVAL; } src_addr = src_start; dst_addr = dst_start; copied = 0; page = NULL; vma_hpagesize = vma_kernel_pagesize(dst_vma); /* * Validate alignment based on huge page size */ err = -EINVAL; if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1)) goto out_unlock; retry: /* * On routine entry dst_vma is set. If we had to drop mmap_sem and * retry, dst_vma will be set to NULL and we must lookup again. */ if (!dst_vma) { |
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err = -ENOENT; |
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dst_vma = find_vma(dst_mm, dst_start); if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) goto out_unlock; |
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/* |
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* Check the vma is registered in uffd, this is * required to enforce the VM_MAYWRITE check done at * uffd registration time. |
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*/ |
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if (!dst_vma->vm_userfaultfd_ctx.ctx) goto out_unlock; |
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if (dst_start < dst_vma->vm_start || dst_start + len > dst_vma->vm_end) goto out_unlock; |
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|
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err = -EINVAL; if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) goto out_unlock; |
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vm_shared = dst_vma->vm_flags & VM_SHARED; |
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} if (WARN_ON(dst_addr & (vma_hpagesize - 1) || (len - copied) & (vma_hpagesize - 1))) goto out_unlock; /* |
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* If not shared, ensure the dst_vma has a anon_vma. |
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*/ err = -ENOMEM; |
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if (!vm_shared) { if (unlikely(anon_vma_prepare(dst_vma))) goto out_unlock; } |
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h = hstate_vma(dst_vma); while (src_addr < src_start + len) { pte_t dst_pteval; BUG_ON(dst_addr >= dst_start + len); VM_BUG_ON(dst_addr & ~huge_page_mask(h)); /* |
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* Serialize via hugetlb_fault_mutex |
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*/ |
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idx = linear_page_index(dst_vma, dst_addr); |
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mapping = dst_vma->vm_file->f_mapping; |
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hash = hugetlb_fault_mutex_hash(h, mapping, idx, dst_addr); |
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mutex_lock(&hugetlb_fault_mutex_table[hash]); err = -ENOMEM; dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h)); if (!dst_pte) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); goto out_unlock; } err = -EEXIST; dst_pteval = huge_ptep_get(dst_pte); if (!huge_pte_none(dst_pteval)) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); goto out_unlock; } err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, dst_addr, src_addr, &page); mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
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vm_alloc_shared = vm_shared; |
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cond_resched(); |
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if (unlikely(err == -ENOENT)) { |
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up_read(&dst_mm->mmap_sem); BUG_ON(!page); err = copy_huge_page_from_user(page, (const void __user *)src_addr, |
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pages_per_huge_page(h), true); |
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if (unlikely(err)) { err = -EFAULT; goto out; } down_read(&dst_mm->mmap_sem); dst_vma = NULL; goto retry; } else BUG_ON(page); if (!err) { dst_addr += vma_hpagesize; src_addr += vma_hpagesize; copied += vma_hpagesize; if (fatal_signal_pending(current)) err = -EINTR; } if (err) break; } out_unlock: up_read(&dst_mm->mmap_sem); out: |
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if (page) { /* * We encountered an error and are about to free a newly |
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* allocated huge page. * * Reservation handling is very subtle, and is different for * private and shared mappings. See the routine * restore_reserve_on_error for details. Unfortunately, we * can not call restore_reserve_on_error now as it would * require holding mmap_sem. * * If a reservation for the page existed in the reservation * map of a private mapping, the map was modified to indicate * the reservation was consumed when the page was allocated. * We clear the PagePrivate flag now so that the global |
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* reserve count will not be incremented in free_huge_page. * The reservation map will still indicate the reservation * was consumed and possibly prevent later page allocation. |
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* This is better than leaking a global reservation. If no * reservation existed, it is still safe to clear PagePrivate * as no adjustments to reservation counts were made during * allocation. * * The reservation map for shared mappings indicates which * pages have reservations. When a huge page is allocated * for an address with a reservation, no change is made to * the reserve map. In this case PagePrivate will be set * to indicate that the global reservation count should be * incremented when the page is freed. This is the desired * behavior. However, when a huge page is allocated for an * address without a reservation a reservation entry is added * to the reservation map, and PagePrivate will not be set. * When the page is freed, the global reserve count will NOT * be incremented and it will appear as though we have leaked * reserved page. In this case, set PagePrivate so that the * global reserve count will be incremented to match the * reservation map entry which was created. * * Note that vm_alloc_shared is based on the flags of the vma * for which the page was originally allocated. dst_vma could * be different or NULL on error. |
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*/ |
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if (vm_alloc_shared) SetPagePrivate(page); else ClearPagePrivate(page); |
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put_page(page); |
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} |
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BUG_ON(copied < 0); BUG_ON(err > 0); BUG_ON(!copied && !err); return copied ? copied : err; } #else /* !CONFIG_HUGETLB_PAGE */ /* fail at build time if gcc attempts to use this */ extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma, unsigned long dst_start, unsigned long src_start, unsigned long len, bool zeropage); #endif /* CONFIG_HUGETLB_PAGE */ |
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static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, struct vm_area_struct *dst_vma, unsigned long dst_addr, unsigned long src_addr, struct page **page, bool zeropage) { ssize_t err; |
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/* * The normal page fault path for a shmem will invoke the * fault, fill the hole in the file and COW it right away. The * result generates plain anonymous memory. So when we are * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll * generate anonymous memory directly without actually filling * the hole. For the MAP_PRIVATE case the robustness check * only happens in the pagetable (to verify it's still none) * and not in the radix tree. */ if (!(dst_vma->vm_flags & VM_SHARED)) { |
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if (!zeropage) err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, src_addr, page); else err = mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma, dst_addr); } else { |
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if (!zeropage) |
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err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, src_addr, page); |
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else err = shmem_mfill_zeropage_pte(dst_mm, dst_pmd, dst_vma, dst_addr); |
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} return err; } |
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static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, unsigned long src_start, unsigned long len, |
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bool zeropage, bool *mmap_changing) |
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{ struct vm_area_struct *dst_vma; ssize_t err; pmd_t *dst_pmd; unsigned long src_addr, dst_addr; |
b6ebaedb4 userfaultfd: avoi... |
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long copied; struct page *page; |
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/* * Sanitize the command parameters: */ BUG_ON(dst_start & ~PAGE_MASK); BUG_ON(len & ~PAGE_MASK); /* Does the address range wrap, or is the span zero-sized? */ BUG_ON(src_start + len <= src_start); BUG_ON(dst_start + len <= dst_start); |
b6ebaedb4 userfaultfd: avoi... |
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src_addr = src_start; dst_addr = dst_start; copied = 0; page = NULL; retry: |
c1a4de99f userfaultfd: mcop... |
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down_read(&dst_mm->mmap_sem); /* |
df2cc96e7 userfaultfd: prev... |
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* 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 && READ_ONCE(*mmap_changing)) goto out_unlock; /* |
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* Make sure the vma is not shared, that the dst range is * both valid and fully within a single existing vma. */ |
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err = -ENOENT; |
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dst_vma = find_vma(dst_mm, dst_start); |
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if (!dst_vma) goto out_unlock; |
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/* |
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* Check the vma is registered in uffd, this is required to * enforce the VM_MAYWRITE check done at uffd registration * time. |
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*/ |
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if (!dst_vma->vm_userfaultfd_ctx.ctx) |
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goto out_unlock; |
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|
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if (dst_start < dst_vma->vm_start || dst_start + len > dst_vma->vm_end) |
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goto out_unlock; |
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|
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err = -EINVAL; /* * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but * it will overwrite vm_ops, so vma_is_anonymous must return false. */ if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) && dst_vma->vm_flags & VM_SHARED)) goto out_unlock; |
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/* |
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* If this is a HUGETLB vma, pass off to appropriate routine */ if (is_vm_hugetlb_page(dst_vma)) return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start, src_start, len, zeropage); |
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if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) |
b6ebaedb4 userfaultfd: avoi... |
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goto out_unlock; |
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/* * Ensure the dst_vma has a anon_vma or this page * would get a NULL anon_vma when moved in the * dst_vma. */ err = -ENOMEM; |
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if (!(dst_vma->vm_flags & VM_SHARED) && unlikely(anon_vma_prepare(dst_vma))) |
b6ebaedb4 userfaultfd: avoi... |
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goto out_unlock; |
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|
b6ebaedb4 userfaultfd: avoi... |
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while (src_addr < src_start + len) { |
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pmd_t dst_pmdval; |
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|
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BUG_ON(dst_addr >= dst_start + len); |
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|
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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)) && |
4cf589249 mm: treewide: rem... |
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unlikely(__pte_alloc(dst_mm, dst_pmd))) { |
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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)); |
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err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, src_addr, &page, zeropage); |
c1a4de99f userfaultfd: mcop... |
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cond_resched(); |
9e368259a userfaultfd: use ... |
547 |
if (unlikely(err == -ENOENT)) { |
b6ebaedb4 userfaultfd: avoi... |
548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 |
void *page_kaddr; up_read(&dst_mm->mmap_sem); 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); |
c1a4de99f userfaultfd: mcop... |
565 566 567 568 569 570 571 572 573 574 575 |
if (!err) { dst_addr += PAGE_SIZE; src_addr += PAGE_SIZE; copied += PAGE_SIZE; if (fatal_signal_pending(current)) err = -EINTR; } if (err) break; } |
b6ebaedb4 userfaultfd: avoi... |
576 |
out_unlock: |
c1a4de99f userfaultfd: mcop... |
577 |
up_read(&dst_mm->mmap_sem); |
b6ebaedb4 userfaultfd: avoi... |
578 579 |
out: if (page) |
09cbfeaf1 mm, fs: get rid o... |
580 |
put_page(page); |
c1a4de99f userfaultfd: mcop... |
581 582 583 584 585 586 587 |
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, |
df2cc96e7 userfaultfd: prev... |
588 589 |
unsigned long src_start, unsigned long len, bool *mmap_changing) |
c1a4de99f userfaultfd: mcop... |
590 |
{ |
df2cc96e7 userfaultfd: prev... |
591 592 |
return __mcopy_atomic(dst_mm, dst_start, src_start, len, false, mmap_changing); |
c1a4de99f userfaultfd: mcop... |
593 594 595 |
} ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, |
df2cc96e7 userfaultfd: prev... |
596 |
unsigned long len, bool *mmap_changing) |
c1a4de99f userfaultfd: mcop... |
597 |
{ |
df2cc96e7 userfaultfd: prev... |
598 |
return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing); |
c1a4de99f userfaultfd: mcop... |
599 |
} |