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1051 lines
28 KiB
1051 lines
28 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* mm/mremap.c |
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* |
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* (C) Copyright 1996 Linus Torvalds |
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* |
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* Address space accounting code <[email protected]> |
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* (C) Copyright 2002 Red Hat Inc, All Rights Reserved |
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*/ |
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|
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#include <linux/mm.h> |
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#include <linux/hugetlb.h> |
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#include <linux/shm.h> |
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#include <linux/ksm.h> |
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#include <linux/mman.h> |
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#include <linux/swap.h> |
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#include <linux/capability.h> |
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#include <linux/fs.h> |
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#include <linux/swapops.h> |
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#include <linux/highmem.h> |
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#include <linux/security.h> |
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#include <linux/syscalls.h> |
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#include <linux/mmu_notifier.h> |
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#include <linux/uaccess.h> |
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#include <linux/userfaultfd_k.h> |
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|
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#include <asm/cacheflush.h> |
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#include <asm/tlb.h> |
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#include <asm/pgalloc.h> |
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#include "internal.h" |
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static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr) |
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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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|
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pgd = pgd_offset(mm, addr); |
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if (pgd_none_or_clear_bad(pgd)) |
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return NULL; |
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p4d = p4d_offset(pgd, addr); |
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if (p4d_none_or_clear_bad(p4d)) |
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return NULL; |
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pud = pud_offset(p4d, addr); |
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if (pud_none_or_clear_bad(pud)) |
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return NULL; |
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|
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return pud; |
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} |
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static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) |
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{ |
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pud_t *pud; |
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pmd_t *pmd; |
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pud = get_old_pud(mm, addr); |
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if (!pud) |
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return NULL; |
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pmd = pmd_offset(pud, addr); |
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if (pmd_none(*pmd)) |
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return NULL; |
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return pmd; |
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} |
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static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma, |
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unsigned long addr) |
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{ |
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pgd_t *pgd; |
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p4d_t *p4d; |
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pgd = pgd_offset(mm, addr); |
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p4d = p4d_alloc(mm, pgd, addr); |
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if (!p4d) |
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return NULL; |
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return pud_alloc(mm, p4d, addr); |
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} |
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static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, |
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unsigned long addr) |
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{ |
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pud_t *pud; |
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pmd_t *pmd; |
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pud = alloc_new_pud(mm, vma, addr); |
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if (!pud) |
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return NULL; |
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pmd = pmd_alloc(mm, pud, addr); |
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if (!pmd) |
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return NULL; |
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VM_BUG_ON(pmd_trans_huge(*pmd)); |
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return pmd; |
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} |
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static void take_rmap_locks(struct vm_area_struct *vma) |
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{ |
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if (vma->vm_file) |
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i_mmap_lock_write(vma->vm_file->f_mapping); |
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if (vma->anon_vma) |
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anon_vma_lock_write(vma->anon_vma); |
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} |
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static void drop_rmap_locks(struct vm_area_struct *vma) |
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{ |
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if (vma->anon_vma) |
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anon_vma_unlock_write(vma->anon_vma); |
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if (vma->vm_file) |
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i_mmap_unlock_write(vma->vm_file->f_mapping); |
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} |
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static pte_t move_soft_dirty_pte(pte_t pte) |
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{ |
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/* |
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* Set soft dirty bit so we can notice |
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* in userspace the ptes were moved. |
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*/ |
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#ifdef CONFIG_MEM_SOFT_DIRTY |
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if (pte_present(pte)) |
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pte = pte_mksoft_dirty(pte); |
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else if (is_swap_pte(pte)) |
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pte = pte_swp_mksoft_dirty(pte); |
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#endif |
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return pte; |
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} |
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static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, |
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unsigned long old_addr, unsigned long old_end, |
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struct vm_area_struct *new_vma, pmd_t *new_pmd, |
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unsigned long new_addr, bool need_rmap_locks) |
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{ |
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struct mm_struct *mm = vma->vm_mm; |
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pte_t *old_pte, *new_pte, pte; |
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spinlock_t *old_ptl, *new_ptl; |
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bool force_flush = false; |
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unsigned long len = old_end - old_addr; |
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|
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/* |
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* When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma |
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* locks to ensure that rmap will always observe either the old or the |
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* new ptes. This is the easiest way to avoid races with |
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* truncate_pagecache(), page migration, etc... |
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* |
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* When need_rmap_locks is false, we use other ways to avoid |
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* such races: |
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* |
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* - During exec() shift_arg_pages(), we use a specially tagged vma |
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* which rmap call sites look for using vma_is_temporary_stack(). |
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* |
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* - During mremap(), new_vma is often known to be placed after vma |
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* in rmap traversal order. This ensures rmap will always observe |
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* either the old pte, or the new pte, or both (the page table locks |
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* serialize access to individual ptes, but only rmap traversal |
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* order guarantees that we won't miss both the old and new ptes). |
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*/ |
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if (need_rmap_locks) |
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take_rmap_locks(vma); |
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|
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/* |
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* We don't have to worry about the ordering of src and dst |
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* pte locks because exclusive mmap_lock prevents deadlock. |
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*/ |
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old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); |
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new_pte = pte_offset_map(new_pmd, new_addr); |
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new_ptl = pte_lockptr(mm, new_pmd); |
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if (new_ptl != old_ptl) |
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spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
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flush_tlb_batched_pending(vma->vm_mm); |
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arch_enter_lazy_mmu_mode(); |
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|
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for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, |
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new_pte++, new_addr += PAGE_SIZE) { |
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if (pte_none(*old_pte)) |
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continue; |
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pte = ptep_get_and_clear(mm, old_addr, old_pte); |
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/* |
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* If we are remapping a valid PTE, make sure |
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* to flush TLB before we drop the PTL for the |
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* PTE. |
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* |
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* NOTE! Both old and new PTL matter: the old one |
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* for racing with page_mkclean(), the new one to |
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* make sure the physical page stays valid until |
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* the TLB entry for the old mapping has been |
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* flushed. |
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*/ |
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if (pte_present(pte)) |
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force_flush = true; |
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pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); |
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pte = move_soft_dirty_pte(pte); |
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set_pte_at(mm, new_addr, new_pte, pte); |
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} |
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arch_leave_lazy_mmu_mode(); |
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if (force_flush) |
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flush_tlb_range(vma, old_end - len, old_end); |
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if (new_ptl != old_ptl) |
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spin_unlock(new_ptl); |
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pte_unmap(new_pte - 1); |
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pte_unmap_unlock(old_pte - 1, old_ptl); |
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if (need_rmap_locks) |
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drop_rmap_locks(vma); |
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} |
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#ifndef arch_supports_page_table_move |
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#define arch_supports_page_table_move arch_supports_page_table_move |
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static inline bool arch_supports_page_table_move(void) |
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{ |
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return IS_ENABLED(CONFIG_HAVE_MOVE_PMD) || |
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IS_ENABLED(CONFIG_HAVE_MOVE_PUD); |
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} |
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#endif |
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#ifdef CONFIG_HAVE_MOVE_PMD |
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static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, |
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unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd) |
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{ |
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spinlock_t *old_ptl, *new_ptl; |
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struct mm_struct *mm = vma->vm_mm; |
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pmd_t pmd; |
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if (!arch_supports_page_table_move()) |
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return false; |
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/* |
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* The destination pmd shouldn't be established, free_pgtables() |
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* should have released it. |
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* |
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* However, there's a case during execve() where we use mremap |
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* to move the initial stack, and in that case the target area |
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* may overlap the source area (always moving down). |
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* |
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* If everything is PMD-aligned, that works fine, as moving |
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* each pmd down will clear the source pmd. But if we first |
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* have a few 4kB-only pages that get moved down, and then |
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* hit the "now the rest is PMD-aligned, let's do everything |
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* one pmd at a time", we will still have the old (now empty |
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* of any 4kB pages, but still there) PMD in the page table |
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* tree. |
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* |
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* Warn on it once - because we really should try to figure |
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* out how to do this better - but then say "I won't move |
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* this pmd". |
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* |
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* One alternative might be to just unmap the target pmd at |
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* this point, and verify that it really is empty. We'll see. |
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*/ |
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if (WARN_ON_ONCE(!pmd_none(*new_pmd))) |
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return false; |
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/* |
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* We don't have to worry about the ordering of src and dst |
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* ptlocks because exclusive mmap_lock prevents deadlock. |
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*/ |
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old_ptl = pmd_lock(vma->vm_mm, old_pmd); |
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new_ptl = pmd_lockptr(mm, new_pmd); |
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if (new_ptl != old_ptl) |
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spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
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/* Clear the pmd */ |
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pmd = *old_pmd; |
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pmd_clear(old_pmd); |
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VM_BUG_ON(!pmd_none(*new_pmd)); |
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pmd_populate(mm, new_pmd, pmd_pgtable(pmd)); |
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flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); |
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if (new_ptl != old_ptl) |
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spin_unlock(new_ptl); |
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spin_unlock(old_ptl); |
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return true; |
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} |
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#else |
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static inline bool move_normal_pmd(struct vm_area_struct *vma, |
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unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd, |
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pmd_t *new_pmd) |
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{ |
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return false; |
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} |
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#endif |
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#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD) |
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static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr, |
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unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) |
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{ |
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spinlock_t *old_ptl, *new_ptl; |
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struct mm_struct *mm = vma->vm_mm; |
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pud_t pud; |
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if (!arch_supports_page_table_move()) |
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return false; |
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/* |
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* The destination pud shouldn't be established, free_pgtables() |
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* should have released it. |
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*/ |
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if (WARN_ON_ONCE(!pud_none(*new_pud))) |
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return false; |
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/* |
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* We don't have to worry about the ordering of src and dst |
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* ptlocks because exclusive mmap_lock prevents deadlock. |
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*/ |
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old_ptl = pud_lock(vma->vm_mm, old_pud); |
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new_ptl = pud_lockptr(mm, new_pud); |
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if (new_ptl != old_ptl) |
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spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
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/* Clear the pud */ |
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pud = *old_pud; |
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pud_clear(old_pud); |
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VM_BUG_ON(!pud_none(*new_pud)); |
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pud_populate(mm, new_pud, pud_pgtable(pud)); |
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flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE); |
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if (new_ptl != old_ptl) |
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spin_unlock(new_ptl); |
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spin_unlock(old_ptl); |
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return true; |
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} |
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#else |
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static inline bool move_normal_pud(struct vm_area_struct *vma, |
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unsigned long old_addr, unsigned long new_addr, pud_t *old_pud, |
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pud_t *new_pud) |
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{ |
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return false; |
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} |
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#endif |
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|
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#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD |
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static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr, |
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unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) |
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{ |
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spinlock_t *old_ptl, *new_ptl; |
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struct mm_struct *mm = vma->vm_mm; |
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pud_t pud; |
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|
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/* |
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* The destination pud shouldn't be established, free_pgtables() |
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* should have released it. |
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*/ |
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if (WARN_ON_ONCE(!pud_none(*new_pud))) |
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return false; |
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|
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/* |
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* We don't have to worry about the ordering of src and dst |
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* ptlocks because exclusive mmap_lock prevents deadlock. |
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*/ |
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old_ptl = pud_lock(vma->vm_mm, old_pud); |
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new_ptl = pud_lockptr(mm, new_pud); |
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if (new_ptl != old_ptl) |
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spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
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|
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/* Clear the pud */ |
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pud = *old_pud; |
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pud_clear(old_pud); |
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VM_BUG_ON(!pud_none(*new_pud)); |
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|
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/* Set the new pud */ |
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/* mark soft_ditry when we add pud level soft dirty support */ |
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set_pud_at(mm, new_addr, new_pud, pud); |
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flush_pud_tlb_range(vma, old_addr, old_addr + HPAGE_PUD_SIZE); |
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if (new_ptl != old_ptl) |
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spin_unlock(new_ptl); |
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spin_unlock(old_ptl); |
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|
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return true; |
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} |
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#else |
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static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr, |
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unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) |
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{ |
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WARN_ON_ONCE(1); |
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return false; |
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|
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} |
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#endif |
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|
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enum pgt_entry { |
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NORMAL_PMD, |
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HPAGE_PMD, |
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NORMAL_PUD, |
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HPAGE_PUD, |
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}; |
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|
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/* |
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* Returns an extent of the corresponding size for the pgt_entry specified if |
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* valid. Else returns a smaller extent bounded by the end of the source and |
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* destination pgt_entry. |
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*/ |
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static __always_inline unsigned long get_extent(enum pgt_entry entry, |
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unsigned long old_addr, unsigned long old_end, |
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unsigned long new_addr) |
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{ |
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unsigned long next, extent, mask, size; |
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|
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switch (entry) { |
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case HPAGE_PMD: |
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case NORMAL_PMD: |
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mask = PMD_MASK; |
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size = PMD_SIZE; |
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break; |
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case HPAGE_PUD: |
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case NORMAL_PUD: |
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mask = PUD_MASK; |
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size = PUD_SIZE; |
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break; |
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default: |
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BUILD_BUG(); |
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break; |
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} |
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|
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next = (old_addr + size) & mask; |
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/* even if next overflowed, extent below will be ok */ |
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extent = next - old_addr; |
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if (extent > old_end - old_addr) |
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extent = old_end - old_addr; |
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next = (new_addr + size) & mask; |
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if (extent > next - new_addr) |
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extent = next - new_addr; |
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return extent; |
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} |
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|
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/* |
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* Attempts to speedup the move by moving entry at the level corresponding to |
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* pgt_entry. Returns true if the move was successful, else false. |
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*/ |
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static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma, |
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unsigned long old_addr, unsigned long new_addr, |
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void *old_entry, void *new_entry, bool need_rmap_locks) |
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{ |
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bool moved = false; |
|
|
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/* See comment in move_ptes() */ |
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if (need_rmap_locks) |
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take_rmap_locks(vma); |
|
|
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switch (entry) { |
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case NORMAL_PMD: |
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moved = move_normal_pmd(vma, old_addr, new_addr, old_entry, |
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new_entry); |
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break; |
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case NORMAL_PUD: |
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moved = move_normal_pud(vma, old_addr, new_addr, old_entry, |
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new_entry); |
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break; |
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case HPAGE_PMD: |
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moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && |
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move_huge_pmd(vma, old_addr, new_addr, old_entry, |
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new_entry); |
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break; |
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case HPAGE_PUD: |
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moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && |
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move_huge_pud(vma, old_addr, new_addr, old_entry, |
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new_entry); |
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break; |
|
|
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default: |
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WARN_ON_ONCE(1); |
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break; |
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} |
|
|
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if (need_rmap_locks) |
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drop_rmap_locks(vma); |
|
|
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return moved; |
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} |
|
|
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unsigned long move_page_tables(struct vm_area_struct *vma, |
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unsigned long old_addr, struct vm_area_struct *new_vma, |
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unsigned long new_addr, unsigned long len, |
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bool need_rmap_locks) |
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{ |
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unsigned long extent, old_end; |
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struct mmu_notifier_range range; |
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pmd_t *old_pmd, *new_pmd; |
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pud_t *old_pud, *new_pud; |
|
|
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old_end = old_addr + len; |
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flush_cache_range(vma, old_addr, old_end); |
|
|
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mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm, |
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old_addr, old_end); |
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mmu_notifier_invalidate_range_start(&range); |
|
|
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for (; old_addr < old_end; old_addr += extent, new_addr += extent) { |
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cond_resched(); |
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/* |
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* If extent is PUD-sized try to speed up the move by moving at the |
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* PUD level if possible. |
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*/ |
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extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr); |
|
|
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old_pud = get_old_pud(vma->vm_mm, old_addr); |
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if (!old_pud) |
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continue; |
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new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr); |
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if (!new_pud) |
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break; |
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if (pud_trans_huge(*old_pud) || pud_devmap(*old_pud)) { |
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if (extent == HPAGE_PUD_SIZE) { |
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move_pgt_entry(HPAGE_PUD, vma, old_addr, new_addr, |
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old_pud, new_pud, need_rmap_locks); |
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/* We ignore and continue on error? */ |
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continue; |
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} |
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} else if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) { |
|
|
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if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr, |
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old_pud, new_pud, true)) |
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continue; |
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} |
|
|
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extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr); |
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old_pmd = get_old_pmd(vma->vm_mm, old_addr); |
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if (!old_pmd) |
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continue; |
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new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); |
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if (!new_pmd) |
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break; |
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if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || |
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pmd_devmap(*old_pmd)) { |
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if (extent == HPAGE_PMD_SIZE && |
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move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr, |
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old_pmd, new_pmd, need_rmap_locks)) |
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continue; |
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split_huge_pmd(vma, old_pmd, old_addr); |
|
if (pmd_trans_unstable(old_pmd)) |
|
continue; |
|
} else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) && |
|
extent == PMD_SIZE) { |
|
/* |
|
* If the extent is PMD-sized, try to speed the move by |
|
* moving at the PMD level if possible. |
|
*/ |
|
if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr, |
|
old_pmd, new_pmd, true)) |
|
continue; |
|
} |
|
|
|
if (pte_alloc(new_vma->vm_mm, new_pmd)) |
|
break; |
|
move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, |
|
new_pmd, new_addr, need_rmap_locks); |
|
} |
|
|
|
mmu_notifier_invalidate_range_end(&range); |
|
|
|
return len + old_addr - old_end; /* how much done */ |
|
} |
|
|
|
static unsigned long move_vma(struct vm_area_struct *vma, |
|
unsigned long old_addr, unsigned long old_len, |
|
unsigned long new_len, unsigned long new_addr, |
|
bool *locked, unsigned long flags, |
|
struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap) |
|
{ |
|
struct mm_struct *mm = vma->vm_mm; |
|
struct vm_area_struct *new_vma; |
|
unsigned long vm_flags = vma->vm_flags; |
|
unsigned long new_pgoff; |
|
unsigned long moved_len; |
|
unsigned long excess = 0; |
|
unsigned long hiwater_vm; |
|
int split = 0; |
|
int err = 0; |
|
bool need_rmap_locks; |
|
|
|
/* |
|
* We'd prefer to avoid failure later on in do_munmap: |
|
* which may split one vma into three before unmapping. |
|
*/ |
|
if (mm->map_count >= sysctl_max_map_count - 3) |
|
return -ENOMEM; |
|
|
|
if (vma->vm_ops && vma->vm_ops->may_split) { |
|
if (vma->vm_start != old_addr) |
|
err = vma->vm_ops->may_split(vma, old_addr); |
|
if (!err && vma->vm_end != old_addr + old_len) |
|
err = vma->vm_ops->may_split(vma, old_addr + old_len); |
|
if (err) |
|
return err; |
|
} |
|
|
|
/* |
|
* Advise KSM to break any KSM pages in the area to be moved: |
|
* it would be confusing if they were to turn up at the new |
|
* location, where they happen to coincide with different KSM |
|
* pages recently unmapped. But leave vma->vm_flags as it was, |
|
* so KSM can come around to merge on vma and new_vma afterwards. |
|
*/ |
|
err = ksm_madvise(vma, old_addr, old_addr + old_len, |
|
MADV_UNMERGEABLE, &vm_flags); |
|
if (err) |
|
return err; |
|
|
|
if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) { |
|
if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT)) |
|
return -ENOMEM; |
|
} |
|
|
|
new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); |
|
new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, |
|
&need_rmap_locks); |
|
if (!new_vma) { |
|
if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) |
|
vm_unacct_memory(new_len >> PAGE_SHIFT); |
|
return -ENOMEM; |
|
} |
|
|
|
moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, |
|
need_rmap_locks); |
|
if (moved_len < old_len) { |
|
err = -ENOMEM; |
|
} else if (vma->vm_ops && vma->vm_ops->mremap) { |
|
err = vma->vm_ops->mremap(new_vma); |
|
} |
|
|
|
if (unlikely(err)) { |
|
/* |
|
* On error, move entries back from new area to old, |
|
* which will succeed since page tables still there, |
|
* and then proceed to unmap new area instead of old. |
|
*/ |
|
move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, |
|
true); |
|
vma = new_vma; |
|
old_len = new_len; |
|
old_addr = new_addr; |
|
new_addr = err; |
|
} else { |
|
mremap_userfaultfd_prep(new_vma, uf); |
|
} |
|
|
|
/* Conceal VM_ACCOUNT so old reservation is not undone */ |
|
if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) { |
|
vma->vm_flags &= ~VM_ACCOUNT; |
|
excess = vma->vm_end - vma->vm_start - old_len; |
|
if (old_addr > vma->vm_start && |
|
old_addr + old_len < vma->vm_end) |
|
split = 1; |
|
} |
|
|
|
/* |
|
* If we failed to move page tables we still do total_vm increment |
|
* since do_munmap() will decrement it by old_len == new_len. |
|
* |
|
* Since total_vm is about to be raised artificially high for a |
|
* moment, we need to restore high watermark afterwards: if stats |
|
* are taken meanwhile, total_vm and hiwater_vm appear too high. |
|
* If this were a serious issue, we'd add a flag to do_munmap(). |
|
*/ |
|
hiwater_vm = mm->hiwater_vm; |
|
vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT); |
|
|
|
/* Tell pfnmap has moved from this vma */ |
|
if (unlikely(vma->vm_flags & VM_PFNMAP)) |
|
untrack_pfn_moved(vma); |
|
|
|
if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) { |
|
/* We always clear VM_LOCKED[ONFAULT] on the old vma */ |
|
vma->vm_flags &= VM_LOCKED_CLEAR_MASK; |
|
|
|
/* |
|
* anon_vma links of the old vma is no longer needed after its page |
|
* table has been moved. |
|
*/ |
|
if (new_vma != vma && vma->vm_start == old_addr && |
|
vma->vm_end == (old_addr + old_len)) |
|
unlink_anon_vmas(vma); |
|
|
|
/* Because we won't unmap we don't need to touch locked_vm */ |
|
return new_addr; |
|
} |
|
|
|
if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { |
|
/* OOM: unable to split vma, just get accounts right */ |
|
if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) |
|
vm_acct_memory(old_len >> PAGE_SHIFT); |
|
excess = 0; |
|
} |
|
|
|
if (vm_flags & VM_LOCKED) { |
|
mm->locked_vm += new_len >> PAGE_SHIFT; |
|
*locked = true; |
|
} |
|
|
|
mm->hiwater_vm = hiwater_vm; |
|
|
|
/* Restore VM_ACCOUNT if one or two pieces of vma left */ |
|
if (excess) { |
|
vma->vm_flags |= VM_ACCOUNT; |
|
if (split) |
|
vma->vm_next->vm_flags |= VM_ACCOUNT; |
|
} |
|
|
|
return new_addr; |
|
} |
|
|
|
static struct vm_area_struct *vma_to_resize(unsigned long addr, |
|
unsigned long old_len, unsigned long new_len, unsigned long flags, |
|
unsigned long *p) |
|
{ |
|
struct mm_struct *mm = current->mm; |
|
struct vm_area_struct *vma; |
|
unsigned long pgoff; |
|
|
|
vma = vma_lookup(mm, addr); |
|
if (!vma) |
|
return ERR_PTR(-EFAULT); |
|
|
|
/* |
|
* !old_len is a special case where an attempt is made to 'duplicate' |
|
* a mapping. This makes no sense for private mappings as it will |
|
* instead create a fresh/new mapping unrelated to the original. This |
|
* is contrary to the basic idea of mremap which creates new mappings |
|
* based on the original. There are no known use cases for this |
|
* behavior. As a result, fail such attempts. |
|
*/ |
|
if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) { |
|
pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid); |
|
return ERR_PTR(-EINVAL); |
|
} |
|
|
|
if ((flags & MREMAP_DONTUNMAP) && |
|
(vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))) |
|
return ERR_PTR(-EINVAL); |
|
|
|
if (is_vm_hugetlb_page(vma)) |
|
return ERR_PTR(-EINVAL); |
|
|
|
/* We can't remap across vm area boundaries */ |
|
if (old_len > vma->vm_end - addr) |
|
return ERR_PTR(-EFAULT); |
|
|
|
if (new_len == old_len) |
|
return vma; |
|
|
|
/* Need to be careful about a growing mapping */ |
|
pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; |
|
pgoff += vma->vm_pgoff; |
|
if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) |
|
return ERR_PTR(-EINVAL); |
|
|
|
if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) |
|
return ERR_PTR(-EFAULT); |
|
|
|
if (vma->vm_flags & VM_LOCKED) { |
|
unsigned long locked, lock_limit; |
|
locked = mm->locked_vm << PAGE_SHIFT; |
|
lock_limit = rlimit(RLIMIT_MEMLOCK); |
|
locked += new_len - old_len; |
|
if (locked > lock_limit && !capable(CAP_IPC_LOCK)) |
|
return ERR_PTR(-EAGAIN); |
|
} |
|
|
|
if (!may_expand_vm(mm, vma->vm_flags, |
|
(new_len - old_len) >> PAGE_SHIFT)) |
|
return ERR_PTR(-ENOMEM); |
|
|
|
if (vma->vm_flags & VM_ACCOUNT) { |
|
unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; |
|
if (security_vm_enough_memory_mm(mm, charged)) |
|
return ERR_PTR(-ENOMEM); |
|
*p = charged; |
|
} |
|
|
|
return vma; |
|
} |
|
|
|
static unsigned long mremap_to(unsigned long addr, unsigned long old_len, |
|
unsigned long new_addr, unsigned long new_len, bool *locked, |
|
unsigned long flags, struct vm_userfaultfd_ctx *uf, |
|
struct list_head *uf_unmap_early, |
|
struct list_head *uf_unmap) |
|
{ |
|
struct mm_struct *mm = current->mm; |
|
struct vm_area_struct *vma; |
|
unsigned long ret = -EINVAL; |
|
unsigned long charged = 0; |
|
unsigned long map_flags = 0; |
|
|
|
if (offset_in_page(new_addr)) |
|
goto out; |
|
|
|
if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) |
|
goto out; |
|
|
|
/* Ensure the old/new locations do not overlap */ |
|
if (addr + old_len > new_addr && new_addr + new_len > addr) |
|
goto out; |
|
|
|
/* |
|
* move_vma() need us to stay 4 maps below the threshold, otherwise |
|
* it will bail out at the very beginning. |
|
* That is a problem if we have already unmaped the regions here |
|
* (new_addr, and old_addr), because userspace will not know the |
|
* state of the vma's after it gets -ENOMEM. |
|
* So, to avoid such scenario we can pre-compute if the whole |
|
* operation has high chances to success map-wise. |
|
* Worst-scenario case is when both vma's (new_addr and old_addr) get |
|
* split in 3 before unmapping it. |
|
* That means 2 more maps (1 for each) to the ones we already hold. |
|
* Check whether current map count plus 2 still leads us to 4 maps below |
|
* the threshold, otherwise return -ENOMEM here to be more safe. |
|
*/ |
|
if ((mm->map_count + 2) >= sysctl_max_map_count - 3) |
|
return -ENOMEM; |
|
|
|
if (flags & MREMAP_FIXED) { |
|
ret = do_munmap(mm, new_addr, new_len, uf_unmap_early); |
|
if (ret) |
|
goto out; |
|
} |
|
|
|
if (old_len >= new_len) { |
|
ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap); |
|
if (ret && old_len != new_len) |
|
goto out; |
|
old_len = new_len; |
|
} |
|
|
|
vma = vma_to_resize(addr, old_len, new_len, flags, &charged); |
|
if (IS_ERR(vma)) { |
|
ret = PTR_ERR(vma); |
|
goto out; |
|
} |
|
|
|
/* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */ |
|
if (flags & MREMAP_DONTUNMAP && |
|
!may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) { |
|
ret = -ENOMEM; |
|
goto out; |
|
} |
|
|
|
if (flags & MREMAP_FIXED) |
|
map_flags |= MAP_FIXED; |
|
|
|
if (vma->vm_flags & VM_MAYSHARE) |
|
map_flags |= MAP_SHARED; |
|
|
|
ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + |
|
((addr - vma->vm_start) >> PAGE_SHIFT), |
|
map_flags); |
|
if (IS_ERR_VALUE(ret)) |
|
goto out1; |
|
|
|
/* We got a new mapping */ |
|
if (!(flags & MREMAP_FIXED)) |
|
new_addr = ret; |
|
|
|
ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf, |
|
uf_unmap); |
|
|
|
if (!(offset_in_page(ret))) |
|
goto out; |
|
|
|
out1: |
|
vm_unacct_memory(charged); |
|
|
|
out: |
|
return ret; |
|
} |
|
|
|
static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) |
|
{ |
|
unsigned long end = vma->vm_end + delta; |
|
if (end < vma->vm_end) /* overflow */ |
|
return 0; |
|
if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ |
|
return 0; |
|
if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, |
|
0, MAP_FIXED) & ~PAGE_MASK) |
|
return 0; |
|
return 1; |
|
} |
|
|
|
/* |
|
* Expand (or shrink) an existing mapping, potentially moving it at the |
|
* same time (controlled by the MREMAP_MAYMOVE flag and available VM space) |
|
* |
|
* MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise |
|
* This option implies MREMAP_MAYMOVE. |
|
*/ |
|
SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, |
|
unsigned long, new_len, unsigned long, flags, |
|
unsigned long, new_addr) |
|
{ |
|
struct mm_struct *mm = current->mm; |
|
struct vm_area_struct *vma; |
|
unsigned long ret = -EINVAL; |
|
unsigned long charged = 0; |
|
bool locked = false; |
|
bool downgraded = false; |
|
struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX; |
|
LIST_HEAD(uf_unmap_early); |
|
LIST_HEAD(uf_unmap); |
|
|
|
/* |
|
* There is a deliberate asymmetry here: we strip the pointer tag |
|
* from the old address but leave the new address alone. This is |
|
* for consistency with mmap(), where we prevent the creation of |
|
* aliasing mappings in userspace by leaving the tag bits of the |
|
* mapping address intact. A non-zero tag will cause the subsequent |
|
* range checks to reject the address as invalid. |
|
* |
|
* See Documentation/arm64/tagged-address-abi.rst for more information. |
|
*/ |
|
addr = untagged_addr(addr); |
|
|
|
if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP)) |
|
return ret; |
|
|
|
if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE)) |
|
return ret; |
|
|
|
/* |
|
* MREMAP_DONTUNMAP is always a move and it does not allow resizing |
|
* in the process. |
|
*/ |
|
if (flags & MREMAP_DONTUNMAP && |
|
(!(flags & MREMAP_MAYMOVE) || old_len != new_len)) |
|
return ret; |
|
|
|
|
|
if (offset_in_page(addr)) |
|
return ret; |
|
|
|
old_len = PAGE_ALIGN(old_len); |
|
new_len = PAGE_ALIGN(new_len); |
|
|
|
/* |
|
* We allow a zero old-len as a special case |
|
* for DOS-emu "duplicate shm area" thing. But |
|
* a zero new-len is nonsensical. |
|
*/ |
|
if (!new_len) |
|
return ret; |
|
|
|
if (mmap_write_lock_killable(current->mm)) |
|
return -EINTR; |
|
|
|
if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) { |
|
ret = mremap_to(addr, old_len, new_addr, new_len, |
|
&locked, flags, &uf, &uf_unmap_early, |
|
&uf_unmap); |
|
goto out; |
|
} |
|
|
|
/* |
|
* Always allow a shrinking remap: that just unmaps |
|
* the unnecessary pages.. |
|
* __do_munmap does all the needed commit accounting, and |
|
* downgrades mmap_lock to read if so directed. |
|
*/ |
|
if (old_len >= new_len) { |
|
int retval; |
|
|
|
retval = __do_munmap(mm, addr+new_len, old_len - new_len, |
|
&uf_unmap, true); |
|
if (retval < 0 && old_len != new_len) { |
|
ret = retval; |
|
goto out; |
|
/* Returning 1 indicates mmap_lock is downgraded to read. */ |
|
} else if (retval == 1) |
|
downgraded = true; |
|
ret = addr; |
|
goto out; |
|
} |
|
|
|
/* |
|
* Ok, we need to grow.. |
|
*/ |
|
vma = vma_to_resize(addr, old_len, new_len, flags, &charged); |
|
if (IS_ERR(vma)) { |
|
ret = PTR_ERR(vma); |
|
goto out; |
|
} |
|
|
|
/* old_len exactly to the end of the area.. |
|
*/ |
|
if (old_len == vma->vm_end - addr) { |
|
/* can we just expand the current mapping? */ |
|
if (vma_expandable(vma, new_len - old_len)) { |
|
int pages = (new_len - old_len) >> PAGE_SHIFT; |
|
|
|
if (vma_adjust(vma, vma->vm_start, addr + new_len, |
|
vma->vm_pgoff, NULL)) { |
|
ret = -ENOMEM; |
|
goto out; |
|
} |
|
|
|
vm_stat_account(mm, vma->vm_flags, pages); |
|
if (vma->vm_flags & VM_LOCKED) { |
|
mm->locked_vm += pages; |
|
locked = true; |
|
new_addr = addr; |
|
} |
|
ret = addr; |
|
goto out; |
|
} |
|
} |
|
|
|
/* |
|
* We weren't able to just expand or shrink the area, |
|
* we need to create a new one and move it.. |
|
*/ |
|
ret = -ENOMEM; |
|
if (flags & MREMAP_MAYMOVE) { |
|
unsigned long map_flags = 0; |
|
if (vma->vm_flags & VM_MAYSHARE) |
|
map_flags |= MAP_SHARED; |
|
|
|
new_addr = get_unmapped_area(vma->vm_file, 0, new_len, |
|
vma->vm_pgoff + |
|
((addr - vma->vm_start) >> PAGE_SHIFT), |
|
map_flags); |
|
if (IS_ERR_VALUE(new_addr)) { |
|
ret = new_addr; |
|
goto out; |
|
} |
|
|
|
ret = move_vma(vma, addr, old_len, new_len, new_addr, |
|
&locked, flags, &uf, &uf_unmap); |
|
} |
|
out: |
|
if (offset_in_page(ret)) { |
|
vm_unacct_memory(charged); |
|
locked = false; |
|
} |
|
if (downgraded) |
|
mmap_read_unlock(current->mm); |
|
else |
|
mmap_write_unlock(current->mm); |
|
if (locked && new_len > old_len) |
|
mm_populate(new_addr + old_len, new_len - old_len); |
|
userfaultfd_unmap_complete(mm, &uf_unmap_early); |
|
mremap_userfaultfd_complete(&uf, addr, ret, old_len); |
|
userfaultfd_unmap_complete(mm, &uf_unmap); |
|
return ret; |
|
}
|
|
|