590 lines
15 KiB
C
590 lines
15 KiB
C
/*
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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 <alan@lxorguk.ukuu.org.uk>
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* (C) Copyright 2002 Red Hat Inc, All Rights Reserved
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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/sched/sysctl.h>
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#include <linux/uaccess.h>
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#include <linux/mm-arch-hooks.h>
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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#include "internal.h"
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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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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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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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pud = pud_offset(pgd, addr);
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if (pud_none_or_clear_bad(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 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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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pgd = pgd_offset(mm, addr);
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pud = pud_alloc(mm, pgd, 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 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 address_space *mapping = NULL;
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struct anon_vma *anon_vma = NULL;
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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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/*
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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 is_vma_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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if (vma->vm_file) {
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mapping = vma->vm_file->f_mapping;
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i_mmap_lock_write(mapping);
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}
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if (vma->anon_vma) {
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anon_vma = vma->anon_vma;
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anon_vma_lock_write(anon_vma);
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}
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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_sem 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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arch_enter_lazy_mmu_mode();
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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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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 (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 (anon_vma)
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anon_vma_unlock_write(anon_vma);
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if (mapping)
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i_mmap_unlock_write(mapping);
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}
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#define LATENCY_LIMIT (64 * PAGE_SIZE)
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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, next, old_end;
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pmd_t *old_pmd, *new_pmd;
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bool need_flush = false;
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unsigned long mmun_start; /* For mmu_notifiers */
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unsigned long mmun_end; /* For mmu_notifiers */
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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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mmun_start = old_addr;
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mmun_end = old_end;
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mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
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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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next = (old_addr + PMD_SIZE) & PMD_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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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 (pmd_trans_huge(*old_pmd)) {
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if (extent == HPAGE_PMD_SIZE) {
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bool moved;
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VM_BUG_ON_VMA(vma->vm_file || !vma->anon_vma,
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vma);
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/* See comment in move_ptes() */
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if (need_rmap_locks)
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anon_vma_lock_write(vma->anon_vma);
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moved = move_huge_pmd(vma, new_vma, old_addr,
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new_addr, old_end,
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old_pmd, new_pmd);
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if (need_rmap_locks)
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anon_vma_unlock_write(vma->anon_vma);
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if (moved) {
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need_flush = true;
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continue;
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}
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}
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split_huge_pmd(vma, old_pmd, old_addr);
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VM_BUG_ON(pmd_trans_huge(*old_pmd));
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}
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if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
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new_pmd, new_addr))
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break;
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next = (new_addr + PMD_SIZE) & PMD_MASK;
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if (extent > next - new_addr)
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extent = next - new_addr;
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if (extent > LATENCY_LIMIT)
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extent = LATENCY_LIMIT;
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move_ptes(vma, old_pmd, old_addr, old_addr + extent,
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new_vma, new_pmd, new_addr, need_rmap_locks);
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need_flush = true;
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}
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if (likely(need_flush))
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flush_tlb_range(vma, old_end-len, old_addr);
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mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
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return len + old_addr - old_end; /* how much done */
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}
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static unsigned long move_vma(struct vm_area_struct *vma,
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unsigned long old_addr, unsigned long old_len,
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unsigned long new_len, unsigned long new_addr, bool *locked)
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{
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struct mm_struct *mm = vma->vm_mm;
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struct vm_area_struct *new_vma;
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unsigned long vm_flags = vma->vm_flags;
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unsigned long new_pgoff;
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unsigned long moved_len;
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unsigned long excess = 0;
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unsigned long hiwater_vm;
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int split = 0;
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int err;
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bool need_rmap_locks;
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/*
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* We'd prefer to avoid failure later on in do_munmap:
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* which may split one vma into three before unmapping.
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*/
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if (mm->map_count >= sysctl_max_map_count - 3)
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return -ENOMEM;
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/*
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* Advise KSM to break any KSM pages in the area to be moved:
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* it would be confusing if they were to turn up at the new
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* location, where they happen to coincide with different KSM
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* pages recently unmapped. But leave vma->vm_flags as it was,
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* so KSM can come around to merge on vma and new_vma afterwards.
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*/
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err = ksm_madvise(vma, old_addr, old_addr + old_len,
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MADV_UNMERGEABLE, &vm_flags);
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if (err)
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return err;
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new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
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new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
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&need_rmap_locks);
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if (!new_vma)
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return -ENOMEM;
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moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
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need_rmap_locks);
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if (moved_len < old_len) {
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err = -ENOMEM;
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} else if (vma->vm_ops && vma->vm_ops->mremap) {
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err = vma->vm_ops->mremap(new_vma);
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}
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if (unlikely(err)) {
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/*
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* On error, move entries back from new area to old,
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* which will succeed since page tables still there,
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* and then proceed to unmap new area instead of old.
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*/
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move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
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true);
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vma = new_vma;
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old_len = new_len;
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old_addr = new_addr;
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new_addr = err;
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} else {
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arch_remap(mm, old_addr, old_addr + old_len,
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new_addr, new_addr + new_len);
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}
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/* Conceal VM_ACCOUNT so old reservation is not undone */
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if (vm_flags & VM_ACCOUNT) {
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vma->vm_flags &= ~VM_ACCOUNT;
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excess = vma->vm_end - vma->vm_start - old_len;
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if (old_addr > vma->vm_start &&
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old_addr + old_len < vma->vm_end)
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split = 1;
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}
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/*
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* If we failed to move page tables we still do total_vm increment
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* since do_munmap() will decrement it by old_len == new_len.
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*
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* Since total_vm is about to be raised artificially high for a
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* moment, we need to restore high watermark afterwards: if stats
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* are taken meanwhile, total_vm and hiwater_vm appear too high.
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* If this were a serious issue, we'd add a flag to do_munmap().
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*/
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hiwater_vm = mm->hiwater_vm;
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vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
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/* Tell pfnmap has moved from this vma */
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if (unlikely(vma->vm_flags & VM_PFNMAP))
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untrack_pfn_moved(vma);
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if (do_munmap(mm, old_addr, old_len) < 0) {
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/* OOM: unable to split vma, just get accounts right */
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vm_unacct_memory(excess >> PAGE_SHIFT);
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excess = 0;
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}
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mm->hiwater_vm = hiwater_vm;
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/* Restore VM_ACCOUNT if one or two pieces of vma left */
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if (excess) {
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vma->vm_flags |= VM_ACCOUNT;
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if (split)
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vma->vm_next->vm_flags |= VM_ACCOUNT;
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}
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if (vm_flags & VM_LOCKED) {
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mm->locked_vm += new_len >> PAGE_SHIFT;
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*locked = true;
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}
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return new_addr;
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}
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static struct vm_area_struct *vma_to_resize(unsigned long addr,
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unsigned long old_len, unsigned long new_len, unsigned long *p)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma = find_vma(mm, addr);
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unsigned long pgoff;
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if (!vma || vma->vm_start > addr)
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return ERR_PTR(-EFAULT);
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if (is_vm_hugetlb_page(vma))
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return ERR_PTR(-EINVAL);
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/* We can't remap across vm area boundaries */
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if (old_len > vma->vm_end - addr)
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return ERR_PTR(-EFAULT);
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if (new_len == old_len)
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return vma;
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/* Need to be careful about a growing mapping */
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pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
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pgoff += vma->vm_pgoff;
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if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
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return ERR_PTR(-EINVAL);
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if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
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return ERR_PTR(-EFAULT);
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if (vma->vm_flags & VM_LOCKED) {
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unsigned long locked, lock_limit;
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locked = mm->locked_vm << PAGE_SHIFT;
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lock_limit = rlimit(RLIMIT_MEMLOCK);
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locked += new_len - old_len;
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if (locked > lock_limit && !capable(CAP_IPC_LOCK))
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return ERR_PTR(-EAGAIN);
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}
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if (!may_expand_vm(mm, vma->vm_flags,
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(new_len - old_len) >> PAGE_SHIFT))
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return ERR_PTR(-ENOMEM);
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if (vma->vm_flags & VM_ACCOUNT) {
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unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
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if (security_vm_enough_memory_mm(mm, charged))
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return ERR_PTR(-ENOMEM);
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*p = charged;
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}
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return vma;
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}
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static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
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unsigned long new_addr, unsigned long new_len, bool *locked)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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unsigned long ret = -EINVAL;
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unsigned long charged = 0;
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unsigned long map_flags;
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if (offset_in_page(new_addr))
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goto out;
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if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
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goto out;
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/* Ensure the old/new locations do not overlap */
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if (addr + old_len > new_addr && new_addr + new_len > addr)
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goto out;
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ret = do_munmap(mm, new_addr, new_len);
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if (ret)
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goto out;
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if (old_len >= new_len) {
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ret = do_munmap(mm, addr+new_len, old_len - new_len);
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if (ret && old_len != new_len)
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goto out;
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old_len = new_len;
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}
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vma = vma_to_resize(addr, old_len, new_len, &charged);
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if (IS_ERR(vma)) {
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ret = PTR_ERR(vma);
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goto out;
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}
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map_flags = MAP_FIXED;
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if (vma->vm_flags & VM_MAYSHARE)
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map_flags |= MAP_SHARED;
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ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
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((addr - vma->vm_start) >> PAGE_SHIFT),
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map_flags);
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if (offset_in_page(ret))
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goto out1;
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ret = move_vma(vma, addr, old_len, new_len, new_addr, locked);
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if (!(offset_in_page(ret)))
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goto out;
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out1:
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vm_unacct_memory(charged);
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out:
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return ret;
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}
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static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
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{
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unsigned long end = vma->vm_end + delta;
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if (end < vma->vm_end) /* overflow */
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return 0;
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if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
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return 0;
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if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
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0, MAP_FIXED) & ~PAGE_MASK)
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return 0;
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return 1;
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}
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/*
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* Expand (or shrink) an existing mapping, potentially moving it at the
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* same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
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*
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* MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
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* This option implies MREMAP_MAYMOVE.
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*/
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SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
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unsigned long, new_len, unsigned long, flags,
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unsigned long, new_addr)
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|
{
|
|
struct mm_struct *mm = current->mm;
|
|
struct vm_area_struct *vma;
|
|
unsigned long ret = -EINVAL;
|
|
unsigned long charged = 0;
|
|
bool locked = false;
|
|
|
|
if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
|
|
return ret;
|
|
|
|
if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
|
|
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;
|
|
|
|
down_write(¤t->mm->mmap_sem);
|
|
|
|
if (flags & MREMAP_FIXED) {
|
|
ret = mremap_to(addr, old_len, new_addr, new_len,
|
|
&locked);
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Always allow a shrinking remap: that just unmaps
|
|
* the unnecessary pages..
|
|
* do_munmap does all the needed commit accounting
|
|
*/
|
|
if (old_len >= new_len) {
|
|
ret = do_munmap(mm, addr+new_len, old_len - new_len);
|
|
if (ret && old_len != new_len)
|
|
goto out;
|
|
ret = addr;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Ok, we need to grow..
|
|
*/
|
|
vma = vma_to_resize(addr, old_len, new_len, &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 (offset_in_page(new_addr)) {
|
|
ret = new_addr;
|
|
goto out;
|
|
}
|
|
|
|
ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
|
|
}
|
|
out:
|
|
if (offset_in_page(ret)) {
|
|
vm_unacct_memory(charged);
|
|
locked = 0;
|
|
}
|
|
up_write(¤t->mm->mmap_sem);
|
|
if (locked && new_len > old_len)
|
|
mm_populate(new_addr + old_len, new_len - old_len);
|
|
return ret;
|
|
}
|