| /* |
| * mm/mremap.c |
| * |
| * (C) Copyright 1996 Linus Torvalds |
| * |
| * Address space accounting code <alan@lxorguk.ukuu.org.uk> |
| * (C) Copyright 2002 Red Hat Inc, All Rights Reserved |
| */ |
| |
| #include <linux/mm.h> |
| #include <linux/hugetlb.h> |
| #include <linux/shm.h> |
| #include <linux/ksm.h> |
| #include <linux/mman.h> |
| #include <linux/swap.h> |
| #include <linux/capability.h> |
| #include <linux/fs.h> |
| #include <linux/highmem.h> |
| #include <linux/security.h> |
| #include <linux/syscalls.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/sched/sysctl.h> |
| |
| #include <asm/uaccess.h> |
| #include <asm/cacheflush.h> |
| #include <asm/tlbflush.h> |
| |
| #include "internal.h" |
| |
| static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) |
| { |
| pgd_t *pgd; |
| pud_t *pud; |
| pmd_t *pmd; |
| |
| pgd = pgd_offset(mm, addr); |
| if (pgd_none_or_clear_bad(pgd)) |
| return NULL; |
| |
| pud = pud_offset(pgd, addr); |
| if (pud_none_or_clear_bad(pud)) |
| return NULL; |
| |
| pmd = pmd_offset(pud, addr); |
| if (pmd_none(*pmd)) |
| return NULL; |
| |
| return pmd; |
| } |
| |
| static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, |
| unsigned long addr) |
| { |
| pgd_t *pgd; |
| pud_t *pud; |
| pmd_t *pmd; |
| |
| pgd = pgd_offset(mm, addr); |
| pud = pud_alloc(mm, pgd, addr); |
| if (!pud) |
| return NULL; |
| |
| pmd = pmd_alloc(mm, pud, addr); |
| if (!pmd) |
| return NULL; |
| |
| VM_BUG_ON(pmd_trans_huge(*pmd)); |
| |
| return pmd; |
| } |
| |
| static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, |
| unsigned long old_addr, unsigned long old_end, |
| struct vm_area_struct *new_vma, pmd_t *new_pmd, |
| unsigned long new_addr, bool need_rmap_locks) |
| { |
| struct address_space *mapping = NULL; |
| struct anon_vma *anon_vma = NULL; |
| struct mm_struct *mm = vma->vm_mm; |
| pte_t *old_pte, *new_pte, pte; |
| spinlock_t *old_ptl, *new_ptl; |
| |
| /* |
| * When need_rmap_locks is true, we take the i_mmap_mutex and anon_vma |
| * locks to ensure that rmap will always observe either the old or the |
| * new ptes. This is the easiest way to avoid races with |
| * truncate_pagecache(), page migration, etc... |
| * |
| * When need_rmap_locks is false, we use other ways to avoid |
| * such races: |
| * |
| * - During exec() shift_arg_pages(), we use a specially tagged vma |
| * which rmap call sites look for using is_vma_temporary_stack(). |
| * |
| * - During mremap(), new_vma is often known to be placed after vma |
| * in rmap traversal order. This ensures rmap will always observe |
| * either the old pte, or the new pte, or both (the page table locks |
| * serialize access to individual ptes, but only rmap traversal |
| * order guarantees that we won't miss both the old and new ptes). |
| */ |
| if (need_rmap_locks) { |
| if (vma->vm_file) { |
| mapping = vma->vm_file->f_mapping; |
| mutex_lock(&mapping->i_mmap_mutex); |
| } |
| if (vma->anon_vma) { |
| anon_vma = vma->anon_vma; |
| anon_vma_lock_write(anon_vma); |
| } |
| } |
| |
| /* |
| * We don't have to worry about the ordering of src and dst |
| * pte locks because exclusive mmap_sem prevents deadlock. |
| */ |
| old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); |
| new_pte = pte_offset_map(new_pmd, new_addr); |
| new_ptl = pte_lockptr(mm, new_pmd); |
| if (new_ptl != old_ptl) |
| spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
| arch_enter_lazy_mmu_mode(); |
| |
| for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, |
| new_pte++, new_addr += PAGE_SIZE) { |
| if (pte_none(*old_pte)) |
| continue; |
| pte = ptep_get_and_clear(mm, old_addr, old_pte); |
| pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); |
| set_pte_at(mm, new_addr, new_pte, pte); |
| } |
| |
| arch_leave_lazy_mmu_mode(); |
| if (new_ptl != old_ptl) |
| spin_unlock(new_ptl); |
| pte_unmap(new_pte - 1); |
| pte_unmap_unlock(old_pte - 1, old_ptl); |
| if (anon_vma) |
| anon_vma_unlock_write(anon_vma); |
| if (mapping) |
| mutex_unlock(&mapping->i_mmap_mutex); |
| } |
| |
| #define LATENCY_LIMIT (64 * PAGE_SIZE) |
| |
| unsigned long move_page_tables(struct vm_area_struct *vma, |
| unsigned long old_addr, struct vm_area_struct *new_vma, |
| unsigned long new_addr, unsigned long len, |
| bool need_rmap_locks) |
| { |
| unsigned long extent, next, old_end; |
| pmd_t *old_pmd, *new_pmd; |
| bool need_flush = false; |
| unsigned long mmun_start; /* For mmu_notifiers */ |
| unsigned long mmun_end; /* For mmu_notifiers */ |
| |
| old_end = old_addr + len; |
| flush_cache_range(vma, old_addr, old_end); |
| |
| mmun_start = old_addr; |
| mmun_end = old_end; |
| mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); |
| |
| for (; old_addr < old_end; old_addr += extent, new_addr += extent) { |
| cond_resched(); |
| next = (old_addr + PMD_SIZE) & PMD_MASK; |
| /* even if next overflowed, extent below will be ok */ |
| extent = next - old_addr; |
| if (extent > old_end - old_addr) |
| extent = old_end - old_addr; |
| old_pmd = get_old_pmd(vma->vm_mm, old_addr); |
| if (!old_pmd) |
| continue; |
| new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); |
| if (!new_pmd) |
| break; |
| if (pmd_trans_huge(*old_pmd)) { |
| int err = 0; |
| if (extent == HPAGE_PMD_SIZE) |
| err = move_huge_pmd(vma, new_vma, old_addr, |
| new_addr, old_end, |
| old_pmd, new_pmd); |
| if (err > 0) { |
| need_flush = true; |
| continue; |
| } else if (!err) { |
| split_huge_page_pmd(vma, old_addr, old_pmd); |
| } |
| VM_BUG_ON(pmd_trans_huge(*old_pmd)); |
| } |
| if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma, |
| new_pmd, new_addr)) |
| break; |
| next = (new_addr + PMD_SIZE) & PMD_MASK; |
| if (extent > next - new_addr) |
| extent = next - new_addr; |
| if (extent > LATENCY_LIMIT) |
| extent = LATENCY_LIMIT; |
| move_ptes(vma, old_pmd, old_addr, old_addr + extent, |
| new_vma, new_pmd, new_addr, need_rmap_locks); |
| need_flush = true; |
| } |
| if (likely(need_flush)) |
| flush_tlb_range(vma, old_end-len, old_addr); |
| |
| mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); |
| |
| 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) |
| { |
| 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; |
| 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; |
| |
| /* |
| * 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; |
| |
| 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) |
| return -ENOMEM; |
| |
| moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, |
| need_rmap_locks); |
| if (moved_len < old_len) { |
| /* |
| * 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 = -ENOMEM; |
| } |
| |
| /* Conceal VM_ACCOUNT so old reservation is not undone */ |
| if (vm_flags & VM_ACCOUNT) { |
| 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, vma->vm_file, new_len>>PAGE_SHIFT); |
| |
| if (do_munmap(mm, old_addr, old_len) < 0) { |
| /* OOM: unable to split vma, just get accounts right */ |
| vm_unacct_memory(excess >> PAGE_SHIFT); |
| excess = 0; |
| } |
| 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; |
| } |
| |
| if (vm_flags & VM_LOCKED) { |
| mm->locked_vm += new_len >> PAGE_SHIFT; |
| *locked = true; |
| } |
| |
| return new_addr; |
| } |
| |
| static struct vm_area_struct *vma_to_resize(unsigned long addr, |
| unsigned long old_len, unsigned long new_len, unsigned long *p) |
| { |
| struct mm_struct *mm = current->mm; |
| struct vm_area_struct *vma = find_vma(mm, addr); |
| |
| if (!vma || vma->vm_start > addr) |
| goto Efault; |
| |
| if (is_vm_hugetlb_page(vma)) |
| goto Einval; |
| |
| /* We can't remap across vm area boundaries */ |
| if (old_len > vma->vm_end - addr) |
| goto Efault; |
| |
| /* Need to be careful about a growing mapping */ |
| if (new_len > old_len) { |
| unsigned long pgoff; |
| |
| if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) |
| goto Efault; |
| pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; |
| pgoff += vma->vm_pgoff; |
| if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) |
| goto Einval; |
| } |
| |
| 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)) |
| goto Eagain; |
| } |
| |
| if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) |
| goto Enomem; |
| |
| if (vma->vm_flags & VM_ACCOUNT) { |
| unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; |
| if (security_vm_enough_memory_mm(mm, charged)) |
| goto Efault; |
| *p = charged; |
| } |
| |
| return vma; |
| |
| Efault: /* very odd choice for most of the cases, but... */ |
| return ERR_PTR(-EFAULT); |
| Einval: |
| return ERR_PTR(-EINVAL); |
| Enomem: |
| return ERR_PTR(-ENOMEM); |
| Eagain: |
| return ERR_PTR(-EAGAIN); |
| } |
| |
| static unsigned long mremap_to(unsigned long addr, unsigned long old_len, |
| unsigned long new_addr, unsigned long new_len, bool *locked) |
| { |
| struct mm_struct *mm = current->mm; |
| struct vm_area_struct *vma; |
| unsigned long ret = -EINVAL; |
| unsigned long charged = 0; |
| unsigned long map_flags; |
| |
| if (new_addr & ~PAGE_MASK) |
| goto out; |
| |
| if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) |
| goto out; |
| |
| /* Check if the location we're moving into overlaps the |
| * old location at all, and fail if it does. |
| */ |
| if ((new_addr <= addr) && (new_addr+new_len) > addr) |
| goto out; |
| |
| if ((addr <= new_addr) && (addr+old_len) > new_addr) |
| goto out; |
| |
| ret = do_munmap(mm, new_addr, new_len); |
| if (ret) |
| goto out; |
| |
| if (old_len >= new_len) { |
| ret = do_munmap(mm, addr+new_len, old_len - new_len); |
| if (ret && old_len != new_len) |
| goto out; |
| old_len = new_len; |
| } |
| |
| vma = vma_to_resize(addr, old_len, new_len, &charged); |
| if (IS_ERR(vma)) { |
| ret = PTR_ERR(vma); |
| goto out; |
| } |
| |
| 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 (ret & ~PAGE_MASK) |
| goto out1; |
| |
| ret = move_vma(vma, addr, old_len, new_len, new_addr, locked); |
| if (!(ret & ~PAGE_MASK)) |
| 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; |
| |
| down_write(¤t->mm->mmap_sem); |
| |
| if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) |
| goto out; |
| |
| if (addr & ~PAGE_MASK) |
| goto out; |
| |
| 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) |
| goto out; |
| |
| if (flags & MREMAP_FIXED) { |
| if (flags & MREMAP_MAYMOVE) |
| 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, vma->vm_file, 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 (new_addr & ~PAGE_MASK) { |
| ret = new_addr; |
| goto out; |
| } |
| |
| ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked); |
| } |
| out: |
| if (ret & ~PAGE_MASK) |
| vm_unacct_memory(charged); |
| up_write(¤t->mm->mmap_sem); |
| if (locked && new_len > old_len) |
| mm_populate(new_addr + old_len, new_len - old_len); |
| return ret; |
| } |