diff options
Diffstat (limited to 'mm/mremap.c')
| -rw-r--r-- | mm/mremap.c | 554 |
1 files changed, 554 insertions, 0 deletions
diff --git a/mm/mremap.c b/mm/mremap.c new file mode 100644 index 00000000..db8d983b --- /dev/null +++ b/mm/mremap.c @@ -0,0 +1,554 @@ +/* + * 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 <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) +{ + struct address_space *mapping = NULL; + struct mm_struct *mm = vma->vm_mm; + pte_t *old_pte, *new_pte, pte; + spinlock_t *old_ptl, *new_ptl; + + if (vma->vm_file) { + /* + * Subtle point from Rajesh Venkatasubramanian: before + * moving file-based ptes, we must lock truncate_pagecache + * out, since it might clean the dst vma before the src vma, + * and we propagate stale pages into the dst afterward. + */ + mapping = vma->vm_file->f_mapping; + mutex_lock(&mapping->i_mmap_mutex); + } + + /* + * 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 (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) +{ + unsigned long extent, next, old_end; + pmd_t *old_pmd, *new_pmd; + bool need_flush = false; + + old_end = old_addr + len; + flush_cache_range(vma, old_addr, old_end); + + mmu_notifier_invalidate_range_start(vma->vm_mm, old_addr, old_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->vm_mm, 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_flush = true; + } + if (likely(need_flush)) + flush_tlb_range(vma, old_end-len, old_addr); + + mmu_notifier_invalidate_range_end(vma->vm_mm, old_end-len, old_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) +{ + 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; + + /* + * 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); + if (!new_vma) + return -ENOMEM; + + moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len); + if (moved_len < old_len) { + /* + * Before moving the page tables from the new vma to + * the old vma, we need to be sure the old vma is + * queued after new vma in the same_anon_vma list to + * prevent SMP races with rmap_walk (that could lead + * rmap_walk to miss some page table). + */ + anon_vma_moveto_tail(vma); + + /* + * 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); + 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; + mm->total_vm += new_len >> PAGE_SHIFT; + 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; + if (new_len > old_len) + mlock_vma_pages_range(new_vma, new_addr + old_len, + new_addr + new_len); + } + + 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) +{ + 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 = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); + if (ret) + 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); + 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. + */ +unsigned long do_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; + + 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); + 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; + } + + mm->total_vm += pages; + vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages); + if (vma->vm_flags & VM_LOCKED) { + mm->locked_vm += pages; + mlock_vma_pages_range(vma, addr + old_len, + addr + new_len); + } + 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 = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); + if (ret) + goto out; + ret = move_vma(vma, addr, old_len, new_len, new_addr); + } +out: + if (ret & ~PAGE_MASK) + vm_unacct_memory(charged); + return ret; +} + +SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, + unsigned long, new_len, unsigned long, flags, + unsigned long, new_addr) +{ + unsigned long ret; + + down_write(¤t->mm->mmap_sem); + ret = do_mremap(addr, old_len, new_len, flags, new_addr); + up_write(¤t->mm->mmap_sem); + return ret; +} |