/* * mm/mremap.c * * (C) Copyright 1996 Linus Torvalds * * Address space accounting code <alan@redhat.com> * (C) Copyright 2002 Red Hat Inc, All Rights Reserved */ #include <linux/mm.h> #include <linux/hugetlb.h> #include <linux/slab.h> #include <linux/shm.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 <asm/uaccess.h> #include <asm/cacheflush.h> #include <asm/tlbflush.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_or_clear_bad(pmd)) return NULL; return pmd; } static pmd_t *alloc_new_pmd(struct mm_struct *mm, 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; if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr)) return NULL; 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 vmtruncate 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; spin_lock(&mapping->i_mmap_lock); if (new_vma->vm_truncate_count && new_vma->vm_truncate_count != vma->vm_truncate_count) new_vma->vm_truncate_count = 0; } /* * 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_nested(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_clear_flush(vma, 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_nested(new_pte - 1); pte_unmap_unlock(old_pte - 1, old_ptl); if (mapping) spin_unlock(&mapping->i_mmap_lock); } #define LATENCY_LIMIT (64 * PAGE_SIZE) static 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; old_end = old_addr + len; flush_cache_range(vma, old_addr, old_end); for (; old_addr < old_end; old_addr += extent, new_addr += extent) { cond_resched(); next = (old_addr + PMD_SIZE) & PMD_MASK; if (next - 1 > old_end) next = old_end; extent = next - old_addr; old_pmd = get_old_pmd(vma->vm_mm, old_addr); if (!old_pmd) continue; new_pmd = alloc_new_pmd(vma->vm_mm, new_addr); if (!new_pmd) 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); } 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; /* * 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; 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) { /* * 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) make_pages_present(new_addr + old_len, new_addr + new_len); } return new_addr; } /* * 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; /* new_addr is only valid if MREMAP_FIXED is specified */ if (flags & MREMAP_FIXED) { if (new_addr & ~PAGE_MASK) goto out; if (!(flags & MREMAP_MAYMOVE)) 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(0, 0, 0, 0, new_addr, 1); if (ret) goto out; ret = do_munmap(mm, new_addr, new_len); if (ret) 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; if (!(flags & MREMAP_FIXED) || (new_addr == addr)) goto out; old_len = new_len; } /* * Ok, we need to grow.. or relocate. */ ret = -EFAULT; vma = find_vma(mm, addr); if (!vma || vma->vm_start > addr) goto out; if (is_vm_hugetlb_page(vma)) { ret = -EINVAL; goto out; } /* We can't remap across vm area boundaries */ if (old_len > vma->vm_end - addr) goto out; if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) { if (new_len > old_len) goto out; } if (vma->vm_flags & VM_LOCKED) { unsigned long locked, lock_limit; locked = mm->locked_vm << PAGE_SHIFT; lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; locked += new_len - old_len; ret = -EAGAIN; if (locked > lock_limit && !capable(CAP_IPC_LOCK)) goto out; } if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) { ret = -ENOMEM; goto out; } if (vma->vm_flags & VM_ACCOUNT) { charged = (new_len - old_len) >> PAGE_SHIFT; if (security_vm_enough_memory(charged)) goto out_nc; } /* old_len exactly to the end of the area.. * And we're not relocating the area. */ if (old_len == vma->vm_end - addr && !((flags & MREMAP_FIXED) && (addr != new_addr)) && (old_len != new_len || !(flags & MREMAP_MAYMOVE))) { unsigned long max_addr = TASK_SIZE; if (vma->vm_next) max_addr = vma->vm_next->vm_start; /* can we just expand the current mapping? */ if (max_addr - addr >= new_len) { int pages = (new_len - old_len) >> PAGE_SHIFT; vma_adjust(vma, vma->vm_start, addr + new_len, vma->vm_pgoff, NULL); 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; make_pages_present(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) { if (!(flags & MREMAP_FIXED)) { 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, map_flags); if (new_addr & ~PAGE_MASK) { ret = new_addr; goto out; } ret = security_file_mmap(0, 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); out_nc: return ret; } asmlinkage unsigned long sys_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; }