diff options
Diffstat (limited to 'mm/mremap.c')
| -rw-r--r-- | mm/mremap.c | 426 |
1 files changed, 426 insertions, 0 deletions
diff --git a/mm/mremap.c b/mm/mremap.c new file mode 100644 index 000000000000..0d1c1b9c7a0a --- /dev/null +++ b/mm/mremap.c @@ -0,0 +1,426 @@ +/* + * 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/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 pte_t *get_one_pte_map_nested(struct mm_struct *mm, unsigned long addr) +{ + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *pte = NULL; + + pgd = pgd_offset(mm, addr); + if (pgd_none_or_clear_bad(pgd)) + goto end; + + pud = pud_offset(pgd, addr); + if (pud_none_or_clear_bad(pud)) + goto end; + + pmd = pmd_offset(pud, addr); + if (pmd_none_or_clear_bad(pmd)) + goto end; + + pte = pte_offset_map_nested(pmd, addr); + if (pte_none(*pte)) { + pte_unmap_nested(pte); + pte = NULL; + } +end: + return pte; +} + +static pte_t *get_one_pte_map(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 pte_offset_map(pmd, addr); +} + +static inline pte_t *alloc_one_pte_map(struct mm_struct *mm, unsigned long addr) +{ + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *pte = NULL; + + pgd = pgd_offset(mm, addr); + + pud = pud_alloc(mm, pgd, addr); + if (!pud) + return NULL; + pmd = pmd_alloc(mm, pud, addr); + if (pmd) + pte = pte_alloc_map(mm, pmd, addr); + return pte; +} + +static int +move_one_page(struct vm_area_struct *vma, unsigned long old_addr, + struct vm_area_struct *new_vma, unsigned long new_addr) +{ + struct address_space *mapping = NULL; + struct mm_struct *mm = vma->vm_mm; + int error = 0; + pte_t *src, *dst; + + 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; + } + spin_lock(&mm->page_table_lock); + + src = get_one_pte_map_nested(mm, old_addr); + if (src) { + /* + * Look to see whether alloc_one_pte_map needs to perform a + * memory allocation. If it does then we need to drop the + * atomic kmap + */ + dst = get_one_pte_map(mm, new_addr); + if (unlikely(!dst)) { + pte_unmap_nested(src); + if (mapping) + spin_unlock(&mapping->i_mmap_lock); + dst = alloc_one_pte_map(mm, new_addr); + if (mapping && !spin_trylock(&mapping->i_mmap_lock)) { + spin_unlock(&mm->page_table_lock); + spin_lock(&mapping->i_mmap_lock); + spin_lock(&mm->page_table_lock); + } + src = get_one_pte_map_nested(mm, old_addr); + } + /* + * Since alloc_one_pte_map can drop and re-acquire + * page_table_lock, we should re-check the src entry... + */ + if (src) { + if (dst) { + pte_t pte; + pte = ptep_clear_flush(vma, old_addr, src); + set_pte_at(mm, new_addr, dst, pte); + } else + error = -ENOMEM; + pte_unmap_nested(src); + } + if (dst) + pte_unmap(dst); + } + spin_unlock(&mm->page_table_lock); + if (mapping) + spin_unlock(&mapping->i_mmap_lock); + return error; +} + +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 offset; + + flush_cache_range(vma, old_addr, old_addr + len); + + /* + * This is not the clever way to do this, but we're taking the + * easy way out on the assumption that most remappings will be + * only a few pages.. This also makes error recovery easier. + */ + for (offset = 0; offset < len; offset += PAGE_SIZE) { + if (move_one_page(vma, old_addr + offset, + new_vma, new_addr + offset) < 0) + break; + cond_resched(); + } + return offset; +} + +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; + 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 (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; + } + + /* 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; + } + + mm->total_vm += new_len >> PAGE_SHIFT; + __vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); + 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 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 = do_munmap(current->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(current->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(current->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) { + if (new_len > old_len) + goto out; + } + if (vma->vm_flags & VM_LOCKED) { + unsigned long locked, lock_limit; + locked = current->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; + } + ret = -ENOMEM; + if ((current->mm->total_vm << PAGE_SHIFT) + (new_len - old_len) + > current->signal->rlim[RLIMIT_AS].rlim_cur) + 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); + + current->mm->total_vm += pages; + __vm_stat_account(vma->vm_mm, vma->vm_flags, + vma->vm_file, pages); + if (vma->vm_flags & VM_LOCKED) { + current->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); + ret = new_addr; + if (new_addr & ~PAGE_MASK) + 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; +} |