fs/romfs/mmap-nommu.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* NOMMU mmap support for RomFS on MTD devices
   3  *
   4  * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/mm.h>
   9 #include <linux/mtd/super.h>
  10 #include "internal.h"
  11
  12 /*
  13  * try to determine where a shared mapping can be made
  14  * - only supported for NOMMU at the moment (MMU can't doesn't copy private
  15  *   mappings)
  16  * - attempts to map through to the underlying MTD device
  17  */
  18 static unsigned long romfs_get_unmapped_area(struct file *file,
  19                                              unsigned long addr,
  20                                              unsigned long len,
  21                                              unsigned long pgoff,
  22                                              unsigned long flags)
  23 {
  24         struct inode *inode = file->f_mapping->host;
  25         struct mtd_info *mtd = inode->i_sb->s_mtd;
  26         unsigned long isize, offset, maxpages, lpages;
  27         int ret;
  28
  29         if (!mtd)
  30                 return (unsigned long) -ENOSYS;
  31
  32         /* the mapping mustn't extend beyond the EOF */
  33         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
  34         isize = i_size_read(inode);
  35         offset = pgoff << PAGE_SHIFT;
  36
  37         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
  38         if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
  39                 return (unsigned long) -EINVAL;
  40
  41         if (addr != 0)
  42                 return (unsigned long) -EINVAL;
  43
  44         if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
  45                 return (unsigned long) -EINVAL;
  46
  47         offset += ROMFS_I(inode)->i_dataoffset;
  48         if (offset >= mtd->size)
  49                 return (unsigned long) -EINVAL;
  50         /* the mapping mustn't extend beyond the EOF */
  51         if ((offset + len) > mtd->size)
  52                 len = mtd->size - offset;
  53
  54         ret = mtd_get_unmapped_area(mtd, len, offset, flags);
  55         if (ret == -EOPNOTSUPP)
  56                 ret = -ENOSYS;
  57         return (unsigned long) ret;
  58 }
  59
  60 /*
  61  * permit a R/O mapping to be made directly through onto an MTD device if
  62  * possible
  63  */
  64 static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
  65 {
  66         return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
  67 }
  68
  69 static unsigned romfs_mmap_capabilities(struct file *file)
  70 {
  71         struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
  72
  73         if (!mtd)
  74                 return NOMMU_MAP_COPY;
  75         return mtd_mmap_capabilities(mtd);
  76 }
  77
  78 const struct file_operations romfs_ro_fops = {
  79         .llseek                 = generic_file_llseek,
  80         .read_iter              = generic_file_read_iter,
  81         .splice_read            = generic_file_splice_read,
  82         .mmap                   = romfs_mmap,
  83         .get_unmapped_area      = romfs_get_unmapped_area,
  84         .mmap_capabilities      = romfs_mmap_capabilities,
  85 };