drivers/staging/erofs/dir.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/drivers/staging/erofs/dir.c
   4  *
   5  * Copyright (C) 2017-2018 HUAWEI, Inc.
   6  *             http://www.huawei.com/
   7  * Created by Gao Xiang <gaoxiang25@huawei.com>
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License.  See the file COPYING in the main directory of the Linux
  11  * distribution for more details.
  12  */
  13 #include "internal.h"
  14
  15 static const unsigned char erofs_filetype_table[EROFS_FT_MAX] = {
  16         [EROFS_FT_UNKNOWN]      = DT_UNKNOWN,
  17         [EROFS_FT_REG_FILE]     = DT_REG,
  18         [EROFS_FT_DIR]          = DT_DIR,
  19         [EROFS_FT_CHRDEV]       = DT_CHR,
  20         [EROFS_FT_BLKDEV]       = DT_BLK,
  21         [EROFS_FT_FIFO]         = DT_FIFO,
  22         [EROFS_FT_SOCK]         = DT_SOCK,
  23         [EROFS_FT_SYMLINK]      = DT_LNK,
  24 };
  25
  26 static int erofs_fill_dentries(struct dir_context *ctx,
  27                                void *dentry_blk, unsigned int *ofs,
  28                                unsigned int nameoff, unsigned int maxsize)
  29 {
  30         struct erofs_dirent *de = dentry_blk;
  31         const struct erofs_dirent *end = dentry_blk + nameoff;
  32
  33         de = dentry_blk + *ofs;
  34         while (de < end) {
  35                 const char *de_name;
  36                 int de_namelen;
  37                 unsigned char d_type;
  38 #ifdef CONFIG_EROFS_FS_DEBUG
  39                 unsigned int dbg_namelen;
  40                 unsigned char dbg_namebuf[EROFS_NAME_LEN];
  41 #endif
  42
  43                 if (unlikely(de->file_type < EROFS_FT_MAX))
  44                         d_type = erofs_filetype_table[de->file_type];
  45                 else
  46                         d_type = DT_UNKNOWN;
  47
  48                 nameoff = le16_to_cpu(de->nameoff);
  49                 de_name = (char *)dentry_blk + nameoff;
  50
  51                 de_namelen = unlikely(de + 1 >= end) ?
  52                         /* last directory entry */
  53                         strnlen(de_name, maxsize - nameoff) :
  54                         le16_to_cpu(de[1].nameoff) - nameoff;
  55
  56                 /* a corrupted entry is found */
  57                 if (unlikely(de_namelen < 0)) {
  58                         DBG_BUGON(1);
  59                         return -EIO;
  60                 }
  61
  62 #ifdef CONFIG_EROFS_FS_DEBUG
  63                 dbg_namelen = min(EROFS_NAME_LEN - 1, de_namelen);
  64                 memcpy(dbg_namebuf, de_name, dbg_namelen);
  65                 dbg_namebuf[dbg_namelen] = '\0';
  66
  67                 debugln("%s, found de_name %s de_len %d d_type %d", __func__,
  68                         dbg_namebuf, de_namelen, d_type);
  69 #endif
  70
  71                 if (!dir_emit(ctx, de_name, de_namelen,
  72                               le64_to_cpu(de->nid), d_type))
  73                         /* stopped by some reason */
  74                         return 1;
  75                 ++de;
  76                 *ofs += sizeof(struct erofs_dirent);
  77         }
  78         *ofs = maxsize;
  79         return 0;
  80 }
  81
  82 static int erofs_readdir(struct file *f, struct dir_context *ctx)
  83 {
  84         struct inode *dir = file_inode(f);
  85         struct address_space *mapping = dir->i_mapping;
  86         const size_t dirsize = i_size_read(dir);
  87         unsigned int i = ctx->pos / EROFS_BLKSIZ;
  88         unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
  89         int err = 0;
  90         bool initial = true;
  91
  92         while (ctx->pos < dirsize) {
  93                 struct page *dentry_page;
  94                 struct erofs_dirent *de;
  95                 unsigned int nameoff, maxsize;
  96
  97                 dentry_page = read_mapping_page(mapping, i, NULL);
  98                 if (IS_ERR(dentry_page))
  99                         continue;
 100
 101                 de = (struct erofs_dirent *)kmap(dentry_page);
 102
 103                 nameoff = le16_to_cpu(de->nameoff);
 104
 105                 if (unlikely(nameoff < sizeof(struct erofs_dirent) ||
 106                              nameoff >= PAGE_SIZE)) {
 107                         errln("%s, invalid de[0].nameoff %u",
 108                               __func__, nameoff);
 109
 110                         err = -EIO;
 111                         goto skip_this;
 112                 }
 113
 114                 maxsize = min_t(unsigned int,
 115                                 dirsize - ctx->pos + ofs, PAGE_SIZE);
 116
 117                 /* search dirents at the arbitrary position */
 118                 if (unlikely(initial)) {
 119                         initial = false;
 120
 121                         ofs = roundup(ofs, sizeof(struct erofs_dirent));
 122                         if (unlikely(ofs >= nameoff))
 123                                 goto skip_this;
 124                 }
 125
 126                 err = erofs_fill_dentries(ctx, de, &ofs, nameoff, maxsize);
 127 skip_this:
 128                 kunmap(dentry_page);
 129
 130                 put_page(dentry_page);
 131
 132                 ctx->pos = blknr_to_addr(i) + ofs;
 133
 134                 if (unlikely(err))
 135                         break;
 136                 ++i;
 137                 ofs = 0;
 138         }
 139         return err < 0 ? err : 0;
 140 }
 141
 142 const struct file_operations erofs_dir_fops = {
 143         .llseek         = generic_file_llseek,
 144         .read           = generic_read_dir,
 145         .iterate_shared = erofs_readdir,
 146 };
 147