fs/squashfs/block.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Squashfs - a compressed read only filesystem for Linux
   4  *
   5  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
   6  * Phillip Lougher <phillip@squashfs.org.uk>
   7  *
   8  * block.c
   9  */
  10
  11 /*
  12  * This file implements the low-level routines to read and decompress
  13  * datablocks and metadata blocks.
  14  */
  15
  16 #include <linux/blkdev.h>
  17 #include <linux/fs.h>
  18 #include <linux/vfs.h>
  19 #include <linux/slab.h>
  20 #include <linux/string.h>
  21 #include <linux/buffer_head.h>
  22 #include <linux/bio.h>
  23
  24 #include "squashfs_fs.h"
  25 #include "squashfs_fs_sb.h"
  26 #include "squashfs.h"
  27 #include "decompressor.h"
  28 #include "page_actor.h"
  29
  30 /*
  31  * Returns the amount of bytes copied to the page actor.
  32  */
  33 static int copy_bio_to_actor(struct bio *bio,
  34                              struct squashfs_page_actor *actor,
  35                              int offset, int req_length)
  36 {
  37         void *actor_addr;
  38         struct bvec_iter_all iter_all = {};
  39         struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
  40         int copied_bytes = 0;
  41         int actor_offset = 0;
  42
  43         squashfs_actor_nobuff(actor);
  44         actor_addr = squashfs_first_page(actor);
  45
  46         if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
  47                 return 0;
  48
  49         while (copied_bytes < req_length) {
  50                 int bytes_to_copy = min_t(int, bvec->bv_len - offset,
  51                                           PAGE_SIZE - actor_offset);
  52
  53                 bytes_to_copy = min_t(int, bytes_to_copy,
  54                                       req_length - copied_bytes);
  55                 if (!IS_ERR(actor_addr))
  56                         memcpy(actor_addr + actor_offset, bvec_virt(bvec) +
  57                                         offset, bytes_to_copy);
  58
  59                 actor_offset += bytes_to_copy;
  60                 copied_bytes += bytes_to_copy;
  61                 offset += bytes_to_copy;
  62
  63                 if (actor_offset >= PAGE_SIZE) {
  64                         actor_addr = squashfs_next_page(actor);
  65                         if (!actor_addr)
  66                                 break;
  67                         actor_offset = 0;
  68                 }
  69                 if (offset >= bvec->bv_len) {
  70                         if (!bio_next_segment(bio, &iter_all))
  71                                 break;
  72                         offset = 0;
  73                 }
  74         }
  75         squashfs_finish_page(actor);
  76         return copied_bytes;
  77 }
  78
  79 static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
  80                              struct bio **biop, int *block_offset)
  81 {
  82         struct squashfs_sb_info *msblk = sb->s_fs_info;
  83         const u64 read_start = round_down(index, msblk->devblksize);
  84         const sector_t block = read_start >> msblk->devblksize_log2;
  85         const u64 read_end = round_up(index + length, msblk->devblksize);
  86         const sector_t block_end = read_end >> msblk->devblksize_log2;
  87         int offset = read_start - round_down(index, PAGE_SIZE);
  88         int total_len = (block_end - block) << msblk->devblksize_log2;
  89         const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
  90         int error, i;
  91         struct bio *bio;
  92
  93         bio = bio_kmalloc(page_count, GFP_NOIO);
  94         if (!bio)
  95                 return -ENOMEM;
  96         bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ);
  97         bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
  98
  99         for (i = 0; i < page_count; ++i) {
 100                 unsigned int len =
 101                         min_t(unsigned int, PAGE_SIZE - offset, total_len);
 102                 struct page *page = alloc_page(GFP_NOIO);
 103
 104                 if (!page) {
 105                         error = -ENOMEM;
 106                         goto out_free_bio;
 107                 }
 108                 if (!bio_add_page(bio, page, len, offset)) {
 109                         error = -EIO;
 110                         goto out_free_bio;
 111                 }
 112                 offset = 0;
 113                 total_len -= len;
 114         }
 115
 116         error = submit_bio_wait(bio);
 117         if (error)
 118                 goto out_free_bio;
 119
 120         *biop = bio;
 121         *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
 122         return 0;
 123
 124 out_free_bio:
 125         bio_free_pages(bio);
 126         bio_uninit(bio);
 127         kfree(bio);
 128         return error;
 129 }
 130
 131 /*
 132  * Read and decompress a metadata block or datablock.  Length is non-zero
 133  * if a datablock is being read (the size is stored elsewhere in the
 134  * filesystem), otherwise the length is obtained from the first two bytes of
 135  * the metadata block.  A bit in the length field indicates if the block
 136  * is stored uncompressed in the filesystem (usually because compression
 137  * generated a larger block - this does occasionally happen with compression
 138  * algorithms).
 139  */
 140 int squashfs_read_data(struct super_block *sb, u64 index, int length,
 141                        u64 *next_index, struct squashfs_page_actor *output)
 142 {
 143         struct squashfs_sb_info *msblk = sb->s_fs_info;
 144         struct bio *bio = NULL;
 145         int compressed;
 146         int res;
 147         int offset;
 148
 149         if (length) {
 150                 /*
 151                  * Datablock.
 152                  */
 153                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
 154                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
 155                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
 156                         index, compressed ? "" : "un", length, output->length);
 157         } else {
 158                 /*
 159                  * Metadata block.
 160                  */
 161                 const u8 *data;
 162                 struct bvec_iter_all iter_all = {};
 163                 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
 164
 165                 if (index + 2 > msblk->bytes_used) {
 166                         res = -EIO;
 167                         goto out;
 168                 }
 169                 res = squashfs_bio_read(sb, index, 2, &bio, &offset);
 170                 if (res)
 171                         goto out;
 172
 173                 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
 174                         res = -EIO;
 175                         goto out_free_bio;
 176                 }
 177                 /* Extract the length of the metadata block */
 178                 data = bvec_virt(bvec);
 179                 length = data[offset];
 180                 if (offset < bvec->bv_len - 1) {
 181                         length |= data[offset + 1] << 8;
 182                 } else {
 183                         if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
 184                                 res = -EIO;
 185                                 goto out_free_bio;
 186                         }
 187                         data = bvec_virt(bvec);
 188                         length |= data[0] << 8;
 189                 }
 190                 bio_free_pages(bio);
 191                 bio_uninit(bio);
 192                 kfree(bio);
 193
 194                 compressed = SQUASHFS_COMPRESSED(length);
 195                 length = SQUASHFS_COMPRESSED_SIZE(length);
 196                 index += 2;
 197
 198                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
 199                       compressed ? "" : "un", length);
 200         }
 201         if (length < 0 || length > output->length ||
 202                         (index + length) > msblk->bytes_used) {
 203                 res = -EIO;
 204                 goto out;
 205         }
 206
 207         if (next_index)
 208                 *next_index = index + length;
 209
 210         res = squashfs_bio_read(sb, index, length, &bio, &offset);
 211         if (res)
 212                 goto out;
 213
 214         if (compressed) {
 215                 if (!msblk->stream) {
 216                         res = -EIO;
 217                         goto out_free_bio;
 218                 }
 219                 res = squashfs_decompress(msblk, bio, offset, length, output);
 220         } else {
 221                 res = copy_bio_to_actor(bio, output, offset, length);
 222         }
 223
 224 out_free_bio:
 225         bio_free_pages(bio);
 226         bio_uninit(bio);
 227         kfree(bio);
 228 out:
 229         if (res < 0) {
 230                 ERROR("Failed to read block 0x%llx: %d\n", index, res);
 231                 if (msblk->panic_on_errors)
 232                         panic("squashfs read failed");
 233         }
 234
 235         return res;
 236 }