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 = squashfs_first_page(actor);
  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         if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
  44                 return 0;
  45
  46         while (copied_bytes < req_length) {
  47                 int bytes_to_copy = min_t(int, bvec->bv_len - offset,
  48                                           PAGE_SIZE - actor_offset);
  49
  50                 bytes_to_copy = min_t(int, bytes_to_copy,
  51                                       req_length - copied_bytes);
  52                 memcpy(actor_addr + actor_offset, bvec_virt(bvec) + offset,
  53                        bytes_to_copy);
  54
  55                 actor_offset += bytes_to_copy;
  56                 copied_bytes += bytes_to_copy;
  57                 offset += bytes_to_copy;
  58
  59                 if (actor_offset >= PAGE_SIZE) {
  60                         actor_addr = squashfs_next_page(actor);
  61                         if (!actor_addr)
  62                                 break;
  63                         actor_offset = 0;
  64                 }
  65                 if (offset >= bvec->bv_len) {
  66                         if (!bio_next_segment(bio, &iter_all))
  67                                 break;
  68                         offset = 0;
  69                 }
  70         }
  71         squashfs_finish_page(actor);
  72         return copied_bytes;
  73 }
  74
  75 static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
  76                              struct bio **biop, int *block_offset)
  77 {
  78         struct squashfs_sb_info *msblk = sb->s_fs_info;
  79         const u64 read_start = round_down(index, msblk->devblksize);
  80         const sector_t block = read_start >> msblk->devblksize_log2;
  81         const u64 read_end = round_up(index + length, msblk->devblksize);
  82         const sector_t block_end = read_end >> msblk->devblksize_log2;
  83         int offset = read_start - round_down(index, PAGE_SIZE);
  84         int total_len = (block_end - block) << msblk->devblksize_log2;
  85         const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
  86         int error, i;
  87         struct bio *bio;
  88
  89         if (page_count <= BIO_MAX_VECS)
  90                 bio = bio_alloc(GFP_NOIO, page_count);
  91         else
  92                 bio = bio_kmalloc(GFP_NOIO, page_count);
  93
  94         if (!bio)
  95                 return -ENOMEM;
  96
  97         bio_set_dev(bio, sb->s_bdev);
  98         bio->bi_opf = READ;
  99         bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
 100
 101         for (i = 0; i < page_count; ++i) {
 102                 unsigned int len =
 103                         min_t(unsigned int, PAGE_SIZE - offset, total_len);
 104                 struct page *page = alloc_page(GFP_NOIO);
 105
 106                 if (!page) {
 107                         error = -ENOMEM;
 108                         goto out_free_bio;
 109                 }
 110                 if (!bio_add_page(bio, page, len, offset)) {
 111                         error = -EIO;
 112                         goto out_free_bio;
 113                 }
 114                 offset = 0;
 115                 total_len -= len;
 116         }
 117
 118         error = submit_bio_wait(bio);
 119         if (error)
 120                 goto out_free_bio;
 121
 122         *biop = bio;
 123         *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
 124         return 0;
 125
 126 out_free_bio:
 127         bio_free_pages(bio);
 128         bio_put(bio);
 129         return error;
 130 }
 131
 132 /*
 133  * Read and decompress a metadata block or datablock.  Length is non-zero
 134  * if a datablock is being read (the size is stored elsewhere in the
 135  * filesystem), otherwise the length is obtained from the first two bytes of
 136  * the metadata block.  A bit in the length field indicates if the block
 137  * is stored uncompressed in the filesystem (usually because compression
 138  * generated a larger block - this does occasionally happen with compression
 139  * algorithms).
 140  */
 141 int squashfs_read_data(struct super_block *sb, u64 index, int length,
 142                        u64 *next_index, struct squashfs_page_actor *output)
 143 {
 144         struct squashfs_sb_info *msblk = sb->s_fs_info;
 145         struct bio *bio = NULL;
 146         int compressed;
 147         int res;
 148         int offset;
 149
 150         if (length) {
 151                 /*
 152                  * Datablock.
 153                  */
 154                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
 155                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
 156                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
 157                         index, compressed ? "" : "un", length, output->length);
 158         } else {
 159                 /*
 160                  * Metadata block.
 161                  */
 162                 const u8 *data;
 163                 struct bvec_iter_all iter_all = {};
 164                 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
 165
 166                 if (index + 2 > msblk->bytes_used) {
 167                         res = -EIO;
 168                         goto out;
 169                 }
 170                 res = squashfs_bio_read(sb, index, 2, &bio, &offset);
 171                 if (res)
 172                         goto out;
 173
 174                 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
 175                         res = -EIO;
 176                         goto out_free_bio;
 177                 }
 178                 /* Extract the length of the metadata block */
 179                 data = bvec_virt(bvec);
 180                 length = data[offset];
 181                 if (offset < bvec->bv_len - 1) {
 182                         length |= data[offset + 1] << 8;
 183                 } else {
 184                         if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
 185                                 res = -EIO;
 186                                 goto out_free_bio;
 187                         }
 188                         data = bvec_virt(bvec);
 189                         length |= data[0] << 8;
 190                 }
 191                 bio_free_pages(bio);
 192                 bio_put(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_put(bio);
 227 out:
 228         if (res < 0) {
 229                 ERROR("Failed to read block 0x%llx: %d\n", index, res);
 230                 if (msblk->panic_on_errors)
 231                         panic("squashfs read failed");
 232         }
 233
 234         return res;
 235 }