fs/squashfs/block.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * Squashfs - a compressed read only filesystem for Linux
0004  *
0005  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
0006  * Phillip Lougher <phillip@squashfs.org.uk>
0007  *
0008  * block.c
0009  */
0010
0011 /*
0012  * This file implements the low-level routines to read and decompress
0013  * datablocks and metadata blocks.
0014  */
0015
0016 #include <linux/blkdev.h>
0017 #include <linux/fs.h>
0018 #include <linux/vfs.h>
0019 #include <linux/slab.h>
0020 #include <linux/string.h>
0021 #include <linux/buffer_head.h>
0022 #include <linux/bio.h>
0023
0024 #include "squashfs_fs.h"
0025 #include "squashfs_fs_sb.h"
0026 #include "squashfs.h"
0027 #include "decompressor.h"
0028 #include "page_actor.h"
0029
0030 /*
0031  * Returns the amount of bytes copied to the page actor.
0032  */
0033 static int copy_bio_to_actor(struct bio *bio,
0034                  struct squashfs_page_actor *actor,
0035                  int offset, int req_length)
0036 {
0037     void *actor_addr;
0038     struct bvec_iter_all iter_all = {};
0039     struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
0040     int copied_bytes = 0;
0041     int actor_offset = 0;
0042
0043     squashfs_actor_nobuff(actor);
0044     actor_addr = squashfs_first_page(actor);
0045
0046     if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
0047         return 0;
0048
0049     while (copied_bytes < req_length) {
0050         int bytes_to_copy = min_t(int, bvec->bv_len - offset,
0051                       PAGE_SIZE - actor_offset);
0052
0053         bytes_to_copy = min_t(int, bytes_to_copy,
0054                       req_length - copied_bytes);
0055         if (!IS_ERR(actor_addr))
0056             memcpy(actor_addr + actor_offset, bvec_virt(bvec) +
0057                     offset, bytes_to_copy);
0058
0059         actor_offset += bytes_to_copy;
0060         copied_bytes += bytes_to_copy;
0061         offset += bytes_to_copy;
0062
0063         if (actor_offset >= PAGE_SIZE) {
0064             actor_addr = squashfs_next_page(actor);
0065             if (!actor_addr)
0066                 break;
0067             actor_offset = 0;
0068         }
0069         if (offset >= bvec->bv_len) {
0070             if (!bio_next_segment(bio, &iter_all))
0071                 break;
0072             offset = 0;
0073         }
0074     }
0075     squashfs_finish_page(actor);
0076     return copied_bytes;
0077 }
0078
0079 static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
0080                  struct bio **biop, int *block_offset)
0081 {
0082     struct squashfs_sb_info *msblk = sb->s_fs_info;
0083     const u64 read_start = round_down(index, msblk->devblksize);
0084     const sector_t block = read_start >> msblk->devblksize_log2;
0085     const u64 read_end = round_up(index + length, msblk->devblksize);
0086     const sector_t block_end = read_end >> msblk->devblksize_log2;
0087     int offset = read_start - round_down(index, PAGE_SIZE);
0088     int total_len = (block_end - block) << msblk->devblksize_log2;
0089     const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
0090     int error, i;
0091     struct bio *bio;
0092
0093     bio = bio_kmalloc(page_count, GFP_NOIO);
0094     if (!bio)
0095         return -ENOMEM;
0096     bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ);
0097     bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
0098
0099     for (i = 0; i < page_count; ++i) {
0100         unsigned int len =
0101             min_t(unsigned int, PAGE_SIZE - offset, total_len);
0102         struct page *page = alloc_page(GFP_NOIO);
0103
0104         if (!page) {
0105             error = -ENOMEM;
0106             goto out_free_bio;
0107         }
0108         if (!bio_add_page(bio, page, len, offset)) {
0109             error = -EIO;
0110             goto out_free_bio;
0111         }
0112         offset = 0;
0113         total_len -= len;
0114     }
0115
0116     error = submit_bio_wait(bio);
0117     if (error)
0118         goto out_free_bio;
0119
0120     *biop = bio;
0121     *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
0122     return 0;
0123
0124 out_free_bio:
0125     bio_free_pages(bio);
0126     bio_uninit(bio);
0127     kfree(bio);
0128     return error;
0129 }
0130
0131 /*
0132  * Read and decompress a metadata block or datablock.  Length is non-zero
0133  * if a datablock is being read (the size is stored elsewhere in the
0134  * filesystem), otherwise the length is obtained from the first two bytes of
0135  * the metadata block.  A bit in the length field indicates if the block
0136  * is stored uncompressed in the filesystem (usually because compression
0137  * generated a larger block - this does occasionally happen with compression
0138  * algorithms).
0139  */
0140 int squashfs_read_data(struct super_block *sb, u64 index, int length,
0141                u64 *next_index, struct squashfs_page_actor *output)
0142 {
0143     struct squashfs_sb_info *msblk = sb->s_fs_info;
0144     struct bio *bio = NULL;
0145     int compressed;
0146     int res;
0147     int offset;
0148
0149     if (length) {
0150         /*
0151          * Datablock.
0152          */
0153         compressed = SQUASHFS_COMPRESSED_BLOCK(length);
0154         length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
0155         TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
0156             index, compressed ? "" : "un", length, output->length);
0157     } else {
0158         /*
0159          * Metadata block.
0160          */
0161         const u8 *data;
0162         struct bvec_iter_all iter_all = {};
0163         struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
0164
0165         if (index + 2 > msblk->bytes_used) {
0166             res = -EIO;
0167             goto out;
0168         }
0169         res = squashfs_bio_read(sb, index, 2, &bio, &offset);
0170         if (res)
0171             goto out;
0172
0173         if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
0174             res = -EIO;
0175             goto out_free_bio;
0176         }
0177         /* Extract the length of the metadata block */
0178         data = bvec_virt(bvec);
0179         length = data[offset];
0180         if (offset < bvec->bv_len - 1) {
0181             length |= data[offset + 1] << 8;
0182         } else {
0183             if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
0184                 res = -EIO;
0185                 goto out_free_bio;
0186             }
0187             data = bvec_virt(bvec);
0188             length |= data[0] << 8;
0189         }
0190         bio_free_pages(bio);
0191         bio_uninit(bio);
0192         kfree(bio);
0193
0194         compressed = SQUASHFS_COMPRESSED(length);
0195         length = SQUASHFS_COMPRESSED_SIZE(length);
0196         index += 2;
0197
0198         TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
0199               compressed ? "" : "un", length);
0200     }
0201     if (length < 0 || length > output->length ||
0202             (index + length) > msblk->bytes_used) {
0203         res = -EIO;
0204         goto out;
0205     }
0206
0207     if (next_index)
0208         *next_index = index + length;
0209
0210     res = squashfs_bio_read(sb, index, length, &bio, &offset);
0211     if (res)
0212         goto out;
0213
0214     if (compressed) {
0215         if (!msblk->stream) {
0216             res = -EIO;
0217             goto out_free_bio;
0218         }
0219         res = squashfs_decompress(msblk, bio, offset, length, output);
0220     } else {
0221         res = copy_bio_to_actor(bio, output, offset, length);
0222     }
0223
0224 out_free_bio:
0225     bio_free_pages(bio);
0226     bio_uninit(bio);
0227     kfree(bio);
0228 out:
0229     if (res < 0) {
0230         ERROR("Failed to read block 0x%llx: %d\n", index, res);
0231         if (msblk->panic_on_errors)
0232             panic("squashfs read failed");
0233     }
0234
0235     return res;
0236 }