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, 53 page_address(bvec->bv_page) + bvec->bv_offset + offset, 54 bytes_to_copy); 55 56 actor_offset += bytes_to_copy; 57 copied_bytes += bytes_to_copy; 58 offset += bytes_to_copy; 59 60 if (actor_offset >= PAGE_SIZE) { 61 actor_addr = squashfs_next_page(actor); 62 if (!actor_addr) 63 break; 64 actor_offset = 0; 65 } 66 if (offset >= bvec->bv_len) { 67 if (!bio_next_segment(bio, &iter_all)) 68 break; 69 offset = 0; 70 } 71 } 72 squashfs_finish_page(actor); 73 return copied_bytes; 74 } 75 76 static int squashfs_bio_read(struct super_block *sb, u64 index, int length, 77 struct bio **biop, int *block_offset) 78 { 79 struct squashfs_sb_info *msblk = sb->s_fs_info; 80 const u64 read_start = round_down(index, msblk->devblksize); 81 const sector_t block = read_start >> msblk->devblksize_log2; 82 const u64 read_end = round_up(index + length, msblk->devblksize); 83 const sector_t block_end = read_end >> msblk->devblksize_log2; 84 int offset = read_start - round_down(index, PAGE_SIZE); 85 int total_len = (block_end - block) << msblk->devblksize_log2; 86 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE); 87 int error, i; 88 struct bio *bio; 89 90 bio = bio_alloc(GFP_NOIO, page_count); 91 if (!bio) 92 return -ENOMEM; 93 94 bio_set_dev(bio, sb->s_bdev); 95 bio->bi_opf = READ; 96 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); 97 98 for (i = 0; i < page_count; ++i) { 99 unsigned int len = 100 min_t(unsigned int, PAGE_SIZE - offset, total_len); 101 struct page *page = alloc_page(GFP_NOIO); 102 103 if (!page) { 104 error = -ENOMEM; 105 goto out_free_bio; 106 } 107 if (!bio_add_page(bio, page, len, offset)) { 108 error = -EIO; 109 goto out_free_bio; 110 } 111 offset = 0; 112 total_len -= len; 113 } 114 115 error = submit_bio_wait(bio); 116 if (error) 117 goto out_free_bio; 118 119 *biop = bio; 120 *block_offset = index & ((1 << msblk->devblksize_log2) - 1); 121 return 0; 122 123 out_free_bio: 124 bio_free_pages(bio); 125 bio_put(bio); 126 return error; 127 } 128 129 /* 130 * Read and decompress a metadata block or datablock. Length is non-zero 131 * if a datablock is being read (the size is stored elsewhere in the 132 * filesystem), otherwise the length is obtained from the first two bytes of 133 * the metadata block. A bit in the length field indicates if the block 134 * is stored uncompressed in the filesystem (usually because compression 135 * generated a larger block - this does occasionally happen with compression 136 * algorithms). 137 */ 138 int squashfs_read_data(struct super_block *sb, u64 index, int length, 139 u64 *next_index, struct squashfs_page_actor *output) 140 { 141 struct squashfs_sb_info *msblk = sb->s_fs_info; 142 struct bio *bio = NULL; 143 int compressed; 144 int res; 145 int offset; 146 147 if (length) { 148 /* 149 * Datablock. 150 */ 151 compressed = SQUASHFS_COMPRESSED_BLOCK(length); 152 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); 153 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", 154 index, compressed ? "" : "un", length, output->length); 155 } else { 156 /* 157 * Metadata block. 158 */ 159 const u8 *data; 160 struct bvec_iter_all iter_all = {}; 161 struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 162 163 if (index + 2 > msblk->bytes_used) { 164 res = -EIO; 165 goto out; 166 } 167 res = squashfs_bio_read(sb, index, 2, &bio, &offset); 168 if (res) 169 goto out; 170 171 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 172 res = -EIO; 173 goto out_free_bio; 174 } 175 /* Extract the length of the metadata block */ 176 data = page_address(bvec->bv_page) + bvec->bv_offset; 177 length = data[offset]; 178 if (offset <= bvec->bv_len - 1) { 179 length |= data[offset + 1] << 8; 180 } else { 181 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 182 res = -EIO; 183 goto out_free_bio; 184 } 185 data = page_address(bvec->bv_page) + bvec->bv_offset; 186 length |= data[0] << 8; 187 } 188 bio_free_pages(bio); 189 bio_put(bio); 190 191 compressed = SQUASHFS_COMPRESSED(length); 192 length = SQUASHFS_COMPRESSED_SIZE(length); 193 index += 2; 194 195 TRACE("Block @ 0x%llx, %scompressed size %d\n", index, 196 compressed ? "" : "un", length); 197 } 198 if (next_index) 199 *next_index = index + length; 200 201 res = squashfs_bio_read(sb, index, length, &bio, &offset); 202 if (res) 203 goto out; 204 205 if (compressed) { 206 if (!msblk->stream) { 207 res = -EIO; 208 goto out_free_bio; 209 } 210 res = squashfs_decompress(msblk, bio, offset, length, output); 211 } else { 212 res = copy_bio_to_actor(bio, output, offset, length); 213 } 214 215 out_free_bio: 216 bio_free_pages(bio); 217 bio_put(bio); 218 out: 219 if (res < 0) 220 ERROR("Failed to read block 0x%llx: %d\n", index, res); 221 222 return res; 223 } 224