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 if (page_count <= BIO_MAX_PAGES) 91 bio = bio_alloc(GFP_NOIO, page_count); 92 else 93 bio = bio_kmalloc(GFP_NOIO, page_count); 94 95 if (!bio) 96 return -ENOMEM; 97 98 bio_set_dev(bio, sb->s_bdev); 99 bio->bi_opf = READ; 100 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); 101 102 for (i = 0; i < page_count; ++i) { 103 unsigned int len = 104 min_t(unsigned int, PAGE_SIZE - offset, total_len); 105 struct page *page = alloc_page(GFP_NOIO); 106 107 if (!page) { 108 error = -ENOMEM; 109 goto out_free_bio; 110 } 111 if (!bio_add_page(bio, page, len, offset)) { 112 error = -EIO; 113 goto out_free_bio; 114 } 115 offset = 0; 116 total_len -= len; 117 } 118 119 error = submit_bio_wait(bio); 120 if (error) 121 goto out_free_bio; 122 123 *biop = bio; 124 *block_offset = index & ((1 << msblk->devblksize_log2) - 1); 125 return 0; 126 127 out_free_bio: 128 bio_free_pages(bio); 129 bio_put(bio); 130 return error; 131 } 132 133 /* 134 * Read and decompress a metadata block or datablock. Length is non-zero 135 * if a datablock is being read (the size is stored elsewhere in the 136 * filesystem), otherwise the length is obtained from the first two bytes of 137 * the metadata block. A bit in the length field indicates if the block 138 * is stored uncompressed in the filesystem (usually because compression 139 * generated a larger block - this does occasionally happen with compression 140 * algorithms). 141 */ 142 int squashfs_read_data(struct super_block *sb, u64 index, int length, 143 u64 *next_index, struct squashfs_page_actor *output) 144 { 145 struct squashfs_sb_info *msblk = sb->s_fs_info; 146 struct bio *bio = NULL; 147 int compressed; 148 int res; 149 int offset; 150 151 if (length) { 152 /* 153 * Datablock. 154 */ 155 compressed = SQUASHFS_COMPRESSED_BLOCK(length); 156 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); 157 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", 158 index, compressed ? "" : "un", length, output->length); 159 } else { 160 /* 161 * Metadata block. 162 */ 163 const u8 *data; 164 struct bvec_iter_all iter_all = {}; 165 struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 166 167 if (index + 2 > msblk->bytes_used) { 168 res = -EIO; 169 goto out; 170 } 171 res = squashfs_bio_read(sb, index, 2, &bio, &offset); 172 if (res) 173 goto out; 174 175 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 176 res = -EIO; 177 goto out_free_bio; 178 } 179 /* Extract the length of the metadata block */ 180 data = page_address(bvec->bv_page) + bvec->bv_offset; 181 length = data[offset]; 182 if (offset < bvec->bv_len - 1) { 183 length |= data[offset + 1] << 8; 184 } else { 185 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 186 res = -EIO; 187 goto out_free_bio; 188 } 189 data = page_address(bvec->bv_page) + bvec->bv_offset; 190 length |= data[0] << 8; 191 } 192 bio_free_pages(bio); 193 bio_put(bio); 194 195 compressed = SQUASHFS_COMPRESSED(length); 196 length = SQUASHFS_COMPRESSED_SIZE(length); 197 index += 2; 198 199 TRACE("Block @ 0x%llx, %scompressed size %d\n", index, 200 compressed ? "" : "un", length); 201 } 202 if (next_index) 203 *next_index = index + length; 204 205 res = squashfs_bio_read(sb, index, length, &bio, &offset); 206 if (res) 207 goto out; 208 209 if (compressed) { 210 if (!msblk->stream) { 211 res = -EIO; 212 goto out_free_bio; 213 } 214 res = squashfs_decompress(msblk, bio, offset, length, output); 215 } else { 216 res = copy_bio_to_actor(bio, output, offset, length); 217 } 218 219 out_free_bio: 220 bio_free_pages(bio); 221 bio_put(bio); 222 out: 223 if (res < 0) 224 ERROR("Failed to read block 0x%llx: %d\n", index, res); 225 226 return res; 227 } 228