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 bio = bio_kmalloc(GFP_NOIO, page_count); 90 if (!bio) 91 return -ENOMEM; 92 bio_set_dev(bio, sb->s_bdev); 93 bio->bi_opf = REQ_OP_READ; 94 95 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); 96 97 for (i = 0; i < page_count; ++i) { 98 unsigned int len = 99 min_t(unsigned int, PAGE_SIZE - offset, total_len); 100 struct page *page = alloc_page(GFP_NOIO); 101 102 if (!page) { 103 error = -ENOMEM; 104 goto out_free_bio; 105 } 106 if (!bio_add_page(bio, page, len, offset)) { 107 error = -EIO; 108 goto out_free_bio; 109 } 110 offset = 0; 111 total_len -= len; 112 } 113 114 error = submit_bio_wait(bio); 115 if (error) 116 goto out_free_bio; 117 118 *biop = bio; 119 *block_offset = index & ((1 << msblk->devblksize_log2) - 1); 120 return 0; 121 122 out_free_bio: 123 bio_free_pages(bio); 124 bio_put(bio); 125 return error; 126 } 127 128 /* 129 * Read and decompress a metadata block or datablock. Length is non-zero 130 * if a datablock is being read (the size is stored elsewhere in the 131 * filesystem), otherwise the length is obtained from the first two bytes of 132 * the metadata block. A bit in the length field indicates if the block 133 * is stored uncompressed in the filesystem (usually because compression 134 * generated a larger block - this does occasionally happen with compression 135 * algorithms). 136 */ 137 int squashfs_read_data(struct super_block *sb, u64 index, int length, 138 u64 *next_index, struct squashfs_page_actor *output) 139 { 140 struct squashfs_sb_info *msblk = sb->s_fs_info; 141 struct bio *bio = NULL; 142 int compressed; 143 int res; 144 int offset; 145 146 if (length) { 147 /* 148 * Datablock. 149 */ 150 compressed = SQUASHFS_COMPRESSED_BLOCK(length); 151 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); 152 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", 153 index, compressed ? "" : "un", length, output->length); 154 } else { 155 /* 156 * Metadata block. 157 */ 158 const u8 *data; 159 struct bvec_iter_all iter_all = {}; 160 struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 161 162 if (index + 2 > msblk->bytes_used) { 163 res = -EIO; 164 goto out; 165 } 166 res = squashfs_bio_read(sb, index, 2, &bio, &offset); 167 if (res) 168 goto out; 169 170 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 171 res = -EIO; 172 goto out_free_bio; 173 } 174 /* Extract the length of the metadata block */ 175 data = bvec_virt(bvec); 176 length = data[offset]; 177 if (offset < bvec->bv_len - 1) { 178 length |= data[offset + 1] << 8; 179 } else { 180 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 181 res = -EIO; 182 goto out_free_bio; 183 } 184 data = bvec_virt(bvec); 185 length |= data[0] << 8; 186 } 187 bio_free_pages(bio); 188 bio_put(bio); 189 190 compressed = SQUASHFS_COMPRESSED(length); 191 length = SQUASHFS_COMPRESSED_SIZE(length); 192 index += 2; 193 194 TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2, 195 compressed ? "" : "un", length); 196 } 197 if (length < 0 || length > output->length || 198 (index + length) > msblk->bytes_used) { 199 res = -EIO; 200 goto out; 201 } 202 203 if (next_index) 204 *next_index = index + length; 205 206 res = squashfs_bio_read(sb, index, length, &bio, &offset); 207 if (res) 208 goto out; 209 210 if (compressed) { 211 if (!msblk->stream) { 212 res = -EIO; 213 goto out_free_bio; 214 } 215 res = squashfs_decompress(msblk, bio, offset, length, output); 216 } else { 217 res = copy_bio_to_actor(bio, output, offset, length); 218 } 219 220 out_free_bio: 221 bio_free_pages(bio); 222 bio_put(bio); 223 out: 224 if (res < 0) { 225 ERROR("Failed to read block 0x%llx: %d\n", index, res); 226 if (msblk->panic_on_errors) 227 panic("squashfs read failed"); 228 } 229 230 return res; 231 } 232