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; 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 squashfs_actor_nobuff(actor); 44 actor_addr = squashfs_first_page(actor); 45 46 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) 47 return 0; 48 49 while (copied_bytes < req_length) { 50 int bytes_to_copy = min_t(int, bvec->bv_len - offset, 51 PAGE_SIZE - actor_offset); 52 53 bytes_to_copy = min_t(int, bytes_to_copy, 54 req_length - copied_bytes); 55 if (!IS_ERR(actor_addr)) 56 memcpy(actor_addr + actor_offset, bvec_virt(bvec) + 57 offset, bytes_to_copy); 58 59 actor_offset += bytes_to_copy; 60 copied_bytes += bytes_to_copy; 61 offset += bytes_to_copy; 62 63 if (actor_offset >= PAGE_SIZE) { 64 actor_addr = squashfs_next_page(actor); 65 if (!actor_addr) 66 break; 67 actor_offset = 0; 68 } 69 if (offset >= bvec->bv_len) { 70 if (!bio_next_segment(bio, &iter_all)) 71 break; 72 offset = 0; 73 } 74 } 75 squashfs_finish_page(actor); 76 return copied_bytes; 77 } 78 79 static int squashfs_bio_read(struct super_block *sb, u64 index, int length, 80 struct bio **biop, int *block_offset) 81 { 82 struct squashfs_sb_info *msblk = sb->s_fs_info; 83 const u64 read_start = round_down(index, msblk->devblksize); 84 const sector_t block = read_start >> msblk->devblksize_log2; 85 const u64 read_end = round_up(index + length, msblk->devblksize); 86 const sector_t block_end = read_end >> msblk->devblksize_log2; 87 int offset = read_start - round_down(index, PAGE_SIZE); 88 int total_len = (block_end - block) << msblk->devblksize_log2; 89 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE); 90 int error, i; 91 struct bio *bio; 92 93 bio = bio_kmalloc(page_count, GFP_NOIO); 94 if (!bio) 95 return -ENOMEM; 96 bio_init(bio, sb->s_bdev, bio->bi_inline_vecs, page_count, REQ_OP_READ); 97 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT); 98 99 for (i = 0; i < page_count; ++i) { 100 unsigned int len = 101 min_t(unsigned int, PAGE_SIZE - offset, total_len); 102 struct page *page = alloc_page(GFP_NOIO); 103 104 if (!page) { 105 error = -ENOMEM; 106 goto out_free_bio; 107 } 108 if (!bio_add_page(bio, page, len, offset)) { 109 error = -EIO; 110 goto out_free_bio; 111 } 112 offset = 0; 113 total_len -= len; 114 } 115 116 error = submit_bio_wait(bio); 117 if (error) 118 goto out_free_bio; 119 120 *biop = bio; 121 *block_offset = index & ((1 << msblk->devblksize_log2) - 1); 122 return 0; 123 124 out_free_bio: 125 bio_free_pages(bio); 126 bio_uninit(bio); 127 kfree(bio); 128 return error; 129 } 130 131 /* 132 * Read and decompress a metadata block or datablock. Length is non-zero 133 * if a datablock is being read (the size is stored elsewhere in the 134 * filesystem), otherwise the length is obtained from the first two bytes of 135 * the metadata block. A bit in the length field indicates if the block 136 * is stored uncompressed in the filesystem (usually because compression 137 * generated a larger block - this does occasionally happen with compression 138 * algorithms). 139 */ 140 int squashfs_read_data(struct super_block *sb, u64 index, int length, 141 u64 *next_index, struct squashfs_page_actor *output) 142 { 143 struct squashfs_sb_info *msblk = sb->s_fs_info; 144 struct bio *bio = NULL; 145 int compressed; 146 int res; 147 int offset; 148 149 if (length) { 150 /* 151 * Datablock. 152 */ 153 compressed = SQUASHFS_COMPRESSED_BLOCK(length); 154 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); 155 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", 156 index, compressed ? "" : "un", length, output->length); 157 } else { 158 /* 159 * Metadata block. 160 */ 161 const u8 *data; 162 struct bvec_iter_all iter_all = {}; 163 struct bio_vec *bvec = bvec_init_iter_all(&iter_all); 164 165 if (index + 2 > msblk->bytes_used) { 166 res = -EIO; 167 goto out; 168 } 169 res = squashfs_bio_read(sb, index, 2, &bio, &offset); 170 if (res) 171 goto out; 172 173 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 174 res = -EIO; 175 goto out_free_bio; 176 } 177 /* Extract the length of the metadata block */ 178 data = bvec_virt(bvec); 179 length = data[offset]; 180 if (offset < bvec->bv_len - 1) { 181 length |= data[offset + 1] << 8; 182 } else { 183 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) { 184 res = -EIO; 185 goto out_free_bio; 186 } 187 data = bvec_virt(bvec); 188 length |= data[0] << 8; 189 } 190 bio_free_pages(bio); 191 bio_uninit(bio); 192 kfree(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 = msblk->thread_ops->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_uninit(bio); 227 kfree(bio); 228 out: 229 if (res < 0) { 230 ERROR("Failed to read block 0x%llx: %d\n", index, res); 231 if (msblk->panic_on_errors) 232 panic("squashfs read failed"); 233 } 234 235 return res; 236 } 237