// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Squashfs - a compressed read only filesystem for Linux
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*
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* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
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* Phillip Lougher <phillip@squashfs.org.uk>
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*
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* block.c
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*/
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/*
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* This file implements the low-level routines to read and decompress
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* datablocks and metadata blocks.
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*/
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#include <linux/blkdev.h>
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#include <linux/fs.h>
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#include <linux/vfs.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/buffer_head.h>
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#include <linux/bio.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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#include "squashfs.h"
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#include "decompressor.h"
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#include "page_actor.h"
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/*
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* Returns the amount of bytes copied to the page actor.
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*/
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static int copy_bio_to_actor(struct bio *bio,
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struct squashfs_page_actor *actor,
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int offset, int req_length)
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{
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void *actor_addr = squashfs_first_page(actor);
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struct bvec_iter_all iter_all = {};
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struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
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int copied_bytes = 0;
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int actor_offset = 0;
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if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
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return 0;
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while (copied_bytes < req_length) {
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int bytes_to_copy = min_t(int, bvec->bv_len - offset,
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PAGE_SIZE - actor_offset);
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bytes_to_copy = min_t(int, bytes_to_copy,
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req_length - copied_bytes);
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memcpy(actor_addr + actor_offset,
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page_address(bvec->bv_page) + bvec->bv_offset + offset,
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bytes_to_copy);
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actor_offset += bytes_to_copy;
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copied_bytes += bytes_to_copy;
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offset += bytes_to_copy;
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if (actor_offset >= PAGE_SIZE) {
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actor_addr = squashfs_next_page(actor);
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if (!actor_addr)
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break;
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actor_offset = 0;
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}
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if (offset >= bvec->bv_len) {
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if (!bio_next_segment(bio, &iter_all))
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break;
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offset = 0;
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}
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}
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squashfs_finish_page(actor);
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return copied_bytes;
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}
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static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
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struct bio **biop, int *block_offset)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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const u64 read_start = round_down(index, msblk->devblksize);
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const sector_t block = read_start >> msblk->devblksize_log2;
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const u64 read_end = round_up(index + length, msblk->devblksize);
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const sector_t block_end = read_end >> msblk->devblksize_log2;
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int offset = read_start - round_down(index, PAGE_SIZE);
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int total_len = (block_end - block) << msblk->devblksize_log2;
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const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
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int error, i;
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struct bio *bio;
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if (page_count <= BIO_MAX_PAGES)
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bio = bio_alloc(GFP_NOIO, page_count);
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else
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bio = bio_kmalloc(GFP_NOIO, page_count);
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if (!bio)
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return -ENOMEM;
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bio_set_dev(bio, sb->s_bdev);
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bio->bi_opf = READ;
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bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
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for (i = 0; i < page_count; ++i) {
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unsigned int len =
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min_t(unsigned int, PAGE_SIZE - offset, total_len);
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struct page *page = alloc_page(GFP_NOIO);
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if (!page) {
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error = -ENOMEM;
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goto out_free_bio;
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}
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if (!bio_add_page(bio, page, len, offset)) {
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error = -EIO;
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goto out_free_bio;
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}
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offset = 0;
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total_len -= len;
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}
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error = submit_bio_wait(bio);
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if (error)
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goto out_free_bio;
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*biop = bio;
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*block_offset = index & ((1 << msblk->devblksize_log2) - 1);
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return 0;
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out_free_bio:
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bio_free_pages(bio);
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bio_put(bio);
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return error;
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}
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/*
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* Read and decompress a metadata block or datablock. Length is non-zero
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* if a datablock is being read (the size is stored elsewhere in the
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* filesystem), otherwise the length is obtained from the first two bytes of
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* the metadata block. A bit in the length field indicates if the block
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* is stored uncompressed in the filesystem (usually because compression
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* generated a larger block - this does occasionally happen with compression
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* algorithms).
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*/
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int squashfs_read_data(struct super_block *sb, u64 index, int length,
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u64 *next_index, struct squashfs_page_actor *output)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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struct bio *bio = NULL;
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int compressed;
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int res;
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int offset;
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if (length) {
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/*
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* Datablock.
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*/
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compressed = SQUASHFS_COMPRESSED_BLOCK(length);
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length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
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TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
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index, compressed ? "" : "un", length, output->length);
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} else {
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/*
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* Metadata block.
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*/
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const u8 *data;
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struct bvec_iter_all iter_all = {};
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struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
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if (index + 2 > msblk->bytes_used) {
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res = -EIO;
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goto out;
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}
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res = squashfs_bio_read(sb, index, 2, &bio, &offset);
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if (res)
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goto out;
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if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
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res = -EIO;
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goto out_free_bio;
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}
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/* Extract the length of the metadata block */
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data = page_address(bvec->bv_page) + bvec->bv_offset;
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length = data[offset];
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if (offset < bvec->bv_len - 1) {
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length |= data[offset + 1] << 8;
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} else {
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if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
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res = -EIO;
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goto out_free_bio;
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}
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data = page_address(bvec->bv_page) + bvec->bv_offset;
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length |= data[0] << 8;
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}
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bio_free_pages(bio);
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bio_put(bio);
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compressed = SQUASHFS_COMPRESSED(length);
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length = SQUASHFS_COMPRESSED_SIZE(length);
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index += 2;
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TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
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compressed ? "" : "un", length);
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}
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if (length < 0 || length > output->length ||
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(index + length) > msblk->bytes_used) {
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res = -EIO;
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goto out;
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}
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if (next_index)
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*next_index = index + length;
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res = squashfs_bio_read(sb, index, length, &bio, &offset);
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if (res)
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goto out;
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if (compressed) {
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if (!msblk->stream) {
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res = -EIO;
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goto out_free_bio;
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}
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res = squashfs_decompress(msblk, bio, offset, length, output);
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} else {
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res = copy_bio_to_actor(bio, output, offset, length);
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}
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out_free_bio:
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bio_free_pages(bio);
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bio_put(bio);
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out:
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if (res < 0)
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ERROR("Failed to read block 0x%llx: %d\n", index, res);
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return res;
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}
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