linuxdebug/fs/squashfs/decompressor.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
 * Phillip Lougher <phillip@squashfs.org.uk>
 *
 * decompressor.c
 */

#include <linux/types.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "decompressor.h"
#include "squashfs.h"
#include "page_actor.h"

/*
 * This file (and decompressor.h) implements a decompressor framework for
 * Squashfs, allowing multiple decompressors to be easily supported
 */

static const struct squashfs_decompressor squashfs_lzma_unsupported_comp_ops = {
	NULL, NULL, NULL, NULL, LZMA_COMPRESSION, "lzma", 0
};

#ifndef CONFIG_SQUASHFS_LZ4
static const struct squashfs_decompressor squashfs_lz4_comp_ops = {
	NULL, NULL, NULL, NULL, LZ4_COMPRESSION, "lz4", 0
};
#endif

#ifndef CONFIG_SQUASHFS_LZO
static const struct squashfs_decompressor squashfs_lzo_comp_ops = {
	NULL, NULL, NULL, NULL, LZO_COMPRESSION, "lzo", 0
};
#endif

#ifndef CONFIG_SQUASHFS_XZ
static const struct squashfs_decompressor squashfs_xz_comp_ops = {
	NULL, NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0
};
#endif

#ifndef CONFIG_SQUASHFS_ZLIB
static const struct squashfs_decompressor squashfs_zlib_comp_ops = {
	NULL, NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0
};
#endif

#ifndef CONFIG_SQUASHFS_ZSTD
static const struct squashfs_decompressor squashfs_zstd_comp_ops = {
	NULL, NULL, NULL, NULL, ZSTD_COMPRESSION, "zstd", 0
};
#endif

static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
	NULL, NULL, NULL, NULL, 0, "unknown", 0
};

static const struct squashfs_decompressor *decompressor[] = {
	&squashfs_zlib_comp_ops,
	&squashfs_lz4_comp_ops,
	&squashfs_lzo_comp_ops,
	&squashfs_xz_comp_ops,
	&squashfs_lzma_unsupported_comp_ops,
	&squashfs_zstd_comp_ops,
	&squashfs_unknown_comp_ops
};


const struct squashfs_decompressor *squashfs_lookup_decompressor(int id)
{
	int i;

	for (i = 0; decompressor[i]->id; i++)
		if (id == decompressor[i]->id)
			break;

	return decompressor[i];
}


static void *get_comp_opts(struct super_block *sb, unsigned short flags)
{
	struct squashfs_sb_info *msblk = sb->s_fs_info;
	void *buffer = NULL, *comp_opts;
	struct squashfs_page_actor *actor = NULL;
	int length = 0;

	/*
	 * Read decompressor specific options from file system if present
	 */
	if (SQUASHFS_COMP_OPTS(flags)) {
		buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
		if (buffer == NULL) {
			comp_opts = ERR_PTR(-ENOMEM);
			goto out;
		}

		actor = squashfs_page_actor_init(&buffer, 1, 0);
		if (actor == NULL) {
			comp_opts = ERR_PTR(-ENOMEM);
			goto out;
		}

		length = squashfs_read_data(sb,
			sizeof(struct squashfs_super_block), 0, NULL, actor);

		if (length < 0) {
			comp_opts = ERR_PTR(length);
			goto out;
		}
	}

	comp_opts = squashfs_comp_opts(msblk, buffer, length);

out:
	kfree(actor);
	kfree(buffer);
	return comp_opts;
}


void *squashfs_decompressor_setup(struct super_block *sb, unsigned short flags)
{
	struct squashfs_sb_info *msblk = sb->s_fs_info;
	void *stream, *comp_opts = get_comp_opts(sb, flags);

	if (IS_ERR(comp_opts))
		return comp_opts;

	stream = squashfs_decompressor_create(msblk, comp_opts);
	if (IS_ERR(stream))
		kfree(comp_opts);

	return stream;
}