linux/kernel/module/decompress.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2021 Google LLC.
 */

#include <linux/init.h>
#include <linux/highmem.h>
#include <linux/kobject.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/vmalloc.h>

#include "internal.h"

static int module_extend_max_pages(struct load_info *info, unsigned int extent)
{ … }

static struct page *module_get_next_page(struct load_info *info)
{ … }

#if defined(CONFIG_MODULE_COMPRESS_GZIP)
#include <linux/zlib.h>
#define MODULE_COMPRESSION …
#define MODULE_DECOMPRESS_FN …

/*
 * Calculate length of the header which consists of signature, header
 * flags, time stamp and operating system ID (10 bytes total), plus
 * an optional filename.
 */
static size_t module_gzip_header_len(const u8 *buf, size_t size)
{ … }

static ssize_t module_gzip_decompress(struct load_info *info,
				      const void *buf, size_t size)
{ … }
#elif defined(CONFIG_MODULE_COMPRESS_XZ)
#include <linux/xz.h>
#define MODULE_COMPRESSION …
#define MODULE_DECOMPRESS_FN …

static ssize_t module_xz_decompress(struct load_info *info,
				    const void *buf, size_t size)
{
	static const u8 signature[] = { 0xfd, '7', 'z', 'X', 'Z', 0 };
	struct xz_dec *xz_dec;
	struct xz_buf xz_buf;
	enum xz_ret xz_ret;
	size_t new_size = 0;
	ssize_t retval;

	if (size < sizeof(signature) ||
	    memcmp(buf, signature, sizeof(signature))) {
		pr_err("not an xz compressed module\n");
		return -EINVAL;
	}

	xz_dec = xz_dec_init(XZ_DYNALLOC, (u32)-1);
	if (!xz_dec)
		return -ENOMEM;

	xz_buf.in_size = size;
	xz_buf.in = buf;
	xz_buf.in_pos = 0;

	do {
		struct page *page = module_get_next_page(info);

		if (IS_ERR(page)) {
			retval = PTR_ERR(page);
			goto out;
		}

		xz_buf.out = kmap_local_page(page);
		xz_buf.out_pos = 0;
		xz_buf.out_size = PAGE_SIZE;
		xz_ret = xz_dec_run(xz_dec, &xz_buf);
		kunmap_local(xz_buf.out);

		new_size += xz_buf.out_pos;
	} while (xz_buf.out_pos == PAGE_SIZE && xz_ret == XZ_OK);

	if (xz_ret != XZ_STREAM_END) {
		pr_err("decompression failed with status %d\n", xz_ret);
		retval = -EINVAL;
		goto out;
	}

	retval = new_size;

 out:
	xz_dec_end(xz_dec);
	return retval;
}
#elif defined(CONFIG_MODULE_COMPRESS_ZSTD)
#include <linux/zstd.h>
#define MODULE_COMPRESSION …
#define MODULE_DECOMPRESS_FN …

static ssize_t module_zstd_decompress(struct load_info *info,
				    const void *buf, size_t size)
{
	static const u8 signature[] = { 0x28, 0xb5, 0x2f, 0xfd };
	ZSTD_outBuffer zstd_dec;
	ZSTD_inBuffer zstd_buf;
	zstd_frame_header header;
	size_t wksp_size;
	void *wksp = NULL;
	ZSTD_DStream *dstream;
	size_t ret;
	size_t new_size = 0;
	int retval;

	if (size < sizeof(signature) ||
	    memcmp(buf, signature, sizeof(signature))) {
		pr_err("not a zstd compressed module\n");
		return -EINVAL;
	}

	zstd_buf.src = buf;
	zstd_buf.pos = 0;
	zstd_buf.size = size;

	ret = zstd_get_frame_header(&header, zstd_buf.src, zstd_buf.size);
	if (ret != 0) {
		pr_err("ZSTD-compressed data has an incomplete frame header\n");
		retval = -EINVAL;
		goto out;
	}
	if (header.windowSize > (1 << ZSTD_WINDOWLOG_MAX)) {
		pr_err("ZSTD-compressed data has too large a window size\n");
		retval = -EINVAL;
		goto out;
	}

	wksp_size = zstd_dstream_workspace_bound(header.windowSize);
	wksp = kvmalloc(wksp_size, GFP_KERNEL);
	if (!wksp) {
		retval = -ENOMEM;
		goto out;
	}

	dstream = zstd_init_dstream(header.windowSize, wksp, wksp_size);
	if (!dstream) {
		pr_err("Can't initialize ZSTD stream\n");
		retval = -ENOMEM;
		goto out;
	}

	do {
		struct page *page = module_get_next_page(info);

		if (IS_ERR(page)) {
			retval = PTR_ERR(page);
			goto out;
		}

		zstd_dec.dst = kmap_local_page(page);
		zstd_dec.pos = 0;
		zstd_dec.size = PAGE_SIZE;

		ret = zstd_decompress_stream(dstream, &zstd_dec, &zstd_buf);
		kunmap_local(zstd_dec.dst);
		retval = zstd_get_error_code(ret);
		if (retval)
			break;

		new_size += zstd_dec.pos;
	} while (zstd_dec.pos == PAGE_SIZE && ret != 0);

	if (retval) {
		pr_err("ZSTD-decompression failed with status %d\n", retval);
		retval = -EINVAL;
		goto out;
	}

	retval = new_size;

 out:
	kvfree(wksp);
	return retval;
}
#else
#error "Unexpected configuration for CONFIG_MODULE_DECOMPRESS"
#endif

int module_decompress(struct load_info *info, const void *buf, size_t size)
{ … }

void module_decompress_cleanup(struct load_info *info)
{ … }

#ifdef CONFIG_SYSFS
static ssize_t compression_show(struct kobject *kobj,
				struct kobj_attribute *attr, char *buf)
{ … }

static struct kobj_attribute module_compression_attr = …;

static int __init module_decompress_sysfs_init(void)
{ … }
late_initcall(module_decompress_sysfs_init);
#endif